JP4812723B2 - Fatigue testing equipment - Google Patents

Description

  The present invention relates to a fatigue test apparatus that applies a repeated load in the twisting, tension, compression, and bending directions to a workpiece.

As a fatigue test apparatus that applies a repeated load to a material and measures the fatigue strength of the material, an apparatus using a servo motor such as that described in Patent Document 1 is used. The servo motor moves the phase of the rotation axis of the servo motor to that angle by inputting a target angle (target angle) to the servo amplifier. The servo motor is provided with a rotary encoder for detecting a change in the phase of the rotary shaft, and the servo amplifier is based on the difference between the phase of the rotary shaft determined from the detected value of the rotary encoder and the target angle. Set the drive power applied to the servo motor.
JP-A-63-37233

  A torsion tester that performs a torsion test amplifies the torque of the servo motor and applies it to the workpiece by a reduction gear (such as a reduction gear) provided between the chuck that holds one end of the workpiece and the rotation shaft of the servo motor. ing. Moreover, the universal testing apparatus which performs a tension | pulling, a compression, and a bending test provides linear motion converters, such as a feed screw mechanism, in the rotating shaft of a servo motor, and converts the rotational motion of a servo motor into linear motion.

  In such a fatigue test apparatus, the applied force (torque or load), displacement, speed, or acceleration fluctuation range (upper limit and / or lower limit) is made uniform, and a repeated load is applied to the workpiece. However, since the servo motor controls the angle of its rotating shaft, when performing a test with a constant fluctuation range of the applied force, the operator must manually load the workpiece before repeating the test. And the angle of the rotation axis of the servo motor necessary for applying a desired force was estimated (trial operation).

  In order to perform such a trial operation by manual operation, skill is required, and it takes a long time to obtain a necessary rotation shaft angle of the servo motor. In addition, there is a possibility that the work may be damaged during the trial operation due to excessive force applied to the work.

  The present invention has been made to solve the above problems. That is, the present invention provides a fatigue test apparatus capable of automatically and quickly obtaining the amplitude of the rotation axis of the servo motor to be set when performing a test with a constant fluctuation range of the force applied to the workpiece. The purpose is to provide.

  In order to achieve the above object, the fatigue test apparatus of the present invention reversely drives the force measuring means for measuring the magnitude of the force applied to the work and the rotation angle of the rotation axis of the servo motor by gradually increasing it. However, a ratio constant calculation means for calculating a ratio constant that is a ratio between the force applied to the workpiece and the rotation angle of the rotation shaft of the servo motor based on the rotation angle of the servo motor and the measurement result of the force measurement means, and the ratio constant calculation means And a control means for controlling the servo motor so that the amplitude of the magnitude of the force applied to the workpiece becomes a predetermined magnitude based on the ratio constant calculated by.

  With such a configuration, the ratio constant can be obtained automatically and promptly, and the servo motor can be driven with an appropriate angular amplitude based on the ratio constant. Further, since the amplitude of the angle of the rotation shaft of the servo motor is gradually increased, there is no possibility that the workpiece is unexpectedly damaged due to a large force applied to the workpiece.

  Further, the ratio constant calculation means is configured to calculate the ratio constant based on the rotation angle of the rotation axis of the servo motor and the measurement result of the force measurement means when the fluctuation of the rotation axis angle of the servo motor substantially stops. Is preferred. That is, when the angular velocity of the rotation axis of the servo motor is fast, that is, when the workpiece deformation speed is high, measurement errors are likely to occur. Therefore, the force applied to the workpiece when the workpiece deformation speed is low, that is, the workpiece is almost stationary. The angle amplitude of the servo motor can be obtained more accurately by calculating the ratio constant based on the size of the servo motor and the rotation angle of the rotation shaft of the servo motor.

