JP2735159B2 - Method for predicting breakage of brittle material structural members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for predicting damage to a structural member to which a load is applied, and more particularly to a method for predicting damage to a structural member to which a load is applied, which is made of a brittle material such as ceramics or glass. It is about.

[0002]

2. Description of the Related Art Conventionally, materials such as ceramics and glass have excellent heat resistance and corrosion resistance. Therefore, structural members of a system such as a structure or a device exposed to a high temperature environment or a corrosive atmosphere. However, there are some problems in applying these materials to structural members.

[0003] That is, since materials such as ceramics and glass are brittle materials, structural members made of these materials are elastically deformed until the start of destruction when an excessive load is applied, and are instantaneously destructed. Cause catastrophic destruction. Such destruction is difficult to predict, and once a destruction occurs, the destructed member breaks down into a plurality of fragments and scatters, causing serious damage to other surrounding members. As a result, fatal damage is likely to be caused to the entire system such as a structure or a device in which the damaged member is incorporated. Therefore, in a system such as a structure or an apparatus using a structural member made of a material such as ceramics or glass, its reliability is extremely low.

Therefore, when an excessive load is applied,
Methods for predicting breakage of structural members made of materials such as ceramics and glass have been devised and implemented to compensate for the low reliability of systems such as structures and devices having such structural members. For example, a method has been performed in which a strain gauge is bonded to an organic adhesive with a structural member and the stress generated in the structural member is measured to predict the destruction of the structural member. However, application of this method is limited to a temperature range of about 200 ° C. or lower where an organic adhesive can be used, and an atmosphere in which the properties of such an adhesive are not affected. This method cannot be applied in an environment where the organic adhesive cannot withstand, such as an environment in a corrosive atmosphere.

Further, a coating layer having conductivity or piezoelectric characteristics is formed directly on the surface of a structural member, and based on the output information, measurement of stress generated in the structural member and search for cracks are performed. Accordingly, a technique for predicting breakage of such members has been developed. However, even such a damage prediction method has the following problems. That is, since a material different from the material forming the structural member is directly adhered to the surface of the structural member, the thermal expansion coefficient of the structural member is generally different from that of the coating layer. When is subjected to a temperature change, thermal stress occurs, which can cause cracks in the coating layer. Furthermore, when the coating layer cannot withstand the environment such as high temperature or corrosive atmosphere,
Scratches can occur on the surface of the coating layer. In the case of a structural member made of a brittle material, the presence of minute surface flaws greatly reduces the strength, and when cracks or surface flaws occur in the coating layer,
The strength characteristic of such a structural member itself is greatly deteriorated.

As described above, in a severe environment such as a high temperature or a corrosive atmosphere, a method for predicting breakage of a brittle material structural member which does not deteriorate the strength characteristics of the structural member itself has been required despite its high necessity. At present, there is no such method, and it is desired to develop a new method for predicting breakage of a brittle material structural member.

[0007]

SUMMARY OF THE INVENTION Here, the present invention has been made in view of such circumstances, and the object of the present invention is to solve the problem under severe environments such as high temperature and corrosive atmosphere. An object of the present invention is to provide a method for predicting breakage of a brittle material structural member that can be used and hardly deteriorates the strength characteristics of the structural member itself.

[0008]

Means for Solving the Problems And the present inventors,
As a result of intensive studies to solve such a problem, in a brittle material structural member, a crack that leads to catastrophic failure of the member (hereinafter referred to as a main crack)
Is capable of being stopped by the occurrence of a separation crack in a plane substantially perpendicular to the direction of the propagation, and
Weak bonding interface strength due to diffusion bonding (below,
It has been found that the formation of a bonding interface having bonding strength) can facilitate the occurrence of such a peeling crack during the growth of the main crack.

On the other hand, in recent studies on diffusion bonding methods between objects made of the same kind of brittle material, the relationship between various conditions during diffusion bonding and the bonding strength is distributed at the bonding interface which controls the bonding strength. Analysis of the pore size and the distribution density of the pores and the like revealed a considerable amount of them. By adjusting these conditions, it became possible to control the bonding strength in diffusion bonding.

