JPH0333638A - Repeated impact fatigue tester - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Application 9 The present invention relates to a testing machine that repeatedly applies impact loads to test pieces.

(2) Prior art In conventional cyclic impact testing machines, tests are performed by feeding back the actual load so that the load acting on the test piece becomes a preset cyclic load waveform (load pattern).

C1 Problems to be Solved by the Invention However, according to such load feedback control, in a no-load state where the punch of the load actuator is far from the test specimen, there is an uncontrolled state, and the speed at the time of punch collision is unstable. As a result, the impact force (maximum load)
It also becomes unstable. Note that the load feedback control method essentially cannot control speed due to its control method.

Therefore, it may be possible to conduct the test by backing the actual displacement of the load actuator from 1 to 1 to obtain a preset displacement waveform (displacement pattern), but in this case, due to the deformation of the test piece due to fatigue, The impact velocity or impact force changes over time.

A technical problem of the present invention is to perform a fatigue test using displacement feedback control so as to obtain a desired collision speed and maximum load even if a test piece is deformed.

01 Means for Solving the Problems To explain with reference to FIG. 1, which is a diagram corresponding to the claims, the cyclic impact fatigue tester according to the present invention performs testing with a waveform displacement pattern determined by a set displacement average value, amplitude, and frequency. A load actuator that repeatedly applies an impact load to the load actuator], OA, a load detection means 12 that detects the load acting on the test piece 11, a variable η detection means 3 that detects the displacement of the load actuator 10A, and a detection means 3 that detects the displacement of the load actuator 10A. The opening control means 15 opens the load actuator IOA so that the test piece 11 is loaded in a displacement pattern while feeding back the displacement that has been applied, and the opening control means 15 opens the load actuator IOA so that the test piece 11 is loaded in a displacement pattern, and the 3- Correct the displacement average value, correct the above amplitude to reduce the difference between the detected maximum load and the predetermined maximum load, and while keeping the corrected amplitude fixed, compare the detected maximum load with the predetermined maximum load. By providing a displacement average (correction means for correcting 11j) 5] so as to reduce the difference from the predetermined maximum load, the technical problem -1-1 is solved.

By directly correcting the displacement average value written in -I-I- to the intermediate value between the displacement at the time of E0 action maximum load detection and the minimum displacement η at no load, the load actuator 10A is calculated as follows: collides with the test piece 11. In addition, by correcting the amplitude so as to reduce the difference between the detected maximum load and the predetermined maximum load, a desired maximum load can be applied to the test piece 11. The displacement average 1111 is corrected so that the difference between the maximum load detected during each repetitive cycle and the predetermined maximum cart is small, while the shoulder width determined in this way is identified. As a result, in each repeated cycle, the load actuator IOA always collides with the test specimen 11 at the same speed, and the desired maximum load is obtained at the maximum displacement of 4, resulting in a stable test.

In the above-mentioned sections and section E, which describe the present invention in detail, reference numerals of the embodiments are used to make the present invention easier to understand, but the present invention is not limited to the embodiments.

F. Example Hereinafter, embodiments of the present invention will be described based on the perspective.

FIG. 2 is an overall configuration diagram showing an embodiment of a cyclic impact fatigue testing machine according to the present invention.

In the figure, an actuator IO that bears a repetitive load
A and actuator 1. Servo valve 10 that controls OA
B and a punch 10C attached to the movable part of the actuator IOA constitute a fatigue tester 10, and the punch 10C
repeatedly applies an impact load to the test piece 11. 12 is a load cell that detects the load acting on the test piece 1''11, and 13 is a displacement cell that detects the stroke of the punch OC.

The control device 15 is composed of a microcomputer, and includes a CPU (central processing unit) 1, 51 that controls the entire system, a ROM 1.52 that stores processing programs, etc., which will be described later.
CPU 15] calculation result and row 1 cell 12. RAM1.53 that stores detection data etc. from the displacement meter 13
, an input interface 154 and an output interface 155, which are connected to C via a bus 156.
It is connected to PU151. Here, the control device 111
5 constitutes a driving control means, and the CPU 151 constitutes a correction means.

The input interface 154 has a load cell 12 and a displacement meter 13 connected to the AID converter 1.6.17, respectively.
connected via. Furthermore, the servo valve 10B of the testing machine main body is connected to the output interface 155 via the D/A converter 18.

Next, the operation of this embodiment configured as described above will be explained with reference to the flowchart of FIG.

First, the control device i'i1. ! ”) to star 1 and star 3
The test begins according to the procedure shown in the figure.

