JPS60111940A - Fatigue testing method and apparatus - Google Patents

Abstract

PURPOSE:To prevent a body to be tested from receiving excessive load or to prevent a test apparatus from getting into a control unabled state even if play or slide is generated in the body to be tested, by repeatedly applying load to the body to be tested at vibration frequency equal to and more than the resonance vibration frequency of a vibration system. CONSTITUTION:An objective rotary speed at the time of a test for vibrating a vibration system at vibration frequency equal to and more than the resonance vibration frequency thereof is set to a rotary speed setting device 30. When a start switch is closed, a variable speed motor 26 is rotated by the signal from a control circuit 28 and the rotary speed of the motor 26 is abruptly raised to the objective rotary speed. The vibration system consisting of a body 10 to be tested and a vibrating lever 2 is vibrated at vibration frequency equal to or more than resonance vibration frequency through a rotary eccentric weight 12. Because vibration frequency of forcible force is not changed abruptly even if skidding or play is generated in the body 10 to be tested and resonance vibration frequency becomes small, no excessive load is applied on the body to be tested.

Description

[Detailed description of the invention]

The present invention relates to a fatigue testing method and apparatus, and more particularly to a fatigue testing method and apparatus in which a vibration system including a failure test object is sensed by a vibrator and a predetermined repeated load is applied to the test object. Figure @1 is a schematic diagram of a conventional fatigue testing device that is the basis of the present invention. A clamping piece 4 fixed to the vibration lever 2 and a clamping piece 8 fixed to the fixed system and connected to the load cell 6.
The test object 1o is held between the two, and a vibration system is composed of the vibrating lever 2, the holding pieces 4 and 8, and the load cell 6. (A rotating eccentric weight 12 is connected to the dragon lever 2, and the rotating eccentric weight 12 is rotated 1υl by a variable speed motor 14.
Ru. The rotating eccentric weight 12 and the variable speed motor 4 constitute a vibrating section. The load cell 6 is connected to an input terminal of a comparator 18 via an amplitude detector 16. The other input 9j of the comparator 18 has a predetermined repetition rate.

[7 Target imaging width lj for load: Target amplitude setter 2 for setting
0 is connected 7'. The output end of the ratio softener 18 is connected to the motor 1 drive circuit 22 valve (Loe variable speed motor 14). According to this fatigue testing apparatus, when the rotating eccentric weight 12 gold is rotated by the motor 14, the vibration lever 2 vibrates, and this vibration is transmitted to the test object. Therefore, if the rotational speed of the motor 14 is steadily increased one by one to bring the vibration a of the vibration system closer to the resonance point fe, the vibration will occur as shown in FIG. The amplitude of the repeated load Jj (acting on the A test object) rises along the resonance curve a of the vibration system, and a load larger than the curve of the forcing force by the rotating eccentric weight 12 can be generated. A fatigue test using such a fatigue test device is carried out as follows.The test object 1 () is held between the holding pieces 4 and 8 without a trench, and the fatigue test is carried out on the target amplitude setting device 20. When the variable speed motor 14 is rotated, the vibration system vibrates and a repeated load is applied to the test object.At this time, the load cell 6
The repetitive load is detected by the amplitude detector 16, and the amplitude of the repetitive load is detected by the amplitude detector 16. The comparator 18 compares the amplitude detected by the amplitude detector 16 with the target amplitude value set in the target amplitude setter 20, and the deviation between the amplitude of the repetitive load and the target amplitude value is always zero. The motor drive circuit 22' (I: fli is controlled as follows. In other words, if the output of the amplitude detection Then, the motor rotation speed increases: b++ 91.At this time, the load amplitude acting on the test object is determined by the resonance curve a in Fig. 2.
1 along K. if (“thicken, control bη1 so that it finally matches the target amplitude value”) 71,
A fatigue test is performed at the target amplitude value. In the above fatigue test equipment, if the resonance curve does not change at all or gradually changes during the test, the feedback control repeatedly controls the width of - ．． 'fc, fatigue test? It can be implemented. (2 or [7) If the test object is a test item with a mechanical joint or a part including a gear pair, increase the load amplitude to prevent local fatigue from occurring during the 7C or fatigue test process. If this occurs, cracking or slipping may occur instantaneously in the closing part, etc. Therefore, when performing the fatigue test on the test object as described above with the conventional fatigue test equipment K, the following should be carried out. In other words, as shown in Figure 3, if the resonance curve before rattling is C, then the resonance curve after rattling is equal to the resiliency constant of the vibration system due to rattling. Due to the decrease, the resonant door life μ, which is proportional to the square root of the spring constant, also decreases, so it changes to d or e in Figure 3 depending on the thickness of the backlash 6. Generally, the backlash occurs rapidly, so the motor The rotational speed of the cart cannot follow this change. When a fatigue test was performed to reach the target amplitude value, a rattling occurred and the resonance curve changed from C to d, and the cart amplitude suddenly became 8 points and 1.
