JP6904890B2 - Fracture cause estimation method and estimation system, and stress level estimation method and estimation system - Google Patents

Description

The present disclosure relates to a method and an estimation system for estimating the cause of fracture of a metallic material, and a method and an estimation system for estimating a stress level at the time of fatigue fracture of a metallic material.

Conventionally, in order to estimate the cause of destruction when a metal material is damaged, the state of the fracture surface has been observed visually or by an optical microscope or the like. However, it is often difficult to observe the fracture surface state of the actually damaged metal material because the surface of the fracture surface is oxidized or crushed. Further, for a metal material such as striation in which the fracture surface condition peculiar to fatigue fracture cannot be observed, it is difficult to estimate the cause of fracture even by observing the fracture surface condition.

In recent years, for example, the electron backscatter diffraction image method (EBSD method) is used to measure the crystal orientation in a metal material in the depth direction of the fracture surface, and the crystal orientation difference distribution is analyzed based on the crystal orientation. , The cause of destruction of metal materials has been estimated (for example, Patent Document 1). The crystal orientation can also be obtained by using an X-ray diffraction method or the like in addition to the EBSD method.

In Patent Document 1, the orientation difference curve obtained from the average value of the depth from the fracture surface and the crystal orientation difference is compared with the standard orientation difference curve obtained by using a standard sample whose fracture cause is known. Describes a method for estimating the cause of destruction of a metal material. The average value of the crystal orientation difference in Patent Document 1 is the crystal orientation difference for each division when a plurality of measurement visual field ranges are measured and then the measurement surface is divided into a plurality of measurement surfaces at predetermined intervals in the depth direction from the fracture surface. It is a value calculated by averaging.

Japanese Patent No. 58558881

In the method for estimating the cause of destruction of a metal material described in Patent Document 1, it is necessary to measure a plurality of measurement field ranges in order to obtain an orientation difference curve of a damaged metal material and a standard orientation difference curve of a standard sample. Since it takes time to measure the measurement field range of the above, there is a problem that it takes time to identify the cause of destruction of the damaged metal material. In addition, the orientation difference characteristic that appears in the vicinity of the fracture surface at a depth of 1 mm or less from the fracture surface cannot be obtained, and there is a possibility that the estimation of the cause of fracture of the metal material may be erroneous.

As a result of diligent studies, the present inventors have determined that whether or not the fracture cause of the metal material is fatigue fracture can be estimated from the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the metal material. I found it. In addition, as a result of diligent studies, the present inventors have conducted a stress intensity factor parameter for a sample formed from the same material as the metal material, and the difference in crystal orientation between two different depth positions on the surface layer of the fracture surface of the sample. The stress intensity factor parameter of the metal material is estimated from the difference between the difference and the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the metal material based on the correlation. I found out what I could do. Here, the stress intensity factor parameter includes a stress intensity factor, a stress intensity factor range, and the like.

In view of the above circumstances, an object of at least one embodiment of the present invention is an estimation method and an estimation system for the cause of fracture of a metal material capable of highly accurate estimation in a short period of time, and a stress level at the time of fatigue fracture of the metal material. To provide an estimation method and an estimation system for the above.

(1) The method for estimating the cause of destruction of a metal material according to at least one embodiment of the present invention is
It is a method of estimating the cause of destruction of metal materials.
A step of measuring one measurement field of view including at least a part of the fracture surface of the metal material and acquiring crystal orientations at a plurality of measurement points included in the one measurement field of view.
A crystal orientation difference acquisition step for acquiring a crystal orientation difference at a plurality of measurement points based on the acquired crystal orientation, and a crystal orientation difference acquisition step.
The first crystal orientation difference, which is the crystal orientation difference at the position near the fracture surface where the depth from the fracture surface is less than a predetermined value, and the position far from the fracture surface, where the depth from the fracture surface is larger than the position near the fracture surface. The first difference acquisition step for acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference in
It includes a first estimation step of estimating whether or not the fracture cause of the metallic material is fatigue fracture based on the first difference.

As described above, as a result of diligent studies, the present inventors have determined whether or not the fracture cause of the metal material is fatigue fracture due to the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the metal material. It was found that it can be estimated. More specifically, the first difference, which is the difference in crystal orientation between the fracture surface near position and the fracture surface distant position included in one measurement viewing range including at least a part of the fracture surface of the metal material, is used to obtain the metal material. It is possible to estimate whether or not the cause of fracture is fatigue fracture.

According to the method (1) described above, the first difference can be acquired by going through the steps of acquiring the crystal orientation, the crystal orientation difference acquisition step, and the first difference acquisition step described above, and the first estimation step is the first. From one difference, it is possible to estimate with high accuracy whether or not the fracture cause of the metal material is fatigue fracture. Further, according to the above method, since it is sufficient to measure one measurement field of view including at least a part of the fracture surface of the metal material, the time required for measurement and processing of the measurement result is short, and the metal material is destroyed in a short period of time. The cause can be estimated.

(2) In some embodiments, in the method of (1) above,
In the first estimation step, when the first difference is equal to or more than a predetermined value, it is estimated that the cause of fracture of the metal material is fatigue fracture, and when the first difference is less than the predetermined value, the metal material is said to be fractured. It is presumed that the cause of the fracture is not fatigue fracture.

According to the method (2) above, it is possible to quantitatively estimate whether or not the fracture cause of the metal material is fatigue fracture by the first difference, so that the time required for the estimation in the first estimation step can be reduced.

(3) In some embodiments, in the method (1) or (2) above,
The method for estimating the cause of destruction of the metal material is
If the inclination of the linear regression line of the fracture surface is equal to or greater than a predetermined angle after the step of acquiring the crystal orientation and before the step of acquiring the crystal orientation difference, the linear regression line is set as the first coordinate axis. Further, a tilt adjusting step of performing coordinate conversion to an orthogonal coordinate system having a straight line along the depth direction of the fracture surface orthogonal to the linear regression straight line as a second coordinate axis is further provided.

According to the method (3) above, when the slope of the linear regression line of the fracture surface is equal to or greater than a predetermined angle, an error in the depth direction of the fracture surface can be obtained by using the measurement coordinate system when one measurement visual field range is measured. Becomes larger. Therefore, when the inclination of the linear regression line described above is equal to or greater than a predetermined angle, it is possible to reduce the error in the depth direction of the fracture surface by performing coordinate conversion to the Cartesian coordinate system.

(4) In some embodiments, in the methods (1) to (3) above,
The first crystal orientation difference includes statistical values of the crystal orientation difference of the plurality of measurement points arranged along a direction orthogonal to the depth direction of the fracture surface at a position near the fracture surface.
The second crystal orientation difference includes statistical values of the crystal orientation difference of the plurality of measurement points arranged along a direction orthogonal to the depth direction of the fracture surface at a position far from the fracture surface.

In the metal material, a portion having a large crystal orientation difference may be locally present at a position deep from the fracture surface. According to the method (4) above, the first crystal orientation difference and the second crystal orientation difference are the crystal orientations of a plurality of measurement points arranged along a direction orthogonal to the depth direction of the fracture surface at a predetermined position. Since the statistical value of the difference is included, the influence of the above-mentioned locally large crystal orientation difference can be reduced, so it is possible to estimate with high accuracy whether or not the cause of the fracture of the metal material is fatigue fracture. can.

(5) The method for estimating the stress level at the time of fatigue fracture of a metal material according to at least one embodiment of the present invention is
It is a method of estimating the stress level at the time of fatigue failure of metallic materials.
A step of measuring one measurement field of view including at least a part of the fracture surface of the metal material and acquiring crystal orientations at a plurality of measurement points included in the one measurement field of view.
A crystal orientation difference acquisition step for acquiring a crystal orientation difference at a plurality of measurement points based on the acquired crystal orientation, and a crystal orientation difference acquisition step.
The first crystal orientation difference, which is the crystal orientation difference at the position near the fracture surface where the depth from the fracture surface is less than a predetermined value, and the position far from the fracture surface, where the depth from the fracture surface is larger than the position near the fracture surface. The first difference acquisition step for acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference in
A step of acquiring a correlation between a stress intensity factor parameter and a second difference, which is a difference in crystal orientation difference at a depth position corresponding to the first difference, for a sample formed from the same material as the metal material. ,
Based on the acquired correlation, the stress intensity factor parameter of the metal material is estimated from the first difference, and the stress level at the time of fatigue failure of the metal material is estimated from the estimated stress intensity factor parameter. It comprises an estimation step.

