Metal fatigue testing machine and fatigue testing method

Abstract

The invention discloses a metal fatigue testing machine and a fatigue testing method, which can test the bending fatigue strength of a rectangular thin-plate metal specimen. By clamping the two ends of the specimen and applying a load, under the action of an alternating load, the stress level of the specimen is lower than the yield limit of the material, and after a long period of repeated stress cycles, the bending fatigue strength of the rectangular thin-plate metal specimen is tested. The load and bending stress can be adjusted, and the frequency can be adjusted at will. It saves electricity and does not require a water source, and has a low cost of use, and the power of a general motor is only a few kilowatts or a few hundred watts. It can realize high-load, high-efficiency, high-precision, and low-consumption experiments, thereby shortening the experimental time and reducing the experimental cost. The parts are less damaged and have a long service life, and the motor that is almost maintenance-free can be used uninterruptedly for a long time. The installation and maintenance are simple and convenient, and there is no need to frequently stop the machine to replace hydraulic oil and the like, and the subsequent motor maintenance cost is almost zero, and the maintenance cost is low. It uses electric energy, which is clean and pollution-free and stable.

Description

Technical Field

[0001] The invention belongs to the field of measurement technology, and relates to a metal fatigue testing machine and a fatigue testing method, and in particular to a rectangular thin plate metal specimen testing machine and a fatigue testing method; and is particularly suitable for testing the fatigue strength of rectangular thin plate metal specimens. Background Art

[0002] The fatigue testing machine is used to measure the fatigue properties, fatigue life, pre-crack and crack propagation tests of metals, alloy materials and their components under tension, compression or tension-compression alternating loads at room temperature.

[0003] Some commonly used test methods for fatigue testing of metal materials usually include single-point fatigue test method, lifting method, high-frequency vibration test method, ultrasonic fatigue test method, infrared thermal imaging technology fatigue test method, metal torsional stress fatigue test method, etc.

[0004] GB / T12443 "Metal Room Temperature Torsional Stress Fatigue Test Method", the working part of the specimen is cylindrical or funnel-shaped; the cross-section of the working part of the specimen is circular; the existing fatigue testing machines can test metal and alloy components such as operating joints, fasteners, and spiral moving parts, but cannot accurately test the bending fatigue strength of rectangular thin plate metal specimens.

[0005] Existing metal torsional stress fatigue testing machines include high-frequency fatigue testing machines and low-frequency fatigue testing machines.

[0006] The high frequency fatigue testing machine works according to the principle of electromagnetic resonance, relying on the oscillation of the electromagnet to apply the load. It is the first choice for large loads of 20KN-300KN, frequencies of 80-250Hz and short test times. The adjustable frequency is only a few fixed gears and cannot be adjusted at will.

[0007] Low-frequency fatigue testing machines work according to the principle of electro-hydraulic servo, relying on the reciprocating motion of hydraulic actuators to apply loads. The pump must run continuously and the energy cost is very high. Due to the friction of the seals of the transmission and / or servo valve, the resolution and fidelity may be limited, and the moving mass of the transmission is very high, and the system is expensive. The first choice for large loads of 5KN-1000KN and low frequencies of 0-10Hz, it is generally recommended to use it at around 10Hz. When working at 20Hz, 30Hz, the friction damage of hydraulic servo valves, seals and other components is too great, and the life of the hydraulic fatigue testing machine will be greatly affected. In multi-axis applications, due to friction, the lateral load of the transmission can also cause problems such as waveform distortion or seal wear. The hydraulic fatigue testing machine has many moving parts and seals, and the hydraulic fatigue testing machine needs to be shut down regularly for some maintenance. Oil is regarded as hazardous waste and must be replaced once contaminated; the maintenance cost is high. Summary of the invention

[0008] The invention discloses a metal fatigue testing machine and a fatigue testing method, so as to solve the problems in the prior art that the bending fatigue strength of rectangular thin plate metal specimens cannot be accurately tested, the frequency of the fatigue testing machine cannot be adjusted at will, the price is high, the parts are damaged quickly, there is leakage pollution, the testing machine has a short life, and the maintenance cost is high.

