Material testing machine and control method for material testing machine

Abstract

During material testing, the user can determine whether the shape of the output waveform is appropriate. [Solution] The fatigue testing machine 1 is a fatigue testing machine that performs a fatigue test to measure the mechanical properties of a test piece TP by applying a test force F to the test piece TP, and comprises a hydraulic actuator 18 that applies a test force F to the test piece TP, a generation unit 511 that generates a sinusoidal input waveform W1 that is a target value of the test force F, a detection unit 513 that detects the test force F applied by the hydraulic actuator 18 to the test piece TP, and a calculation unit 514 that calculates the strain rate HD of the output waveform W2 that is the detection result of the detection unit 513 while the fatigue test is being performed.

Description

Technical Field

[0001] The present invention relates to a material testing machine and a control method for a material testing machine.

Background Art

[0002] Conventionally, various techniques related to tester characteristics are known in material testing machines such as fatigue testing machines For example, Patent Document 1 discloses an experimental execution step of changing the frequency of the displacement applied to a test piece of a fatigue testing machine and performing an experiment to obtain the relationship between the frequency and the amplitude corresponding to the displacement, and a curve approximation step of calculating at least one of a maximum speed curve and a maximum acceleration curve that approximates the relationship between the frequency and the amplitude. The maximum speed curve represents a curve in which the maximum speed corresponding to the displacement is constant, and the maximum acceleration curve represents a curve in which the maximum acceleration corresponding to the displacement is constant.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in conventional fatigue testing machines such as the fatigue testing machine described in Patent Document 1, a delay (phase difference) occurs between the input waveform and the output waveform, but it can only be confirmed visually, and it was difficult to compare the waveform shape of the output waveform with the waveform shape of the input waveform during the execution of the fatigue test. [[ID=T39]]Also, for example, during the execution of a fatigue test, it was impossible to confirm whether the degree of deviation of the output waveform from the ideal state was within the range desired by the user.

[0005] This invention has been made in view of these circumstances, and aims to provide a material testing machine that allows the user to quantitatively grasp the degree of deviation of the output waveform from a sine wave (corresponding to an example of an ideal state) while performing a material test, and a display control method for the material testing machine. [Means for solving the problem]

[0006] A material testing machine according to a first aspect of the present invention is a material testing machine that performs a material test to measure the mechanical properties of a test specimen by applying a load to the specimen, comprising: a load mechanism for applying a load to the specimen; an output unit that generates a sinusoidal input waveform indicating a target value of the load and outputs an instruction signal to the load mechanism based on the target value; a detection unit for detecting the load applied by the load mechanism to the specimen; and a calculation unit that calculates the strain rate of the output waveform indicating the detection result of the detection unit while the material test is being performed.

[0007] A control method for a material testing machine according to a second aspect of the present invention is a control method for a material testing machine that includes a load mechanism for applying a load to a test specimen and performs a material test for measuring the mechanical properties of the test specimen, and includes an output step of generating a sinusoidal input waveform indicating a target value of the load and outputting an instruction signal to the load mechanism based on the target value; a detection step of detecting the load applied by the load mechanism to the test specimen; and a calculation step of calculating the strain rate of the output waveform indicating the detection result in the detection step while the material test is being performed. [Effects of the Invention]

[0008] The material testing machine according to the first aspect of the present invention and the control method for the material testing machine according to the second aspect of the present invention calculate the strain rate of the output waveform while performing a material test. Therefore, the degree of deviation of the output waveform from a sine wave can be quantitatively determined while performing material testing. [Brief explanation of the drawing]

[0009] [Figure 1]This figure shows an example of the configuration of a fatigue testing machine according to this embodiment. [Figure 2] This diagram shows an example of the configuration of the main control unit. [Figure 3] This is a screenshot showing an example of a strain rate display screen. [Figure 4] This is a screenshot showing another example of the strain rate display screen. [Figure 5] This flowchart shows an example of processing performed by the main control unit. [Modes for carrying out the invention]

[0010] First, the inventors will explain below how they came to identify the "problem that the invention aims to solve." In feedback systems used to control material testing machines, there is a discrepancy between the input waveform (target waveform) and the output waveform (detected waveform). For example, the output waveform lags behind (is in phase) the input waveform. Also, for example, if the input waveform is a sine wave, the output waveform will deviate from the sine wave.

