JP2009085850A - Fatigue testing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide fatigue testing equipment capable of performing an acceleration amplitude constant sweep test in a wide frequency band including a high frequency region. <P>SOLUTION: The fatigue testing equipment has an acceleration detection means for detecting the deformation speed of a workpiece and a control means for controlling a servomotor on the basis of the detection result of the acceleration detection means so that the ratio of the deformation speed and predetermined speed of the workpiece is received in a predetermined range regardless of a cycle for adding repeated load at each time when the cycle for adding the repeated load to the workpiece is changed. <P>COPYRIGHT: (C)2009,JPO&INPIT

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.

2. Description of the Related Art As a fatigue test apparatus that measures a physical property of a material by applying a static load or a repeated load to the material, a device using a servo motor such as that described in Patent Document 1 is widely used. The servo motor moves the phase of the rotation axis of the servo motor to that angle by inputting a target angle (set angle) to the servo amplifier. The servo motor is provided with a rotary encoder for detecting changes in the phase of the shaft, and the servo amplifier performs servo based on the difference between the rotational axis phase determined from the detected value of the rotary encoder and the set angle. Drive power to be applied to the motor is generated.
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 recent years, servo motors with high responsiveness are being put into practical use, and repeated loads of waveforms such as sine waves, rectangular waves, and triangular waves can be applied to workpieces at high frequencies. In such a test apparatus, a constant acceleration amplitude sweep test that changes the frequency while keeping the amplitude of the deformation acceleration (angular acceleration in the torsion test) of the workpiece constant, which is a kind of fatigue test, can be performed.

  In such a sweep test, it is necessary to make the amplitude of the deformation acceleration of the workpiece constant. Conventionally, the angle of the servo motor is based on the reduction ratio of the reduction gear if it is a torsion test device, and the conversion rate of the linear motion converter if it is a universal test device (lead screw lead if it is a feed screw mechanism). By controlling the acceleration, the workpiece is repeatedly subjected to a load at a desired angular acceleration or acceleration. However, especially in the high frequency range, because of the elasticity and viscosity of the workpiece itself or the power transmission system (reduction gear and linear motion converter), it is based on the amount of phase change of the rotation axis of the servo motor and the characteristics of the power transmission system. The calculated angular acceleration and acceleration of the workpiece do not always match the actual angular acceleration and acceleration of the workpiece. For this reason, the conventional fatigue test apparatus could not perform a constant acceleration amplitude sweep test in a wide frequency band including a high frequency range.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a fatigue test apparatus capable of performing a constant acceleration amplitude sweep test in a wide frequency band including a high frequency range.

  In order to achieve the above object, the fatigue testing apparatus of the present invention includes an acceleration detecting means for detecting a deformation acceleration of a work, and a cycle of repeatedly applying a load to the work based on a detection result of the acceleration detecting means. And a control means for controlling the servo motor so that the ratio between the deformation acceleration of the workpiece and the predetermined acceleration is within a predetermined range regardless of the period of applying the repeated load.

  Further, it is preferable that the control means performs control so as to change the amplitude of the rotation axis of the servo motor based on the ratio between the maximum value of the speed measured by the acceleration detecting means during the predetermined period and the predetermined acceleration.

  The predetermined range is, for example, between 0.95 and 1.05. Alternatively, the predetermined range is between 0.99 and 1.01.

  Further, for example, the fatigue test apparatus is a torsion test apparatus that applies a torsional load to the work, and the deformation acceleration of the work is an angular acceleration around the rotation axis of the work at a specific position 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 deformation acceleration of the workpiece is the component of the feed screw mechanism in the feed direction of the acceleration at a specific position of the workpiece. It is.

  As described above, according to the present invention, a fatigue test apparatus capable of performing a constant acceleration amplitude sweep test in a wide frequency band including a high frequency range 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 the present 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 outer surface of the case 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 torsion test 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 torsional testing apparatus 1 according to the present embodiment varies the angular acceleration of the workpiece W according to a sine wave waveform and gradually increases or decreases the frequency of this waveform to apply a repeated load to the workpiece in a wide frequency range. A constant angular acceleration amplitude sweep test can be performed.