Yl. Therefore, there is a problem in that an unsuitable excessive load is applied to the test object during a fatigue test. In addition, if the resonance curve suddenly changes from C to e, the cart amplitude suddenly decreases from 0 to 1 (7,
At this point, no excessive load occurs, but since the relationship between the motor rotation speed and the load image width has an inverse characteristic, the load amplitude is smaller than the target amplitude value A, so even if the motor rotation continues to increase -g fL There is a problem that the load amplitude is reduced and the control becomes uncontrollable. Note that if the characteristic changes from C to e relatively slowly, a problem arises in that excessive vibration occurs when passing through resonance test #p. The cause of the excessive load acting on the above-mentioned test object is that the conventional fatigue test equipment sets the target amplitude value [2] (the amplitude is directly feedback controlled to the target yarn width), so it is less than the resonant frequency. In other words, in order to control the amplitude of the vibration system from zero to the target amplitude value, the motor rotational speed rSf must be increased. This is because it is necessary to gradually increase the amplitude of the vibration system, and as the amplitude of the vibration system is gradually increased, the amplitude of the imaging system will match the target amplitude value before the 4he point. , the comparator 18 of the conventional fatigue testing device needs to output a signal to increase the motor rotational speed to 11J' when the output of the amplitude detector 16 is smaller than the output of the target section width setter 20. By doing this, when the resonance curve changes from C to e in Fig. 3, the output of the amplitude detector 16 becomes less effective than the output of the scale setting width setting device 20, and the motor rotation speed is controlled so as to increase. However, the amplitude detector output is
As the size of the motor becomes smaller, the rotational speed of the motor increases to the limit, resulting in an uncontrolled state. The present invention was created to solve the above problems, and even if the resonant frequency becomes small due to rattling or slipping of the test object, an excessive load will not be applied to the test object. The overall object is to provide a method for testing trabecular bones that does not cause the test device to become uncontrollable, and a device that can be used continuously for carrying out this method. In order to achieve the above object, the first invention provides a vibration system for a ramus test method in which a vibration tip containing a test object is forcibly vibrated and a predetermined repeated load is applied to the test object to perform a fatigue test. It is characterized in that a predetermined repeated load is applied at a number of imaging at a resonance frequency or higher. Here, the resonance curve of the vibration system before rattling or slipping occurs is g in Figure 4, and the resonance curve when rattling or slipping occurs is h in Figure 4. The vibration exceeds the resonance point fc before it occurs! 1tII
Assume that the imaging system is forced into a vibration field n at El, and the load amplitude of the vibration system is the magnitude of point E in FIG. When rattling or slipping occurs, the resonance curve changes sharply to h1-, but the number of forced force shots does not change rapidly, so the load amplitude of the vibrating string depends on the magnitude of point F on the resonance curve. It changes. At this time,
Since the magnitude of the load convergence at point F is smaller than the large load amplitude at point E, it is easy for an excessive load to act on the test object. If the frequency of the force is reduced to pebbles, the load amplitude increases along the resonance curve and can be controlled to point G, which has the same large heat as point E. In addition, even in the 4th case where rattling and slipping were expected to occur relatively slowly, the +lvX for load 1 only changes slowly from point E to point F, and I
QLarge loads will not occur. In order to force the vibration system to vibrate, a rotational bias 11 > a vibration device using a weight and a variable speed motor, or a magnetic chip by turning on and off an electromagnet 7 (an vibration device etc. can be used. According to the invention of f+, even if the test object rattles or slides, the resonant frequency does not pass when the characteristics of the mechanical vibration system change, so that an excessive cart does not act on the test object. Furthermore, in order to achieve the above object, a second invention includes a rotating eccentric weight that vibrates a vibration system including a test object, and a rotating eccentric weight that causes the vibration system to vibrate. Resonant vibration of the vomiting motor and the photographing system! Set the constant rotation speed of the j lami in order to vibrate at a frequency higher than the OJ number. Control the motor rotation speed to a predetermined rotation speed based on -J
- A control circuit for outputting a signal sound for the purpose of the control is provided in one piece. The second invention will be explained with reference to FIG.