As described above, as a result of diligent studies, the present inventors have found that the stress intensity factor parameter of a sample formed from the same material as the metal material and the crystals at two different depth positions on the surface layer of the fracture surface of the sample. The stress intensity factor of the metal material is due to the correlation between the difference in orientation and the difference in crystal orientation at two different depth positions on the surface of the fracture surface of the metal material based on the correlation. We found that the parameters can be estimated.

According to the method (5) above, the above-mentioned crystal orientation is acquired based on the correlation between the second difference, which is the difference in crystal orientation difference at the depth position corresponding to the first difference, and the stress intensity factor parameter. The stress intensity factor parameter of the metal material can be estimated with high accuracy from the first difference acquired through the step, the crystal orientation difference acquisition step, and the first difference acquisition step. Then, the stress level at the time of fatigue fracture of the metal material can be estimated from the stress intensity factor parameter of the metal material. Further, according to the above method, it is sufficient to acquire the above-mentioned correlation and measure one measurement visual field range including at least a part of the fracture surface of the metal material, so that it takes time to measure and process the measurement result. It is possible to estimate the stress level at the time of fatigue fracture of a metal material in a short period of time.

(6) In some embodiments, in the method of (5) above,
The stress intensity factor parameters are obtained by performing a fatigue crack growth test on the sample.
For the second difference, the crystal orientations at a plurality of measurement points of the sample subjected to the fatigue crack growth test are acquired, and the crystal orientation differences at the plurality of measurement points are acquired based on the acquired crystal orientations. At the same time, the third crystal orientation difference, which is the crystal orientation difference at the position near the fracture surface where the depth from the fracture surface generated in the fatigue crack growth test is equal to or less than a predetermined value, and the fracture at the position near the fracture surface. It is a difference from the fourth crystal orientation difference, which is the crystal orientation difference at the fracture surface distant position where the depth from the plane is large and the depth from the fracture surface is 100 μm or less.

According to the method (6) above, the second difference is obtained for the sample subjected to the fatigue crack growth test in order to obtain the stress intensity factor parameter, so that the difference between the stress intensity factor parameter and the second difference is obtained. The accuracy of the correlation can be improved. Further, since the third crystal orientation difference and the fourth crystal orientation difference of the sample correspond to the first crystal orientation difference and the second crystal orientation difference of the metal material, the second difference of the sample is the first difference of the metal material. Can be accurately associated with. Further, according to the above method, crystals at a position near the fracture surface and a position far from the fracture surface where the depth from the fracture surface is larger than the position near the fracture surface and the depth from the fracture surface is 100 μm or less. Since the second difference is acquired based on the orientation difference, the size of one measurement field range including the position near the fracture surface and the position far from the fracture surface can be reduced. Then, by reducing one measurement field of view range, it is possible to reduce the time required for measurement and processing of measurement results.

(7) In some embodiments, in the method (5) or (6) above,
The stress intensity factor parameter includes at least one of a stress intensity factor, a stress intensity factor range, and an effective stress intensity factor range.
According to the method (7) above, the stress intensity factor, the stress intensity factor range, or the effective stress intensity factor range can be estimated from the first difference. The stress level at time can be estimated.

(8) The system for estimating the cause of destruction of a metallic material according to at least one embodiment of the present invention is
It is a system for estimating the cause of destruction of metallic materials.
A measuring device capable of measuring one measurement visual field range including at least a part of a fracture surface of the metal material, and a measuring device capable of acquiring crystal orientations at a plurality of measurement points included in the one measurement visual field range.
An analysis device capable of acquiring crystal orientation differences at a plurality of measurement points based on the crystal orientation acquired by the measuring device, and an analysis device capable of acquiring crystal orientation differences at the plurality of measurement points.
The first crystal orientation difference, which is the crystal orientation difference at a position near the fracture surface where the depth from the fracture surface acquired by the analyzer is equal to or less than a predetermined value, and the position near the fracture surface acquired by the analyzer. A computing device capable of acquiring a first difference, which is a difference between the second crystal orientation difference, which is the crystal orientation difference at a position far from the fracture surface having a large depth from the fracture surface, is provided.

As described above, as a result of diligent studies, the present inventors have determined whether or not the fracture cause of the metal material is fatigue fracture due to the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the metal material. It was found that it can be estimated. More specifically, the first difference, which is the difference in crystal orientation between the fracture surface near position and the fracture surface distant position included in one measurement viewing range including at least a part of the fracture surface of the metal material, is used to obtain the metal material. It is possible to estimate whether or not the cause of fracture is fatigue fracture.

According to the configuration of the above (8), the estimation system of the cause of destruction of the metal material uses the above-mentioned measuring device capable of acquiring the crystal orientation, the above-mentioned analysis device capable of acquiring the crystal orientation difference, and the above-mentioned first difference. Since the arithmetic unit that can be acquired is provided, the above-mentioned first difference can be acquired. Therefore, it is possible to estimate with high accuracy whether or not the fracture cause of the metal material is fatigue fracture from the acquired first difference. Further, according to the above configuration, since the measuring device only needs to measure one measurement field of view including at least a part of the fracture surface of the metal material, the time required for the measurement and the processing of the measurement result is short, and the metal material is destroyed. The cause estimation system can estimate the cause of destruction of a metallic material in a short period of time.

(9) The stress level estimation system at the time of fatigue fracture of a metal material according to at least one embodiment of the present invention is
A system for estimating stress levels during fatigue failure of metallic materials.
A measuring device capable of measuring one measurement visual field range including at least a part of a fracture surface of the metal material, and a measuring device capable of acquiring crystal orientations at a plurality of measurement points included in the one measurement visual field range.
An analysis device capable of acquiring crystal orientation differences at a plurality of measurement points based on the crystal orientation acquired by the measuring device, and an analysis device capable of acquiring crystal orientation differences at the plurality of measurement points.
The first crystal orientation difference, which is the crystal orientation difference at a position near the fracture surface where the depth from the fracture surface acquired by the analyzer is equal to or less than a predetermined value, and the position near the fracture surface acquired by the analyzer. An arithmetic device capable of acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference at a position far from the fracture surface having a large depth from the fracture surface, and
A storage device that stores the correlation between the stress intensity factor parameter and the second difference, which is the difference in crystal orientation at the depth position corresponding to the first difference, for a sample formed from the same material as the metal material. When,
An estimation device for estimating the stress intensity factor parameter of the metal material from the first difference based on the correlation stored in the storage device is provided.

As described above, as a result of diligent studies, the present inventors have found that the stress intensity factor parameter of a sample formed from the same material as the metal material and the crystals at two different depth positions on the surface layer of the fracture surface of the sample. The stress intensity factor of the metal material is due to the correlation between the difference in orientation and the difference in crystal orientation at two different depth positions on the surface of the fracture surface of the metal material based on the correlation. We found that the parameters can be estimated.

According to the configuration of (9) above, the stress level estimation system at the time of fatigue fracture of the metal material can acquire the above-mentioned measuring device capable of acquiring the crystal orientation of the metal material and the above-mentioned difference in crystal orientation of the metal material. Since the analysis device and the calculation device capable of acquiring the above-mentioned first difference are provided, the first difference of the above-mentioned metal material can be acquired. Further, the stress level estimation system at the time of fatigue failure of the metal material uses a storage device that stores the above-mentioned correlation and a stress intensity factor parameter of the metal material from the first difference based on the correlation stored in the storage device. Since the estimation device for estimation is further provided, the stress intensity factor parameter of the metal material can be estimated with high accuracy from the value of the first difference described above. Then, the stress level at the time of fatigue fracture of the metal material can be estimated from the stress intensity factor parameter of the metal material. Further, according to the above configuration, the above-mentioned correlation may be stored in the storage device, and the measuring device may measure one measurement field range including at least a part of the fracture surface of the metal material. The processing time for processing the measurement results is short, and the stress level estimation system at the time of fatigue failure of the metal material can estimate the stress level at the time of fatigue failure of the metal material in a short period of time.