[0009] The fatigue testing machine of the present invention comprises: a base bracket, a lower clamping device, a sensor bracket, a photoelectric sensor, an upper clamping device, a connecting plate, a bearing fixing device, a connecting shaft, a bearing, a rotating disk, a motor, and a control electric box; the base bracket comprises a horizontal base, a central support platform, and symmetrical side support platforms on both sides; the horizontal base of the base bracket is provided with a slideway, and the side support platforms can adjust the spacing along the slideway; the lower clamping device, the sensor bracket, the photoelectric sensor, and the upper clamping device are each provided in two quantities and are arranged on both sides of the central support platform; the lower clamping device is fastened to the side of the side support platform of the base bracket; the sensor bracket is fastened to the upper part of the side support platform of the base bracket; the photoelectric sensor is fastened to the sensor bracket; the upper clamping device is hinged to the connecting plate Connection; the connecting plate is fastened to the bearing fixing device; the bearing is fixedly installed in the bearing fixing device; the connecting shaft passes through the bearing and is vertically fastened to the rotating disk; the motor is fastened to the central support platform of the base bracket; the motor drive shaft is fastened to the rotating disk; the control box electrically connects the photoelectric sensor and the motor; the lower clamping device clamps the lower end of the specimen, and the upper clamping device clamps the upper end of the specimen; the control box starts the motor, and the motor drives the rotating disk, driving the connecting shaft, the connecting plate and the upper clamping device to apply a uniform and stable load on the upper end of the specimen, so that the specimen produces reciprocating cyclic deflection changes; the PLC controller in the control box records experimental data such as the number of movements and time; after a long period of repeated stress cycles, the bending fatigue strength of the rectangular thin plate metal specimen can be tested.

[0010] The metal fatigue testing method of the present invention comprises:

[0011] The first step is to make the test piece; the working part is in the shape of a thin plate-like rectangle, and the cross-section of the working part of the specimen is a rectangle; the length of the test piece is equal to the sum of the span of the clamped test piece and the clamping width of the upper and lower clamping devices; according to the selected bending stress, and the deflection, width, thickness, and elastic modulus of the test piece, the single-span straight beam model is used to calculate the formula:

[0012] σ max =M / W ......Formula (1)

[0013] M=FL ......Formula (2)

[0014] W=I / (t / 2) ......Formula (3)

[0015] y max =F*L3 / (3*E*I)......Formula (4)

[0016] Where:

[0017] σ max - maximum bending stress; M- bending moment; W- bending interface coefficient; y- deflection;

[0018] F-force acting on the specimen; L-distance from the force point to the fixed end (span);

[0019] I-moment of inertia; t-specimen thickness; E-elastic modulus.

[0020] From equations (1), (2), (3) and (4), we can derive: max =1.5*E*t*y max / L 2 ,

[0021] Calculate and derive the span of the clamped specimen L = (1.5*E*t*y max / σ max ) 1 / 2 ;

[0022] The cutting direction is the length direction of the raw material, and the production quantity is an even number of pieces, not less than 10 pieces;

[0023] The second step is to clamp the specimen, and clamp two specimens for each test; mark the upper and lower positions of the clamped span on the surface of the specimen to ensure that the span after clamping is consistent with the calculation; first clamp the lower end of the specimen, insert the specimen into the middle position of the lower clamping device, keep the marked position and the upper surface of the lower clamping device in the same horizontal plane, and keep the length direction of the specimen horizontal and vertical to the upper surface of the lower clamping device, and tighten the bolts to clamp the specimen; then clamp the upper end of the specimen, insert the specimen into the middle position of the upper clamping device, keep the marked position and the upper surface of the upper clamping device in the same horizontal plane, and keep the length direction of the specimen horizontal and vertical to the upper surface of the lower clamping device, and tighten the bolts to clamp the specimen; the photoelectric sensors on both sides are located at a position where they can always detect and record the number of times the specimen moves;

[0024] The third step is to adjust the state of the fatigue testing machine; adjust the motor to the appropriate frequency, clear the running time and record the number of times;

[0025] The fourth step is experimental testing. Two specimens are tested simultaneously in each test. Turn on the switch to rotate the motor and start testing the specimen under a certain cyclic bending stress. After fatigue fracture occurs in the specimen, stop the experiment and record the data. If 50% of the specimens can withstand two million cyclic loads, and above a certain cyclic bending stress, no 50% of the specimens can withstand it, and this stress is the fatigue strength. If 50% of the specimens can withstand two million cyclic loads, increase the bending stress and repeat the above experimental steps for multiple times. If the specimen cannot meet the requirement that 50% of the specimens can withstand two million cyclic loads under a certain cyclic bending stress, reduce the bending stress and repeat the above experimental steps for multiple times to obtain the specimen fatigue strength test data.