  In such a sweep test, it is desirable to make the upper and lower limits of the angular acceleration applied to the workpiece W, that is, the amplitude constant. However, in order to keep the amplitude constant in the sweep test, the response delay due to the elasticity of the transmission system such as the speed reducer 13 (FIG. 1) and the work W itself, and the effect of damping due to friction and viscosity, particularly in the high frequency range. In consideration of this, it is necessary to calculate a target value (target waveform) to be sent to the servo amplifier 20. In this embodiment, the set angle given to the servo amplifier 20 is feedback controlled based on the measured value of the actual displacement of the workpiece W so that the sweep test is performed with a desired amplitude. The specific procedure will be described below.

  FIG. 3 is a flowchart showing a procedure for performing a constant acceleration amplitude frequency sweep test on the workpiece W attached to the test apparatus 1 in the present embodiment. The following description is made based on this flow.

First, the operator of the apparatus 1 operates the operation means 35 to “upper limit frequency F _max and lower limit frequency F _min for performing frequency sweep”, “whether frequency sweep is performed at equal intervals or equal ratio intervals”, “frequency Parameters such as “sweep interval Δf”, “amplitude α _S of workpiece W angular acceleration”, and “number of sweeps K” are input to control unit 30 (step S1).

Among the above parameters, the interval Δf is a difference when the frequency sweep is performed at equal intervals, and is a ratio when the frequency sweep is performed at equal intervals. In the present embodiment, if the frequency at which the frequency sweep is performed is F _n (n = 1, 2,... N), the relationship of Formula 1 is established among F _min , Δf, n, and F _n. .

In addition, regardless of whether the frequency sweep is performed at equal intervals or equal ratio intervals, the relationship of Formula 2 is established between F _n , N, and F _max .

That is, the minimum value of _{F n} are _{F min,} the maximum value _{F N} of _{F n} is the maximum frequency does not exceed _{F max.}

Next, when the angular acceleration amplitude constant frequency sweep test is performed based on the following equation (3), the angle amplitude D _n of the rotation axis of the servo motor 12 is obtained (step S2).

  In the above equation 3, R is the reduction ratio of the speed reducer 13.

Subsequently, the servo motor 12 is driven with a sine wave having an amplitude D ₁ and a frequency F ₁ = F _min as a set angle (that is, D _n × sin (2π × F _n × t)) (step S3).

Next, the angular acceleration of the workpiece W is measured (step S4). In the present embodiment, in order to measure the twist angle of the workpiece W more accurately, an acceleration sensor is attached to the workpiece W, and the acceleration around the rotation axis of the workpiece W is measured. The output of the acceleration sensor is connected to an analog port 39 (FIG. 2) of the control unit 30 through an amplifier, and the controller 31 detects the acceleration a _M measured by the acceleration sensor, the mounting position of the accelerometer, and the rotation axis of the workpiece W. From the distance l, the angular acceleration α _M (unit: rad / s ² ) of the workpiece W can be obtained based on the following formula 4. Controller 31, at least one period of the angular acceleration alpha _M, that is, the time 1 / _{F n} is measured to obtain the maximum value of the angular acceleration (i.e., the angular acceleration amplitude) the alpha _Mmax.

Next, the angular acceleration α _S set in step S1 is compared with the angular acceleration α _Mmax measured in step S4 (step S5). That is, if the ratio of both angular accelerations satisfies 0.95 ≦ α _S / α _Mmax ≦ 1.05, it is determined that there is no need to change the set angle given to the servo amplifier 20 (step S5: YES). Proceed to S6. On the other hand, if the ratio of the two angular accelerations does not satisfy the above-mentioned rule, it is determined that the set angle given to the servo amplifier 20 needs to be changed (step S5: NO), and the process proceeds to step S21. In the present embodiment, the difference between the two angular accelerations is within ± 5% as described above. However, when performing a more accurate test, the above criterion is ± 1% (that is, 0.99 ≦ α _S / α _Mmax ≦ 1.01).

In step S21, it is determined which of the angular acceleration α _S set in step S1 and the angular acceleration α _Mmax measured in step S4 is greater. That is, if the measured value α _Mmax is larger than the set value α _S (step S21: YES), the process proceeds to step S22.