  The force measuring means measures the magnitude of the force applied to the workpiece at least twice, and the ratio constant calculating means is the difference between the magnitude of the force in the first measurement and the magnitude of the force in the second measurement. It is desirable that the value obtained by dividing the difference between the rotation angle of the rotation axis of the servo motor in the first measurement and the rotation angle of the rotation axis of the servo motor in the second measurement be the spring constant of the workpiece. For example, in the case of a tensile test or compression test, the workpiece may be distorted when it is attached to the test equipment, so the rotation angle of the servo motor's rotation shaft does not necessarily correspond to the amount of deformation from the natural state. I can't say that. According to the present invention, it is possible to calculate the ratio constant more accurately based on the difference in deformation amount and the difference in magnitude when the workpiece is deformed with different forces.

  In addition, the fatigue test apparatus can apply a load to the workpiece along both the first direction and the second direction opposite to the first direction. Calculates a first ratio constant when the workpiece is deformed in the first direction and a second ratio constant when the workpiece is deformed in the second direction. When the workpiece is deformed in the direction of, the servo motor is controlled so that the amount of deformation obtained by dividing the predetermined size by the first ratio constant becomes the upper limit of the amount of deformation of the workpiece, and the workpiece is deformed in the second direction. Preferably, the servo motor is controlled so that the deformation amount obtained by dividing the predetermined size by the second ratio constant becomes the upper limit of the deformation amount of the workpiece. That is, for example, in a fatigue test in which a tensile load is applied to a workpiece, when the workpiece is deformed in the tensile direction (first direction) and when the load is unloaded from this state (the workpiece is deformed in the second direction). And may have different ratio constants. Therefore, it is preferable to obtain the first ratio constant and the second ratio constant separately as in the configuration of the present invention.

  Further, for example, the fatigue test apparatus is a torsion test apparatus that applies a torsional load to the work, and the force applied to the work is a torque around the rotation axis of the work.

  Alternatively, the fatigue testing device is a universal testing device that applies a tensile, compression or bending load to the workpiece via the feed screw mechanism, and the force applied to the workpiece is a component in the feed direction of the feed screw mechanism applied to the workpiece. is there.

  As described above, according to the present invention, it is possible to automatically and promptly obtain the amplitude of the rotation axis of the servo motor to be set when performing the test with a constant fluctuation range of the force applied to the workpiece. A possible fatigue test apparatus is realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a block diagram of a fatigue test apparatus according to a first embodiment of the present invention. The fatigue test apparatus of this embodiment is a fatigue test apparatus that can repeatedly apply a torsional load to a test piece (workpiece).

  As shown in FIG. 1, the fatigue test apparatus 1 of the present embodiment includes an apparatus main body 10 that applies a torsional load to a workpiece W, a servo amplifier 20 for driving a servo motor 12 of the apparatus main body 10, and a servo amplifier 20. And a control unit 30 for controlling.

  The apparatus main body 10 includes chucks 11 a and 11 b, a servo motor 12, a speed reducer 13, a torque sensor 14, and an angle sensor 15. The chucks 11a and 11b grip the workpiece W from both ends. The speed reducer 13 is disposed between the drive shaft of the servo motor 12 and the one chuck 11a, and increases the torque of the drive shaft of the servo motor 12 to be applied to the workpiece W. The other chuck 11b is fixed to a frame of the apparatus main body (not shown) via a torque sensor 14.

  In the configuration described above, when the servo motor 12 is driven, a torsional load is applied to the workpiece W gripped by the chucks 11 a and 11 b, and the magnitude thereof is measured by the torque sensor 14. An angle sensor 15 is provided on the output shaft of the speed reducer 13 to detect the twist angle of the workpiece W in the vicinity of the chuck 11a.

  The servo motor 12 is controlled by a servo amplifier 20. That is, the servo amplifier 20 generates drive power for driving the servo motor 12 based on a set angle (target angle of the rotation axis of the servo motor) transmitted from the control unit 30, and generates this drive power. To drive it. The servo motor 12 is provided with a rotary encoder 12a for detecting the number of rotations and the angle of the rotation shaft of the servo motor 12. The signal output of the rotary encoder 12a is connected to a servo amplifier 20, and the servo amplifier 20 performs feedback control of drive power based on the measurement result of the rotary encoder 12a.