[0011] In conventional material testing machine applications, it was not known that users had requests regarding the degree of deviation of the output waveform from a sine wave. However, the inventors realized that in fields such as dynamic characteristic testing of shock absorbers, there is a demand to confirm the degree of deviation of the output waveform from a sine wave, which had previously been ignored. This is because, in fields such as dynamic characteristic testing of shock absorbers, the influence of the degree of deviation of the output waveform from a sine wave on the test results cannot be ignored.

[0012] On the other hand, in order to evaluate the degree of deviation of the output waveform from a sine wave, it is envisioned that the input waveform and the output waveform be displayed on a single screen, for example, with time on the horizontal axis. In this way, the degree of deviation of the output waveform from a sine wave can be judged to some extent by visual inspection. However, in the feedback system used to control material testing machines, a delay (phase difference) occurs between the input waveform and the output waveform, making accurate visual judgment difficult.

[0013] In order to solve the above problems, in the feedback system used for controlling a material testing machine, it is also required to quantitatively evaluate the degree of deviation from a sine wave of an output waveform. The inventors have found that, as a method for quantitatively evaluating the degree of deviation from a sine wave of an output waveform, calculating the "strain rate" of the output waveform. Note that the "strain rate" has been conventionally used, for example, when evaluating the characteristics of an electric circuit such as an amplifier circuit, but there has been no idea of applying it to a material testing machine.

[0014] Hereinafter, this embodiment will be described with reference to the drawings.

[0015] [1. Configuration of Fatigue Testing Machine] FIG. 1 is a diagram showing an example of the configuration of a fatigue testing machine 1 according to this embodiment. The fatigue testing machine 1 of this embodiment performs a fatigue test for measuring the mechanical properties of a sample by repeatedly applying a test force F to a test piece TP. The test force F is, for example, a tensile force. The fatigue testing machine 1 includes a testing machine main body 2 that repeatedly applies a test force F to a test piece TP, which is a material to be tested, to perform a fatigue test, a control unit 3 that controls the fatigue test operation by the testing machine main body 2, and a display mechanism 60. Note that the test force F corresponds to an example of "load". The test piece TP corresponds to an example of "specimen". The fatigue testing machine 1 corresponds to an example of "material testing machine".

[0016] As shown in FIG. 1, the testing machine main body 2 forms a load frame on a base 26 by a pair of columns 28 and 29 and a yoke 13, and a crosshead 10 is fixed to the columns 28 and 29.

[0017] A hydraulic actuator 18 is disposed on the base 26, and a lower gripper 22 for gripping the lower end portion of the test piece TP is attached to a piston rod 181 of the hydraulic actuator 18. Further, an upper gripper 21 for gripping the upper end portion of the test piece TP is attached to the crosshead 10 via a load cell 14.

[0018] The hydraulic actuator 18's piston rod 181 extends and retracts, controlled by a servo valve 20, which regulates the direction and volume of the pressurized oil. As a result, the distance between the upper grip 21 and the lower grip 22 expands and contracts, and a test force F is applied to the test piece TP fixed between the upper grip 21 and the lower grip 22. The stroke of the hydraulic actuator 18, i.e., the displacement of the test piece TP, is detected by a differential transformer 19 attached to the hydraulic actuator 18. The hydraulic actuator 18 corresponds to an example of a "load mechanism".

[0019] The load cell 14 is a sensor that measures the test force F, which is the tensile load applied to the test specimen TP, and outputs a test force measurement signal SG1 to the control unit 3. The differential transformer 19 is a sensor that measures the displacement of the test specimen TP and outputs a displacement measurement signal SG2 corresponding to the displacement to the control unit 3.

[0020] An elongation sensor 15 is placed on the test specimen TP. For example, a dumbbell-shaped test specimen TP with a constricted center is used. The elongation sensor 15 is a sensor that measures the amount of elongation E by measuring the distance between a pair of gauge marks on the test specimen TP and outputs an elongation measurement signal SG3 to the control unit 3. The pair of gauge marks are placed at the top and bottom of the constricted region of the test specimen TP.

[0021] The control unit 3 comprises a signal input / output device 40 and a main control device 50. The signal input / output device 40 constitutes an input / output interface circuit that transmits and receives signals to and from the test machine body 2, and in this embodiment, it includes a first sensor amplifier 42, a second sensor amplifier 43, a third sensor amplifier 45, and a servo amplifier 44.