According to at least one embodiment of the present invention, a method and an estimation system for estimating the cause of fracture of a metal material capable of highly accurate estimation in a short period of time, and a method and an estimation system for estimating a stress level at the time of fatigue failure of the metal material Provided.

It is a flow chart which shows an example of the method of estimating the cause of destruction of a metal material which concerns on one Embodiment of this invention. It is a schematic block diagram which shows typically an example of the structure of the estimation system for carrying out the method of estimating the cause of destruction of a metal material which concerns on one Embodiment of this invention. It is a figure which shows the sample used for the measurement in one Embodiment of this invention. It is a layout drawing for demonstrating the arrangement of a plurality of measurement points in one Embodiment of this invention. It is a layout drawing for demonstrating the arrangement of a plurality of measurement points in another embodiment of this invention. It is a figure for demonstrating the distribution of the crystal orientation in one measurement field of view of the sample which is the sample in one Embodiment of this invention and was formed from the metal material which was fatigue fractured. It is a figure for demonstrating the distribution of the crystal orientation difference in one measurement visual field range of the sample which is the sample in one Embodiment of this invention and was formed from the metal material which was fatigue fractured. It is a graph for demonstrating the relationship between the crystal orientation difference of the sample which is the sample in one Embodiment of this invention and formed from the tensile fracture metal material, and the distance from a fracture surface. It is a graph for demonstrating the relationship between the crystal orientation difference of the sample which is the sample in one Embodiment of this invention, and was formed from the metal material which was fatigue-broken, and the distance from a fracture surface. It is a flow chart which shows an example of the method of estimating the cause of destruction of a metal material which concerns on another Embodiment of this invention, and is the flow chart which shows a part of the flow chart shown in FIG. 1 enlarged. It is a figure which shows the fracture surface in one measurement field of view of the sample which is the sample in another embodiment of this invention and was formed from the metal material which was fatigue fracture, and the linear regression line of the fracture surface. It is a flow chart which shows an example of the method of estimating the stress level at the time of fatigue fracture of the metal material which concerns on one Embodiment of this invention. It is a figure for demonstrating the fatigue crack growth test, and is the figure which shows roughly the structure of the fatigue crack growth test, and the test piece used for the fatigue crack growth test. It is a figure for demonstrating the distribution of the crystal orientation difference in one measurement visual field range of the sample which is the sample in one Embodiment of this invention and was formed from the same material as the metal material which was fatigue fractured. It is a graph for demonstrating the correlation between the difference of the crystal orientation difference of two different depth positions in the surface layer of the fracture surface of a sample, and the stress intensity factor for a sample. It is a graph for demonstrating the correlation between the difference of the crystal orientation difference of two different depth positions in the surface layer of the fracture surface of a sample, and the stress intensity factor range. It is a graph for demonstrating the correlation between the difference of the crystal orientation difference of two different depth positions in the surface layer of the fracture surface of a sample, and the effective stress intensity factor range.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, and are merely explanatory examples. do not have.
For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, the expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or chamfering within a range where the same effect can be obtained. The shape including the part and the like shall also be represented.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions that exclude the existence of other components.
The same components may be designated by the same reference numerals and the description thereof may be omitted.

FIG. 1 is a flow chart showing an example of a method for estimating a cause of destruction of a metal material according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram schematically showing an example of the configuration of an estimation system for implementing the method for estimating the cause of destruction of a metal material according to an embodiment of the present invention. Hereinafter, the configuration of the metal material destruction cause estimation system 1 for carrying out the metal material destruction cause estimation method 10 will be described first.

As shown in FIG. 2, the estimation system 1 of the cause of destruction of the metal material includes an EBSD detection device 2, an information processing device 3, an SEM control unit 12, a stage control unit 13, and a camera control unit 14. I have. The information processing device 3 is electrically connected to the EBSD detection device 2, the SEM control unit 12, the stage control unit 13, and the camera control unit 14, and is configured to enable transmission and reception of signals between the devices.

The information processing device 3 is configured to be able to control the components constituting the estimation system 1 of the cause of destruction of the metal material. Specifically, the information processing device 3 is composed of a microcomputer including an input / output device 31 (input / output interface), a storage device 32 (ROM, RAM), a display device 33 (display), and an arithmetic unit 34 (CPU). However, general configurations and controls will be omitted as appropriate.

The input / output device 31 of the information processing device 3 is input with various information from each component (EBSD detection device 2 or the like) used in the estimation system 1 of the cause of destruction of the metal material, and various information based on the calculation result or the like. Is output to each of the above-mentioned components. Further, the input / output device 31 includes a keyboard, a mouse, and the like. The storage device 32 is configured to be able to store various input information, various programs necessary for performing control, calculation results, and the like. The arithmetic unit 34 performs arithmetic processing based on the various information described above. The display device 33 displays information such as various input information and the calculation result by the above-mentioned arithmetic unit 34.

The EBSD detection device 2 (crystal orientation detection device) is configured to be capable of measuring the crystal orientations of a plurality of measurement points P in the first sample 5 formed of a damaged metal material by an electron backscatter diffraction image method. Specifically, the EBSD detector 2 includes at least a scanning electron microscope 4 (SEM), as shown in FIG. The scanning electron microscope 4 is configured so that the tissue of the first sample 5 can be observed and can be measured at predetermined step intervals for an arbitrary field of view. Further, as shown in FIG. 2, the scanning electron microscope 4 has a sample stage 41 capable of fixing the first sample 5 formed of a metal material, a sample chamber 42 for accommodating the sample stage 41, and the first sample 5. It is equipped with an electron gun 43 capable of irradiating an electron beam. The general configuration and control of the EBSD detection device 2 and the scanning electron microscope 4 will be omitted as appropriate.

The SEM control unit 12 is configured to be able to control the electron beam irradiation operation including the electron beam irradiation amount, irradiation timing, scanning direction, etc. by the electron gun 43 under the control of the arithmetic unit 34. The stage control unit 13 controls a multi-axis motor (not shown) provided in the sample stage 41 and a drive device (not shown) driven by the multi-axis motor under the control of the arithmetic unit 34, thereby controlling the sample stage 41. The position and tilt of the are adjustable.

As shown in FIG. 2, the EBSD detection device 2 is provided inside the sample chamber 42 and displays an electron backscatter diffraction image (Kikuchi pattern) generated by the electron gun 43 irradiating the first sample 5 with an electron beam. It further includes a screen 21 for projection and a camera 22 for capturing an electron backscatter diffraction image projected on the screen 21. The camera 22 includes a high-sensitivity camera and is provided inside the sample chamber 42 along a direction orthogonal to the electron beam irradiation direction. The camera control unit 14 is configured to control the shooting timing of the camera 22 and the like under the control of the arithmetic unit 34.

Hereinafter, the method 10 for estimating the cause of destruction of the metal material will be described in detail. As shown in FIG. 1, in the method 10 for estimating the cause of destruction of a metal material according to some embodiments, one measurement field range 6 including at least a part of a fracture surface 51 of the metal material is measured to determine the crystal orientation. The measurement step S101 to be acquired, the crystal orientation difference acquisition step S102 to acquire the crystal orientation difference based on the acquired crystal orientation, the first crystal orientation difference OD1 which is the crystal orientation difference at the position near the fracture surface 55, and the vicinity of the fracture surface. The first difference acquisition step S103 for acquiring the first difference D1 which is the difference between the second crystal orientation difference OD2 which is the crystal orientation difference at the fracture surface distant position 56 where the depth from the fracture surface 51 is larger than the position 55. A first estimation step S104 is provided for estimating whether or not the fracture cause of the metallic material is fatigue fracture based on the first difference D1.

