JPH0540083A - Cyclic fatigue test equipment - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] The inspection of test piece p in a high temperature atmosphere shall be reproducible without being affected by the high temperature creep. [Structure] A predetermined strain signal value of the load cell 12 is held in advance and compared with this value. If this value is small, vibration is caused by increasing the alternating voltage value applied to the electrostrictive element layers 5a and 5b. The amplitude of the plate 2 was increased to equalize the maximum strain amounts applied to the test piece p. [Effect] Due to high temperature creep, the entire device may be stretched,
Even if the test piece p is plastically deformed, the test conditions can be kept constant and good test values can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cyclic fatigue test apparatus for inspecting the strength of ceramic test pieces and the like.

[0002]

2. Description of the Related Art In a cyclic fatigue test of a ceramic test piece or the like, one surface is held at two points, the other surface is held at the center, and a three-point bending test in which a dynamic load is applied from one surface side There is a method of measuring bending fatigue. Conventionally, in the cyclic fatigue test apparatus used in this method, a mechanical linear reciprocating drive mechanism such as a piston and a cylinder is used as a drive source, and a dynamic load is applied from one surface side of the test piece. By the way, in such a conventional configuration, it is troublesome to adjust and change the driving force, a driving force of high frequency cannot be generated, a large driving sound is generated, and further mechanical friction causes mechanical friction. Wear is severe,
There were drawbacks such as difficulty in keeping the test conditions constant.

Therefore, as shown in FIG. 4, a diaphragm a having an electrostrictive element layer c disposed on at least one surface of a curved plate b.
One end or both ends of the test piece p are supported on the base d, and the holding member e for the test piece p is attached to the swinging surface of the diaphragm a, and the test piece p is held on the holding member e by the holding member e. It has been proposed that a load cell f provided with a test piece pressing end g for sandwiching is provided (Japanese Patent Application No. 62-250208).

In such a structure, when an alternating voltage of a predetermined frequency is applied to the front and back electrodes of the electrostrictive element layer c, bending vibration is generated in the bending plate b. Along with this, the holding member e supported on the swing surface of the diaphragm a vibrates. Therefore, one surface is supported by the holding member e and the other surface is pressed by the pressing end g.
The test piece p held by means of the vibration of the holding member e,
As shown in FIG. 5, a dynamic load based on a voltage having a predetermined resonance frequency is applied, and eventually damage occurs. At this time, the strength of the test piece can be detected by measuring the speed of failure and the frequency of the dynamic load.

Therefore, in this structure, by repeatedly selecting the alternating applied voltage to the electrostrictive element layer c, the repetitive stress and the cycle thereof can be adjusted, and various test conditions can be arbitrarily set. Further, unlike the conventional means for applying a dynamic load by the mechanical linear reciprocating drive mechanism, there is an advantage that the generation of noise and wear due to mechanical friction are small and it is easy to maintain the same test condition.

[0006]

In such a structure,
When inspecting the strength of the test piece p in a high temperature atmosphere, if strain is applied by high temperature creep, the entire apparatus will stretch or the test piece will gradually deform. By the way, the bending stress (center value of bending stress in FIGS. 3 and 5; F _mean ) in the state where no voltage is applied to the electrostrictive element layer c applied to the intermediate position of the test piece p is as shown in FIG. The screw rod h screwed to the frame i is manually moved up and down to determine the position of the pressing end g, and the pressing end g serves as a fixed point. Therefore, when the test piece p is deformed as described above, since the initially set position of the pressing end g is a fixed point, the center value F _mean of the bending stress waveform is gradually increased as shown by the chain line in FIG. Drop to
The maximum value F _max becomes smaller than the initial value. For this reason, there is a drawback that stable test results cannot be obtained. The present invention aims to solve such technical problems.

[0007]

The present invention compares a maximum strain signal value from a load cell with a predetermined strain signal value set in advance, and if the maximum strain signal value is less than this, an alternating voltage applied to an electrostrictive element layer is compared. A voltage control means for increasing the voltage value is provided.

[0008]

As described above, when the repeated fatigue test is performed in a high temperature atmosphere, the entire apparatus is stretched due to high temperature creep and the test piece p is plastically deformed, so that the bending of the stress waveform of the solid line of FIG. The stress center value F _mean decreases. Along with this, the maximum strain signal value from the load cell also decreases. Therefore, the predetermined strain signal value f _max of the load cell is held in advance and compared with this value. If it is smaller than this value, the alternating voltage value applied to the electrostrictive element layer is increased to increase the vibration of the diaphragm. The amplitude becomes large. Therefore, the maximum strain signal value F _max from the load cell approaches the predetermined strain signal value f _max , and finally becomes equal to this as shown by the chain line in FIG. Thus, since the maximum strain signal value F _max is always corrected to the predetermined strain signal value f _max , the same dynamic load is applied to the test piece, and an accurate test result can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. Reference numeral 1 denotes a base having an elastic support material 17 such as soft rubber, sponge, and metal spring disposed on the lower surface thereof, which is fixed to the installation surface 18 in a semi-floating manner. A vibration plate 2 having a bimorph structure serving as a drive source is supported on the base 1 in a cantilever manner at one side by a support shaft 3a screwed to the base 1 and a nut 3b. The diaphragm 2 is, as shown in FIG.
Electrostrictive element layers 5a and 5b having electrodes on the front and back are provided on the upper and lower surfaces of the rectangular curved plate 4, and a weight 6 is fixed to the other side of the curved plate 4. ing.