[0022] The first sensor amplifier 42 is an amplifier that amplifies the test force measurement signal SG1 output by the load cell 14 to generate a test force detection value FD, and outputs the test force detection value FD to the main control device 50. The second sensor amplifier 43 amplifies the displacement measurement signal SG2 output by the differential transformer 19 and outputs a displacement measurement signal A3 indicating the detected displacement value XD as a digital signal to the main control device 50. The third sensor amplifier 45 is an amplifier that amplifies the elongation measurement signal SG3 output by the elongation sensor 15 to generate an elongation detection value ED, and outputs the elongation detection value ED to the main control device 50. The servo amplifier 44 is a device that controls the servo valve 20 according to the control of the main control unit 50. The main control unit 50 calculates an instruction value dX based on, for example, the test force detection value FD and the test force target value TF, and transmits an instruction signal A4 indicating the instruction value dX to the servo valve 20.

[0023] The main control unit 50 controls the operation of the testing machine body 2 based on user input. The main control unit 50 also causes the testing machine body 2 to perform fatigue tests. In this embodiment, "user" includes the operator who operates the testing machine body 2.

[0024] The main control unit 50 includes a computer that has an interface circuit between a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive) and a signal input / output device 40, as well as various electronic circuits. Furthermore, an A / D converter is provided in the interface circuit with the signal input / output device 40, and the analog test force measurement signal SG1, displacement measurement signal SG2, and elongation measurement signal SG3 are converted into digital signals by the A / D converter.

[0025] The display mechanism 60 is connected to the main control unit 50 in a communicative manner and displays various information. The display mechanism 60 also includes a display 61 such as an LCD (Liquid Crystal Display), and the display mechanism 60 displays various images on the display 61.

[0026] [2. Configuration of the main control unit] Next, the configuration of the main control unit 50 will be described with reference to Figure 2. Figure 2 is a diagram showing an example of the configuration of the main control unit 50 according to this embodiment. The main control unit 50 is composed of, for example, a personal computer. The main control unit 50 comprises a control unit 50A and an FPGA (Field Programmable Gate Array) 53. The control unit 50A also comprises a processor 51 and memory 52. The processor 51 consists of a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), and other components. Memory 52 consists of ROM (Read Only Memory), RAM (Random Access Memory), etc. Memory 52 stores the control program 521.

[0027] The main control unit 50 is not limited to a personal computer; it may be composed of one or more appropriate circuits, such as integrated circuits (IC chips or LSIs). Furthermore, the main control unit 50 may be composed of, for example, a tablet terminal or a smartphone.

[0028] As shown in Figure 2, the control unit 50A includes a generation unit 511, a test execution unit 512, a detection unit 513, a calculation unit 514, a determination unit 515, a display control unit 516, and a detection result storage unit 522. Specifically, the processor 51 functions as a generation unit 511, a test execution unit 512, a detection unit 513, a calculation unit 514, a determination unit 515, and a display control unit 516 by executing a control program 521 stored in the memory 52. ​​Furthermore, the processor 51 causes the memory 52 to function as a detection result storage unit 522 by executing a control program 521 stored in the memory 52.

[0029] The detection result storage unit 522 stores the test force detection value FD and the strain rate HD in association with each other. The test force detection value FD is detected by the detection unit 513 and stored in the detection result storage unit 522 by the detection unit 513. The strain rate HD is calculated by the calculation unit 514 and stored in the detection result storage unit 522 by the calculation unit 514.

[0030] The generation unit 511 generates a sinusoidal input waveform W1 that represents the target value of the test force F, which is the target value of the test force. The generation unit 511 may also generate a sinusoidal input waveform W1 that represents the target value of the elongation E, which is the target value of the elongation. The generation unit 511 may also generate a sinusoidal input waveform W1 that represents the target value of the displacement, which is the target value of the displacement.

[0031] The test execution unit 512 performs a fatigue test. The test execution unit 512 controls the testing machine body 2, for example, by PID (Proportional-Integral-Differential) control, so that the detected test force value FD matches the target test force value TF. For example, the test execution unit 512 controls the hydraulic actuator 18 so that the test force F becomes the target test force value TF, based on the detected test force value FD. In other words, the test execution unit 512 calculates an instruction value dX based on the detected test force value FD and the target test force value TF, and transmits an instruction signal A4 indicating the instruction value dX to the servo valve 20 of the hydraulic actuator 18.