A mechanical vibrating section consisting of a vibration system including a test object 30 and two oscillating weights, a rotating eccentric weight 12, a variable speed motor 26,
It consists of a control circuit 28 and a rotation speed setting device 30. In the rotation speed setting device 30, a target rotation speed at the time of testing is set in order to generate a vibration field with a frequency higher than the total resonance frequency of the vibration system. When the starting switch is fully turned on, the motor 26 rotates due to a signal output from the control circuit 28, and the motor rotation speed rapidly increases to the target rotation speed set in the rotation speed setting device. Since the vibration system vibrates at -6n at a frequency higher than the resonance frequency, the load amplitude acting on the test object when rattling or slipping occurs is the first
Although it is smaller like the second invention, it is possible to control so that a predetermined edge turning load is obtained by adjusting the setting value of the rotation speed setting device 30. is a fatigue test I at a frequency higher than the resonance frequency of the vibration system! i! Because we are implementing IT, the first
Similar to the invention, it has the effect of preventing excessive load and motor over-rotation when rattling or sliding starts. Next, an embodiment of the second invention will be described with reference to FIG. In FIG. 6, the same parts as in FIG. 5 are designated by the same reference numerals, and their explanation will be omitted. In this embodiment, the rotation speed setter is set to a target rotation speed tW setter 3 (lA and target The initial rotation speed setting device 3013 is configured to set an initial rotation speed sufficiently higher than the rotation speed.In the fatigue test, first, the setting signal of the initial rotation speed setting device 30B is sent to the control circuit 28. Manually, the variable speed motor 26 is quickly rotated at the initial rotation speed 1. Then, after the rotation speed 1 of the motor is slowed down to the initial rotation speed, the setting signal of the target rotation speed setter 30A is sent to the control circuit 28. Then, manually lower the motor rotation speed at the target rotation speed housing.As a result, a predetermined cyclic load is applied to the test object according to the target rotation speed.Please note that if rattling or slipping occurs. JICd, by directly adjusting the setting of the target rotation speed setting device 30A, it is possible to control so that a certain repeated load is applied.Here, the reason for setting the initial rotation speed higher than the target rotation speed is generally due to resonance. In the equation fatigue test, the frequency of the vibration system during the test is relatively close to the resonance imaging frequency, so if the motor rotation speed is controlled from 0 to the target rotation speed, there is a possibility that excessive resonance vibration will occur when the resonance frequency passes. This is because this excessive resonance vibration can be avoided by setting the initial rotation speed set in the initial speed setting device to a value exceeding the total target rotation speed to shorten the time required to pass through the resonance frequency (near tj). In this embodiment, by setting the initial rotational speed to a value sufficiently higher than the target rotational speed, a comparatively low horsepower and inexpensive variable speed motor can be used. Also, it is possible to make the j5r5 time when the rotational speed of the motor passes the resonance frequency very short.Therefore, there is a publication that the resonance phenomenon that occurs when the motor rotation speed passes the resonance frequency can be reduced. If a horsepower motor is used, it is possible to increase the speed at which the motor rotates, so it is also possible to lower the initial set rotation speed and set it close to the rotation speed during the test. can use a variable speed motor with a low rotational speed for a high customer base.Furthermore, according to this embodiment, since the initial rotational speed setter and the target rotational speed setter are switched and used at t'1. This has the effect of eliminating the need to adjust the rotation speed setter at the start of the test.In addition, the initial rotation speed setter and the target rotation speed setter are configured with one rotation speed setter. , the setting value of this rotational speed setting device may be adjusted. A third invention is to directly achieve the above object. A rotating eccentric weight that vibrates the entire vibration system including the test object, a motor that rotates the rotating eccentric weight, a width detector that detects the full amplitude of the repetitive cart acting on the fatigue test object, and a a target load amplitude setter for setting a target amplitude value of the repetitive load in the test; an initial rotation speed setter for setting an initial rotation speed for vibrating the vibration system at a frequency equal to or higher than the resonance frequency before the start of the test; A comparator that outputs a signal according to the deviation between the signal from the amplitude detector and the setting signal from the target load amplitude setter, and the setting from the initial rotation speed setter (adding the signals from No. U and the comparator) According to the present invention, a control circuit consisting of an adder and a control circuit is provided to output a signal for controlling the motor rotational speed based on the signal from the adder. The motor rotation speed is quickly controlled so that the vibration system vibrates at a frequency higher than the resonance frequency based on the setting signal from the initial rotation speed setting device, and during testing, the vibration system is controlled based on the signal from the comparator. Feedback control is performed so that the load amplitude becomes the target amplitude value. Therefore, during testing, a predetermined repeated load is applied at a frequency higher than the resonance frequency of the vibration system according to the target amplitude value. In this invention, the test is conducted at a frequency higher than the resonant frequency of the vibration system, which prevents excessive loads from being applied to the test object due to rattling or slipping, and excessive rotation of the motor of the test equipment. In addition, since feedback control is performed, when the load amplitude decreases due to rattling or slipping, it can be automatically controlled to the target amplitude.Next, the third effect is obtained. An embodiment of the invention will be described with reference to FIG. 7. In FIG. 7, the same parts as those in FIG. It is equipped with an amplitude detector 32 that detects the amplitude of the repeated load -?lL acting on the test specimen, and a target load amplitude setter 34 that sets the target amplitude value of the repeated load during the test. The load amplitude setter 34 is the comparator 3
6 and the drive circuit 28 via the adder 38 fif
I'm here. The comparator 36 and the adder 38 form a control circuit I:M+. Further, an initial rotation speed setter 30B is connected to the adder 38 to set an initial rotation speed for causing the vibration system to vibrate at an imaging frequency equal to or higher than the resonance frequency before the start of the test. When performing a fatigue test, first set the target digging width value in the target load amplitude setting device 34, and set the initial rotation speed in the initial rotation speed setting device 30B. In this state, when the step-like setting signal outputted from the initial rotation speed +W setting device 301J is inputted to the drive circuit 28 via the adder 18, the variable speed motor 26 suddenly increases at the initial rotation speed 1 -gn,・When the rotational speed is rapidly increased in this way, the object under test becomes
Because iJJ is rarely performed, the load on the test object is low.