In step S1 of FIG.
1.52, and sends the lamp displacement command data to the servo valve 1.1 of the testing machine main body 10 through the output interface 155 and the D/A converter 8. Output to OR and control the displacement of actuator] and OA. Here, the displacement control is a control method in which the displacement output from the displacement meter 13 is fed back to the control device ↓5 to control the actuator 10A to be displaced in accordance with displacement command data. As a result, a static load is started on the test piece 11 from an unloaded state to a preset maximum load P maxo. At this time, the load applied to the test piece 11 is detected by the load cell 12, converted into a digital quantity by the A/D converter 16, and inputted to the control device 15. Further, the stroke displacement of the actuator IOA is detected by displacement 1113, converted into a digital quantity by the A/D converter 17, and inputted to the control device 15. These load and displacement data are stored in the RAM 1.53 as a static load-displacement diagram for ITII: specimen = 711 (step S2).

In the next step S3, based on the load-displacement diagram obtained in step S2, the displacement Sm[+ at the point where the load starts to occur (this is called the minimum load) is read, and this displacement S m o is calculated. Set the displacement average setting value S'm.

Also, read the displacement SmaXo with respect to the maximum load Pmax, and add a constant C (<
1) and set this result as the target initial amplitude S'a. Furthermore, from the preset punch speed V and the read displacement S maXo, f = V/2 x S
u+ax.

Find the frequency of the displacement pattern. Then, the displacement command waveform is a habersine wave, and the frequency is f.

A load pattern signal as shown in FIG. 4 of the displacement average set value S' m g vibration @S''a is supplied to the servo valve 10B.As a result, the actuator 1.OA vibrates and applies a repeated impact load to the test piece 11. is given (step S
4. ).

Next, in step S5, the load on the test piece 11 and the actuator I which are excited in the displacement pattern shown in FIG.
In step S6, the displacement at the beginning of load application (1'Z, that is, the displacement S at the minimum load) and the displacement Smax with respect to the maximum load Pmax are read.
x (see FIG. 4) and the maximum displacement Sm1n in the no-load direction when the load is zero (see FIG. 4, referred to as minimum displacement). That is, the load detected by the load cell 12 and the displacement detected by the displacement side 13 are stored in the RAM of the control device 15.
153, and based on this data, the above S. +
Find S 1llaXIS min. Then, in step S7, ΔS m''S.

, and determine whether 1ΔSml<ES. this is,
The test piece 11 deforms due to repeated impact loading, and the punch 1
Since the displacement point at which 0C starts colliding with the test specimen L varies, the displacement average setting value Sm of the displacement pattern is adjusted according to this deformation.
' must always be corrected, and this is the step to determine whether or not the correction is necessary.

That is, when it is determined that 1ΔSml is larger than the standard deviation FS, the true displacement average value of OC is far from the displacement Sl corresponding to the minimum load measured in step S6 at the start of the test, S m' = S
The calculation of m' + (S m , -) is executed to correct the displacement average set value S m ' of the displacement pattern.

In other words, when the displacement average set value S m' is given during the test, the punch 10C always strikes the specimen 11 at that position.
The correction is made so that the collision begins to occur, and the process returns to step S6. Furthermore, when it is determined that ΔSml is smaller than the standard deviation ES, step S8 is skipped and the process proceeds to step S9.

In step S9, the maximum load P max is read from the displacement-load curve collected in step S5, and in step S1
0, ΔP=Pmaxo-Pmax is calculated and it is determined whether IPmaxo-Pmaxl<FP. That is, the preset maximum load Pm+ixu and the maximum (l!f P m
It is determined whether the absolute value 1ΔP1 of the difference with ax is smaller than the standard deviation EP. Here, when it is determined that the value is larger than E1), the process proceeds to step Sll, and when it is determined that it is smaller than Fp, the process proceeds to step S12.

In step Sll, S ;l'"" S i
l' + (P town ax, -P max) Xα is calculated to correct the swing @S a ', and the process returns to step S6.

However, a=((Smaxo Smo)/(Pm
axo O) ) XC, a load with good linearity -
It represents the slope of the displacement characteristic curve. In addition, C is O<C
<1.

In other words, as fatigue of the test piece 11 progresses, even if the test piece 11 is changed (+i) by the amplitude @Sa'' set at the start of the test, the maximum load will not become Pmax, so the amplitude Sa' was given by the above correction. Sometimes, the correction is made so that the maximum load Pmax is obtained.