[0026] The optimization scheme of the present invention: by adjusting the distance between the side support platforms on both sides of the base bracket, the bending stress required for the experiment can be changed, and the deflection of the test piece required for the experiment can be adjusted and changed;

[0027] The optimization scheme of the present invention is as follows: the sensor bracket is provided with a photoelectric sensor position adjustment slide, which adjusts the distance between the side support platforms on both sides of the base bracket and can adjust the specimen clamping length; when the specimen clamping length is adjusted and changed, the position of the photoelectric sensor on the sensor bracket is adjusted so that the photoelectric sensors on both sides are located at a position where they can always detect and record the number of specimen movements.

[0028] Advantages: can accurately test the bending fatigue strength of rectangular thin metal specimens; by clamping the two ends of the specimen and applying load to achieve reciprocating motion, under the action of this alternating load, the stress level of the specimen is lower than the yield limit of the material, and after a long period of repeated stress cycles, the bending fatigue strength of the rectangular thin metal specimen is tested; load, bending stress can be adjusted, frequency can be adjusted at will; power saving does not require water source, the use cost is low, the power of the general motor is only a few kilowatts or a few hundred watts; can achieve high load, high efficiency, high precision, low consumption experiments, thereby shortening the experimental time and reducing the experimental cost; parts are less damaged, long service life, almost maintenance-free motor can be used for a long time without interruption; installation and maintenance are simple and convenient, no need to stop frequently to replace hydraulic oil and other work, the subsequent motor maintenance cost is almost zero, and the maintenance cost is low; use of electricity, clean and pollution-free, safe, no need to worry about the long-term use of high-pressure oil pipes, aging of high-pressure oil leakage and causing personal safety impact; stable, will not affect the stability of equipment operation due to changes in resistance; low noise, traditional hydraulic servo must put the pump farther to reduce noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the first embodiment of the present invention;

[0030] Figure 2 It is a structural schematic diagram of a second embodiment of the present invention;

[0031] In the figure: 1 base bracket, 2 bolts, 3 lower clamping device, 4 sensor bracket, 5 test piece, 6 photoelectric sensor, 7 upper clamping device, 8 hinge, 9 connecting plate, 10 bearing fixing device, 11 connecting shaft, 12 bearing, 13 rotating disk, 14 motor, 15 cable, 16 control electric box. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] The first embodiment of the present invention tests a stainless steel plate specimen with a thickness of 3.0 mm.

[0034] like Figure 1 ,like Figure 2As shown, the fatigue testing machine of the present invention comprises: a base bracket 1, a bolt 2, a lower clamping device 3, a sensor bracket 4, a photoelectric sensor 6, an upper clamping device 7, a hinge 8, a connecting plate 9, a bearing fixing device 10, a connecting shaft 11, a bearing 12, a rotating disk 13, a motor 14, a cable 15, and a control electric box 16; the base bracket 1 has a central support platform and symmetrical side support platforms on both sides; the lower clamping device 3, the sensor bracket 4, the photoelectric sensor 6, and the upper clamping device 7 are each provided in two quantities; the base bracket 1 is placed horizontally, and the motor 14 The lower clamping device 3 and the sensor bracket 4 are symmetrical with the central support platform of the base bracket 1 and are fastened to the side support platform of the base bracket 1; the horizontal base of the base bracket 1 is provided with a slideway, and the side support platform of the base bracket 1 can adjust the side support platform distance along the slideway; the lower clamping device 3 is fastened to the side of the side support platform of the base bracket 1 by bolts 2; the sensor bracket 4 is fastened to the upper part of the side support platform of the base bracket 1; the photoelectric sensor 6 is fastened to the sensor bracket 4; The specimen 5 is in a vertical state, the lower clamping device 3 clamps the lower end of the specimen 5, and the upper clamping device 7 is equipped with bolts to clamp the upper end of the specimen 5; the hinge 8 is fastened to the upper clamping device 7 and the connecting plate 9 by bolts respectively; the connecting plate 9 is fastened to the bearing fixing device 10 by bolts; there are 3 bearings 12, which are fixedly installed in the bearing fixing device 10 respectively; the connecting shaft 11 passes through the bearing 12 and is vertically fastened to the rotating disk 13; the motor shaft is fastened to the rotating disk 13; the control electric box 16 is connected to the photoelectric sensor 6 and the motor 14 by the cable 15; the control electric box 16 starts the motor 14, and the motor shaft drives the rotating disk 13 to connect The shaft 11 rotates; the connecting shaft 11 drives the bearing fixing devices 10, the connecting plates 9, and the clamping devices 7 on the hinges 8 on both sides, thereby applying a uniform and stable load on the upper end of the specimen, causing the specimen to perform reciprocating cyclic motion, and controlling the PLC controller in the electrical box to record experimental data such as the number of movements and time; by adjusting the clamping length of the specimen 5, the bending stress required for the experiment is changed; by adjusting the distance between the side support platforms on both sides of the base bracket 1, the deflection of the specimen 5 can be adjusted; the position of the photoelectric sensor 6 is adjusted by the sensor bracket 4; after a long period of repeated stress cycles, the bending fatigue strength of the rectangular thin plate metal specimen can be tested.