[0032] In this embodiment, we describe a case in which the test execution unit 512 controls the hydraulic actuator 18 so that the test force detection value FD becomes the test force target value TF, but the embodiment is not limited thereto. The test execution unit 512 may also control the hydraulic actuator 18 so that the elongation detection value ED becomes the elongation target value TE, which is the target value of the elongation amount E. Alternatively, the test execution unit 512 may also control the hydraulic actuator 18 so that the displacement detection value XD becomes the displacement target value, which is the target value of the displacement amount.

[0033] The test execution unit 512 terminates the execution of the fatigue test by the testing machine body 2 when it applies a test force F to the test specimen TP that corresponds to the number of repetitions NR specified in the test conditions. The number of repetitions NR is the number of times the test force F is repeatedly applied. The number of repetitions NR is, for example, 10 3 10 times 8 This is the number of cycles. One cycle of the number of repetitions NR corresponds to the change in the test force F in one cycle W of the input waveform W1. Furthermore, the test execution unit 512 terminates the fatigue test by the testing machine body 2 if the test specimen TP breaks during the period in which the test specimen TP is being subjected to a test force F corresponding to the number of repetitions NR specified in the test conditions.

[0034] The detection unit 513 acquires the test force detection value FD. The test force detection value FD is the detected value of the test force F applied by the testing machine body 2 to the test piece TP. The detection unit 513 acquires the test force detection value FD output from the load cell 14 via the first sensor amplifier 42.

[0035] The calculation unit 514 calculates the strain rate HD of the output waveform W2, which shows the detection result of the detection unit 513, while the testing machine body 2 is performing a fatigue test. The output waveform W2 is, for example, the output waveform W2 of the test force detection value FD. The calculation unit 514 applies an FFT (Fast Fourier Transform) to the output waveform W2 of the test force detection value FD to calculate the strain rate HD.

[0036] The calculation unit 514 calculates the distortion rate HD each time the detection unit 513 detects an output waveform W2 corresponding to a sine wave with one period W. In this case, the calculation unit 514 generates a virtual output waveform W2 that repeats the output waveform W2 corresponding to a sine wave with one period W a number of times corresponding to a predetermined number M. Then, the calculation unit 514 performs an FFT on the virtual output waveform W2 and calculates the distortion rate HD. The predetermined number M is, for example, 100. In this case, the strain rate HD can be calculated accurately, and the strain rate HD can be calculated frequently.

[0037] Furthermore, the calculation unit 514 may calculate the distortion rate HD each time the detection unit 513 detects an output waveform W2 corresponding to a predetermined number M of periods W. The predetermined number M is, for example, 10. Alternatively, the predetermined number M may be, for example, 100. The larger the predetermined number M, the more accurately the strain rate HD can be calculated. The smaller the predetermined number M, the more frequently the strain rate HD can be calculated.

[0038] The calculation unit 514 causes the FPGA 53 to perform an FFT to calculate the RMS values ​​of the fundamental wave and harmonics of the output waveform W2 of the test force detection value FD. The calculation unit 514 also calculates the strain rate HD using the following equation (1). HD=(E2 2 +E3 2 +···+EN 2 ) 1 / 2 / E1×100 (1) The RMS value E1 represents the RMS value of the fundamental wave. The RMS value E2 represents the RMS value of the second harmonic. The RMS value E3 represents the RMS value of the third harmonic. The RMS value EN represents the RMS value of the Nth harmonic. The coefficient N is, for example, a value between 10 and 100. FPGA 53 constitutes a part of the calculation unit 514. Furthermore, FPGA53 corresponds to an example of a "PLD (Programmable Logic Device)".

[0039] The determination unit 515 determines that the control accuracy of the hydraulic actuator 18 is poor if the strain rate HD is greater than or equal to a preset threshold TH. The threshold TH is, for example, 5%. The threshold TH may also be, for example, 10%. The threshold TH is set, for example, according to the control accuracy required by the user.

[0040] The display control unit 516 displays the strain rate HD on the display 61 while the fatigue test is being performed. In addition, the display control unit 516 updates the strain rate HD displayed on the display 61 each time the calculation unit 514 calculates the strain rate HD. Furthermore, the display control unit 516 displays the input waveform W1 and the output waveform W2 as graphs on the display 61. The display control unit 516 also displays the determination result of the determination unit 515 on the display 61. The distortion rate HD, input waveform W1, and output waveform W2 will be further explained with reference to Figures 3 and 4.