In step S22, it calculated based amplitude D _n of the rotary shaft of the servo motor 12 to the number 5 below, on the basis of the modified D _n, to change the setting angle to be given to the servo amplifier 20. Next, returning to step S4, the angular acceleration amplitude α _Mmax is calculated again.

In step S21, if the measured value α _Mmax is smaller than the set value α _S (step S21: NO), the process proceeds to step S23.

In step S23, based on the following equation 6 is calculated based on the amplitude D _n of the rotary shaft of the servo motor 12 to the number 5 below, on the basis of the modified D _n, to change the setting angle to be given to the servo amplifier 20 . Next, returning to step S4, the angular velocity amplitude ω _Mmax is calculated again.

As described above, when the ratio between the angular velocity α _S set in step S1 and the angular velocity α _Mmax measured in step S4 exceeds a predetermined reference, the servo motor 12 is processed by the processing in steps S21 to S23. The amplitude of the rotation axis is adjusted.

In step S6, in a state in which the measured value α _Mmax and the set value α _S are within the reference, the process waits until a predetermined cyclic load is applied to the workpiece. Next, the process proceeds to step S7.

In the present embodiment, the frequency is increased from the minimum value F ₁ to the maximum value F _N (forward path), and after the frequency reaches the maximum value F _N , the frequency is decreased to F ₁ (return path). This is defined as one cycle, and a K cycle test is executed. In step S7, it is determined whether the current execution is the outbound path or the inbound path. If it is the outbound path (step S7: YES), the process proceeds to step S8. If it is a return path (step S7: NO), it will progress to step S9.

Step S8 the frequency being currently tested is determined whether reaches the maximum value F _N. If the maximum value F _N has been reached (step S8: YES), it is determined that the forward path has been completed, and the process proceeds to step S32. On the other hand, if the frequency has not reached the maximum value _{F N} (step S8: NO), the process proceeds to step S31.

In step S31, the frequency is increased. That the current frequency if a _{F n,} the frequency _{F n + 1.} Next, returning to step S4, the amplitude α _Mmax of the angular acceleration is measured at this frequency.

In step S9, it is determined whether the frequency being currently tested reaches the minimum value F _1. If it has reached the minimum value _{F 1} (step S9: YES), determines that return is completed, the process proceeds to step S10. On the other hand, if the frequency has not reached the minimum value _{F 1} (step S9: NO), the process proceeds to step S32.

In step S32, the frequency is decreased. That the current frequency if a _{F n,} the frequency _{F n-1.} Next, returning to step S4, the amplitude α _Mmax of the angular acceleration is measured at this frequency.

  In step S10, it is checked how many cycles of the test have been completed. That is, when it is determined that the test of the K cycle set in step S1 is completed (step S10: YES), the servo motor 12 is stopped in step S11, and this flow is finished. On the other hand, if the number of cycles completed in step S10 is less than K (step S10: NO), the process returns to step S4 and the next cycle is tested.

As described above, according to the present embodiment, the angular acceleration amplitude constant frequency sweep test can be performed so that the set angular acceleration amplitude α _S and the measured angular acceleration amplitude α _Mmax substantially coincide with each other.

  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 according to the present embodiment can repeatedly apply a tensile, compression, or bending load to a test piece (workpiece).

  As shown in FIG. 4, the test apparatus 101 of the present embodiment controls the apparatus main body 110 that applies a load to the workpiece W, the servo amplifier 120 for driving the servo motor 112 of the apparatus main body 110, and the servo amplifier 120. And a control unit 130. 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 210 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 action waveform applied to the workpiece W is set using the operation means 35. The operator of the test apparatus 101 according to the present embodiment can set the width of the load, the amount of deformation, and the like when performing the repeated test by operating the operation unit 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.

  Similarly to the first embodiment, the test apparatus 101 according to the present embodiment varies the acceleration of the workpiece W according to a sine wave waveform and gradually increases or decreases the frequency of the waveform, thereby repeatedly in a wide frequency range. A constant acceleration amplitude sweep test can be performed in which a load can be applied to the workpiece.