FIG. 3 is a diagram showing a sample used for measurement in one embodiment of the present invention. In the measurement step S101, the measurement of the first sample 5 formed from the damaged metal material is performed. As shown in FIG. 3, the first sample 5 is formed by solidifying a metal component 53 cut out from a damaged metal material so as to include a fracture surface 51, and for example, an epoxy resin or the like to protect the fracture surface 51. The resin constituent portion 54 includes a resin constituent portion 54 provided on the opposite side of the fracture surface 51 from the metal constituent portion 53. In the first sample 5, the measurement surface 52, which is a surface perpendicular to the fracture surface 51, is polished by a polishing device or the like before measurement.

Specifically, in the measurement step S101, the first sample 5 is fixed to the sample stage 41 as shown in FIG. After the first sample 5 is fixed to the sample stage 41, the stage control unit 13 controls a multi-axis motor (not shown) and a drive device (not shown) to tilt the sample stage 41 at about 70 ° with respect to the horizontal. Let me.

The arithmetic unit 34 of the information processing device 3 operates a program (software) for measuring the crystal orientation recorded in the storage device 32. The arithmetic unit 34 controls the SEM control unit 12 based on the above-mentioned program for measuring the crystal orientation, scans the electron beam emitted from the electron gun 43 on the measurement surface 52, and scans the electron beam at a predetermined pitch. A plurality of measurement points P (see FIG. 4A) separated from each other are irradiated. FIG. 4A shows the case of a hexagonal lattice as the crystal orientation measurement coordinates (data extraction coordinates), while FIG. 4B shows the case of a square lattice.

Here, as shown in FIG. 3, the EBSD detection device 2 measures one measurement visual field range 6 including at least a part of the fracture surface 51 of the first sample 5 in one measurement. One measurement visual field range 6 has an X-axis dimension of 1000 μm or less and a Y-axis dimension of 600 μm or less when the measurement surface 52 of the first sample 5 is defined as a reference surface having an X-axis and a Y-axis orthogonal to each other. .. One measurement field of view 6 preferably has an X-axis dimension of 500 μm or less and a Y-axis dimension of 500 μm or less, and more preferably an X-axis dimension of 300 μm or less and a Y-axis dimension of 100 μm or less. Here, the Y-axis is an axis toward the depth of the fracture surface 51 so that the inclination of the fracture surface 51 with the linear regression line LR (see FIG. 10) is larger than the X-axis. The X-axis dimension and the Y-axis dimension of one measurement field of view range 6 are configured to be changeable by executing the program for measuring the crystal orientation described above by the arithmetic unit 34.

FIG. 4A is a layout diagram for explaining the arrangement of a plurality of measurement points in one embodiment of the present invention. As shown in FIG. 4A, a plurality of measurement points P are provided at the center of a hexagonal lattice, which is a measurement lattice, and a reference surface having an X-axis and a Y-axis orthogonal to each other on the measurement surface 52 of the first sample 5. Is provided at positions separated from the other measurement points P by 0.5XS in the X-axis direction and 0.5XS × tan (π / 3) in the Y-axis direction. XS is the distance between two measurement points P arranged along the X-axis direction with each other, and is 1.6 μm as an example. The XS is configured to be changeable by the arithmetic unit 34 executing the program for measuring the crystal orientation described above. In addition, the shape of the measurement grid can be changed to a square grid or the like.

FIG. 4B is a layout diagram for explaining the arrangement of a plurality of measurement points in another embodiment of the present invention. In the embodiment shown in FIG. 4B, a plurality of measurement points P are provided at the center of a square grid, which is a measurement grid, and a reference having an X-axis and a Y-axis in which the measurement surfaces 52 of the first sample 5 are orthogonal to each other. When defined as a surface, it is provided at a position separated from another measurement point P by the above-mentioned XS in the X-axis direction and the Y-axis direction.

The electron beam is irradiated to a plurality of measurement points P provided within the range of one measurement field of view 6, and an electron backscatter diffraction image (Kikuchi pattern) generated by the irradiation of the electron beam is projected on the screen 21. The electron backscatter diffraction image projected on the screen 21 is imaged by the camera 22 at each measurement point P. The camera 22 transmits the image data (image signal) of the electron backscatter diffraction image captured at each measurement point P to the storage device 32 via the camera control unit 14 and the input / output device 31.

As shown in FIG. 2, the arithmetic unit 34 of the information processing device 3 includes an image processing device 35. The image processing device 35 acquires the crystal orientation at each measurement point P by performing image processing on the image data of the electron backscatter diffraction image captured at each measurement point P. Here, the above-mentioned image processing is performed by an analysis program such as "OIM" manufactured by TLS, which is stored in the storage device 32. The crystal orientation information acquired for each measurement point P is stored in the storage device 32 together with the position information (position coordinates) of the measurement point P.

Further, the image processing device 35 forms a distribution map of the crystal orientation based on the crystal orientation information for each measurement point P and the position information of the measurement point P stored in the storage device 32. FIG. 5 is a diagram for explaining the distribution of crystal orientation in one measurement field of view of a sample formed from a fatigue-fractured metal material, which is a sample according to an embodiment of the present invention. In FIG. 5, the same hatching is applied to the crystal grains having the same crystal orientation.

Next, in the crystal orientation difference acquisition step S102, the crystal orientation difference for each measurement point P is acquired based on the crystal orientation acquired in the measurement step S101 described above. As the crystal orientation difference, a local orientation difference (KAM) or the like is used. Here, the local orientation difference includes the crystal orientation of the target measurement point P as shown in FIGS. 4A and 4B, and a plurality of measurement points P arranged adjacent to the target measurement point P. The average value obtained by averaging the differences between the two is used as the crystal orientation difference of the target measurement point P. Specifically, the arithmetic unit 34 of the information processing device 3 includes the analysis device 36 as shown in FIG. The analysis device 36 acquires the crystal orientation difference for each measurement point P based on the crystal orientation by executing an analysis program such as the above-mentioned "OIM" manufactured by TLS. As the crystal orientation difference, a value other than the local orientation difference (KAM) may be used. For example, the local orientation difference grain average (GAM) defined by the average value of the orientation differences between adjacent measurement points in the crystal grain, the local orientation difference region average which is the region average of the local orientation difference, and the measurement points P within the same crystal grain. Intra-grain orientation difference (GROD) defined by the orientation difference between and the average orientation of the crystal, and the intra-grain orientation defined by the average value of the orientation differences of the measurement point P in the same crystal grain with respect to other measurement points P. You may use the difference grain average (GOS), the local orientation difference grain average, the intra-grain orientation difference region average which is the region average of the intra-grain orientation difference grain average, and the like.

FIG. 6 is a diagram for explaining the distribution of the crystal orientation difference in one measurement field of view of a sample formed from a fatigue-fractured metal material, which is a sample according to an embodiment of the present invention. In FIG. 6, dots are struck in the portion where the crystal orientation difference is large. As shown in FIG. 6, in the first sample 5 formed from the fatigue-fractured metal material, dots are struck in a wider area in the vicinity of the fracture surface 51 than in a portion away from the fracture surface 51.

As shown in FIG. 6, the fracture surface near position 55 in which the depth from the fracture surface 51 is equal to or less than a predetermined value, and the fracture surface distant position 56 in which the depth from the fracture surface 51 is larger than the fracture surface near position 55. Is stipulated. The middle dotted line in FIG. 6 is a line connecting the position near the fracture surface 55 and the position having the same depth from the fracture surface 51, and the alternate long and short dash line in FIG. It is a line connecting. Here, the depth near the fracture surface 55 is 50 μm or less from the fracture surface 51. The depth near the fracture surface 55 is preferably 40 μm or less from the fracture surface 51, and more preferably 20 μm or less from the fracture surface 51. Further, the depth of the fracture surface far position 56 from the fracture surface 51 is 400 μm or less. Further, the depth of the fracture surface far position 56 is preferably 200 μm or less from the fracture surface 51, and more preferably 100 μm or less from the fracture surface 51.