It is possible to suppress the width of the bow to a value sufficiently lower than the target amplitude value during testing. On the other hand, the amplitude of the repeated load on the test object is detected by the amplitude detector 32.
After converting the signal into an electric signal by 1fl, it is manually input to the comparator 36. Furthermore, the comparator 36 receives the setting signal output from the target load amplitude setting device 34 as an input. Comparator 36
is the signal from the amplitude detector 32 and the target load width setting device 3.
A signal corresponding to the deviation from the setting signal from 4 is output. That is, when the signal from the amplitude detector 32 is lower than the set signal, a signal is output that reduces the motor rotational speed and increases the load amplitude, and conversely, when the signal from the amplitude detector 32 is higher than the set signal. In this case, a full signal is output that changes the motor rotation speed from the top to the outside. The operation of the comparator of this embodiment has opposite characteristics to the operation of a conventional comparator. The reason for this is that in conventional fatigue testing equipment, tests are conducted in a frequency range lower than the resonance frequency (71°), so there is a positive correlation between motor rotational speed and load amplitude, whereas in this embodiment This is because there is a negative correlation between the 7C motor rotation speed and the load amplitude, which are all tested in a range of imaging numbers higher than the resonance frequency. No. 43 outputted from the comparator 36 is input to the drive circuit 28 via the adder 38, and is controlled so that the load amplitude of the test object becomes the target amplitude value. As explained above, this embodiment has the effect that a fatigue test on a test object that is prone to wobbling or slipping can be stably performed. In other words, if the vibration frequency of the vibration system decreases due to rattling or slipping, and as a result, the width of the load acting on the test object decreases, No. 43 from the amplitude detector also decreases and the target is not reached. A deviation from the amplitude value occurs. For this reason, depending on the deviation, 7cG? If the number is output from the comparator, the output thereof is input to the adder 38 and input to the drive circuit 28, and the motor rotational speed 1 is controlled so that the deviation becomes small. Examples of the third invention will be described in detail below. Figure 8 shows
FIG. 2 is a block diagram showing a first embodiment. The mechanical vibration section 53 of this tEl embodiment constitutes a test device for conducting a fatigue test on the gear pair 52, as shown in FIG. One gear of the test gear pair is held by a shaft to which a strain gauge 54, which will be described later, is attached. The other gear of the test gear pair is gripped and protruded by a shaft integrated with the vibration lever 53b, and is vibrated by a rotating eccentric weight 53aK. The rotating eccentric weight 53a is connected to DC via a flexible joint 53g.
Driven by C motor 3n. In addition, an average load lever 53 is connected to the shaft of the vibration lever 53B via a torsion type 54Ci.
The shaft integrated with e is connected tightly, and the average load M is applied to the test gear pair 52 by the weight 53f. The spring constant of the torsion bar 53c is set to be sufficiently lower than the spring constant of the portion including the test gear pair 52 and the shaft to which the strain gauge 54 is attached. By this, by vibrationally separating the average load lever 53e and the inertial type -f of the weight 53f from the imaging part including the vibration lever 53bt,
The resonance number of the vibrating part including the test gear pair is kept high to prevent a drop in test speed. A strain gauge 54 mechanically connected to a test object installed in a mechanical vibration section 53 is connected to a test gear pair 52 which is a test object.
The load applied to the
Output as It. A strain gauge amplifier 56 connected to the strain gauge 54 converts the resistance change ΔIL of the strain gauge 54 into an electrical signal, and outputs a load M (signal e) that changes according to the load.
Output as w. A peak hold circuit 58 connected to the strain gauge amplifier 56 inputs the load (M ew) and detects one-half of the candy in volume weight, that is, the load half amplitude value, from the peak of the changing load signal ew, and determines the amplitude. It is output as signal C,1). This peak hold circuit 58 is connected to the differential amplifier 6
Connected to the negative input terminal of 0. It's a trench, differential amplifier 6.