  Next, the configuration of the control unit 30 will be described. FIG. 2 is a block diagram of the control unit 30 of the present embodiment. As shown in FIG. 2, the control unit 30 of this embodiment includes a controller 31, a signal conversion unit 32, an A / D conversion unit 33, a torque sensor amplifier 34a, an angle sensor amplifier 34b, an operation unit 35, A waveform generation circuit 36, a flexible disk drive (FDD) 37, a memory 38, and an analog port 39 are included. In FIG. 1 and FIG. 2, the control unit 30 is described as one block, but is actually formed by a plurality of units. For example, the torque sensor amplifier 34a and the angle sensor amplifier 34b are formed as independent units. The operation means 35 is a control panel provided on the case side surface of the unit including the controller 31, but may be an independent unit (for example, a personal computer) connected to the controller 31 via a cable.

  The control unit 30 of the present embodiment refers to the torque and angle of the workpiece W detected by the torque sensor 14 and the angle sensor 15 (both in FIG. 1) so that the torque or angle variation with time shows a desired waveform. The set angle is transmitted to the servo amplifier 20 (FIG. 1).

The waveform of the action (load or deformation) applied to the workpiece W is set using the operation means 35. The operation unit 35 includes an input unit such as a keyboard and a display unit for confirming an input result by the input unit. The operator of the fatigue testing apparatus 1 according to the present embodiment operates the operation unit 35. Thus, it is possible to set a range of torque, angle, or angular velocity when performing the repeated torsion test. For example, it is possible to set the amplitude of the angle fluctuation when the reciprocating torsional motion is performed in a sine wave shape. The setting result by the operation means 35 is transmitted to the controller 31 and stored in the memory 38.

  The waveform generation circuit 36 is a circuit that generates a signal waveform such as a sine wave, a triangular wave, or a rectangular wave at a desired cycle / timing. More specifically, when f (t) is a function having time t as an argument, a value s represented by the expression s = f (t) is sequentially output to the controller 31. In the above equation, for example, if the waveform is a sine wave, f (t) = sin (2π (ta) / T) where T is the period and a is the phase. Here, the period T and the phase a can be set to arbitrary values by operating the operation means 35.

  The controller 31 calculates the target waveform by multiplying the value transmitted from the waveform generation circuit 36 to the controller 31 by the value set by the operation means 35, and calculates the set angle to be sent to the servo amplifier 20 from the target waveform. . The calculated set angle set by the operation means 35 is transmitted to the servo amplifier 20 via the signal conversion means 32.

  With the configuration described above, the servo motor 12 can be driven so that the torsion angle of the workpiece W varies according to a prescribed waveform such as a sine wave, a triangular wave, or a rectangular wave.

In addition, the fatigue test apparatus 1 of the present embodiment, when performing a fatigue test in which a load is repeatedly applied to the workpiece W with a torque amplitude (set torque amplitude) set by an operator, The amplitude can be set automatically. The procedure will be described below with reference to FIG. FIG. 3 is a graph in which the horizontal axis represents time t and the vertical axis represents the angle θ of the rotation axis of the servo motor 12.

  As described above, in order to be able to repeatedly apply a load to the workpiece W with the set torque amplitude, in the present embodiment, the spring constant of the workpiece W is measured prior to the fatigue test. The specific measuring method will be described next. First, the workpiece W is attached to the chucks 11a and 11b, and then the servo motor 12 is driven. Then, at the beginning of the drive of the servo motor 12, the rotation shaft of the servo motor 12 is driven with a sufficiently small angle fluctuation amplitude. Thereafter, the angular amplitude of the rotating shaft is gradually increased. At this time, the torque applied to the workpiece W is detected by the torque sensor 14. In addition, the period T of change in the angle of the rotating shaft is constant regardless of the amplitude.

