JP7844851B2 - Test equipment and test method - Google Patents

Description

This disclosure relates to a test apparatus and test method for testing test specimens.

For example, Patent Document 1 discloses the acquisition of images of a test specimen before and after deformation during a small punch test. In Patent Document 1, the strain distribution of the test specimen is measured using Digital Image Correlation (DIC) based on the acquired images.

Japanese Patent Publication No. 2014-102131

Incidentally, in fatigue testing, an example of strength testing for a test specimen, the test machine repeatedly applies dynamic or static loads to the specimen, and the load and displacement acting on the specimen are measured multiple times. Furthermore, when digital image correlation is applied to fatigue testing, multiple images of the specimen are captured during the loading process to analyze the displacement behavior.

However, since load and displacement measurements are performed by a testing machine and image acquisition is performed by an imaging device, the measurement results and captured images may be recorded separately. This can lead to unclear or inaccurate correspondences between multiple captured images and multiple measurement results. As a result, the reliability of image analysis or verification of test accuracy may be reduced.

This disclosure aims to provide a test apparatus and test method that can accurately determine the relationship between test measurement results and captured images.

To solve the above problems, a test apparatus according to one aspect of the present disclosure comprises a testing machine that performs a test to measure the load and displacement applied to a test specimen by alternately repeating dynamic loading, which applies a periodically changing load to a test specimen, and static loading, which applies a load to a test specimen under the condition that the load applied to the test specimen is a constant value or the displacement applied to the test specimen is a constant value; an imaging device that images the test specimen during static loading; a data processing device that synchronously records the test measurement results and the image of the test specimen output from the imaging device to a storage device; and a control device provided separately from the data processing device that controls the dynamic loading and static loading by the testing machine, wherein the control device transmits a predetermined trigger signal to the data processing device multiple times during the execution of static loading, and the data processing device acquires and synchronously records the test measurement results and the image of the test specimen in response to the receipt of the trigger signal.

Furthermore, the test results may include measurement data output from the testing machine during static loading, and this measurement data may include the load and displacement applied to the test specimen by the testing machine.

Furthermore, the test machine may be equipped with a separate sensor that measures at least the displacement of the test specimen, and the test results may include measurement data output from the sensor during static loading.

Furthermore, the control device may be configured to perform dynamic loading on the testing machine by outputting a periodically changing signal, or to perform static loading on the testing machine by outputting a constant signal whose value does not change regardless of the passage of time .

Furthermore, the data processing device may derive the displacement distribution or strain distribution of the test specimen using a digital image correlation method based on multiple captured images of the specimen.

To solve the above problems, a test method according to one aspect of the present disclosure alternately repeats dynamic loading, in which a periodically changing load is applied to a test specimen, and static loading, in which a load is applied to a test specimen under the condition that the load applied to the test specimen is a constant value or the displacement applied to the test specimen is a constant value, and while performing a test to measure the load and displacement applied to the test specimen, the dynamic loading and static loading are controlled, a predetermined trigger signal is transmitted multiple times during the execution of static loading, the test specimen is imaged during static loading, and the measurement results of the test and the imaged specimen are acquired in response to the receipt of the trigger signal and recorded synchronously in a storage device.

According to this disclosure, it becomes possible to accurately understand the relationship between the test measurement results and the captured images.

Figure 1 is a schematic diagram illustrating the outline of the test apparatus according to this embodiment. Figure 2 illustrates the operation of the load control unit and trigger signal control unit according to this embodiment. Figure 3 shows an example of an image captured according to this embodiment. Figure 4 is a flowchart illustrating the flow of the test method according to this embodiment.

The embodiments of this disclosure will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values shown in these embodiments are merely illustrative examples for ease of understanding and, unless otherwise specified, do not limit this disclosure. In this specification and the drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to avoid redundant explanations, and elements not directly related to this disclosure are omitted from the illustrations.

Figure 1 is a schematic diagram illustrating the outline of the test apparatus 1 according to this embodiment. The test apparatus 1 is a device for performing tests to measure the strength of a test specimen 10, such as fatigue tests. In this embodiment, the strength test is described using an example of a fatigue test in which tensile and compressive loads are repeatedly applied to the test specimen 10. However, the tests of this disclosure are not limited to this example and can be applied to tests measuring various strengths of the test specimen 10, such as compressive strength, tensile strength, bending strength, and torsional strength. Furthermore, the direction in which the load is applied to the test specimen 10 in the test may be uniaxial or multiaxial.