In recent years, studies on the evaluation of the characteristics of ceramics have shown that artificial surface flaws can be formed on ceramics by means such as the indentation of a Vickers indenter to produce dense brittle materials such as ceramics and glass. It has been found that the strength of the component can be reduced quite accurately to a predetermined value.

From these findings, a thin plate member made of the same material as the structural member is diffusion-bonded to the surface of the brittle material structural member with a lower bonding strength than the strength of the structural member. The present inventors have found that the above-mentioned problems can be solved by forming the thin plate member and setting the strength of the thin plate member to a predetermined value lower than that of the structural member, and have completed the present invention.

That is, the present invention provides a thin plate member made of the same brittle material as the structural member with a bonding strength lower than the strength of the structural member on the surface of the structural member made of a brittle material such as ceramics and glass. In addition to the diffusion bonding, the surface of the thin plate member is given a surface scratch, and when a load is applied to the structural member, only the thin plate member is damaged with a smaller load than the structural member is damaged. Accordingly, a gist of the present invention is a method for predicting breakage of a brittle material structural member, wherein the method predicts breakage of the structural member.

According to the method for predicting breakage of a brittle material-made structural member according to the present invention, a thin plate member made of the same brittle material as the structural member and having been subjected to surface flaws is provided on the surface of the brittle material-made structural member. When the load applied to the structural member reaches a predetermined value determined by such surface flaws, the thin plate member causes the surface flaws because the diffusion bonding is performed at a bonding strength lower than the strength of the structural member. In addition to being damaged by the in-plane direction and the thickness direction of the main crack as the starting point, the growth of the main crack generated in the thin plate member in the thickness direction is stopped by the peeling crack generated at the joint surface, Therefore, by detecting such breakage of the thin plate member by a known detection method, the structural member made of brittle material itself is not damaged, and the load applied to the structural member is It found close to the limit value to withstand the, it become possible to predict the breakage of the brittle material-made structural member Te following.

[0014] In this way, the possibility of damage to the member due to the application of an excessive load can be predicted. As a result, the catastrophic damage of such a structural member can be reduced by reducing the applied load. As a result, it is possible to effectively prevent catastrophic damage to the entire system such as a structure or a device in which the device is incorporated.

Further, according to the method for predicting breakage of a brittle material structural member according to the present invention, the thin plate member is of the same quality as the structural member, and is formed by diffusion bonding without using any dissimilar material. Because it is joined to the member,
As long as the brittle material forming the structural member can withstand the environment, no matter how severe the environment, it can stably predict the damage of the structural member and generate thermal stress due to temperature change. Therefore, even when the structural member receives a large temperature change, it is possible to predict the damage.

Further, in the present invention, a detecting means having a stress measuring function or a crack detecting function can be further provided on the surface of the thin plate member. As a result, even when the detecting means cannot withstand a severe environment such as a high temperature or a corrosive atmosphere, the strength characteristics of the brittle material structural member due to minute surface flaws that may occur in the detecting means are reduced. Such a mechanism similar to that for stopping a main crack by a peeling crack can be effectively prevented.

In the above, when a detecting means having a crack detecting function is provided, the detecting means can be used to detect the progress of a main crack in a thin plate member, the occurrence of a peeling crack, and the breakage of the thin plate member. There is an advantage that the detection can be reliably performed without providing a complicated detection means outside the member, and the failure of the brittle material structural member can be more reliably predicted. In addition, when the detecting means having the stress measurement function is provided, the thin plate member to be joined to the structural member has a sufficiently small thickness as compared with the structural member. Such a sensing means provides an accurate measurement of the stresses occurring in the structural member until it is approximately the same as that of the structural member directly below the surface and the load applied thereby reaches the breaking load of the thin plate member. There are advantages that can be made.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to clarify the present invention more specifically, a specific configuration of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows an example in which the method for predicting breakage of a brittle material structural member according to the present invention is mainly applied to a structural member subjected to bending and shearing. Specifically, the thin plate member 12 is diffusion-bonded to the surface of the structural member 10 having a rectangular cross-sectional shape where a tensile stress is generated when a load is applied, and the thin plate member 1
2, a surface flaw 14 is formed to reduce the strength to a predetermined value.