In the first difference acquisition step S103, as shown in FIG. 2, the first crystal orientation difference OD1 which is the crystal orientation difference at the fracture surface near position 55 and the second crystal orientation difference which is the crystal orientation difference at the fracture surface distant position 56. The first difference D1 which is the difference between the difference OD2 and the difference OD2 is acquired. Specifically, the arithmetic unit 34 of the information processing apparatus 3 includes the difference arithmetic unit 37 as shown in FIG. The difference calculation device 37 acquires the first crystal orientation difference OD1 and the second crystal orientation difference OD2 stored in the storage device 32, and calculates the first difference D1 from the first crystal orientation difference OD1 and the second crystal orientation difference OD2. do.

FIG. 7 is a graph for explaining the relationship between the crystal orientation difference of a sample formed from a tensilely fractured metal material and the distance from a fracture surface, which is a sample according to an embodiment of the present invention. FIG. 8 is a graph for explaining the relationship between the crystal orientation difference of the sample formed from the fatigue-broken metal material and the distance from the fracture surface, which is the sample according to the embodiment of the present invention. As shown in FIG. 7, a sample formed from a tensilely fractured metal material tends to have a uniform crystal orientation difference regardless of the distance from the fracture surface. On the other hand, as shown in FIG. 8, in the sample formed from the fatigue-fractured metal material, the crystal orientation difference is uniform in the portion away from the fracture surface, but the crystal orientation difference increases as the fracture surface approaches. Tends to increase exponentially.

In the first estimation step S104, as shown in FIG. 2, it is estimated whether or not the fracture cause of the metallic material is fatigue fracture based on the first difference D1.

As described above, the methods for estimating the cause of destruction of the metal material according to some embodiments are the above-mentioned measurement step S101, the above-mentioned crystal orientation difference acquisition step S102, and the above-mentioned first method, as shown in FIG. It includes one difference acquisition step S103 and the above-mentioned first estimation step S104.

As described above, as a result of diligent studies, the present inventors have determined whether or not the fracture cause of the metal material is fatigue fracture due to the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the metal material. It was found that it can be estimated. More specifically, the crystal orientation difference between the fracture surface near position 55 and the fracture surface distant position 56 included in one measurement viewing range 6 including at least a part of the fracture surface 51 of the metal material (first crystal orientation difference OD1, From the first difference D1 which is the difference of the second crystal orientation difference OD2), it is possible to estimate whether or not the fracture cause of the metal material is fatigue fracture.

According to the above method, the first difference D1 can be acquired by passing through the above-mentioned measurement step S101, crystal orientation difference acquisition step S102, and first difference acquisition step S103, and the first difference in the first estimation step S104. With D1, it is possible to estimate with high accuracy whether or not the fracture cause of the metal material is fatigue fracture. Further, according to the above method, since it is sufficient to measure one measurement visual field range 6 including at least a part of the fracture surface 51 of the metal material, the measurement takes less time and the cause of destruction of the metal material can be estimated in a short period of time. It can be performed.

In some embodiments, as shown in FIG. 1, in the first estimation step S104 described above, when the first difference D1 is equal to or greater than the threshold value D0 (predetermined value) (when “YES” in S141), If the cause of fracture of the metal material is presumed to be fatigue fracture (S142) and the first difference D1 is less than the threshold value D0 (predetermined value) (when “NO” in S141), the cause of fracture of the metal material is It is presumed that it is not fatigue fracture (S143). The threshold value D0 is stored in the storage device 32, and a different value may be used for each metal material. According to the above method, it is possible to quantitatively estimate whether or not the fracture cause of the metal material is fatigue fracture by the first difference D1, so that the time required for estimation in the first estimation step S104 can be reduced.

FIG. 9 is a flow chart showing an example of a method for estimating the cause of destruction of the metal material according to another embodiment of the present invention, and is an enlarged flow chart showing a part of the flow chart shown in FIG. .. As shown in FIG. 9, in some embodiments, the method 10 for estimating the cause of destruction of the metal material described above is performed after the above-mentioned measurement step S101 and before the above-mentioned crystal orientation difference acquisition step S102. The slope adjustment step S123 for adjusting the slope of the linear regression line LR is further provided.

Specifically, as shown in FIG. 9, after the measurement step S101 and before the crystal orientation difference acquisition step S102, the fracture surface coordinate acquisition step S121 for acquiring the fracture surface coordinates and the alignment of the fracture surface 51 The linear regression line creation step S122 for creating the regression line LR and the inclination adjustment step S123 described above are provided. The fracture surface coordinate acquisition step S121 may be performed before the above-mentioned measurement step S101, or may be performed at the same time as the measurement step S101.

In the fracture surface coordinate acquisition step S121, the position coordinates of the fracture surface 51 within the range of one measurement visual field range 6 of the first sample 5 are acquired. Specifically, in the above-mentioned measurement step S101, the information processing apparatus 3 of the above-mentioned metal material destruction cause estimation system 1 has a reliability index (direction identification accuracy, CI value) not only at the crystal orientation but also at the measurement point P. Is supposed to be obtained. The resin component 54 of the first sample 5 has a CI value of zero or negative, unlike the metal component 53 having a positive CI value. Therefore, the information processing device 3 is combined with the metal component 53 by the arithmetic unit 34. The position coordinates on the measurement surface 52 of the fracture surface 51, which is the boundary with the resin component 54, are estimated, and the estimated position coordinates are stored in the storage device 32.

FIG. 10 is a diagram of a sample according to another embodiment of the present invention, in which a fracture surface of a sample formed from a fatigue-broken metal material in one measurement field of view and a linear regression line of the fracture surface are shown together. Is. In the linear regression line creation step S122, the linear regression line LR of the fracture surface 51 as shown in FIG. 10 is created from the fracture surface coordinates acquired in the fracture surface coordinate acquisition step S121 described above.

As shown in FIG. 10, when the position coordinates in the measurement coordinate system (X-axis, Y-axis) when one measurement field range 6 is measured are used as the position information of the plurality of measurement points P, for example, the first sample. The linear regression line LR obtained by linearly retreating the fracture surface 51 may have an inclination θ1 with respect to the X axis due to a misalignment at the time of installation of 5. When the inclination θ1 is equal to or greater than a predetermined angle θ0 (threshold value) which is 5 ° as an example, the error between the actual depth of the fracture surface and the value on the Y axis becomes large.

In the inclination adjustment step S123 described above, as shown in FIG. 9, when the inclination θ1 of the linear regression line LR of the fracture surface 51 is equal to or greater than the predetermined angle θ0 (when “YES” in S124), the linear regression line LR Is used as the first coordinate axis (X1 axis), and a straight line along the depth direction of the fracture surface 51 orthogonal to the linear regression straight line LR is used as the second coordinate axis (Y1 axis). Conversion step S125). In some other embodiments, coordinate conversion may be performed on a Cartesian coordinate system having an X1 axis and a Y1 axis regardless of the magnitude of the inclination θ1.

According to the above method, when the slope θ1 of the linear regression line LR of the fracture surface 51 is a predetermined angle θ0 or more, the measurement coordinate system (X-axis, Y-axis) when one measurement visual field range 6 is measured is used. And the error in the depth direction of the fracture surface 51 becomes large. Therefore, when the slope θ1 of the linear regression line LR described above is equal to or greater than the predetermined angle θ0, the coordinates are converted to the Cartesian coordinate system (X1 axis, Y1 axis) described above to obtain an error in the depth direction of the fracture surface. Can be reduced.

In some embodiments, the first crystal orientation difference OD1 described above is the crystal orientation difference of a plurality of measurement points P arranged along a direction orthogonal to the depth direction of the fracture surface 51 at a position near the fracture surface 55. The second crystal orientation difference OD2 described above includes statistical values, and the above-mentioned second crystal orientation difference OD2 is a statistical value of the crystal orientation difference of a plurality of measurement points P arranged along a direction orthogonal to the depth direction of the fracture surface 51 at the fracture surface far position 56. including.