By the above procedure, the initial displacement average value is S or
An initial steady state is set in which the initial displacement amplitude is Smax. After that, in order to keep the collision speed constant, the amplitude is Sm
With ax constant, the average 4W S o is corrected by 1 to maintain the maximum load.

That is, when it is determined in steno knob S10 that ΔPI<EP, the repeated impact test is continued in step S12, and load and displacement data are collected in step 813. Next, the process proceeds to step S14, where the displacement S when the load starts to be applied, that is, the minimum front mold time, and the maximum load Pmax are detected, and the process proceeds to step S15. In step S15, it is determined whether the difference between the detected displacement S and the initial average value So is greater than a predetermined reference value Sn. This step 813
If it is affirmative, the test piece 11 has been considerably deformed and the test is terminated. If step S15 is denied, the process proceeds to 6, where the maximum load P ma at the start of the test is determined.
The absolute value of the difference between xo and the detected maximum load PIIlax l P max, -P + nax l is the standard deviation Fp
Determine whether it is smaller. If steps 51 and 6 are affirmed, the process returns to step 81.2 to continue the test; if negative, the process proceeds to step 813, where S m'= S m'+ (Pmaxo- Pmax)
A correction of X a2 is applied. Thereby, by keeping the amplitude constant at Smax and correcting the initial average value So according to the deformation of the test piece 11, the impact test is repeatedly performed with a substantially constant maximum load while keeping the collision speed constant.

In Matsumoto's example, when applying a repeated impact load to a test piece by displacement control, the actuator IO
Punch at the midpoint between the maximum and minimum actual displacement of A],
The average displacement value is corrected so that the OC starts colliding with the specimen TP, then the amplitude is corrected so that the desired maximum load is obtained, and this amplitude is fixed so that the desired maximum load is obtained. The displacement average value is now corrected. Therefore, even as the test progresses, the maximum load occurs at the highest value of the displacement pattern, as shown in Figure 5, and the maximum load occurs at the highest value of the displacement pattern, as shown in Figure 5.
As shown in the figure, the amount of displacement under no load and the amount of displacement under load are 1:1, and the collision speed and impact force are maintained with high accuracy, making it possible to perform a highly accurate fatigue test.

In addition, in conventional repeated impact fatigue testing machines, the test takes a long time because the test is performed until the test piece breaks or the test piece breaks, such as when the punch pierces the test piece.

However, in this example, the test is stopped when the displacement of the actuator IOA at the beginning of the load exceeds a predetermined value, so there is no need to perform the test until the specimen is completely destroyed, reducing the test time. At the same time, the fatigue status of the test piece can be clearly understood.

In the above example, after the initial steady state, the amplitude was kept constant to reduce the impact velocity, but if the stiffness of the test piece changes significantly, the frequency of the displacement pattern may be gradually changed. There is a need. Further, the fatigue testing machine of the present invention is not limited to the circuit system of the above embodiment.

G1 Effects of the Invention Since the present invention is constructed as described in (2) below, when conducting a fatigue test using displacement control based on a set displacement pattern, even if the test piece is deformed due to fatigue or its rigidity is reduced, it is always possible to The load actuator can collide with the test piece at a constant speed, and a desired impact load can be applied, allowing stable and highly accurate testing to be performed.

[Brief explanation of drawings]

FIG. 1 is a corresponding diagram of clay 13 according to the present invention. FIG. 2 is a configuration diagram of a cyclic impact fatigue tester showing an embodiment of the present invention. FIG. 3 is a flowchart showing the operating procedure of fatigue test processing in this embodiment. FIG. 4 is a waveform diagram of the displacement pattern. Figure 5 shows the load of the test results by the fatigue testing machine of this example.
It is a displacement time diagram. FIG. 6 is also a load-displacement diagram. 10: Testing machine main body 1.0 A: Actuator 10
B: Servo valve], OC: Punch 1]: Test piece
12: Load cell 13: Displacement meter 152 Control device] 51: Correction means

Claims (1)

[Claims] a load actuator that repeatedly applies an impact load to a test piece in a waveform displacement pattern determined by a set average displacement value, amplitude, and frequency; a load detection means that detects a load acting on the test piece; and a displacement of the load actuator. a displacement detection means for detecting the displacement, a drive control means for driving the load actuator so that the test piece is loaded in the displacement pattern while feeding back the detected displacement, and a displacement detection means for detecting the displacement when the maximum load is detected and when no load is applied. The displacement average value is corrected to an intermediate value between the minimum displacement of A cyclic impact fatigue tester comprising: a correction means for correcting the displacement average value so as to reduce the difference between the maximum load applied and a predetermined maximum load.