The structural member 10 to which the damage prediction method according to the present invention can be applied is made of a known brittle material that can be creep-deformed at high temperature, in other words, can be diffusion-bonded, such as ceramics such as silicon nitride and glass. The cross-sectional shape is not particularly limited to a rectangle, and may be a polygon, as well as a shape having a curved outer periphery such as a circle or an ellipse. Even if there is, it does not matter at all.

On the other hand, the thin plate member 12 to be joined to such a structural member 10 is made of the same material as that of the structural member 10 and has a predetermined plate thickness, and is in a range where the thin plate member 12 of the structural member 10 is joined. It is molded by a known method so as to have a corresponding shape. In addition, such a thin plate member 12
The plate thickness is determined appropriately depending on the type of material, workability of diffusion bonding, formability of surface flaws, etc.
As far as possible in these respects, the structural member 1 to be joined
It is desirable that the thickness be sufficiently smaller than the thickness of the area where the thin plate member 12 is bonded, ie, 0, and the thickness satisfies at least the following conditions.

That is, such a plate thickness is set to such a thickness that the stress distribution of the structural member 10 does not change much due to the joining of the thin plate member 12. Specifically, the thin plate member 1
The stress concentration that may occur at the end of the thin plate member 12 and the portion of the structural member 10 in the vicinity thereof due to the bonding to the second structural member 10 is set to such an extent that the strength of the structural member 10 is not affected. After the breakage and peeling of the sheet member 12, the stress just below the range where the thin plate member 12 is joined is increased by the load of the load held by the thin plate member 12 so that the strength of the structural member 10 is not affected. Is done. The dimensions such as the width and length of the thin plate member 12 are appropriately determined according to the plate thickness, the dimensions of the structural member 10, the number of surface flaws to be formed, and the like. Such a thin plate member 1
2, the strength of the structural member 10 after the joining is prevented as much as possible, and a detecting means having a stress measuring function such as a coating layer made of a piezoelectric material described later is used as a thin plate member. In the case where the stress generated in the thin plate member 12 is formed on the surface of the thin plate 12 and the stress generated in the thin plate member 12 is measured, the stress generated in the thin plate member 12 is substantially the same as the stress of the structural member 10 immediately below the joined area. Thus, accurate estimation of the stress of the structural member 10 becomes possible.

The bonding surface of the thin plate member 12 having such a predetermined shape and the bonding surface of the structural member 10 are used for controlling the bonding strength between the structural member 10 and the thin plate member 12 as described later. The surface roughness is adjusted to a predetermined value by a known method such as grinding.

The thin plate member 12 obtained in this manner has a surface portion which is expected to be a starting point of breakage of the structural member 10 due to the load applied to the structural member 10, in other words, generally the maximum. Diffusion bonding is performed on the surface portion where tensile stress is generated. That is, the thin plate member 12 is superimposed on a predetermined position of the structural member 10, and the thin plate member 12 and the structural member 10 are heated at a predetermined temperature by a known heating device such as an electric furnace in an atmosphere of an inert gas such as nitrogen. Then, the thin plate member 12 and the structural member 10 are diffusion-bonded by applying a predetermined pressure from both sides in the overlapping direction with a known pressing device. More specifically, the thin plate member 12
And the structural member 10 undergo creep deformation by pressurization under heating, and mass transfer occurs by diffusion in the vicinity of the surface on which the thin plate member 12 is superimposed. Then, the mass transfer from the thin plate member 12 to the structural member 10 across the surface and the mass transfer in the opposite direction closes such a surface, and a joint having a predetermined joint strength is completed. is there.