The test specimen 10 is, for example, a composite material such as metal, plastic, or fiber-reinforced plastic. The test specimen 10 is, for example, a flat plate shape. However, the shape of the test specimen 10 is not limited to a flat plate; it may be any shape depending on the purpose of the test, such as a cylindrical shape, cubic shape, rectangular prism shape, curved plate shape, or tubular shape.

The test apparatus 1 comprises a test machine 20, an imaging device 22, a sensor 24, a control device 26, and a data processing device 28.

The testing machine 20 applies a load to the test specimen 10, deforming it, and measures the load and displacement applied to the test specimen 10.

Furthermore, in tests using test apparatus 1, the Digital Image Correlation (DIC) method can be applied. In the DIC method, first, a random pattern is formed on the surface of the test specimen 10. Then, before deformation occurs to the test specimen 10, a digital image of the random pattern on the test specimen 10 is captured by the imaging device 22. Afterward, the test specimen 10 is deformed, and another digital image of the random pattern is captured by the imaging device 22. Multiple subsets are then defined in the digital image before deformation. A subset is a region of a predetermined size set on the digital image and is used to analyze the displacement of each position of the test specimen 10. Subsequently, multiple subsets corresponding to the multiple subsets set in the digital image before deformation are identified in the digital image after deformation. Then, the displacement behavior of the test specimen 10 is analyzed by calculating the displacement of representative points (e.g., center points) of the subsets before and after deformation. Hereafter, the captured digital image may be referred to as the captured image.

As described above, the load and displacement applied to the test specimen 10 are measured by the testing machine 20, and images of the test specimen 10 are captured by the imaging device 22. If the test measurement results and captured images were recorded separately, it may become unclear which of the multiple measurement results corresponds to each of the multiple captured images. As a result, the reliability of image analysis or verification of test accuracy may decrease.

Therefore, in the test apparatus 1 of this embodiment, the measurement results of the fatigue test and the captured images are recorded in synchronization. The configuration and operation of the test apparatus 1 will be described in detail below.

The testing machine 20 comprises a frame 30, a movable part 32, a first chuck 34, a second chuck 36, a load cell 38, and a control panel 40.

The frame 30 consists of a base 30a, two side column sections 30b, and a ceiling section 30c. The base 30a is, for example, formed in a flat plate shape and placed on the floor. The two side column sections 30b are spaced apart from each other and rise upward from the edge of the base 30a. The ceiling section 30c connects the two side column sections 30b at the ends opposite to the base 30a.

The movable part 32 is formed, for example, in a rod shape. The first end of the movable part 32 is supported by the first side column 30b of the two side column portions 30b. The second end of the movable part 32 is supported by the second side column portion 30b of the two side column portions 30b. The movable part 32 is slidable in the direction of extension of the side column portions 30b, i.e., in the vertical direction in Figure 1.

The first chuck 34 is connected to the bottom 30a of the frame 30. The second chuck 36 is connected to the movable part 32 via a load cell 38. The first chuck 34 and the second chuck 36 are positioned opposite each other. The test specimen 10 is placed between the first chuck 34 and the second chuck 36. The first chuck 34 grips the first end of the test specimen 10, i.e., the lower end in Figure 1. The second chuck 36 grips the second end of the test specimen 10, opposite to the first end, i.e., the upper end in Figure 1. Hereafter, the act of gripping the test specimen 10 with the first chuck 34 and the second chuck 36 may be referred to as "setting the test specimen 10 in the testing machine 20."

The load cell 38 is provided between the second chuck 36 and the movable part 32. The lower end of the load cell 38 is connected to the second chuck 36, and the upper end of the load cell 38 is connected to the movable part 32. When the movable part 32 slides with the test specimen 10 set in the testing machine 20, a load is applied to the test specimen 10, causing it to deform. The load cell 38 transmits the load received from the movable part 32 to the test specimen 10 via the second chuck 36, and measures the load applied to the test specimen 10.