The statistical value of the first crystal orientation difference OD1 is a statistical value of a plurality of measurement points P having the same depth from the fracture surface 51 and the fracture surface vicinity position 55 as located on the line indicated by the dotted line in FIG. Is. Further, the statistical value of the second crystal orientation difference OD2 is a plurality of measurement points having the same depth from the fracture surface distant position 56 and the fracture surface 51, such as those located on the line indicated by the alternate long and short dash line in FIG. It is a statistical value of P. Here, the statistical value includes an average value, a standard deviation, a percentile value, and the like. If the statistical values of the first crystal orientation difference OD1 and the second crystal orientation difference OD2 are the statistical values of a plurality of measurement points P on a straight line along the X-axis and the X1 axis described above, the uneven shape of the fracture surface 51 When is remarkable, the error becomes larger than the statistical value of a plurality of measurement points P having the same depth.

As shown in FIG. 6, the metal material may have a portion (extreme value portion 57) having a large crystal orientation difference locally at a position deep from the fracture surface 51. According to the above method, the first crystal orientation difference OD1 and the second crystal orientation difference OD2 are crystal orientations of a plurality of measurement points P arranged along a direction orthogonal to the depth direction of the fracture surface at a predetermined position. Since the statistical value of the difference is included, the influence of the above-mentioned locally large crystal orientation difference (extreme value portion 57) can be reduced. It can be estimated with accuracy.

As shown in FIG. 2, the estimation system 1 of the cause of destruction of the metal material according to some embodiments is a measuring device 11 capable of measuring one measurement viewing range 6 including at least a part of the fracture surface 51 of the metal material. The measurement device 11 capable of acquiring the crystal orientations at the plurality of measurement points P included in one measurement field range 6 and the crystal orientation difference at the plurality of measurement points P based on the crystal orientations acquired by the measurement device 11 are obtained. The above-mentioned analysis device 36 that can be acquired, the first crystal orientation difference OD1 of the above-mentioned fracture surface near position 55 acquired by the analysis device 36, and the second crystal orientation of the above-mentioned fracture surface distant position 56 acquired by the analysis device 36. The above-mentioned difference calculation device 37 (calculation device) capable of acquiring the first difference D1 which is the difference between the difference OD2 and the difference OD2 is provided.

As shown in FIG. 2, the measuring device 11 includes at least an EBSD detection device 2, an SEM control unit 12, a stage control unit 13, a camera control unit 14, and an image processing device 35 of the information processing device 3.

According to the above configuration, the estimation system 1 of the cause of destruction of the metal material includes the measurement device 11 capable of acquiring the above-mentioned crystal orientation, the analysis device 36 capable of acquiring the above-mentioned crystal orientation difference, and the above-mentioned first difference D1. Since the difference calculation device 37 capable of acquiring the above-mentioned first difference D1 can be acquired. Therefore, it is possible to estimate with high accuracy whether or not the fracture cause of the metal material is fatigue fracture from the acquired first difference D1. Further, according to the above configuration, since the measuring device 11 only needs to measure one measurement visual field range 6 including at least a part of the fracture surface 51 of the metal material, the time required for the measurement and the processing of the measurement result is short, and the metal The material destruction cause estimation system 1 can estimate the metal material destruction cause in a short period of time.

FIG. 11 is a flow chart showing an example of a method for estimating a stress level at the time of fatigue fracture of a metal material according to an embodiment of the present invention. As shown in FIG. 11, the stress level estimation method 70 at the time of fatigue failure of the metal material according to some embodiments includes the above-mentioned measurement step S101, the above-mentioned crystal orientation difference acquisition step S102, and the above-mentioned first. 1 This is the difference between the stress intensity factor parameter and the difference in crystal orientation at the depth position corresponding to the first difference D1 for the difference acquisition step S103 and the second sample 8 (sample) formed of the same material as the metal material. Based on the correlation acquisition step S204 for acquiring the correlation with the second difference D2 and the acquired correlation, the stress intensity factor parameter of the metal material is estimated from the first difference D1 and the stress intensity factor parameter of the metal material is estimated from the estimated stress intensity factor parameter. It includes a second estimation step S205 for estimating the stress level at the time of fatigue failure of the metal material. Here, as shown in FIG. 2, the stress level estimation system 7 at the time of fatigue fracture of the metal material for carrying out the method 70 of estimating the stress level at the time of fatigue fracture of the metal material is the above-mentioned metal material. It has the same configuration as the destruction cause estimation system 1.

Prior to the correlation acquisition step S204, the test piece 9 is prepared from the same material as the metal material to be estimated by the stress level estimation method 70 at the time of fatigue fracture of the metal material. FIG. 12 is a diagram for explaining a fatigue crack growth test, and is a diagram schematically showing a configuration of the fatigue crack growth test and a test piece used for the fatigue crack growth test. As shown in FIG. 12, the test piece 9 is called a CT test piece in which a plate-shaped notch 91 having a thickness in the vertical direction of the paper surface in FIG. 12 is formed, and is a pair of through holes 92. It is arranged at a test position in a material tester (not shown) by being connected to a test jig (not shown) via a pin (not shown) inserted into each. Then, a material tester repeatedly applies a load. Here, as shown in FIG. 12, the test piece width W when calculating the crack length a by the compliance method is from the center of the through hole 92 to the end on the side opposite to the side where the notch 91 is formed. Distance.

As shown in FIG. 12, the test piece 9 is provided with a back strain gauge 93 at an end opposite to the side on which the notch 91 is formed. The rear strain gauge 93 is connected to the measuring device 94, and transmits the measured strain value to the measuring device 94. Further, as shown in FIG. 12, a current source 95 is connected to two points at the upper end and the lower end of the test piece 9, and a direct current is applied. The value of the current is transmitted to the measuring instrument 94. Further, as shown in FIG. 12, a measuring instrument 94 is connected to two points sandwiching the notch 91 of the test piece 9, and the potential difference between the two points is measured. The measuring device 94 stores the strain measured by the back strain gauge 93, the above-mentioned current value, and the above-mentioned change behavior of the potential difference during the fatigue crack growth test. The stress intensity factor parameter of the second sample 8 is estimated from the data stored in the measuring instrument 94 described above.

As shown in FIG. 3, the second sample 8 has a metal component 83 cut out so as to include a fracture surface 81 and a fracture surface 81 from a test piece 9 that has been fatigued and fractured by a fatigue crack growth test. A resin component 84 made of, for example, an epoxy resin, which is hardened for protection, includes a resin component 84 provided on the opposite side of the fracture surface 81 from the metal component 83. In the second sample 8, the measurement surface 82, which is a surface perpendicular to the fracture surface 81, is polished by a polishing device or the like before measurement.

The second sample 8 is subjected to the same steps as the above-mentioned measurement step S101 and the above-mentioned crystal orientation difference acquisition step S102, similarly to the above-mentioned first sample 5, and a plurality of measurement points P included in one measurement field range 6. Information on the crystal orientation for each measurement point P, the position coordinates of the measurement point P, the crystal orientation difference for each measurement point P, and the like are stored in the storage device 32.

FIG. 13 is a diagram for explaining the distribution of the crystal orientation difference in one measurement field of view of a sample formed from the same material as the fatigue-fractured metal material in the sample according to the embodiment of the present invention. As shown in FIG. 13, a fracture surface near position 85 in which the depth from the fracture surface 81 is equal to or less than a predetermined value, and a fracture surface distant position 86 in which the depth from the fracture surface 81 is larger than the fracture surface near position 85. Is stipulated. The alternate long and short dash line in FIG. 13 connects the position near the fracture surface 85 and the depth from the fracture surface 81, and the alternate long and short dash line in FIG. It is a line connecting. Here, the depth near the fracture surface 85 is 80 μm or less from the fracture surface 81. The depth near the fracture surface 85 is preferably 40 μm or less from the fracture surface 81, and more preferably 20 μm or less from the fracture surface 81. Further, the depth of the fracture surface far position 86 from the fracture surface 81 is 400 μm or less. The depth from the fracture surface 81 is preferably 200 μm or less, and more preferably 100 μm or less from the fracture surface 81.

Then, the second difference D2, which is the difference between the third crystal orientation difference OD3, which is the crystal orientation difference at the position 85 near the fracture surface, and the fourth crystal orientation difference OD4, which is the crystal orientation difference at the position 86 far from the fracture surface, is calculated. do. Here, the third crystal orientation difference OD3 and the fourth crystal orientation difference OD4 may be statistical values like the first crystal orientation difference OD1 and the second crystal orientation difference OD2.