Here, the thin plate member 12 and the structural member 10 in the method for predicting breakage of a brittle material structural member according to the present invention.
The joining strength between the members is made of the same material as that of the structural member 10 and the thin plate member 12 and is equal to the surface roughness of the joining surface of the thin plate member 12 and the structural member 10 except for a case where a lower limit condition described later is mentioned. A bending test is performed on a joint obtained by butt-joining two objects having a joint surface having a surface roughness by diffusion bonding under the same conditions as diffusion bonding between the thin plate member 12 and the structural member 10. It refers to the strength obtained, the so-called bending strength. Such a bonding strength is made sufficiently smaller than the bending strength of the structural member 10,
Desirably, the bending strength is not more than 20% of the bending strength of the structural member 10 empirically obtained from an experiment conducted by the present inventors. This is because the joining strength is 2 times the bending strength of the structural member 10.
If it exceeds 0%, at the time of breakage of the thin plate member 12, peeling cracks at the joint surface are less likely to occur, whereby the main crack generated in the thin plate member 12 in the thickness direction does not stop at the joint surface. This is because there is a possibility that the structure member 10 may go inside the structure member 10 and be destroyed.

The bonding strength is specifically obtained as follows, for example. There, first, two cubic members made of the same material as the structural member 10 and the thin plate member 12 and having a joint surface with a surface roughness equal to the surface roughness of the joint surface of the thin plate member 12 and the structural member 10 respectively. The object is butt-joined by diffusion bonding under the same conditions as the diffusion bonding between the thin plate member 12 and the structural member 10 to form a rectangular parallelepiped bonded article. Then
From the rectangular parallelepiped joint obtained in this manner, a rod-shaped test piece having a rectangular cross-sectional shape was cut out such that the joint portion was located substantially at the center in the longitudinal direction, and then, for such a test piece. A four-point bending test or the like in accordance with JISR1601, etc. is performed to determine the bending strength.

On the other hand, the bonding strength between the thin plate member 12 and the structural member 10 indicates the shear strength of the bonding surface between them near the lower limit thereof. It is necessary to have a shear strength that does not cause peeling of the thin plate member 12 before breakage of the thin plate member 12. However, if the joining strength is smaller than such shear strength, before the load applied to the structural member 10 reaches the breaking load of the thin plate member 12 determined by surface scratches described below, the thin plate member 12 This is because, at the joint surface, it is separated from the structural member 10.

Further, the bonding strength can be controlled by increasing or decreasing the true bonding area between the thin plate member 12 and the structural member 10, thereby increasing or decreasing the defect size and the number of defects on the bonding surface. That is, by increasing the true bonding area, the defect size is reduced and the number of defects is reduced, and the bonding strength can be increased, while reducing the defect size increases the defect size and the number of defects. The joining strength can be reduced. In particular,
Such a true bonding area, and thus the bonding strength, can be generally increased by increasing the temperature, increasing the bonding surface pressure, increasing the pressing time at a high temperature, etc. during diffusion bonding, Thin plate member 12 and / or structural member 1
0 can be increased by adjusting the processing conditions of the bonding surfaces to reduce the surface roughness of such bonding surfaces, while reducing them by changing the bonding conditions in the opposite direction. Can be done.

Then, a surface flaw for reducing the strength of the thin plate member 12 is spread at a predetermined position on the surface of the thin plate member 12 diffused and bonded to the structural member 10 so as to have a predetermined bonding strength. The condition at the time of forming the surface flaw and the reduction in the strength of the thin plate member 12 due to the formation are formed by a known method having a predetermined relationship so that the strength of the thin plate member 12 becomes a predetermined value. For example, a Vickers indenter is pressed into the thin plate member 12 with a predetermined load, whereby a substantially square pyramid-shaped indentation is formed on the surface of the thin plate member 12, and, from such an indentation, outward by a size corresponding to the indentation load. Extended cracks (surface flaws) can be formed. FIG. 2 shows the general relationship between the indentation load of the Vickers indenter and the bending strength of the brittle material member into which the Vickers indenter has been pushed. By pushing into the thin plate member 12, the strength of the thin plate member 12 can be set to a value corresponding to the pushing load.
It can be seen that the intensity of No. 2 can be controlled.