The control panel 40 has a user interface that accepts input operations from operators and displays the status of the testing machine 20 to the operators. The control panel 40 is connected to an actuator (not shown) that moves the movable part 32, and the movable part 32 can be moved using this actuator. The control panel 40 can measure the distance the movable part 32 is moved by the actuator. The distance the movable part 32 is moved roughly corresponds to the displacement of the test specimen 10. Therefore, the control panel 40 can indirectly measure the displacement applied to the test specimen 10 using the distance the movable part 32 is moved. Furthermore, the control panel 40 is connected to a load cell 38 and can acquire the load measured by the load cell 38.

The control panel 40 has external input and output terminals that allow it to be electrically connected to external devices of the testing machine 20. Control signals are input to the control panel 40 from an external source via the external input terminals. As will be described later, the testing operation of the testing machine 20 is automatically controlled based on the control signals input to the testing machine 20 from an external source. The control panel 40 can also output measurement data externally via the external output terminals. The measurement data output from the testing machine 20 includes the load and displacement applied to the test specimen 10 by the testing machine 20.

The imaging device 22 is positioned in front of the test specimen 10 set in the testing machine 20 and can image the test specimen 10. As will be described later, the imaging device 22 performs imaging when it receives an imaging command from the data processing device 28, and generates a still image.

The sensor 24 is, for example, a displacement meter and is provided separately from the testing machine 20. The sensor 24 is directly attached to the test specimen 10. The sensor 24 measures at least the displacement of the test specimen 10 to which the sensor 24 is attached. The sensor 24 outputs measurement data, including the displacement measured by the sensor 24. The sensor 24 is connected to the data processing device 28, for example, via a predetermined cable. The measurement data from the sensor 24 is input to the data processing device 28.

More specifically, the sensor 24 is mounted on the surface of the test specimen 10 opposite to the surface imaged by the imaging device 22. If the test specimen 10 is tubular, the sensor 24 may be mounted on the inner surface of the tubular test specimen 10. Mounting the sensor 24 on the surface opposite to the surface imaged by the imaging device 22 allows for the acquisition of displacement in areas where an image cannot be obtained. Furthermore, it prevents the sensor 24 from interfering with imaging by the imaging device 22.

The control device 26 is, for example, composed of a personal computer. The control device 26 includes a communication unit 50 and a control unit 52. The communication unit 50 is connected to the external input terminal of the control panel 40 of the test machine 20 via a predetermined cable. Note that the control device 26 is not limited to being connected to the test machine 20 by wire; it may also be connected wirelessly. Furthermore, the communication unit 50 can communicate with the data processing device 28 by wire or wireless connection.

The control unit 52 comprises one or more processors 60 and one or more memories 62 connected to the processors 60. The memories 62 include ROM for storing programs and RAM as a work area. The processors 60 cooperate with the programs contained in the memories 62 to control the entire control device 26. Furthermore, by executing programs, the control unit 52 also functions as a load control unit 70 and a trigger signal control unit 72.

Figure 2 illustrates the operation of the load control unit 70 and trigger signal control unit 72 according to this embodiment. The load control unit 70 performs control to transmit control signals to the test machine 20 via the communication unit 50 and the external input terminals of the test machine 20. The control signals are represented, for example, by the time variation of an analog voltage.

When the fatigue test begins, the load control unit 70 generates a control signal (e.g., voltage) as illustrated in the upper waveform of Figure 2, and outputs the generated control signal to the test machine 20. The test machine 20 moves the movable part 32 according to the control signal input from the control device 26.

More specifically, when the test begins, the load control unit 70 outputs a periodically changing control signal to the test machine 20. This periodically changing control signal may be, for example, a sine wave signal, a triangular wave signal, a trapezoidal wave signal, or a square wave signal. For the sake of explanation, this periodically changing control signal may hereafter be referred to as a dynamic signal.

The testing machine 20 applies a tensile load to the test specimen 10 when the input control signal is positive, and moves the movable part 32 so that the tensile load increases as the value of the control signal increases. The testing machine 20 applies a compressive load to the test specimen 10 when the input control signal is negative, and moves the movable part 32 so that the compressive load increases as the value of the control signal decreases.

As illustrated by the upper waveform in Figure 2, when a dynamic signal is input to the testing machine 20, the testing machine 20 moves the movable part 32 so as to alternately repeat tensile and compressive loads. Hereafter, the operation of applying such periodically changing loads to the test specimen 10 is sometimes referred to as dynamic loading. While this example shows alternating tensile and compressive loads, dynamic loading is not limited to alternating tensile and compressive loads. For example, dynamic loading may involve applying only a tensile load with a periodically changing magnitude, or applying only a compressive load with a periodically changing magnitude.