[0035] The first step is to make the test piece; according to the selected bending stress, the clamping length is calculated, and the deflection, width, thickness, elastic modulus, and bending stress of the test piece are set. The span of the clamped test piece can be calculated as L = (1.5*E*t*y max / σ max ) 1 / 2, 3.0mm thick, 25mm wide specimen, deflection 25mm, 500Mpa bending stress applied, the calculated span of the clamped specimen is 212mm, plus the clamping width of the lower clamping device 90mm, it can be concluded that the required length of the intercepted specimen is 302mm, so only the specimen with the size of 302*25*3.0mm needs to be made. Generally, the interception direction is the length direction of the raw material, and 10 pieces are made.

[0036] The second step is to clamp the specimen; mark the upper and lower positions of the clamped span on the surface of the specimen to ensure that the span after clamping is consistent with the calculation. First clamp the lower end of the specimen, insert the specimen into the middle position of the lower clamping device, keep the marked position at the same level as the upper surface of the lower clamping device, and keep the length direction of the specimen horizontal and vertical to the upper surface of the lower clamping device, and tighten the bolts to clamp the specimen. Clamp the upper end of the specimen, insert the specimen into the middle position of the upper clamping device, keep the marked position at the same level as the upper surface of the upper clamping device, and keep the length direction of the specimen horizontal and vertical to the upper surface of the lower clamping device, and tighten the bolts to clamp the specimen. The specimen needs to be clamped on both sides of the testing machine. The specimen movement deflection is adjusted by adjusting the distance between the two side legs of the base bracket 1, that is, the distance when the upper end of the specimen moves from the horizontal vertical position to the extreme position on both sides is the same. Turn on the control box switch and adjust the position of the photoelectric sensors on both sides so that they can always detect and record the number of movements of the specimen.

[0037] The third step is to adjust the state of the fatigue testing machine; use the control box to adjust the motor to the appropriate frequency, clear the running time and record the number of times;

[0038] The fourth step is experimental testing; turn on the switch to rotate the motor, and start the test under the 500Mpa cyclic bending stress of the sample; after the fatigue fracture of the specimen occurs, stop the experiment and record the data; data statistics and analysis are in accordance with "GB T24176 Metal Material Fatigue Test Data Statistical Program and Analysis Method"; if 50% of the samples can withstand 2 million cycles of load, then increase the bending stress to 550Mpa, and repeat the above experimental steps for multiple experiments; at a cyclic bending stress above 550Mpa, no 50% of the samples can withstand it, and the fatigue strength of the material is defined as approximately 550Mpa; if 50% of the samples cannot withstand 2 million cycles of load under 500Mpa cyclic bending stress, reduce the bending stress, and repeat the above experimental steps for multiple experiments. If 50% of the samples can withstand 2 million cycles of load under a certain reduced cyclic bending stress, and no 50% of the samples can withstand it above a certain reduced cyclic bending stress, the stress is the fatigue strength.

[0039] The second embodiment of the present invention tests a stainless steel plate specimen with a thickness of 2.0 mm.