Next, the torques F _A , F _B , F _C , F _D applied to the workpiece W at four points A, B, C, and D in the graph of FIG. 3 and the angle θ _A of the rotation axis of the servo motor 12 at that time, θ _B , θ _C , and θ _D were measured. Here, points A and C are measured when the angle fluctuates in one direction (hereinafter defined as a positive direction) from the angle O of the rotation axis at the start of the test. Is measured when the angle fluctuates in the direction opposite to the positive direction (hereinafter referred to as the negative direction).

  Each of the points A to D is a point in time when the rotation of the rotation axis of the servo motor 12 almost stops. In the present embodiment, as shown in FIG. 3, the fluctuation of the rotation axis of the servo motor 12 is controlled to be a sine wave. Therefore, after time T / 4 + nT (n: natural number) has elapsed since the start of the test, the angular velocity of the rotating shaft becomes zero on the positive direction side. Similarly, after the time 3T / 4 + nT has elapsed from the start of the test, the angular velocity of the rotating shaft becomes zero on the positive direction side. In the present embodiment, the point after 9T / 4 from the start of the test is point A, the point after 11T / 4 is point B, the point after 13T / 4 is point C, and the point after 15T / 4 is point D.

Then, using the measurement value at the point to D, the ratio a is the ratio constant between the torque and the rotation angle of the servo motor in the positive and negative directions of the workpiece W to calculate the S _P, S _N by the number 1.

Next, based on the measured S _P and S _N , an upper limit value and a lower limit value of an angular variation of the rotation axis of the servo motor 12 for repeatedly applying a load to the workpiece W with a set torque amplitude are determined. That is, the set torque amplitude on the positive direction side is F _SP , the set torque amplitude on the negative direction side is F _SN , and the upper limit value and the lower limit value of the angular fluctuation of the rotation axis of the servo motor 12 are θ _P and θ _N , respectively. Θ _P and θ _N are calculated by the following formula 2.

Based on the obtained θ _P and θ _N , a desired setting is obtained by changing the set angle θ to be given to the servo amplifier 20 so that the change in the angle of the rotation shaft of the servo motor 12 satisfies the equation (3). A load can be repeatedly applied to the workpiece based on the torque amplitude.

  The first embodiment of the present invention described above relates to a torsion test apparatus. However, the present invention is not limited to the above configuration. That is, the present invention can be applied to other types of fatigue test apparatuses using a servo motor. The fatigue test apparatus according to the second embodiment of the present invention described below is a so-called universal test apparatus capable of applying a tensile, compression, or bending load to a workpiece by a feed screw mechanism driven by a servo motor. It is.

FIG. 4 shows a block diagram of the fatigue test apparatus 101 of the present embodiment. The fatigue test apparatus 101 of the present embodiment can repeatedly apply a tensile, compression, or bending load to a test piece (workpiece).

As shown in FIG. 4, the fatigue test apparatus 101 of the present embodiment includes an apparatus main body 110 that applies a load to the workpiece W, a servo amplifier 120 that drives a servo motor 112 of the apparatus main body 110, and a servo amplifier 120. And a control unit 130 for controlling. The apparatus main body 110 includes a frame 111, a servo motor 112, a linear motion converter 113, a load cell 114, a displacement sensor 115, and adapters 118a and 118b.

  The linear motion converter 113 is for converting the rotational motion of the rotation shaft of the servo motor 112 into motion in the straight direction, and includes a feed screw 113a, a nut 113b, a pair of guide rails 113c, and a guide rail 113c. Runner blocks 113d corresponding to the respective ones. The nut 113b is engaged with the feed screw 113a. The runner block 113d is fixed to the nut 113b. The runner block 113d can move along the corresponding guide rail 113c and cannot move in any direction other than this direction. For this reason, the motion of the runner block 113d and the nut 113b is limited to one degree of freedom along the direction in which the guide rail 113c extends. Furthermore, since the axial direction of the feed screw 113a is parallel to the direction in which the guide rail 113c extends (that is, the vertical direction), when the feed screw 113a is rotated by the servo motor 112, the nut 113b moves along the guide rail 113c. To do. As shown in FIG. 4, the servo motor 112 is fixed below the table portion 111a of the frame 111, and the guide rail 113c is fixed on the table portion 111a. For this reason, the nut 113b moves up and down with respect to the table portion 111a. A lower adapter 118a for holding the workpiece W from below is attached on the nut.