The load control unit 70 stops outputting the dynamic signal after it has been continuously transmitted for a predetermined period of time. In other words, dynamic loading is performed for a predetermined period of time. This predetermined period can be arbitrarily set depending on the purpose of the fatigue test, for example, by allowing the load to be varied 10,000 times.

After the dynamic signal stops, the load control unit 70 outputs a constant control signal to the testing machine 20. This constant control signal is, in practice, a substantially constant control signal, meaning its value does not substantially change regardless of the passage of time. A constant or substantially constant control signal allows for slight fluctuations, such as noise. For example, the constant control signal corresponds to the maximum load applied to the test specimen 10 during the fatigue test. However, the constant control signal is not limited to the maximum load; it can be arbitrarily set according to the purpose of the fatigue test, for example, to a control signal corresponding to half the maximum load. Hereafter, for convenience of explanation, the constant control signal may be referred to as a static signal.

As illustrated by the upper waveform in Figure 2, when a static signal is input to the testing machine 20, the testing machine 20 restricts the movement of the movable part 32 to apply a constant load corresponding to the static signal to the test specimen 10. This constant load is, in practice, a substantially constant load, meaning it does not substantially change in value regardless of the passage of time. A constant or substantially constant load allows for load fluctuations within a predetermined range caused by slight variations in the substantially constant control signal. For example, a load 2.5% higher than a predetermined value indicating a constant load is set as the upper limit, and a load 2.5% lower than that predetermined value is set as the lower limit, allowing load fluctuations within a predetermined range. Hereafter, this operation of applying a constant load to the test specimen 10 may be referred to as static loading.

The load control unit 70 stops outputting the static signal after it has been continuously outputting for a predetermined period of time. In other words, static loading is performed for a predetermined period of time. This predetermined period can be arbitrarily set depending on the purpose of the fatigue test, for example, several tens of minutes.

After the static signal stops, the load control unit 70 outputs a dynamic signal to the testing machine 20 again. After the dynamic signal output continues for a predetermined time, it outputs a static signal to the testing machine 20 again.

In this manner, the loading control unit 70 outputs a periodically changing control signal to the testing machine 20, causing it to perform dynamic loading, and outputs a constant control signal to the testing machine 20, causing it to perform static loading. The loading control unit 70 then repeatedly alternates between dynamic and static loading.

The trigger signal control unit 72 performs control to transmit a predetermined trigger signal to the data processing unit 28 via the communication unit 50 during static loading (i.e., the period during which the loading control unit 70 outputs a static signal to the test machine 20). The trigger signal is, for example, a voltage pulse signal.

The trigger signal control unit 72 generates a trigger signal (e.g., voltage) as illustrated in the lower waveform of Figure 2 during static loading and transmits the generated trigger signal to the data processing unit 28. The trigger signal instructs the data processing unit 28 to synchronize the recording of the fatigue test measurement results and the captured image of the test specimen 10. Upon receiving the trigger signal transmitted from the control unit 26, the data processing unit 28 synchronously records the fatigue test measurement results and the captured image of the test specimen 10.

The trigger signal control unit 72 may transmit multiple trigger signals (see Figure 2) to the data processing unit 28 during a single static loading operation. This causes the data processing unit 28 to continuously perform multiple imaging operations on the imaging device 22 during a single static loading operation, and to continuously record multiple images obtained through these operations. The number of trigger signal transmissions can be arbitrarily set by the operator depending on the number of images to be recorded. For example, if only one image is recorded during a single static loading operation, and that single image is unclear, proper image analysis may not be possible. However, by supplementarily capturing and recording multiple images during a single static loading operation, the likelihood of recording clear images increases, and as a result, proper image analysis can be performed.

Furthermore, the trigger signal control unit 72 is not limited to transmitting multiple trigger signals during a single static load; it may also transmit at least one trigger signal during a single static load. In this configuration, one image can be recorded during a single static load, and image analysis can be performed using this single image.