[0041] [3.Display screen] Next, with reference to Figures 3 and 4, the strain rate display screen that the display control unit 516 displays on the display 61 will be described. Figure 3 is a screen diagram showing an example of the strain rate display screen 700. The strain rate display screen 700 is displayed on the display 61 of the display mechanism 60 by the display control unit 516, for example. In Figure 3, for example, the strain rate HD is 0.5%.

[0042] As shown in Figure 3, the strain rate display screen 700 includes a graph display unit 701 and a strain rate display unit 702. The graph display unit 701 displays graphs G11 and G21. Graph G11 corresponds to an example of graph G1 showing the input waveform W1. Graph G21 corresponds to an example of graph G2 showing the output waveform W2.

[0043] The graph display unit 701 displays time T as the horizontal axis for graphs G11 and G21. The graph display unit 701 also displays the test force F as the vertical axis for graphs G11 and G21. As shown in graph G11, the input waveform W1 is a sine wave. As shown in graph G21, the output waveform W2 is a waveform that approximates a sine wave. The display control unit 516 updates graphs G11 and G21 at predetermined intervals. The predetermined interval is, for example, 1 second.

[0044] The strain rate display unit 702 displays the most recent strain rate HD calculated by the calculation unit 514. The strain rate display unit 702 displays "Strain rate: 0.5%", indicating that the most recent strain rate HD1 is "0.5%". In this embodiment, the calculation unit 514 calculates the distortion rate HD each time the detection unit 513 detects an output waveform W2 corresponding to a sine wave with one period W. Therefore, the distortion rate HD1 displayed in the distortion rate display unit 702 represents the distortion rate HD of the output waveform W2 with one period W on the right side of the graph G21 shown in Figure 3.

[0045] Figure 4 is a screen diagram showing another example of the strain rate display screen 710. The strain rate display screen 710 is displayed on the display 61 of the display mechanism 60 by, for example, the display control unit 516. In Figure 4, for example, the strain rate HD is 5.7%.

[0046] As shown in Figure 4, the strain rate display screen 710 includes a graph display unit 711 and a strain rate display unit 712. The graph display unit 711 displays graphs G12 and G22. Graph G12 corresponds to an example of graph G1 showing the input waveform W1. Graph G22 corresponds to an example of graph G2 showing the output waveform W2.

[0047] The graph display unit 711 displays time T as the horizontal axis for graphs G12 and G22. The graph display unit 711 also displays the test force F as the vertical axis for graphs G12 and G22. As shown in graph G12, the input waveform W1 is a sine wave. As shown in graph G22, the output waveform W2 is a waveform that deviates significantly from a sine wave compared to the output waveform W2 shown in graph G21 in Figure 3. The display control unit 516 updates graphs G12 and G22 at predetermined intervals. The predetermined interval is, for example, 1 second.

[0048] The strain rate display unit 712 displays the most recent strain rate HD calculated by the calculation unit 514. The strain rate display unit 702 displays "Strain rate: 5.7%", indicating that the most recent strain rate HD2 is "5.7%". In this embodiment, the calculation unit 514 calculates the distortion rate HD each time the detection unit 513 detects an output waveform W2 corresponding to a sine wave with one period W. Therefore, the distortion rate HD2 displayed in the distortion rate display unit 712 represents the distortion rate HD of the output waveform W2 with one period W on the right side of the graph G22 shown in Figure 4.

[0049] If the threshold TH is, for example, 5%, the determination unit 515 determines that the control accuracy of the hydraulic actuator 18 is poor. As described above, in Figure 4, the strain rate HD is 5.7%, so the determination unit 515 determines that the control accuracy of the hydraulic actuator 18 is poor. Therefore, the display control unit 516 flashes a text image, for example, "Strain rate: 5.7%", in red.

[0050] [4. Processing by the main control unit] Next, with reference to Figure 5, the processes executed by the main control unit 50 will be described. Figure 5 is a flowchart showing an example of the processes performed by the main control unit 50. As shown in Figure 5, first, in step S101, the generation unit 511 generates a sinusoidal input waveform W1 that represents the target value of the test force F, which is the target value of the test force F. Next, in step S103, the test execution unit 512 starts the fatigue test. The test execution unit 512 starts the fatigue test, for example, based on an operation from the user. Next, in step S105, the detection unit 513 acquires the test force detection value FD output from the load cell 14 via the first sensor amplifier 42. The display control unit 516 also displays the input waveform W1 and the output waveform W2 on the display 61.