A 1b5 pressure setting device 62 is connected to the positive human power j'i+4 of 0, which is configured with a constant voltage power supply, a variable resistor, etc., and outputs a predetermined voltage E corresponding to the target amplitude value. This differential amplifier 60 calculates the deviation between the voltage E1 and the amplitude signal ep, that is, E, -ep, and outputs it as a deviation signal Δe. An integrating circuit 64 is connected to the differential amplifier 60, and a parallel circuit of an integrating capacitor C and a switch SW is connected in parallel to the integrating circuit 64. Therefore, if the switch SW2 is off, the integrating circuit 64
performs the partial division q- of the deviation signal Δe, and the J51i signal C]! That is, it outputs. On the other hand, when the switch SW2 is turned on, both ends of the integrating capacitor C are short-circuited, so the integrating operation of the integrating circuit 64 is stopped, and the integrating signal C1 becomes 0 [V
). That is, the switch SW2 can issue an on/off command for the integral operation. The integrating circuit 64 with
It is connected to the negative input Δ111 of the differential amplifier 66. An upper voltage setting device 68 configured similarly to the voltage setting device 62 and outputting a predetermined voltage E2 corresponding to the initial rotation speed is connected to the positive input terminal of the differential amplifier 66 via a switch SW. The differential amplifier 66 outputs the difference between the voltage E and the integral signal el, that is, E, (3r). A of
C voltage to D C'f's pressure and control voltage signal E. The motor is connected to a motor 5ityy fN fit circuit 70 which supplies a DC motor 72 with a motor voltage E m proportional to . Accordingly, l) C motor 72, motor control direction I Tlj, pressure No. 417 1j: by the motor crow h zo sewing circuit 70. It is suppressed at a rotational speed N proportional to . The DC motor 72 is connected to a rotating eccentric bell in the mechanical vibration section 53 via a flexible joint 53f. Next, the operation of the first embodiment will be explained with reference to FIGS. 10 and 11. Turn on the switch SW, and the differential amplifier 6
Let the human power to the positive input terminal of the differential amplifier 66 be (1) (v), turn on the switch SWZ, set the integral No. 111 (・, to 0 [■]), and make the human power to the negative input terminal of the differential amplifier 66 O [: V
], then control '#1 is set to pressure signal 1. ;o becomes 0 [■], so motor voltage ]';m also becomes o Cv ),
The DC motor 68 is in a stopped state 1z↓1. In this state,
'The Mf pressure setter 62 is supplied with a predetermined voltage l·] corresponding to the target amplitude value, that is, the same voltage as the amplitude signal ep output from the peak hold circuit 58 when the test object vibrates at the moon=1 standard amplitude value. Set the value. In addition, the voltage setting device 68
is a predetermined voltage E2 corresponding to the initial rotational speed, that is, a control voltage signal E during a test to obtain a predetermined frequency higher than the resonance frequency. Set a larger value. Here, the voltage 1'y
2 to the control ill 'Fl'i pressure signal 1 during the test. J:
The reason for increasing the voltage E2 is to increase the voltage E2 from the control voltage signal J! :. If it is made too small, the test object will vibrate with a load amplitude larger than the target load amplitude. This is because it is inappropriate as a ramus bone test. Therefore, the initial rotation speed N1 needs to be higher than the target rotation speed N2 during the test, and the voltage E
2 is the control voltage signal 1 etc. during the test. A larger value is set. The above situation is shown at time t in figure te11. or 1. The signal waveforms of each part are shown below. After setting voltage E and %E as above. When the switch SW is turned on as shown in switch No. 18 SA~1 shown in FIG. Signal E. As shown in , the control voltage signal L!
]. rises rapidly in the same way as the voltage E, and the DC motor 72 is rotated at an initial rotational speed N that is higher than the resonant rotational speed N0 for vibrating the test object at the resonant frequency. This situation is shown in waveform N between time 1 and time 17 in FIG. Figure 10 shows the relationship between the motor rotational speed and the amplitude signal e. The broken line shows the characteristics when the motor rotational speed N is gradually increased by 2. This shows the characteristics when the temperature is increased rapidly. As can be understood from the figure, when the motor rotation speed N is gradually increased, the amplitude signal ep varies from 0 to N as the motor rotation speed increases. -C increases slowly as the motor rotation speed increases between 1 and 2, and reaches a maximum at the resonance rotation speed N0, when the motor rotation speed is N. If it exceeds , it will gradually drop as the motor rotation speed increases. However, when the motor rotational speed is rapidly increased to more than the resonance rotational speed N0, the motor rotational speed is 111' and passes near the resonance rotational speed No in a short time. Since there is a response delay before the is transmitted to the vibration system, a resonance state does not occur and the amplitude signal ep is N. A magnitude ep, corresponding to an initial rotational speed N, exceeding , is reached. Also in this embodiment, the control voltage signal E shown in FIG. In order to rapidly rotate the DC motor 72, the motor rotation speed is an initial rotation speed N that is higher than the resonance rotation speed. In this state, that is, in the state shown by the waveform N between time t and time 18 in FIG. 11, the motor continues to rotate at a constant speed at D. When the DC motor 72 is rotated, the rotating eccentric weight is rotated, and this rotation causes vibration! l! The υ thread is vibrated. The amplitude of the repeated load on the vibration system at this time is detected by the strain gauge 154, and sent to the differential amplifier 6 as an amplitude signal ep via the strain gauge amplifier 56 and the peak hold circuit 58.