Returning to Figure 1, let's continue the explanation. The data processing unit 28 is, for example, a high-spec personal computer with image analysis capabilities. In this embodiment, the data processing unit 28 is provided separately from the relatively low-spec control device 26. The data processing unit 28 includes a communication unit 80, a storage device 82, and a control unit 84. The communication unit 80 is connected to the external output terminal of the control panel 40 of the test machine 20 via a predetermined cable. Note that the data processing unit 28 is not limited to being connected to the test machine 20 by wire; it may also be connected wirelessly. Furthermore, the communication unit 80 can communicate with the control device 26 by wire or wirelessly.

The storage device 82 is composed of a non-volatile storage element, such as a hard disk or flash memory. The storage device 82 stores the measurement results and captured images from the fatigue test. Note that the storage device 82 is not limited to being included in the data processing device 28; it may also be externally connected to the data processing device 28.

The control unit 84 comprises one or more processors 90 and one or more memories 92 connected to the processors 90. The memories 92 include ROM for storing programs and RAM as a work area. The processors 90 cooperate with the programs contained in the memories 92 to control the entire data processing unit 28. Furthermore, by executing programs, the control unit 84 also functions as a recording execution unit 100 and an image analysis unit 102.

The recording execution unit 100, upon receiving a trigger signal transmitted from the control device 26, synchronously records the fatigue test measurement results and the captured images in the storage device 82.

More specifically, upon receiving a trigger signal, the recording execution unit 100 transmits an imaging command to the imaging device 22. Upon receiving the imaging command, the imaging device 22 performs still image capture at that time. The imaging device 22 then transmits the captured image to the data processing device 28. In this manner, the recording execution unit 100 acquires the captured image at the moment it receives the trigger signal during static loading.

Furthermore, during the fatigue test, the testing machine 20 outputs its measurement data to the data processing device 28 in real time via an external output terminal. The data processing device 28 receives the measurement data from the testing machine 20 in real time via the communication unit 80. When the recording execution unit 100 receives a trigger signal, it latches and acquires the measurement data from the testing machine 20 at that moment. In this way, the recording execution unit 100 acquires measurement data, including load and displacement, from the testing machine 20 at the moment it receives a trigger signal during static loading.

Furthermore, during the fatigue test, the sensor 24 outputs its measurement data to the data processing unit 28 in real time. The data processing unit 28 receives the measurement data from the sensor 24 in real time via the communication unit 80. When the recording execution unit 100 receives a trigger signal, it latches and acquires the measurement data from the sensor 24 at that moment. In this way, the recording execution unit 100 acquires measurement data, including displacement from the sensor 24, at the moment it receives a trigger signal during static loading.

The recording execution unit 100 simultaneously performs the acquisition of captured images, the acquisition of measurement data from the test machine 20, and the acquisition of measurement data from the sensor 24, in accordance with the trigger signal.

The recording execution unit 100 acquires the captured image, the measurement data from the test machine 20, and the measurement data from the sensor 24. It then records the acquired image, the measurement data from the test machine 20, and the measurement data from the sensor 24 in the storage device 82 in a synchronized manner. More specifically, the recording execution unit 100 records the captured image, the measurement data from the test machine 20, and the measurement data from the sensor 24 in the storage device 82, associating them with a common recording time. This ensures that the captured image, the measurement data from the test machine 20, and the measurement data from the sensor 24, acquired in response to a single trigger signal, are recorded in a synchronized manner, i.e., linked to each other.

Here, the measurement data from the test machine 20 and the measurement data from the sensor 24 are sometimes collectively referred to as the fatigue test measurement results. That is, the recording execution unit 100 synchronously records the fatigue test measurement results and the captured image of the test specimen 10 output from the imaging device into the storage device 82.

Furthermore, the recording execution unit 100 is not limited to recording all of the captured images, measurement data from the test machine 20, and measurement data from the sensor 24 in a synchronized manner. For example, the recording execution unit 100 may omit the synchronization of the measurement data from the sensor 24 and record the measurement data from the test machine 20 and the captured images in a synchronized manner. Alternatively, the recording execution unit 100 may omit the synchronization of the measurement data from the test machine 20 and record the measurement data from the sensor 24 and the captured images in a synchronized manner.

The image analysis unit 102 performs image analysis using the digital image correlation method based on the captured images recorded during the fatigue test.

Figure 3 shows an example of an image captured according to this embodiment. Note that in Figure 3, subset 112 is shown relatively large for ease of understanding. In Figure 3, the random pattern 114 is shown using cross-hatching.