  In such a sweep test, it is desirable to make the upper and lower limits of acceleration applied to the workpiece W, that is, the amplitude constant. However, in order to keep the amplitude constant in the sweep test, the response delay due to the elasticity of the transmission system such as the feed screw mechanism 113 (FIG. 4) and the work W itself, and the attenuation due to the friction and viscosity, particularly in the high frequency range. In consideration of the above, it is necessary to calculate a target value (target waveform) to be sent to the servo amplifier 120. In this embodiment, the set angle given to the servo amplifier 120 is feedback controlled based on the measured value of the actual displacement of the workpiece W so that the sweep test is performed with a desired amplitude. The specific procedure will be described below.

  Also in this embodiment, the acceleration amplitude constant frequency sweep test is performed according to the flowchart shown in FIG. Therefore, the following description is made based on FIG.

First, the operator of the apparatus 101 operates the operation means 35 to “upper limit frequency F _max and lower limit frequency F _min for performing frequency sweep”, “whether frequency sweep is performed at equal intervals or equal ratio intervals”, “frequency Parameters such as “sweep interval Δf”, “amplitude A _S of acceleration of workpiece W”, and “number of sweeps K” are input to control unit 30 (step S1).

Among the above parameters, the interval Δf is a difference when the frequency sweep is performed at equal intervals, and is a ratio when the frequency sweep is performed at equal intervals. In the present embodiment, if the frequency at which the frequency sweep is performed is F _n (n = 1, 2,... N), the relationship of the above-described formula 1 is present among F _min , Δf, n, and F _n. To establish. Further, whether the frequency sweep is performed at an equal difference interval or an equal ratio interval, the relationship of Formula 2 described above is established between F _n , N and F _max .

That is, the minimum value of _{F n} are _{F min,} the maximum value _{F N} of _{F n} is the maximum frequency does not exceed _{F max.}

Next, when the constant acceleration amplitude frequency sweep test is performed based on the following Equation 7, the amplitude D _n of the rotation axis angle of the servo motor 12 is obtained (step S2).

  In the above equation 7, L is the lead (unit: mm / rotation) of the feed screw 113.

Subsequently, the servo motor 12 is driven with a sine wave having an amplitude D ₁ and a frequency F ₁ = F _min as a set angle (that is, D _n × sin (2π × F _n × t)) (step S3).

Next, the speed of the workpiece W is measured (step S4). In the present embodiment, in order to more accurately measure the acceleration of the workpiece W, an acceleration sensor is attached to the workpiece W, and the acceleration at a specific position on the surface of the workpiece W is measured. The output of the acceleration sensor is connected to an analog port 39 (FIG. 2) of the control unit 30 via an amplifier, and the controller 31 obtains the acceleration A _M (unit: mm / s ² ) of the workpiece W measured by the acceleration sensor. be able to. The controller 31 measures the acceleration A _M for at least one period, that is, time 1 / F _n , and obtains the maximum value of acceleration (that is, acceleration amplitude) A _Mmax .

Next, the speed A _S set in step S1 is compared with the speed A _Mmax measured in step S4 (step S5). That is, if the ratio between the two accelerations satisfies 0.95 ≦ A _S / A _Mmax ≦ 1.05, it is determined that there is no need to change the set angle given to the servo amplifier 20 (step S5: YES), and step Proceed to S6. On the other hand, if the ratio between the two accelerations does not satisfy the above-mentioned rule, it is determined that the set angle given to the servo amplifier 20 needs to be changed (step S5: NO), and the process proceeds to step S21. In the present embodiment, the standard is that the difference between the two accelerations is within ± 5% as described above. However, when performing a more accurate test, the standard is ± 1% (that is, 0.99 ≦ A _S / A _Mmax ≦ 1.01) may be stricter.

In step S21, a determination either the greater of the acceleration A _Mmax which is measured by the acceleration A _S and S4 set by the step S1 is performed. That is, if larger of the than the measured value _{A Mmax} set value _{A S} (step S21: YES), the process proceeds to step S22.

In step S22, calculated based amplitude D _n of the rotary shaft of the servo motor 12 to the number 8 below, based on the modified D _n, to change the setting angle to be given to the servo amplifier 20. Next, returning to step S4, the acceleration amplitude _AMmax is calculated again.

Further, in step S21, if less of the than the measured value _{A Mmax} set value _{A S} (step S21: NO), the process proceeds to step S23.