FIG. 14 is a graph for explaining the correlation between the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the sample and the stress intensity factor for the sample. FIG. 15 is a graph for explaining the correlation between the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the sample and the stress intensity factor range for the sample. FIG. 16 is a graph for explaining the correlation between the difference in crystal orientation difference between two different depth positions on the surface layer of the fracture surface of the sample and the effective stress intensity factor range for the sample.

As shown in FIGS. 14 to 16, the stress intensity factor parameters including the stress intensity factor K, the stress intensity factor range ΔK, and the effective stress intensity factor range ΔKeff for the second sample 8 formed from the same material as the metal material. , There is a correlation between the second difference D2 and. The storage device 32 may store numerical data, graphs, formulas, tables, and the like representing the above-mentioned correlation with respect to the second sample 8 in advance.

In the correlation acquisition step S204 described above, the stress intensity factor parameter for the second sample 8 and the second difference D2, which is the difference in the crystal orientation difference at the depth position corresponding to the first difference D1, are obtained from the storage device 32. Get the correlation of.

As shown in FIG. 11, the second estimation step S205 described above is the same as the step S206 for estimating the stress intensity factor parameter of the metal material from the first difference D1 based on the correlation acquired in the correlation acquisition step S204. Includes step S207, which estimates the stress level at the time of fatigue failure of the metal material from the stress intensity factor parameter of the metal material acquired in step S206 described above.

As described above, the method 70 for estimating the stress level at the time of fatigue failure of the metal material according to some embodiments is the above-mentioned measurement step S101 and the above-mentioned crystal orientation difference acquisition step S102, as shown in FIG. The first difference acquisition step S103 described above, the correlation acquisition step S204 described above, and the second estimation step S205 described above are provided.

As described above, as a result of diligent studies, the present inventors have found that the stress intensity factor parameter of a sample formed from the same material as the metal material and the crystals at two different depth positions on the surface layer of the fracture surface of the sample. The stress intensity factor of the metal material is due to the correlation between the difference in orientation and the difference in crystal orientation at two different depth positions on the surface of the fracture surface of the metal material based on the correlation. We found that the parameters can be estimated.

According to the above method, the measurement step S101 and the crystal orientation described above are based on the correlation between the second difference D2, which is the difference in the crystal orientation difference at the depth position corresponding to the first difference D1, and the stress intensity factor parameter. The stress intensity factor parameter of the metal material can be estimated with high accuracy by the first difference D1 acquired through the difference acquisition step S102 and the first difference acquisition step S103. Then, the stress level at the time of fatigue fracture of the metal material can be estimated from the stress intensity factor parameter of the metal material. Further, according to the above method, it is sufficient to acquire the above-mentioned correlation and measure one measurement visual field range 6 including at least a part of the fracture surface 51 of the metal material, so that the measurement and the processing of the measurement result are performed. It takes less time and can estimate the stress level at the time of fatigue fracture of a metal material in a short period of time.

In some embodiments, as described above, the stress intensity factor parameter is obtained by performing a fatigue crack growth test on the second sample 8 (sample) and the second difference D2 is the fatigue crack. The crystal orientations at a plurality of measurement points P of the second sample 8 in which the growth test was carried out are acquired, and the crystal orientation differences at the plurality of measurement points P are acquired based on the acquired crystal orientations, and in the fatigue crack growth test. The third crystal orientation difference OD3, which is the crystal orientation difference at the fracture surface vicinity position 85 where the depth from the generated fracture surface 81 is less than a predetermined value, and the depth from the fracture surface 81 are larger than the fracture surface vicinity position 85. This is the difference from the fourth crystal orientation difference OD4, which is the crystal orientation difference at the fracture surface distant position 86 and the depth from the fracture surface 81 is 100 μm or less.

According to the above method, since the second difference D2 is obtained for the second sample 8 (sample) in which the fatigue crack growth test is carried out in order to obtain the stress intensity factor parameter, the stress intensity factor parameter and the second sample are obtained. The accuracy of the correlation with the difference D2 can be improved. Further, since the third crystal orientation difference OD3 and the fourth crystal orientation difference OD4 of the second sample 8 correspond to the first crystal orientation difference OD1 and the second crystal orientation difference OD2 of the metal material, the second sample 8 The second difference D2 can be accurately made to correspond to the first difference D1 of the metal material. Further, according to the above method, the depth from the fracture surface 81 is larger than the fracture surface vicinity position 85 and the fracture surface vicinity position 85, and the depth from the fracture surface 81 is 100 μm or less. Since the second difference D2 is acquired based on the crystal orientation difference at the position 86, the size of one measurement viewing range 6 including the fracture surface near position 85 and the fracture surface distant position 86 can be reduced. Then, by reducing the one measurement field of view range 6, the time required for measurement and processing of the measurement result can be reduced.

In some embodiments, the stress intensity factor parameters described above include at least one of a stress intensity factor K, a stress intensity factor range ΔK, and an effective stress intensity factor range ΔKeff. According to the above method, the stress intensity factor K, the stress intensity factor range ΔK, or the effective stress intensity factor range ΔKeff can be estimated from the first difference D1, so that the stress intensity factor K or the like can be used to estimate the stress intensity factor K or the like. The stress level at the time of fatigue failure can be estimated.

As shown in FIG. 2, the stress level estimation system 7 at the time of fatigue failure of the metal material according to some embodiments can measure one measurement field range 6 including at least a part of the fracture surface 51 of the metal material. The above-mentioned measuring device 11 capable of acquiring crystal orientations at a plurality of measuring points P included in one measurement field range 6, and a plurality of measuring points based on the crystal orientations acquired by the measuring device 11. The above-mentioned analysis device 36 capable of acquiring the crystal orientation difference in P, the first crystal orientation difference OD1 of the above-mentioned fracture surface vicinity position 55 acquired by the analysis device 36, and the above-mentioned fracture surface distant position acquired by the analysis device 36. The above-mentioned difference calculation device 37 (calculation device) capable of acquiring the first difference D1 which is the difference between the second crystal orientation difference OD2 of 56 and the second sample 8 (sample) formed of the same material as the metal material. The above-mentioned storage device 32 and the storage device 32 store the correlation between the stress expansion coefficient parameter and the second difference D2, which is the difference in crystal orientation difference at the depth position corresponding to the first difference D1. It is provided with an estimation device 38 that estimates the stress expansion coefficient parameter of the metal material from the first difference D1 based on the correlation. As shown in FIG. 2, the arithmetic unit 34 includes an estimation device 38.

According to the above configuration, the stress level estimation system 7 at the time of fatigue failure of the metal material is the measuring device 11 capable of acquiring the crystal orientation of the metal material described above, and the analysis capable of acquiring the crystal orientation difference of the metal material described above. Since the device 36 and the difference calculation device 37 capable of acquiring the above-mentioned first difference D1 are provided, the first difference D1 of the above-mentioned metal material can be acquired. Further, the stress level estimation system 7 at the time of fatigue failure of the metal material has a storage device 32 that stores the above-mentioned correlation and a stress of the metal material from the first difference D1 based on the correlation stored in the storage device 32. Since the estimation device 38 for estimating the expansion coefficient parameter is further provided, the stress intensity factor parameter of the metal material can be estimated with high accuracy from the value of the first difference D1 described above. Then, the stress level at the time of fatigue fracture of the metal material can be estimated from the stress intensity factor parameter of the metal material. Further, according to the above configuration, the above-mentioned correlation may be stored in the storage device 32, and the measuring device 11 may measure one measurement field range 6 including at least a part of the fracture surface 51 of the metal material. Therefore, the time required for measurement and processing of the measurement results is short, and the stress level estimation system at the time of fatigue failure of the metal material can estimate the stress level at the time of fatigue failure of the metal material in a short period of time.

In some of the above-described embodiments, the image processing device 35, the analysis device 36, the difference calculation device 37, and the estimation device 38 are included in the calculation device 34 of the information processing device 3. For example, a microcomputer provided separately from the arithmetic unit 34 and the information processing device 3 may be used.