Here, the image of the test specimen 10 before deformation may be referred to as the first image, and the image of the test specimen 10 after deformation may be referred to as the second image. Note that "before deformation" is not limited to before the start of the fatigue test; it can be any time before the "deformation" that defines "post-deformation," or any time before dynamic loading. For example, if the second dynamic loading corresponds to a specific "deformation," the static loading before the second dynamic loading (i.e., the static loading after the first dynamic loading) may be considered "before deformation," and the static loading after the second dynamic loading may be considered "after deformation."

The image analysis unit 102 sets a subset 112 in the first captured image. The subset 112 in the first captured image is a region of a predetermined size set on the first captured image. For example, the subset 112 in the first captured image is a 21x21 pixel square region, but it can be set to any size.

The image analysis unit 102 identifies a subset 112 in the second captured image that corresponds to a subset 112 in the first captured image. The subset 112 in the second captured image is a region of a predetermined size identified on the second captured image. The subset 112 in the second captured image is set to the same size as the subset 112 in the first captured image.

More specifically, the image analysis unit 102 identifies the subset 112 on the second image that has the highest correlation with the random pattern 114 of the subset 112 in the first image. Various existing techniques can be applied to identify the subset 112 on the second image.

The image analysis unit 102 derives the displacement of the representative point P of the subset 112 of the second image relative to the representative point P of the subset 112 of the first image. The representative point P is set, for example, to the center or centroid of the subset 112, but can be set to any point within the subset 112.

The image analysis unit 102 then sets subsets 112 in the first captured image at various positions in the first captured image, and for each subset 112 in the first captured image, it repeatedly identifies the subset 112 in the second captured image and derives its displacement. In this way, the image analysis unit 102 can obtain the displacement behavior of the entire test specimen 10. Furthermore, by converting the displacement into strain, the image analysis unit 102 can obtain the strain behavior of the entire test specimen 10.

Figure 4 is a flowchart illustrating the flow of the test method according to this embodiment. First, the operator prepares to start the fatigue test (S10). More specifically, the operator forms a random pattern on the surface of the test specimen 10 to be imaged. The operator sets the test specimen 10, on which the random pattern has been formed, into the testing machine 20. The operator positions the imaging device 22 so that its optical axis is perpendicular to the surface of the test specimen 10 on which the random pattern has been formed. The operator focuses the imaging device 22 on the test specimen 10. The operator also attaches the sensor 24 to the surface of the test specimen 10 opposite to the surface on which the random pattern has been formed.

Once preparations are complete, before deforming the test specimen 10, the operator records initial images (S11). More specifically, before instructing the control device 26 to start the fatigue test, the operator instructs the control device 26 to send an initial trigger signal to the data processing device 28. Upon receiving this initial trigger signal, the data processing device 28 sends an imaging command to the imaging device 22. The imaging device 22 generates an image in accordance with the imaging command and transmits the generated image to the data processing device 28. This allows the data processing device 28 to acquire the initial images. The data processing device 28 also latches the initial load and displacement output from the testing machine 20 and the initial displacement output from the sensor 24. The data processing device 28 then synchronously records the initial load and displacement from the testing machine 20, the initial displacement from the sensor 24, and the initial images in the storage device 82.

After recording the initial images, the operator initiates the fatigue test using the control device 26. The load control unit 70 of the control device 26 then transmits a periodically changing voltage to the testing machine 20, causing the machine 20 to perform dynamic loading (S12).

When a predetermined time has elapsed in the dynamic loading state, the loading control unit 70 stops transmitting the periodically changing voltage and stops the dynamic loading. Then, the loading control unit 70 transmits a constant voltage corresponding to a predetermined constant load to the testing machine 20, causing the testing machine 20 to perform static loading (S13). The loading control unit 70 then maintains the static loading state until a predetermined time has elapsed.

During static loading, the trigger signal control unit 72 of the control device 26 transmits a predetermined trigger signal to the data processing device 28 (S14). The trigger signal control unit 72 may transmit the trigger signal multiple times during the current static loading.

The recording execution unit 100 of the data processing device 28, upon receiving a trigger signal, executes the acquisition of measurement results and captured images (S15). More specifically, the recording execution unit 100 transmits an imaging command to the imaging device 22. The imaging device 22 performs imaging in accordance with the imaging command and transmits the generated captured image to the data processing device 28. The recording execution unit 100 acquires the captured image transmitted from the imaging device 22. In parallel, the recording execution unit 100 latches and acquires the load and displacement measurement data of the testing machine 20, and latches and acquires the displacement measurement data of the sensor 24.