[0051] Next, in step S107, the calculation unit 514 determines whether or not the detection unit 513 has detected an output waveform W2 corresponding to a sine wave with one period W. If the calculation unit 514 determines that the detection unit 513 has not detected an output waveform W2 corresponding to a sine wave with one period W (step S107; NO), the process enters a standby state. If the calculation unit 514 determines that the detection unit 513 has detected an output waveform W2 corresponding to a sine wave with one period W (step S107; YES), the process proceeds to step S109. Then, in step S109, the calculation unit 514 generates a virtual output waveform W2 that is repeated a number of times corresponding to a predetermined number M, which corresponds to a sine wave with one period W.

[0052] Next, in step S111, the calculation unit 514 causes the FPGA 53 to perform an FFT on the virtual output waveform W2 to obtain the RMS values ​​E1 to EN of the fundamental wave and harmonics of the output waveform W2. Next, in step S113, the calculation unit 514 calculates the distortion rate HD from the fundamental wave and the effective values ​​E1 to EN of the harmonics of the output waveform W2. The display control unit 516 displays the distortion rate HD on the display 61. Next, in step S115, the determination unit 515 determines whether the strain rate HD is equal to or greater than a preset threshold TH.

[0053] If the determination unit 515 determines that the strain rate HD is not equal to or greater than the threshold TH (step S115; NO), the process proceeds to step S119. If the determination unit 515 determines that the strain rate HD is equal to or greater than the threshold TH (step S115; YES), the process proceeds to step S117. Then, in step S117, the determination unit 515 determines that the control accuracy of the hydraulic actuator 18 is poor. The display control unit 516 then notifies that the control accuracy of the hydraulic actuator 18 is poor. For example, the display control unit 516 flashes the strain rate HD in red on the display 61. Next, in step S119, the test execution unit 512 determines whether or not to terminate the execution of the fatigue test. If the test execution unit 512 determines that the fatigue test should not be terminated (step S119; NO), the process returns to step S105. If the test execution unit 512 determines that the fatigue test should be terminated (step S119; YES), the process is then terminated.

[0054] Step S101 corresponds to an example of a "generation step". Step S105 corresponds to an example of a "detection step". Steps S109, S111, and S113 correspond to an example of a "calculation step".

[0055] [5. Modes and Effects] Those skilled in the art will understand that the above-described embodiment is a specific example of the following embodiments.

[0056] (Section 1) The material testing machine according to this embodiment is a material testing machine that performs a material test to measure the mechanical properties of a test specimen by applying a load to the specimen, and comprises a load mechanism for applying a load to the specimen, a generation unit for generating a sinusoidal input waveform indicating a target value of the load, a detection unit for detecting the load applied to the specimen by the load mechanism, and a calculation unit for calculating the strain rate of the output waveform indicating the detection result of the detection unit while the material test is being performed.

[0057] According to the material testing machine described in paragraph 1, the distortion rate of the output waveform is calculated while the material test is being performed. Therefore, during material testing, the user can quantitatively determine the degree of deviation of the output waveform from a sine wave based on the distortion rate of the output waveform. This improves user convenience.

[0058] (Section 2) In the material testing machine described in paragraph 1, the calculation unit performs an FFT on the output waveform to calculate the strain rate.

[0059] According to the material testing machine described in paragraph 2, the output waveform is subjected to FFT and the strain rate is calculated. Therefore, the distortion rate can be calculated accurately. Consequently, the user can quantitatively and accurately grasp the degree of deviation of the output waveform from a sine wave.

[0060] (Section 3) In the material testing machine described in paragraph 2, the calculation unit is equipped with a PLD, and the PLD performs the FFT on the output waveform.

[0061] According to the material testing machine described in paragraph 3, the calculation unit is equipped with a PLD, and the PLD performs the FFT on the output waveform. Therefore, because the PLD performs an FFT on the output waveform, the FFT processing of the output waveform can be completed in a shorter time compared to when the FFT is performed by software. Consequently, the strain rate can be calculated accurately while the material test is being performed. As a result, the strain rate can be calculated almost in real time.

[0062] (Section 4) In the material testing machine described in any one of paragraphs 1 to 3, the material test is a fatigue test, and the machine includes a display control unit that displays the strain rate on a display while the fatigue test is being performed.

[0063] According to the material testing machine described in paragraph 4, the strain rate is displayed on the display while the fatigue test is being performed. Therefore, during the fatigue test, the user can visually observe the distortion rate of the output waveform. Thus, the distortion rate of the output waveform can be easily determined. As a result, user convenience can be improved.