Further, in some of the above-described embodiments, the EBSD detection device 2 (crystal orientation detection device) measures the crystal orientations of a plurality of measurement points P by the electron backscatter diffraction image method, but X-rays are used. The crystal orientation may be acquired by a method other than the electron backscatter diffraction image method such as a diffraction method.

The present invention is not limited to the above-described embodiment, and includes a modified form of the above-described embodiment and a combination of these embodiments as appropriate.

1 System for estimating the cause of destruction of metal materials 10 Method for estimating the cause of destruction of metal materials 12 SEM control unit 13 Stage control unit 14 Camera control unit 2 EBSD detection device 21 Screen 22 Camera 3 Information processing device 31 Input / output device 32 Storage device 33 Display 34 Computing device 35 Image processing device 36 Analytical device 37 Difference computing device 38 Estimating device 4 Scanning electron microscope 41 Sample stage 42 Sample room 43 Electron gun 5 First sample 51 Fracture surface 52 Measuring surface 53 Metal component 54 Resin component 55 Fracture surface near position 56 Fracture surface distant position 57 Extreme value part 6 1 Measurement field range 7 Stress level estimation system at the time of fatigue failure of metal material 70 Method of estimating stress level at the time of fatigue failure of metal material 8 Second sample 81 Fracture surface 82 Measurement surface 83 Metal component 84 Resin component 85 Fracture surface near position 86 Fracture surface distant position 9 Specimen 11 Measuring device D0 Crystal orientation difference difference threshold D1 First difference D2 Second difference LR Linear regression line OD1 1st crystal orientation difference OD2 2nd crystal orientation difference OD3 3rd crystal orientation difference OD4 4th crystal orientation difference

Claims (9)

It is a method of estimating the cause of destruction of metal materials.
A step of measuring one measurement field of view including at least a part of the fracture surface of the metal material and acquiring crystal orientations at a plurality of measurement points included in the one measurement field of view.
A crystal orientation difference acquisition step for acquiring a crystal orientation difference at a plurality of measurement points based on the acquired crystal orientation, and a crystal orientation difference acquisition step.
The first crystal orientation difference, which is the crystal orientation difference at the position near the fracture surface where the depth from the fracture surface is less than a predetermined value, and the position far from the fracture surface, where the depth from the fracture surface is larger than the position near the fracture surface. The first difference acquisition step for acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference in
A method for estimating the cause of fracture of a metal material, comprising: a first estimation step of estimating whether or not the cause of fracture of the metal material is fatigue fracture based on the first difference. In the first estimation step, when the first difference is equal to or more than a predetermined value, it is estimated that the cause of fracture of the metal material is fatigue fracture, and when the first difference is less than the predetermined value, the metal material is said to be fractured. The method for estimating the cause of fracture of a metal material according to claim 1, wherein the cause of fracture is not fatigue fracture. The method for estimating the cause of destruction of the metal material is
If the inclination of the linear regression line of the fracture surface is equal to or greater than a predetermined angle after the step of acquiring the crystal orientation and before the step of acquiring the crystal orientation difference, the linear regression line is set as the first coordinate axis. The metal according to claim 1 or 2, further comprising a tilt adjustment step of performing coordinate conversion to an orthogonal coordinate system having a straight line along the depth direction of the fracture surface orthogonal to the linear regression straight line as a second coordinate axis. How to estimate the cause of material destruction. The first crystal orientation difference includes statistical values of the crystal orientation difference of the plurality of measurement points arranged along a direction orthogonal to the depth direction of the fracture surface at a position near the fracture surface.
The second crystal orientation difference includes the statistical value of the crystal orientation difference of the plurality of measurement points arranged along the direction orthogonal to the depth direction of the fracture surface at the position far from the fracture surface. The method for estimating the cause of destruction of a metallic material according to any one of 3. It is a method of estimating the stress level at the time of fatigue failure of metallic materials.
A step of measuring one measurement field of view including at least a part of the fracture surface of the metal material and acquiring crystal orientations at a plurality of measurement points included in the one measurement field of view.
A crystal orientation difference acquisition step for acquiring a crystal orientation difference at a plurality of measurement points based on the acquired crystal orientation, and a crystal orientation difference acquisition step.
The first crystal orientation difference, which is the crystal orientation difference at the position near the fracture surface where the depth from the fracture surface is less than a predetermined value, and the position far from the fracture surface, where the depth from the fracture surface is larger than the position near the fracture surface. The first difference acquisition step for acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference in
A step of acquiring a correlation between a stress intensity factor parameter and a second difference, which is a difference in crystal orientation difference at a depth position corresponding to the first difference, for a sample formed from the same material as the metal material. ,
Based on the acquired correlation, the stress intensity factor parameter of the metal material is estimated from the first difference, and the stress level at the time of fatigue failure of the metal material is estimated from the estimated stress intensity factor parameter. An estimation step and a method of estimating the stress level at the time of fatigue failure of a metallic material. The stress intensity factor parameters are obtained by performing a fatigue crack growth test on the sample.
For the second difference, the crystal orientations at a plurality of measurement points of the sample in which the fatigue crack growth test is performed are acquired, and the crystal orientation differences at the plurality of measurement points are acquired based on the acquired crystal orientations. At the same time, the third crystal orientation difference, which is the crystal orientation difference at the position near the fracture surface where the depth from the fracture surface generated in the fatigue crack growth test is equal to or less than a predetermined value, and the fracture at the position near the fracture surface. Claimed to be the difference from the fourth crystal orientation difference, which is the crystal orientation difference at the fracture surface distant position where the depth from the plane is large and the depth from the fracture surface is 100 μm or less. Item 5. The method for estimating the stress level at the time of fatigue failure of the metal material according to Item 5. The method for estimating a stress level at the time of fatigue failure of a metal material according to claim 5 or 6, wherein the stress intensity factor parameter includes at least one of a stress intensity factor, a stress intensity factor range, and an effective stress intensity factor range. It is a system for estimating the cause of destruction of metallic materials.
A measuring device capable of measuring one measurement visual field range including at least a part of a fracture surface of the metal material, and a measuring device capable of acquiring crystal orientations at a plurality of measurement points included in the one measurement visual field range.
An analysis device capable of acquiring crystal orientation differences at a plurality of measurement points based on the crystal orientation acquired by the measuring device, and an analysis device capable of acquiring crystal orientation differences at the plurality of measurement points.
The first crystal orientation difference, which is the crystal orientation difference at a position near the fracture surface where the depth from the fracture surface acquired by the analyzer is equal to or less than a predetermined value, and the position near the fracture surface acquired by the analyzer. Estimating the cause of destruction of a metal material provided with an arithmetic device capable of acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference at a position far from the fracture surface having a large depth from the fracture surface. system. A system for estimating stress levels during fatigue failure of metallic materials.
A measuring device capable of measuring one measurement visual field range including at least a part of a fracture surface of the metal material, and a measuring device capable of acquiring crystal orientations at a plurality of measurement points included in the one measurement visual field range.
An analysis device capable of acquiring crystal orientation differences at a plurality of measurement points based on the crystal orientation acquired by the measuring device, and an analysis device capable of acquiring crystal orientation differences at the plurality of measurement points.
The first crystal orientation difference, which is the crystal orientation difference at a position near the fracture surface where the depth from the fracture surface acquired by the analyzer is equal to or less than a predetermined value, and the position near the fracture surface acquired by the analyzer. An arithmetic device capable of acquiring the first difference, which is the difference between the second crystal orientation difference, which is the crystal orientation difference at a position far from the fracture surface having a large depth from the fracture surface, and
A storage device that stores the correlation between the stress intensity factor parameter and the second difference, which is the difference in crystal orientation at the depth position corresponding to the first difference, for a sample formed from the same material as the metal material. When,
A system for estimating a stress level at the time of fatigue failure of a metal material, comprising an estimation device for estimating the stress intensity factor parameter of the metal material from the first difference based on the correlation stored in the storage device.

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