Next, the recording execution unit 100 records the acquired measurement results and captured images in the storage device 82 in a synchronized manner (S16). That is, the recording execution unit 100 stores the acquired measurement data from the test machine 20, the measurement data from the sensor 24, and the captured images, associating them with a common recording time.

After the recording execution unit 100 completes the recording process in step S16, the image analysis unit 102 performs image analysis (S17) using the image recorded during the current static loading as the second image after deformation, and the image recorded during the previous static loading as the first image before deformation. This obtains a displacement distribution based on two images, one before and one after the dynamic loading immediately preceding the current static loading. The image analysis unit 102 records the obtained displacement distribution in the storage device 82, associating it with the image recorded this time. Alternatively, the image analysis unit 102 may convert the displacement into strain to derive a strain distribution, and record the derived strain distribution in the storage device 82, associating it with the image recorded this time.

After image analysis, the loading control unit 70 determines whether the fatigue test termination conditions have been met (S18). For example, the data processing unit 28 determines that the termination conditions have been met if the number of repetitions of dynamic and static loading exceeds a predetermined number. The predetermined number can be arbitrarily set depending on the material of the test specimen 10, etc. The loading control unit 70 also determines that the termination conditions have been met if the test specimen 10 is destroyed and the fatigue test can no longer be continued.

If the fatigue test termination conditions are not met (NO in S18), the loading control unit 70 maintains the static loading state until a predetermined time has elapsed, and then returns to the process in step S12. That is, the loading control unit 70 stops transmitting a constant voltage to stop static loading, and then transmits a periodically changing voltage to the testing machine 20 to perform dynamic loading (S12). On the other hand, if the fatigue test termination conditions are met (YES in S18), the loading control unit 70 terminates the fatigue test.

As described above, in the test apparatus 1 of this embodiment, a fatigue test is performed by repeatedly applying dynamic and static loading alternately, measuring the load and displacement applied to the test specimen 10. Furthermore, in the test apparatus 1 of this embodiment, the measurement results of the test and the captured images output from the imaging device 22 that captures images of the test specimen 10 are recorded synchronously.

Therefore, according to the test apparatus 1 of this embodiment, the test measurement results and captured images can be recorded in a clear and accurate correspondence, allowing the operator to accurately grasp this correspondence.

For example, in the test apparatus 1 of this embodiment, when performing image analysis, it is easy to understand the correspondence between each of the multiple captured images and the state of the measurement data in which the image was captured. As a result, the reliability of the displacement distribution or strain distribution derived from the image analysis can be improved in the test apparatus 1 of this embodiment.

Furthermore, the accuracy of the test may be verified by comparing the displacement distribution derived from image analysis with the displacement distribution obtained from the test measurement results. In the test apparatus 1 of this embodiment, the relationship between the test measurement results and the captured images can be accurately understood, thus enabling accurate verification of the test accuracy and improving the reliability of the verification.

Furthermore, in the test apparatus 1 of this embodiment, dynamic and static loading by the testing machine 20 are automatically controlled, and the measurement results and captured images of the test are automatically recorded in sync. This eliminates the need for manual intervention by the operator in interrupting dynamic loading, applying load during static loading, and capturing and recording images of the test specimen 10. Therefore, the test apparatus 1 of this embodiment reduces the workload and burden on the operator. Moreover, the test apparatus 1 of this embodiment allows fatigue testing to be conducted not only during times when the operator is available, but also, for example, at night.

Furthermore, processing related to captured images tends to have a higher processing load compared to load control for dynamic and static loading. In the test apparatus 1 of this embodiment, the control device 26 performs the load control, while a separate data processing device 28 performs the processing related to captured images. This allows the data processing device 28 to concentrate on processing the captured images, which has a relatively high processing load. Also, because the control device 26 performs load control, which has a relatively low processing load, it can use a computer with lower specifications than the data processing device 28.

While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally fall within the technical scope of this disclosure.