The ratio of the strength of the thin plate member 12 having such a surface flaw to the fracture strength of the material used for the member design in consideration of the variation in strength that appears universally in brittle materials is 60%. % Is preferably in the range of about 80%. Because, if such a ratio is greater than 80%, the possibility that the structural member 10 itself will break before the sheet member 12 breaks due to defects such as micro-cracks that may be present in the structural member 10 is very large. Conversely, if it is less than 60%, only a load much lower than the load
In addition, no load can be applied, and the ability of the structural member 10 cannot be fully utilized.

The surface flaw formed on the surface of the thin plate member 12 is desirably formed at a portion sufficiently distant from the end of the thin plate member 12. The load is
Since the shear force is transmitted from the structural member 10 to the thin plate member 12 mainly by shearing, the load from the structural member 10 is not sufficiently transmitted near the end of the thin plate member 12, and the stress of the thin plate member 12 is reduced. This is because it is significantly different from that of 10.

Further, the number of such surface flaws is not particularly limited, but it is desirable to provide a plurality of them. However, there is an error in the strength reduction effect of the brittle material member due to the formation of surface flaws, and there is some variation in the strength of the thin plate member with the surface flaws. By forming the surface flaw, the strength of the thin plate member 12 becomes the smallest value among the strengths determined by the respective surface flaws. That is, by forming a plurality of surface flaws, the strength of the thin plate member 12 is on the safe side with respect to the structural member 10 and, consequently, a system such as a structure or a device into which the structural member 10 is incorporated. However, in the case where a plurality of surface flaws are provided, it is necessary to provide a sufficient space so that the influence of the surface flaws on the strength of the thin plate member does not interfere with each other.

In the method for predicting breakage of a brittle material structural member according to the present invention, when measuring the stress occurring in the thin plate member 12 or detecting a crack, the surface of the thin plate member 12 has a stress measurement function or A detecting means having a crack detecting function can be provided. And such a detecting means is formed after the formation of the surface flaw,
This is preferable because the formed detecting means is hardly affected by distortion due to the surface flaw. However, even when the detecting means is formed before the formation of the surface flaw, the detecting means is formed after the detecting means and the surface flaw are sequentially formed. There is no problem if the function of the detecting means is reconfirmed.

As a detecting means for measuring such stress, a coating layer formed of a piezoelectric or pyroelectric material such as PZT or AlN, formed by a known method such as sputtering, or a sputtering method may be used. There is a formed strain gauge, etc., the use environment of the structural member, that is, temperature,
It is appropriately selected according to the atmosphere and the like. Then, the stress generated in the thin plate member 12 can be measured from a change in a voltage generated due to a strain in the coating layer made of a piezoelectric or pyroelectric material, a change in an electric resistance value of a strain gauge, and the like. Thus, the stress occurring in the structural member 10 can be estimated. On the other hand, as a detecting means for detecting a crack generated in the thin plate member 12, there is a crack gauge, for example, it can be formed by combining sputtering of conductive ceramics and processing of a wiring pattern by excimer laser, By using the fact that a part of the wiring made of conductive ceramics is cut by the propagation of the crack and the electrical resistance of the system changes, the main crack in the thin plate member 12 is detected and the like is detected. It becomes possible to detect.

Thus, a predetermined surface flaw is formed in this way, and in some cases, the thin plate member 12 provided with a detecting means having a stress measuring function or a crack detecting function.
Is a structural member 10 diffusion bonded with a predetermined bonding strength,
After the systems such as structures and devices are completed by incorporating them into a predetermined portion of the systems such as structures and devices by a known method, the systems such as structures and devices are brought under a predetermined environment. A predetermined load is applied to such a structural member 10 accordingly.