0 is man-powered. On the other hand, since the voltage E from the voltage setter 62 is input to the differential amplifier 60, the deviation signal Δe shown in FIG. 11 is output from the differential amplifier 60. At this time, the magnitude eP+ of the load amplitude signal eP with respect to the initial rotational speed N1 is the magnitude EI of the load amplitude signal ep during the test.
Therefore, the deviation signal Δe has a positive value as shown in the signal Δe at times t2 to t3 in FIG. Note that since the switch 5Vv2 is turned on, the integral signal e1 is
Eleventh, as shown in the figure, it is 0 [■]. When the switch sw is turned off at time t3, the integration circuit 64 starts the integration operation, and the integration signal e becomes the 11th
As shown by the signal e1 in the figure, it increases in the positive direction. As the integral signal +'ic1 increases, the control 'rh: pressure signal E output from the differential amplifier 66. (-Eter
) gradually decreases, the motor voltage Em also decreases, and the motor rotational speed N decreases. This situation can be seen at time t in FIG. The signals between el, I, Eo, and N are not shown, respectively. Motor rotation speed N is resonance rotation speed N. , l), the motor rotational speed N and the load amplitude signal ep are inversely proportional, and as the motor rotational speed decreases, the load amplitude signal ep changes to point A in Fig. 10.
It changes from to point B direction. When the magnitude of the amplitude signal ep matches the target voltage E1, the deviation signal Δe becomes 0 (V) as shown in the waveform ΔC at time t4 in FIG. 11, and the integral signal eH stops increasing and reaches the fixed value. becomes. Therefore, the motor rotation speed also becomes a constant value, that is, the target rotation speed N2, and becomes stable. This state does not change as long as the deviation signal Δe is 0 [V], and the state of the target load amplitude is maintained for a long time. When repeated loads are applied to the test object over a long period of time, and the spring stiffness decreases due to fatigue, rattling, stiffness, etc. of the test object,
A change in vibration characteristics occurs, and even if the rotational speed is controlled to the target rotational speed, the load amplitude signal gradually or sharply decreases as shown by the waveform ep at time t11 in FIG. As a result, the deviation signal Δe increases, the integral signal eH increases, and the control voltage signal E increases. decreases, and the motor rotational speed decreases. This allows the first
As shown in the waveform at time t6 in FIG. 1, the load amplitude increases, the deviation signal Δe decreases, and the deviation signal Δe is controlled to match the target voltage E. This situation is shown between times t5 and 16 in FIG. On the other hand, due to some reason, the time t in FIG. As shown in the waveform ep, when the load amplitude ep becomes larger than the target voltage E, the deviation signal Δe becomes a negative value, and contrary to the above, the motor rotation speed increases and the target load amplitude increases. controlled to obtain. As explained above, the voltage setting device and switch SWl are used to rapidly increase the motor rotation speed above the resonance rotation speed,
Thereafter, by controlling the amplitude (tj) to 461L pressure E, it is possible to perform a fatigue test by repeatedly applying a load at a frequency higher than the resonant frequency of the test object. This is an example of a lateral leg.
If the 1A-difference Δe deviates from O■, the correction is immediately made and responsive control is possible. Furthermore, even the occurrence of a small deviation Δe is magnified by the time integration operation of the xit circuit 64, so that it can be detected.
This has the advantage of providing highly accurate control. Next, a second embodiment of the third invention is shown in Fig. 12''.The major difference between the first embodiment and the second embodiment is that the first embodiment uses continuous analog control, The second embodiment uses intermittent on-off proportional control.For this reason, the second embodiment uses a manual huffle motor as a variable speed motor and a super shunt motor that can change speed by changing the brush position with a pilot motor. As shown in the figure, a displacement detector 74 for detecting the fluctuating displacement X of the vibration system within the mechanical vibrating section 53 is attached to the mechanical vibrating section 53 configured similarly to the first embodiment. The displacement detector 74 is connected to the AC voltmeter 7 via the displacement meter ANGUAR 6.