[0064] (Section 5) In the material testing machine described in paragraph 4, each time the calculation unit calculates the strain rate, the display control unit updates the strain rate displayed on the display.

[0065] According to the material testing machine described in paragraph 5, each time the calculation unit calculates the strain rate, the display control unit updates the strain rate displayed on the display. Therefore, the distortion rate displayed on the screen can be updated as frequently as possible. Consequently, the user can view the distortion rate of the output waveform in near real-time.

[0066] (Section 6) In the material testing machine described in paragraph 4, the display control unit displays the input waveform and the output waveform as a graph on the display.

[0067] According to the material testing machine described in paragraph 6, the display control unit displays the input waveform and the output waveform as a graph on the display. Therefore, the user can compare the graph of the input waveform with the graph of the output waveform, and compare the distortion rate of the output waveform. Thus, the user can compare the degree of deviation of the output waveform graph from a sine wave with the distortion rate of the output waveform.

[0068] (Section 7) The material testing machine described in paragraph 4 includes a determination unit that determines that the control accuracy of the loading mechanism is poor when the strain rate is above a preset threshold, and the display control unit displays the determination result of the determination unit on the display.

[0069] According to the material testing machine described in paragraph 7, if the strain rate is above a preset threshold, it is determined that the control accuracy of the loading mechanism is poor, and the determination result is displayed on the display. Therefore, by setting the threshold to an appropriate value, it is possible to properly determine whether or not the control accuracy of the load mechanism is poor. Furthermore, since the determination result is displayed on the screen, the user can visually confirm whether or not the control accuracy of the load mechanism is poor. Thus, user convenience can be improved.

[0070] (Section 8) The control method for a material testing machine according to this embodiment is a control method for a material testing machine that is equipped with a load mechanism for applying a load to a test specimen and performs a material test to measure the mechanical properties of the test specimen, and includes a generation step of generating a sinusoidal input waveform that indicates a target value of the load, a detection step of detecting the load applied to the test specimen by the load mechanism, and a calculation step of calculating the strain rate of the output waveform that indicates the detection result in the detection step while the material test is being performed.

[0071] The display control method for the material testing machine described in paragraph 8 produces the same effects and benefits as the material testing machine described in paragraph 1.

[0072] [6. Other Embodiments] It should be noted that the fatigue testing machine 1 according to this embodiment is merely an example of a material testing machine according to the present invention, and can be arbitrarily modified and applied without departing from the spirit of the present invention.

[0073] In this embodiment, the case where the material testing machine is a fatigue testing machine 1 is described, but the embodiment is not limited to this. The material testing machine can perform a material test in which it applies a load to the test specimen and measures the mechanical properties of the specimen. For example, the material testing machine may be a tensile testing machine, a compression testing machine, a bending testing machine, or a torsion testing machine.

[0074] Furthermore, this embodiment describes the case where the load applied by the fatigue testing machine 1 to the test specimen TP is the test force F, but the embodiment is not limited to this. The load applied by the fatigue testing machine 1 to the test specimen TP may be, for example, the elongation amount E of the test specimen TP, or the displacement of the test specimen TP.

[0075] Furthermore, although this embodiment describes the case where the test specimen is test piece TP, the embodiment is not limited to this. The test specimen may be a vehicle part such as a shock absorber.

[0076] Furthermore, although this embodiment describes a case in which the fatigue testing machine 1 is equipped with a main control device 50 and a display mechanism 60 as separate components, the embodiment is not limited to this. For example, the main control device 50 and the display mechanism 60 may be configured as an integrated unit.

[0077] Furthermore, although this embodiment describes a case where the main control device 50 comprises a generation unit 511, a test execution unit 512, a detection unit 513, a calculation unit 514, a determination unit 515, a display control unit 516, and a detection result storage unit 522, the embodiment is not limited thereto. For example, the display mechanism 60 may comprise at least one of the generation unit 511, the test execution unit 512, the detection unit 513, the calculation unit 514, the determination unit 515, the display control unit 516, and the detection result storage unit 522. For example, the display mechanism 60 may comprise a display control unit 516.

[0078] In this embodiment, the case in which the main control unit 50 includes an FPGA is described, but the embodiment is not limited to this. The main control unit 50 may include, for example, a PLD (Programmable Logic Device). The main control unit 50 may also include, for example, a CPLD (Complex Programmable Logic Device), or the main control unit 50 may include, for example, a SoC (System-on-a-Chip)-FPGA.