  The upper stage 116 is suspended from the lower surface of the ceiling 111b of the frame 111. In addition, a guide bar 117c extending upward in the drawing is provided on the upper surface of the table portion 111a. A through hole 116a drilled in the vertical direction is formed at the left and right end portions of the upper stage 116, and a guide bar 117c is passed through the through hole 116a. Therefore, the upper stage 116 can move in the vertical direction along the guide bar 117c. Further, by tightening a bolt (not shown) provided on the upper stage 116, the inner diameter of the through-hole 116a can be reduced, so that the upper stage 116 can be fixed to the guide bar 117c. It has become.

  An upper adapter 118b for holding the workpiece W from above is attached to the lower surface of the upper stage 116. In the present embodiment, a load can be applied to the workpiece W by moving the nut 113b up and down while holding the workpiece W between the upper adapter 118b and the lower adapter 118a. The upper and lower adapters 118a and 118b are configured to be detachable from the upper stage 116 and the nut 113b, respectively, and an appropriate adapter can be selected according to the type of load to be applied to the workpiece W. Since FIG. 4 is a structure which applies a compressive load to the workpiece | work W, the lower surface of the upper adapter 118b and the upper surface of a lower adapter are formed in planar shape. When applying a tensile load to the workpiece W, adapters 118a and 118b provided with chucks for gripping the workpiece W are used. When performing a three-point bending test, a compression test adapter and a three-point bending jig are used in combination.

  The upper stage 116 is suspended from a ceiling 111b of the frame 111 by a feed screw 117a. The ceiling 111b is embedded with a rotatable nut (not shown) that engages with the feed screw 117a. The nut is rotationally driven by a motor 117b disposed on the ceiling 111b. Further, the link connecting the feed screw 117a and the upper stage 116 prevents the feed screw 117a from rotating about its axis with respect to the upper stage 116. Therefore, in a state where the bolts of the upper stage 116 are loosened and the upper stage 116 is movable, the nut is rotated by the motor 117b, whereby the feed screw 117a and the upper stage 116 connected to the feed screw 117a are moved. It can be driven in the vertical direction. This function is used when adjusting the distance between the adapters 118a and 118b in accordance with the dimensions of the workpiece W. That is, when performing the test, the bolts are tightened to fix the upper stage 116 to the guide bar 117c.

  In the configuration described above, when the workpiece W is held by the adapters 118a and 118b and the servo motor 112 is driven, a tensile, compression, or bending load is applied to the workpiece W, and the magnitude thereof is measured by the load cell 114. The displacement sensor 115 is a sensor (for example, a dial gauge incorporating a rotary encoder) that detects the displacement of the lower adapter, that is, the deformation amount of the workpiece W.

As in the first embodiment, the servo motor 112 is controlled by the servo amplifier 120. In other words, the servo amplifier 120 generates drive power for driving the servo motor 112 based on the target value (target rotation axis angle of the servo motor) transmitted from the control unit 130, and this is used as the servo motor 112. To drive it. The servo motor 112 is provided with a rotary encoder 112a for detecting the rotation speed, angle, and the like of the rotation shaft of the servo motor 112. The signal output of the rotary encoder 112a is connected to the servo amplifier 120, and the servo amplifier 120 performs feedback control based on the measurement result of the rotary encoder 112a.

  Next, the configuration of the control unit 130 will be described. FIG. 5 is a block diagram of the control unit 130 of the present embodiment. As shown in the drawing, the control unit 130 of the present embodiment is configured so that the load cell can be connected instead of the torque sensor, and the displacement sensor can be connected instead of the angle sensor. This is the same as the first embodiment. Therefore, the same reference numerals are assigned to the same or similar components in the control unit 130 as in the first embodiment of the present invention, and a detailed description of the control unit 130 is omitted.