Then, the thin plate member 12 bonded to the structural member 10 is externally monitored by a monitoring system or the like including a camera, a sound collecting device, or the like which can withstand the use environment, or a crack is removed. In the case where a detecting means having a detecting function is provided on the thin plate member 12, such a detecting means can be used for such a structural member 1.
It is possible to predict the damage of 0. That is, the thin plate member 1
When a load exceeding a predetermined load determined by the surface scratch 14 formed on the structural member 2 is applied to the structural member 10, the thin plate member 12 is broken starting from the surface scratch 14, and such a thin plate member 12 is detected by a monitoring system or a detecting means having a crack detecting function, and the like, as a result, it is found that the load applied to the structural member 10 is close to the limit value that the structural member 10 can withstand. It is possible to predict the breakage of the structural member. Further, in the case where the detecting means having the stress measuring function is provided on the thin plate member 12, the thin plate member 12 is provided by a predetermined method according to the type of the detecting unit until the thin plate member 12 is broken.
Can be measured.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, representative embodiments of the present invention will be described in detail with reference to the drawings. It goes without saying that the description of the simple embodiment does not impose any restrictions. In addition, the present invention, in addition to the following examples, and in addition to the above specific description, unless departing from the spirit of the present invention,
It should be understood that various changes, modifications, improvements, and the like can be made based on the knowledge of those skilled in the art.

First, a rectangular parallelepiped base (length: 40 mm, made of sintered silicon nitride) corresponding to a structural member
A rectangular parallelepiped thin plate made of the same material and corresponding to a thin plate member (width: 4 mm, thickness: 3 mm) (length: 40 m)
m, width: 4 mm, thickness: 0.8 mm) according to a known method. Then, the main surfaces on one side of each of the obtained thin plate and substrate were roughened with a # 400 diamond grindstone. Grinding was performed so that the height (Rmax) was about 1 μm. Then, the thin plate is superimposed on the substrate such that the ground surfaces of the thin plate and the substrate face each other, and the temperature is 1500 ° C. and the bonding surface pressure is 10 MPa in a nitrogen gas atmosphere.
In a, by holding for 60 minutes, the thin plate was diffusion-bonded to the substrate to form a bonded body (16). The dimensions of the obtained joined body (16) were as follows: length: 40 mm, width:
4 mm, thickness: 3.8 mm, and the bonding strength was about 20% of the bending strength of the silicon nitride sintered body.

After the main surface of the joined body (16) obtained in this manner, on which the thin plate is joined, is mirror-polished by a known method, a Vickers indenter is extended from four vertexes of the indenter. In a state where the images projected on the main surface are parallel to the longitudinal direction or the width direction of the joined body (16), the image is pushed into the main surface with a force of 98N as shown in FIG. Surface scratch 1
8, as shown in FIG. 3, near the center on the main surface of the joined body 16 on the side where the thin plate was joined, at intervals of about 1.5 mm,
The test piece a was formed at three places.

The surface flaw 1 formed as described above
Reference numeral 8 denotes a regular square whose opening has a substantially square shape and whose diagonal direction of such an opening corresponds to the longitudinal direction or the width direction of the test piece a, which substantially corresponds to the tip shape of the Vickers indenter. The pyramid-shaped indentation 20 and the four sides extending from the apex of its deepest portion toward the surface extend outwardly of the indentation 20 along the diagonal direction of the opening, that is, the longitudinal direction or width of the test piece. It consists of four cracks 22 extending in the direction. The distance between the ends of the two cracks 22 facing each other across the indentation 20 is about 0.21 mm.

The test piece a thus formed
As a comparison object of the above, the substrate itself as described above was used as a test piece b, and a rectangular parallelepiped having the same dimensions as the test piece a was produced from the same material as the above-described substrate by the same known manufacturing method. Main surface (40mm x 4mm)
Was provided with the same surface flaw as the test piece a, and the test piece c
And

With respect to the three kinds of test pieces thus formed, except for the thicknesses of the test pieces a and c, JI
In accordance with SR1601 (inner span: 10 mm, outer span: 30 mm, cross head speed: 0.5 mm / min), the constant displacement speed of the test piece a was determined with the main surface of the side where the thin plate was joined as the tensile side. Was performed, and the results are shown in FIG. FIG. 5 shows the relationship between the load applied to the test piece by the material testing machine and the displacement of the crosshead of the material testing machine, obtained by the bending test. In this figure, the results of the test pieces b and c are shifted in the horizontal axis direction so that the results of the test pieces do not overlap.