For example, in the static loading of the above embodiment, the load applied to the test specimen 10 was constant under test conditions (i.e., constant load conditions). However, the example is not limited to this, and in static loading, the load may be applied to the test specimen 10 under test conditions (i.e., constant displacement conditions) where the displacement applied to the test specimen 10 is constant. More specifically, the loading control unit 70 acquires the displacement of the test specimen 10 from the testing machine 20 during static loading. The loading control unit 70 controls the control signal by feedback control so that the acquired displacement becomes constant, and outputs the control signal to the testing machine 20. A constant displacement is actually a substantially constant displacement, that is, a substantially constant displacement, and is a displacement whose value does not substantially change regardless of the passage of time. A constant or substantially constant displacement allows for fluctuations in displacement within a predetermined range due to control errors or control delays in the feedback control. For example, a displacement variation within a predetermined range is permitted, with an upper limit set at a displacement 2.5% higher than a predetermined value representing a constant displacement, and a lower limit set at a displacement 2.5% lower than that predetermined value. Even in this embodiment, the test specimen 10 can be imaged during static loading.

Furthermore, the sensor 24 in the above embodiment was a displacement meter. However, the sensor 24 may also be a strain gauge, outputting strain as measurement data.

Furthermore, in the above embodiment, the control device 26 and the data processing device 28 were provided separately. However, the functions of the control device 26 may be incorporated into the data processing device 28, or the functions of the data processing device 28 may be incorporated into the control device 26.

Furthermore, in the above embodiment, image analysis was performed during the fatigue test. However, the image analysis unit 102 may perform image analysis after the fatigue test is completed.

Furthermore, in the above embodiment, the imaging device 22 may have a wide field of view capable of imaging the entire test specimen 10, or it may be combined with a microscope to magnify and image a specific portion of the test specimen 10.

Furthermore, the above embodiment was described using tensile and compressive load applications as examples. However, the tests performed by the test apparatus 1 are not limited to those applying tensile and compressive loads. For example, the test apparatus 1 may perform tests applying bending loads or tests applying torsional loads.

Furthermore, in addition to the test apparatus 1 of the above embodiment, a test method for performing the test described in the above embodiment is also provided.

1 Test apparatus 10 Test specimen 20 Test machine 22 Imaging device 24 Sensor 26 Control device 28 Data processing device 82 Storage device

Claims (6)

A testing machine that performs a test by repeatedly alternating between dynamic loading, which applies a periodically changing load to a test specimen, and static loading, which applies a load to the test specimen under the condition that the load applied to the test specimen is a constant value or the displacement applied to the test specimen is a constant value , and measuring the load and displacement applied to the test specimen.
An imaging device for imaging the test specimen during the static loading described above,
A data processing device that synchronously records the measurement results of the aforementioned test and the image of the test specimen output from the imaging device into a storage device,
A control device is provided separately from the data processing device, which controls the dynamic loading and static loading by the testing machine,
Equipped with,
The control device transmits a predetermined trigger signal to the data processing device multiple times during the execution of the static loading.
The data processing device, upon receiving the trigger signal, acquires and synchronously records the measurement results of the test and the captured image of the test specimen.
Testing equipment. The measurement results of the aforementioned test include measurement data output from the testing machine during static loading.
The test apparatus according to claim 1, wherein the measurement data includes the load and displacement applied to the test specimen by the testing machine. Separately from the aforementioned testing machine, the machine further includes a sensor that measures at least the displacement of the test specimen,
The test apparatus according to claim 1 or 2, wherein the measurement results of the test include measurement data output from the sensor during static loading. The test apparatus according to any one of claims 1 to 3, wherein the control device causes the test machine to perform the dynamic loading by outputting a periodically changing signal to the test machine, and causes the test machine to perform the static loading by outputting a constant signal whose value does not change regardless of the passage of time to the test machine. The test apparatus according to any one of claims 1 to 4, wherein the data processing device derives the displacement distribution or strain distribution of the test specimen by digital image correlation based on a plurality of captured images of the test specimen. While performing a test in which a dynamic loading, in which a periodically changing load is applied to the test specimen, and a static loading, in which a load is applied to the test specimen under the condition that the load applied to the test specimen is a constant value or the displacement applied to the test specimen is a constant value , are repeated alternately, the load and displacement applied to the test specimen are measured,
Controlling the dynamic loading and the static loading,
During the execution of the static loading described above, a predetermined trigger signal is transmitted multiple times.
During the static loading described above, the test specimen is imaged,
A test method comprising acquiring the measurement results of the test and an image of the test object in response to the reception of the trigger signal, and recording them synchronously in a storage device.