  The control unit 130 according to the present embodiment refers to the load or deformation amount of the workpiece W detected by the load cell 114 and the displacement sensor 115 (both shown in FIG. 4), and the variation with time of the load or deformation amount has a desired waveform. As shown, the set angle is transmitted to the servo amplifier 120 (FIG. 1).

The waveform of the action given to the workpiece W is set using the operation means 35. The operator of the fatigue test apparatus 101 of the present embodiment can set the fluctuation range of the load, the amount of deformation, and the like when performing the repeated test by operating the operation means 35. For example, it is possible to set the amplitude of displacement when applying a sinusoidal repetitive compression displacement to the workpiece W.

  The controller 31 calculates a target value by multiplying the value transmitted from the waveform generation circuit 36 to the controller 31 by the value set by the operation means 35, and the load detected by the load cell 114 or the displacement sensor 115. Is compared with the deformation amount (or the deformation speed that is the time differential value thereof) detected by, and the set angle to be sent to the servo amplifier 120 is calculated. The calculated set angle is transmitted to the servo amplifier 120 via the signal conversion means 32.

  With the configuration described above, the servo motor 112 can be driven so that the load applied to the workpiece W and the deformation amount of the workpiece W vary according to a prescribed waveform such as a sine wave, a triangular wave, or a rectangular wave. Yes.

Also, as in the first embodiment, the fatigue test apparatus 101 of the present embodiment, when performing the fatigue test to apply a repetitive load to the workpiece W with an amplitude of the load set by the operator (set load amplitude), the servo motor The amplitude of the angle fluctuation of the twelve rotation axes can be automatically set. This configuration is almost the same as that of the embodiment of the present invention described with reference to FIG. Therefore, also in this embodiment, it demonstrates with reference to FIG.

As described above, in order to be able to repeatedly apply a load to the workpiece W with the set torque amplitude, in the present embodiment, the spring constant of the workpiece W is measured prior to the fatigue test. A specific measurement method will be described next. First, the workpiece W is attached to the fatigue test apparatus 101, and then the servo motor 12 is driven. Then, at the beginning of the drive of the servo motor 12, the rotation shaft of the servo motor 12 is driven with a sufficiently small angle fluctuation amplitude. Thereafter, the angular amplitude of the rotating shaft is gradually increased. At this time, the torque applied to the workpiece W is detected by the torque sensor 14. In addition, the period T of change in the angle of the rotating shaft is constant regardless of the amplitude.

Next, the loads P _A , P _B , P _C , P _D applied to the workpiece W at the four points A, B, C and D in FIG. 3 and the angles θ _A , θ _B of the rotation axis of the servo motor 12 at that time , Θ _C , θ _D were measured. Here, points A and C are measured when the angle fluctuates in one direction (hereinafter defined as a positive direction) from the angle O of the rotation axis at the start of the test. Is measured when the angle fluctuates in the direction opposite to the positive direction (hereinafter referred to as the negative direction).

  Each of the points A to D is a point in time when the rotation of the rotation axis of the servo motor 12 almost stops. In the present embodiment, as shown in FIG. 3, the fluctuation of the rotation axis of the servo motor 12 is controlled to be sinusoidal. Therefore, after time T / 4 + nT (n: natural number) has elapsed since the start of the test, the angular velocity of the rotating shaft becomes zero on the positive direction side. Similarly, after the time 3T / 4 + nT has elapsed from the start of the test, the angular velocity of the rotating shaft becomes zero on the positive direction side. In the present embodiment, the point after 9T / 4 from the start of the test is point A, the point after 11T / 4 is point B, the point after 13T / 4 is point C, and the point after 15T / 4 is point D.

Next, using the measured values at the points A to D, the spring constants S _P and S _N in the positive and negative directions of the workpiece W are calculated according to Equation 4.