[0040] The first step is to make the test piece; according to the selected bending stress, the clamping length is calculated, and the deflection, width, thickness, elastic modulus, and bending stress of the test piece are set to calculate the span of the clamped test piece. For a 2.0mm thick, 25mm wide test piece, the deflection is 25mm, and a bending stress of 500Mpa is applied. The calculated span of the clamped test piece is 173.2mm. Adding the clamping width of the lower clamping device of 90mm, it can be concluded that the length of the required intercepted test piece is 263mm, so only a test piece with a size of 263*25*2.0mm needs to be made. The general interception direction is the length direction of the raw material, and 10 pieces are made.

[0041] The second step is to clamp the test piece. The second embodiment is based on the first embodiment and improves some structural functions. The upper and lower positions of the clamped span are marked on the surface of the test piece to ensure that the span after clamping is consistent with the calculation. The height of the legs on both sides is adjusted up and down according to the calculated span, so that the connecting plates on both sides are always horizontal when the test pieces on both sides move to the left and right limit positions. Clamp the lower end of the test piece, insert the test piece into the middle position of the lower clamping device, keep the marked position and the upper surface of the lower clamping device at the same level, and keep the length direction of the test piece horizontal and vertical to the upper surface of the lower clamping device, tighten the bolts to clamp the test piece; clamp the upper end of the test piece, insert the test piece into the middle position of the upper clamping device, keep the marked position and the upper surface of the upper clamping device at the same level, and keep the length direction of the test piece horizontal and vertical to the upper surface of the lower clamping device, tighten the bolts to clamp the test piece; the test piece needs to be clamped on both sides of the testing machine; turn on the control box switch, and adjust the positions of the photoelectric sensors on both sides so that they can always detect and record the number of movements of the test piece.

[0042] The third step is to adjust the state of the fatigue testing machine; use the control box to adjust the motor to the appropriate frequency, clear the running time and record the number of times;

[0043] The fourth step is experimental testing; turn on the switch to rotate the motor and start the test; experimental testing; turn on the switch to rotate the motor, and start the test under the 500Mpa cyclic bending stress of the sample; after the specimen is fatigue fractured, stop the experiment and record the data; data statistics and analysis are in accordance with "GB T24176 Metal Material Fatigue Test Data Statistical Program and Analysis Method"; if 50% of the samples can withstand 2 million cycles of load, then increase the bending stress to 550Mpa, and repeat the above experimental steps for multiple experiments; at a cyclic bending stress above 550Mpa, no 50% of the samples can withstand it, and the fatigue strength of the material is defined as approximately 550Mpa; at a cyclic bending stress of 500Mpa, if 50% of the samples cannot withstand 2 million cycles, then reduce the bending stress, and repeat the above experimental steps for multiple experiments. If 50% of the samples can withstand 2 million cycles of load under a reduced cyclic bending stress, and no 50% of the samples can withstand it above a reduced cyclic bending stress, the stress is the fatigue strength.

[0044] The fatigue testing machine of the second embodiment heightens the base support 1 and changes the structure of the legs on both sides so that the legs can be adjusted up and down to match the different spans of the specimen clamping under different stresses, so that the connecting plate 9 always remains horizontal when the specimen moves to the left and right extreme positions, thereby achieving the purpose of maintaining a fixed deflection during the movement of the specimen and greatly improving the accuracy of the experiment. The bearing fixing device 10 is also structurally improved to make the assembly of the bearing more convenient and the structural stability better. The lower clamping device 3 and the upper clamping device 7 are increased in larger size to accommodate specimens of different sizes.

[0045] By clamping the two ends of the specimen and applying load to achieve reciprocating motion, the stress level of the specimen under the action of this alternating load can be lower than the yield limit of the material. After a long period of repeated stress cycles, the bending fatigue strength of the rectangular thin plate metal specimen is tested.

[0046] The motor-driven fatigue testing machine of the present invention can realize experiments with a bending stress of 250Mpa-1000Mpa, a load range of 100N-1000N, and a frequency of 0-50Hz, and the frequency can be set arbitrarily.