8 is connected. The AC voltmeter 78 extracts the AC component of the displacement signal ex output from the displacement meter amplifier 76 and outputs a displacement AC signal eAC. A Ciltl stylus pressure gauge is connected to the negative input terminal of the differential amplifier 80. A target voltage E having the same magnitude as the displacement AC signal eAC corresponding to the target displacement value is supplied to the positive input terminal of the differential amplifier 80 as the target displacement value. A voltage setting device 82 is connected thereto. Therefore, the differential amplifier 80 generates a deviation signal Δe (=Eo es
c) Output. Differential amplifier 80 is connected to one positive input terminal of adder 84 . At the other positive input terminal of the adder 84, there is a triangular wave No. 41 e whose frequency is constant and changes around O [■]. , C is connected thereto. Therefore, the adder 84 outputs the deviation signal Δe and the triangular wave signal e. Addition signal C0 (=Δe
10e. Output sc>. Adder 84 is connected to the positive input of first comparator 88 and the negative input of second comparator 90 . The negative input terminal of the first comparator 88 is connected to a power source that outputs a constant voltage e, which is the same as the maximum value of the triangular wave (No. 8 e., .). outputs an on-off signal eB which becomes a high level when the voltage e and the triangular wave signal e.5c become larger and becomes a low level otherwise. A power source is connected that outputs a constant voltage e, which is the same as the minimum value of the signal.Therefore, the second comparator 90 outputs a triangular wave signal eelsc.
It outputs an on/off signal ep which becomes high level when the voltage C4 becomes larger and becomes low level otherwise. A first comparator 88 is connected to a first relay 92;
A second comparator 90 is connected to a second relay 94. The first relay 92 and the second relay 94 are turned on when the on/off signal becomes high level, and the switch SW is turned on.
A C'+ij force supplied via 2 is supplied to the pilot motor 96B of the motor 96. Mori 9f1. , main motor 96A1 pilot motor 9
6B and manual handle 9 as initial rotation speed setting device
6C, and is a super shunt motor whose speed can be varied by moving a brush to the υ main motor 96 using a manual handle and a pilot motor 96B. When the pilot motor 96B is supplied with AC power via the second relay 94, it rotates forward and moves the brush to increase the rotational speed of the main motor. When a force is applied, the brushes are moved in reverse to reduce the rotational speed of the main motor. The main motor 96B is connected to an AC power source via a switch SW1, and is also connected to a rotating eccentric weight of the mechanical vibration section 53. The operation of this embodiment will be explained below. switch s'
When vv and SW are turned off, the main motor 9
6A and pilot motor 9613 are stopped. In this state, operate the manual handle 96C of the motor 96 to set the brush position of the main motor so that the rotation speed of the main motor 96A is rotated at the initial rotation speed N, which makes the vibration system resonate. move. When the switch SW is turned on, AC power is supplied to the main motor 96A, and the rotational speed of the main motor 96A reaches the initial rotational speed N. At this time, the vibration system resonates as described above. Displacement due to vibration of the vibration system in the mechanical vibration unit 52 is detected by a displacement detector 74, and is detected by a displacement meter amplifier 70 and an AC
The displacement AC signal eAc is output via the voltmeter 78. At this time, since the vibration system vibrates at a frequency higher than the resonance frequency, the voltage setter 82 has a target voltage E that is larger than the displacement AC signal eAC due to the initial rotational speed. is set, the deviation ratio Δe output from the differential amplifier 80 is a positive value. Therefore, the addition signal e is output from the adder 84. As shown in FIG. 13, the voltage C1 becomes intermittently larger than the voltage C1 when the triangular wave signal eo5c is increased by Δe. Therefore, the ON/OFF No. 43 eB output from the first comparator 88 is intermittently at a high level as shown in FIG. On the other hand, the addition signal e. is larger than the voltage e2, so the second
The on/off signal ep output from the comparator 88 continues to be at a low level. As a result, the first relay 92 is repeatedly turned on and off by the on-off signal eH, and the second relay 94 is in the off state. When the switch SW is turned on, AC power is intermittently supplied to the pilot motor 96B via the first relay 92 which is turned on and off, the pilot motor 9613 is intermittently reversed, and the rotational speed of the main motor 96A is reduced. As the rotational speed of the motor decreases, the width of the repeated load on the vibration system increases, the variable ILAc signal eAC increases, and the deviation signal ΔC decreases. Therefore, when the addition signal eo decreases and the deviation signal Δe reaches 0 [V],
That is, the displacement AC signal e A c is the target voltage 1s. When they match, the maximum value of the addition signal e0 is 1IEe,
Since the on/off No. 43 eB continues to be in a low level state, the first relay 92 is turned off, the rotation of the pilot motor 9613 is stopped, and the main motor 96A is in a stable rotation state. On the other hand, when the displacement AC signal ehc becomes larger than the target voltage E0, the deviation signal Δe becomes a negative value, and the addition signal e
. is a triangular wave signal e. 5o becomes a signal shifted by Δe in the negative direction. Therefore, contrary to the case described above, the on/off signal ep output from the second comparator 90 is intermittently at a high level, and the second relay 94 repeats on/off. Therefore, the pilot motor 96B is intermittently rotated forward, the rotational speed of the main motor increases, the displacement AC signal eAC decreases, the deviation signal Δe approaches 0 (V), and the deviation signal ΔC becomes O[~ The main motor rotates stably in the state ゛゛〕. As mentioned above, the manual handle and switch SW are used to rapidly increase the main motor to the initial rotation speed, cause the vibration system to vibrate 11 times at a frequency higher than the resonance frequency, and then turn on switch SW2. Intermittent on/off proportional control is performed by rotating the pilot motor from the V and controlling the displacement AC signal to match the target 11°C pressure. Tests can be performed by applying a load. In this embodiment, the rotation speed can be controlled by on/off control of a relay without using the relatively expensive motor voltage control circuit used in the first embodiment, so that an inexpensive device can be provided. FIG. 14 shows a third embodiment of the third invention. This embodiment has a buzzer for notifying an abnormality and a seventh
It is equipped with an abnormality detector that causes the engine to stop suddenly. Therefore, in FIG. 14, the same parts as in FIG. 8 are given the same reference numerals, and their explanation will be omitted. The output end of the differential amplifier 60 is connected to the abnormality detector 100 via a switch SW. That's right, differential amplifier 6.