From the results shown in FIG. 5, it can be seen that, in the test piece a, the thin plate is broken by a relatively small load due to the surface flaw formed by the indentation of the Vickers indenter, and the load temporarily decreases at that time. However, the substrate itself is hardly damaged, is again subjected to a load only by the substrate, and finally breaks under substantially the same load as the test piece b consisting only of the substrate that does not form a surface flaw. It can be seen that the test piece c in which the thin plate was not bonded and the surface flaw was formed directly on the surface was broken at the strength reduced by the formation of the surface flaw. Further, under the same conditions, the damage of the thin plate of the test piece a and the damage of the test piece c occur at substantially the same load (420 N) due to surface scratches formed on the thin plate of the test piece a and the test piece c, respectively. Can be recognized.

As described above, a thin plate made of the same material as that of the base is diffusion-bonded to the surface of the base with a predetermined bonding strength that is weaker than the strength of the base, and a surface flaw is formed on the thin plate. The substrate breaks at a predetermined lower load than the substrate, and the substrate itself can withstand the load to the original strength of the substrate. Thus, the effectiveness of the method for predicting failure of a brittle material structural member according to the present invention has been demonstrated. It was done.

[0045]

As is apparent from the above description, according to the method for predicting breakage of a brittle material-made structural member according to the present invention, if the brittle material forming the structural member is in an environment that can withstand it,
No matter how severe the environment, or even if the structural member undergoes a large temperature change, the structural member made of brittle material itself will not be damaged, and the prediction of breakage of such a structural member will be stable. It becomes possible.

As a result, it is possible to predict the possibility of breakage of the brittle material structural member due to the application of an excessive load. As a result, by reducing the load, etc., such structural member can be catastrophically damaged, and as a result, The use of brittle materials with excellent properties as structural materials in more diverse areas can effectively prevent catastrophic damage to structures, equipment, and other systems in which they are incorporated. And its superior properties allow for improved performance of systems such as structures and devices.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a brittle material structural member to which a thin plate member is joined, to which a method for predicting breakage of a brittle material structural member according to the present invention is applied.

FIG. 2 is a view showing a relationship between a pushing load of a Vickers indenter and a bending strength of the brittle material member into which the Vickers indenter is pushed in the method for predicting breakage of a brittle material structural member according to the present invention.

FIG. 3 is a plan view showing a formation position of a surface flaw in an embodiment according to the method for predicting breakage of a brittle material structural member according to the present invention.

FIG. 4 is a plan view showing the shape of a surface flaw in an example according to the method for predicting breakage of a brittle material structural member according to the present invention.

FIG. 5 is a diagram showing a relationship between applied load and displacement as a result of a four-point bending test of a test piece in an example according to a method for predicting breakage of a brittle material structural member according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Structural member 12 Thin plate member 14, 18 Surface flaw 16 Joint 20 Indentation 22 Crack

Claims (2)

(57) [Claims] 1. A thin plate member made of the same brittle material as a structural member is diffusion-bonded to a surface of a structural member made of a brittle material such as ceramics and glass with a bonding strength lower than the strength of the structural member. Along with causing a surface scratch on the surface of the thin plate member, when a load is applied to the structural member, by causing only the thin plate member to be damaged with a smaller load than the structural member is damaged, A method for predicting breakage of a brittle material-made structural member, comprising predicting breakage of the structural member. 2. The method for predicting breakage of a brittle material structural member according to claim 1, wherein a detecting means having a stress measuring function or a crack detecting function is further provided on the surface of the thin plate member.