Claims

1. A test method for a metal fatigue testing machine, which is composed of a base bracket, a lower clamping device, a sensor bracket, a photoelectric sensor, an upper clamping device, a connecting plate, a bearing fixing device, a connecting shaft, a bearing, a rotating disk, a motor, and a control electric box to form a metal fatigue testing machine; the base bracket includes a horizontal base, a central support platform, and symmetrical side support platforms on both sides; the horizontal base of the base bracket is provided with a slideway, and the side support platforms can adjust the spacing along the slideway; the lower clamping device, the sensor bracket, the photoelectric sensor, and the upper clamping device are each provided in two pieces and symmetrically arranged on both sides of the central support platform; the lower clamping device is fastened to the side of the side support platform of the base bracket; the sensor bracket is fastened to the upper part of the side support platform of the base bracket; The photoelectric sensor is fastened and installed on the sensor bracket; the upper clamping device is hingedly connected to the connecting plate; the connecting plate is fastened and connected to the bearing fixing device; the bearing is fixedly installed in the bearing fixing device; the connecting shaft passes through the bearing and is vertically fastened and connected to the rotating disk; the motor is fastened and installed on the central support platform of the base bracket; the motor drive shaft is fastened and connected to the rotating disk; the control box is electrically connected to the photoelectric sensor and the motor; the lower clamping device clamps the lower end of the test piece, and the upper clamping device clamps the upper end of the test piece; The test method described, The following steps are involved: The first step is to make the specimen; the working part is in the shape of a thin plate-like rectangle, and the cross-section of the working part of the specimen is a rectangle; the length of the specimen is equal to the sum of the span of the clamped specimen and the clamping width of the upper and lower clamping devices; according to the selected bending stress, and the deflection, width, thickness, and elastic modulus of the specimen, the span of the clamped specimen L is calculated to be (1.5*E*t*y max / σ max ) 1 / 2 ; The cutting direction is the length direction of the raw material, and the production quantity is an even number of pieces, not less than 10 pieces; Where, E-elastic modulus; t-specimen thickness; y max - Maximum deflection; σ max - maximum bending stress; The second step is to clamp the specimen, and clamp two specimens for each test; mark the upper and lower positions of the clamped span on the surface of the specimen to ensure that the span after clamping is consistent with the calculation; first clamp the lower end of the specimen, insert the specimen into the middle position of the lower clamping device, keep the marked position and the upper surface of the lower clamping device in the same horizontal plane, and keep the length direction of the specimen horizontal and vertical to the upper surface of the lower clamping device, and tighten the bolts to clamp the specimen; then clamp the upper end of the specimen, insert the specimen into the middle position of the upper clamping device, keep the marked position and the upper surface of the upper clamping device in the same horizontal plane, and keep the length direction of the specimen horizontal and vertical to the upper surface of the lower clamping device, and tighten the bolts to clamp the specimen; the photoelectric sensors on both sides are located at a position where they can always detect and record the number of times the specimen moves; The third step is to adjust the state of the fatigue testing machine; adjust the motor to the appropriate frequency, clear the running time and record the number of times; The fourth step is experimental testing. Two specimens are tested simultaneously in each test. Turn on the switch to rotate the motor and start testing the specimen under a certain cyclic bending stress. After fatigue fracture occurs in the specimen, stop the experiment and record the data. If 50% of the specimens can withstand two million cyclic loads, and above a certain cyclic bending stress, no 50% of the specimens can withstand it, and this stress is the fatigue strength. If 50% of the specimens can withstand two million cyclic loads, increase the bending stress and repeat the above experimental steps for multiple times. If the specimen cannot meet the requirement that 50% of the specimens can withstand two million cyclic loads under a certain cyclic bending stress, reduce the bending stress and repeat the above experimental steps for multiple times to obtain the specimen fatigue strength test data.

2. The testing method of the metal fatigue testing machine according to claim 1, characterized in that: By adjusting the distance between the side support platforms on both sides of the base bracket, the bending stress required for the experiment can be changed, and the deflection of the specimen required for the experiment can be adjusted and changed.

3. The testing method of the metal fatigue testing machine according to claim 1, characterized in that: The sensor bracket is provided with a photoelectric sensor position adjustment slide, which can adjust the distance between the side support platforms on both sides of the base bracket to adjust the specimen clamping length; when the specimen clamping length is adjusted and changed, the position of the photoelectric sensor on the sensor bracket is adjusted so that the photoelectric sensors on both sides are located at a position where they can always detect and record the number of specimen movements.

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