The output terminal of 6 is connected to the motor lα via the contact of relay 104.
The output end of the detector 100 is connected to the excitation coil of the scissor 102 and the relay 104. , is turned on when the side leg is in a normal state.As a result, the deviation Δe is manually inputted to the sensor 100.At the same time as the start of the fatigue test, the test object is continuously subjected to repeated loads. However, over time, the test specimen becomes fatigued, the spring constant decreases, and eventually fatigue failure occurs.When fatigue failure occurs, the mechanical vibrating part cannot maintain stable vibration and becomes unstable. It becomes a vibration state.When this state occurs, the rotational speed of the motor is suppressed and -C
However, the amplitude of the load J does not reach the target handling width value, and the deviation signal ΔC gradually changes to positive or negative, but not suddenly. Abnormality Detector] (l Ot): This abnormality or deviation, 11g
Detect whether No. 1 Δe is too large or small.
J, l LC relay 1 By turning on the contact of F)-1, the motor is suddenly stopped and the buzzer is driven to notify the end of the test. Note that, although the example in which the load amplitude is detected using a strain gauge or a displacement detector has been described above, the load amplitude can also be detected using a torque meter, an electromagnetic strain meter, or the like. '1) It is also possible to rotate a rotating eccentric weight using an AC motor and an inverter, and it is also possible to detect abnormalities from the motor rotation speed and amplitude signal. Further, the switches sw and -5w3 can be automatically turned on and off using a timer, and various signal processing can be performed by a microcomputer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional fatigue testing device, FIGS. 2 and 3 are diagrams showing the relationship between motor rotation speed and load amplitude, and FIG. 4 is a diagram for explaining the present invention in detail. Figure, 5th
6 is a block diagram showing an embodiment of the second invention, FIG. 7 is a block diagram showing an embodiment of the third invention, and FIG. 8 is a block diagram showing an embodiment of the third invention. A block diagram showing the first embodiment of the invention, FIG. 9 is a diagram showing changes in the load signal of the embodiment, FIG. 10 is a diagram showing the relationship between the motor rotation speed and the amplitude signal of the embodiment, FIG. 11 is a diagram showing the timing of various signals in the embodiment, 121st digit is a block diagram showing the second embodiment of the third invention, and FIG. 13 does not show the triangular wave signal of the second embodiment. Line r:! ! j, FIG. 14 is a block diagram showing a third embodiment of the third invention. 6°・'Load cell, 10...Test object, 12...
Rotating eccentric weight, 26... variable speed motor, 28... control circuit, 30... rotation speed setting device. Agent Tatsuyuki Uke (1Jq□1 leg. Figure 1)

Claims (3)

[Claims] (1) In a fatigue test method in which the vibration system including the test object is forcibly stationary and a predetermined repeated load 'N is applied to the test object to conduct a fatigue test, vibrations exceeding the resonant frequency of the vibration system A fatigue testing method that is characterized by applying a predetermined cyclic load. (2) A rotating eccentric weight that can be used to rotate the vibration system including the test object, a tanabata that can rotate the rotating eccentric weight, and a vibration system that causes a disturbance at a frequency higher than the resonance frequency. Outputs a signal for controlling one set of motor rotational speeds to a predetermined rotational speed based on the setting signal shift from the rotational speed setting device and the rotational speed setting device No. 111. A fatigue testing device that includes a control circuit. (3) A rotating eccentric weight that makes the vibrating string containing the test object vibrate; a motor that rotates the rotating eccentric weight; and an amplitude that detects the amplitude of the repetitive load that acts on the test object. A detector, a target load amplitude setting device for setting the target amplitude value of the repetitive load during the test, and an initial rotational speed for photographing the vibrating string at a frequency higher than the resonance frequency before starting the test. an initial rotation speed setter to be set; a comparator that outputs a signal corresponding to a deviation between the signal from the amplitude detector and the setting signal from the target load amplitude setter; and 7. A control circuit comprising a setting signal and an adder that adds the signal from the comparator, and outputs a signal for controlling the motor rotation speed based on the signal from the adder. Device.