In step S23, based on the following equation 9 is calculated based on the amplitude D _n of the rotary shaft of the servo motor 12 to the number 9, below, on the basis of the modified D _n, to change the setting angle to be given to the servo amplifier 20 . Next, the process returns to step S4, and the acceleration amplitude _AMmax is measured again.

As described above, if the ratio between the acceleration _{A Mmax} which is measured by the acceleration _{A S} and S4 set in step S1 is exceeds the predetermined reference, the process of step S21 to S23, the servo motor 12 The amplitude of the rotation axis is adjusted.

In step S6, in a state where the measured value A _Mmax and the set value A _S are within the reference, the process waits until a load is repeatedly applied to the workpiece for a predetermined period. Next, the process proceeds to step S7.

In the present embodiment, the frequency is increased from the minimum value F ₁ to the maximum value F _N (forward path), and after the frequency reaches the maximum value F _N , the frequency is decreased to F ₁ (return path). This is defined as one cycle, and a K cycle test is executed. In step S7, it is determined whether the current execution is the outbound path or the inbound path. If it is the outbound path (step S7: YES), the process proceeds to step S8. If it is a return path (step S7: NO), it will progress to step S9.

Step S8 the frequency being currently tested is determined whether reaches the maximum value F _N. If the maximum value F _N has been reached (step S8: YES), it is determined that the forward path has been completed, and the process proceeds to step S32. On the other hand, if the frequency has not reached the maximum value _{F N} (step S8: NO), the process proceeds to step S31.

In step S31, the frequency is increased. That the current frequency if a _{F n,} the frequency _{F n + 1.} Next, returning to step S4, the angular velocity amplitude ω _Mmax is measured at this frequency.

In step S9, it is determined whether the frequency being currently tested reaches the minimum value F _1. If it has reached the minimum value _{F 1} (step S9: YES), determines that return is completed, the process proceeds to step S10. On the other hand, if the frequency has not reached the minimum value _{F 1} (step S9: NO), the process proceeds to step S32.

In step S32, the frequency is decreased. That the current frequency if a _{F n,} the frequency _{F n-1.} Next, returning to step S4, the velocity amplitude _VMmax is measured at this frequency.

  In step S10, it is checked how many cycles of the test have been completed. That is, when it is determined that the test of the K cycle set in step S1 is completed (step S10: YES), the servo motor 12 is stopped in step S11, and this flow is finished. On the other hand, if the number of cycles completed in step S10 is less than K (step S10: NO), the process returns to step S4 and the next cycle is tested.

As described above, according to this embodiment, it is possible acceleration amplitude A _Mmax which is measured with the acceleration amplitude A _S which is set to be substantially coincident, performing acceleration constant amplitude frequency sweep test.

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 flowchart of the acceleration amplitude constant frequency sweep test 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,
Test means for applying a repeated load to the workpiece while changing a cycle in which the deformation acceleration of the workpiece has a predetermined waveform and repeatedly applying the load;
Acceleration detecting means for detecting deformation acceleration of the workpiece;
Based on the detection result of the acceleration detecting means, the ratio between the deformation acceleration of the workpiece and the predetermined acceleration is within a predetermined range regardless of the cycle of applying the repeated load every time the cycle of repeatedly applying the load to the workpiece changes. Control means for controlling the servo motor so as to fit;
A fatigue test apparatus.   The control means controls the amplitude of the rotation axis of the servo motor to be changed based on a ratio between a maximum value of deformation acceleration measured by the speed detection means during a predetermined period and the predetermined acceleration. The fatigue test apparatus according to claim 1.   The fatigue test apparatus according to claim 1, wherein the predetermined range is between 0.95 and 1.05.   The fatigue test apparatus according to claim 3, wherein the predetermined range is between 0.99 and 1.01.   The fatigue test apparatus is a torsion test apparatus that applies a torsional load to the workpiece, and the deformation acceleration of the workpiece is an angular acceleration around the rotation axis of the workpiece at a specific position of the workpiece. The fatigue test apparatus according to any one of 1 to 4.   The fatigue testing device is a universal testing device that applies a tensile, compression or bending load to the workpiece via a feed screw mechanism, and the deformation acceleration of the workpiece is the acceleration of the feed screw mechanism at a specific position of the workpiece. The fatigue test apparatus according to any one of claims 1 to 4, wherein the fatigue test apparatus is a feed direction component.

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