Then, the measured S _P, on the basis of the S _N, determines the upper limit value and the lower limit value of the angular variation of the rotation axis of the servo motor 12 for applying a repeated load to the workpiece W by the setting load amplitude. That is, the set load amplitude on the positive direction side is P _SP , the set load amplitude on the negative direction side is P _SN , and the upper limit value and the lower limit value of the angular fluctuation of the rotation axis of the servo motor 12 are θ _P and θ _N , respectively. Θ _P and θ _N are calculated by the following equation (5).

Then, based on the obtained θ _P and θ _N , a desired angle θ can be obtained by changing the set angle θ given to the servo amplifier 20 so that the change in the angle of the rotation axis of the servo motor 12 satisfies the above-described equation (3). It becomes possible to repeatedly apply a load to the workpiece based on the set load amplitude.

1 shows an overview of a fatigue test apparatus according to a first embodiment of the present invention. It is a block diagram of the control part of the fatigue test apparatus of the 1st Embodiment of this invention. It is a graph which shows the fluctuation | variation of the angle of the rotating shaft of a servomotor in the 1st and 2nd embodiment of this invention. The outline | summary of the fatigue test apparatus of the 2nd Embodiment of this invention is shown. It is a block diagram of the control part of the fatigue test apparatus of the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fatigue test apparatus 10 Apparatus main body 12 Servo motor 20 Servo amplifier 30 Control part 31 Controller 33 Conversion means 35 Operation means 37 Flexible disk drive W Workpiece

Claims (6)

A fatigue testing device that repeatedly applies a load to a workpiece by a servo motor,
Force measuring means for measuring the magnitude of the force applied to the workpiece;
While gradually increasing the amplitude of the rotation angle of the rotation axis of the servo motor and driving it in reverse, the force applied to the workpiece and the rotation of the servo motor based on the rotation angle of the servo motor and the measurement result of the force measuring means A ratio constant calculating means for calculating a ratio constant which is a ratio to the rotation angle of the shaft;
A fatigue test apparatus comprising: control means for controlling the servo motor so that the amplitude of the magnitude of the force applied to the workpiece becomes a predetermined magnitude based on the ratio constant calculated by the ratio constant calculation means .   The ratio constant calculation means calculates the ratio constant based on the rotation angle of the rotation axis of the servo motor and the measurement result of the force measurement means when the fluctuation of the rotation axis angle of the servo motor substantially stops. The fatigue test apparatus according to claim 1. The force measuring means measures the magnitude of the force applied to the workpiece at least twice;
The ratio constant calculating means calculates the difference between the magnitude of the force in the first measurement and the magnitude of the force in the second measurement, and the rotation angle of the rotation shaft of the servomotor in the first measurement and the second measurement. The fatigue test apparatus according to claim 1, wherein a value obtained by dividing a difference from a rotation angle of a rotation shaft of the servo motor in measurement is the ratio constant. The fatigue test apparatus can apply a load to the workpiece along both the first direction and the second direction opposite to the first direction.
The ratio constant calculating means includes a first ratio constant when the workpiece is deformed in the first direction, and a second ratio constant when the workpiece is deformed in the second direction. And
When the workpiece is deformed in the first direction, the control means is configured so that a deformation amount obtained by dividing the predetermined size by the first ratio constant is an upper limit of the deformation amount of the workpiece. When the servo motor is controlled and the workpiece is deformed in the second direction, the deformation amount obtained by dividing the predetermined size by the second ratio constant is the upper limit of the deformation amount of the workpiece. fatigue testing apparatus according to any one of controlling the servo motor, it from claim 1, wherein 3. The fatigue test apparatus is a torsion test apparatus that applies a torsional load to the workpiece,
Force applied to the workpiece, the torque of the rotation axis of the workpiece, it fatigue testing device according to any one of claims 1 to 4, characterized in. The fatigue testing device is a universal testing device for applying a tensile, compression or bending load to the workpiece via a feed screw mechanism;
The force applied to the workpiece is a feed direction component of the feed screw mechanism of the load applied to the workpiece.
The fatigue test apparatus according to any one of claims 1 to 4, wherein the apparatus is a fatigue test apparatus.

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