[0079] Furthermore, the functional units shown in Figure 2 represent functional configurations, and the specific implementation form is not particularly limited. In other words, it is not necessarily required that hardware corresponding to each functional unit be implemented individually, and it is certainly possible to have a configuration in which a single processor executes a program to realize the functions of multiple functional units. Also, in the above embodiment, some of the functions realized by software may be realized by hardware, or conversely, some of the functions realized by hardware may be realized by software.

[0080] Furthermore, the processing units in the flowchart shown in Figure 5 are divided according to their main processing content in order to make the processing of the main control device 50 easier to understand. The way the processing units are divided and the names of the processing units shown in the flowchart in Figure 5 do not limit the process; it is possible to divide the process into even more processing units depending on the processing content, or to divide it so that one processing unit contains even more processing. Also, the processing order in the flowchart above is not limited to the example shown.

[0081] Furthermore, as explained with reference to Figure 2, in this embodiment, the processor 51 of the main control unit 50 is instructed to execute the control program 521 stored in the memory 52. ​​This control program 521 can also be recorded on a recording medium that is readable by a computer. A magnetic, optical, or semiconductor memory device can be used as the recording medium. Specifically, these include portable or fixed recording media such as flexible disks, HDDs, CD-ROMs (Compact Disk Read Only Memory), DVDs, Blu-ray® Discs, magneto-optical disks, flash memory, and card-type recording media. Furthermore, the recording medium may be a non-volatile storage device such as RAM, ROM, or HDD, which is an internal storage device provided by the main control unit 50. Alternatively, the control program 521 may be stored in a server device or the like, and the control program 521 may be downloaded from the server device to the main control unit 50. [Explanation of Symbols]

[0082] 1. Fatigue testing machine (material testing machine) 2. Test machine body 3. Control Unit 14 load cells 15. Stretch Sensor 18. Hydraulic actuator (load mechanism) 19 Differential transformer 20 Servo valves 40 Signal Input / Output Devices 50 Main control unit 50A Control Unit 51 processors 511 Generation part 512 Test Execution Unit 513 Detection unit 514 Calculation Unit 515 Judgment section 52 memory 521 Control Program 522 Detection result storage unit 53 FPGA (part of the calculation unit, PLD) 60 Display mechanism 61 displays E1-EN RMS value F Test force (load) FD test force detection value G1, G11, G12 graphs HD, HD1, HD2 distortion rate SG1 Test force measurement signal TF Test Force Target Value TH threshold TP test specimen (test sample) W1 Input Waveform W2 Output Waveform

Claims

1. A material testing machine that performs a material test by applying a load to a test specimen and measuring the mechanical properties of the specimen, A loading mechanism for applying a load to the specimen, A generation unit that generates a sinusoidal input waveform indicating the target value of the load, A detection unit for detecting the load applied by the load mechanism to the test specimen, During the execution of the material test, a calculation unit calculates the distortion rate of the output waveform showing the detection result of the detection unit, A materials testing machine equipped with the following features.

2. The calculation unit performs an FFT on the output waveform and calculates the distortion rate. The material testing machine according to claim 1.

3. The calculation unit includes a PLD, The PLD applies the FFT to the output waveform. The material testing machine according to claim 2.

4. The aforementioned material test is a fatigue test, The system includes a display control unit that displays the strain rate on a display while the fatigue test is being performed. A material testing machine according to any one of claims 1 to 3.

5. Each time the calculation unit calculates the strain rate, the display control unit updates the strain rate displayed on the display. The material testing machine according to claim 4.

6. The display control unit displays the input waveform and the output waveform as a graph on the display. The material testing machine according to claim 4.

7. The system includes a determination unit that determines that the control accuracy of the load mechanism is poor if the strain rate is above a preset threshold. The display control unit displays the determination result of the determination unit on the display. The material testing machine according to claim 4.

8. A control method for a material testing machine that is equipped with a loading mechanism for applying a load to a test specimen and performs a material test to measure the mechanical properties of the test specimen, A generation step of generating a sinusoidal input waveform that represents the target value of the load, A detection step for detecting the load applied by the load mechanism to the test specimen, During the execution of the material test, a calculation step is performed to calculate the strain rate of the output waveform showing the detection result in the detection step, A control method for a material testing machine, including the following.

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