The electrostrictive element layers 5a and 5b are polarized in opposite directions, their outer electrodes are connected to the power supply generator 15, and their inner electrodes are grounded via the curved plate 4, and the voltage is applied to them. , Wire so that when one expands, the other contracts. As shown in FIG.
As shown in, a sample holding member 7 having two support ends 8 located in the width direction is provided on the upper portion. A loadle 12 supported by a screw rod 11 screwed onto a machine frame 14 is disposed above the vibrating plate 2, and a lower end of the load cell 12 is provided between the support ends 8 of the sample holding member 7. There is provided a sample pressing end 13 which is located at the position a and contacts the upper surface of the test piece p.

In the above structure, the test piece p is mounted on the supporting ends 8 of the sample holding member 7, and the screw rod 11 is manually rotated to move up and down to bring the screw rod 11 to the proper position. It descends and the pressing end 13 is brought into contact with the test piece p between the supporting ends 8 to support it at three points. At this time, when the screw rod 11 is slightly lowered from the proper position, the elastic support member 17 arranged on the lower surface of the base 1 is compressed and the vibrating body 2 and the base 1 are displaced downward. The test piece p is always held with a constant pressing force without breaking. After that, the electrostrictive element layers 5a, 5
An alternating voltage having a predetermined resonance frequency is applied from the power source generator 15 to b.

As a result, strain is generated in the electrostrictive element layers 5a and 5b, and the other piece is held by the inertial force of the weight 6 to generate bending vibration. Then, the test piece p is pressed from below on both sides by the up-and-down movement of the supporting ends 8 and 8 due to the bending vibration, and bending strain is periodically imparted around the pressing end 13. And this fatigue causes fatigue,
Eventually, it will be damaged, and by measuring the time until this damage, the applied voltage, the number of times of bending, etc., it becomes possible to measure the strength such as the transverse rupture force of the sample p.

The cyclic fatigue test apparatus is provided with voltage control means for controlling the value of the alternating voltage output from the power supply generator 15. The configuration will be described below.

The voltage control means includes the power source generator 1.
5, distortion amplifier 20, reference voltage setting device 21, comparator 22 and the like. That is, the distortion voltage signal from the load cell 12 is amplified by the distortion amplifier 20, and the maximum distortion signal value F _max is extracted from this. This maximum distortion signal value F _max is displayed on the display 23 and its value can be confirmed. On the other hand, a predetermined distortion signal value f _max is set in advance in the reference voltage setter 21, and the maximum distortion signal value F _max is compared with the predetermined distortion signal value f _max by the comparator 22. Information is input to the generator 15, the applied alternating voltage is amplified, and a larger voltage is applied to the electrostrictive element layer 5.
applied to a and 5b, a large amplitude is generated in the diaphragm 2,
The strain applied to the test piece p increases. Therefore, the maximum distortion signal value F _max becomes high, and by repeating the above steps, the maximum distortion signal value F _max matches the predetermined distortion signal value f _max .

As described above, since the above-described voltage control means is provided, the strain applied to the test piece p is adjusted so that the maximum strain amounts become equal in the above-mentioned configuration.
Even if the fatigue applied to the test piece p becomes equal, the test piece p is deformed by the high temperature creep, and the center value F _{mean of the} bending stress falls below the initial value of the solid line in FIG. The maximum distortion signal value F _max becomes constant because the waveform is amplified like a three-dot chain line. Therefore, the maximum strain amount applied to the test piece p becomes equal, and it becomes possible to obtain a good test result under the same dynamic load. The predetermined distortion signal value f
_max is the initial maximum strain signal value F when the sample p is mounted
_Max may be input, and in this case, the initial maximum distortion signal value F _max can be maintained even in a high temperature state. This is achieved by manually inputting the initial value shown on the display 23 to the reference voltage setting device 21, or by making it possible to automatically set the initial value by an input operation of the initial setting switch. ..

By measuring the time, the applied voltage, the number of times of repeated bending, etc., which lead to such damage, the strength of the test piece p, such as the transverse rupture force, can be properly measured.

In addition, although the present invention is particularly useful for a three-point bending test, the present invention has a test mode in which the entire periphery of the test piece p is held by a supporting edge and the pressing end is brought into contact with the center of the test piece p. Can also fit.

[0018]

As described above, according to the present invention, the predetermined strain signal value of the load cell is held in advance and compared with this value. When this is small, the alternating voltage applied to the electrostrictive element layer is applied. By increasing the value, the amplitude of the vibration plate was increased and the maximum strain amount applied to the test piece p was made equal. Therefore, even if the entire device was stretched by high temperature creep or the test piece p was plastically deformed, the test It is possible to keep the conditions constant, and it is possible to obtain a good test value, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a stress waveform diagram according to the present invention.

FIG. 4 is a schematic side view of a conventional configuration.

FIG. 5 is a stress waveform diagram according to a conventional configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 3 Vibration plate 4 Bending plate 5a, 5b Electrostrictive element layer 12 Load cell 15 Power generator 20 Strain amplifier 21 Reference voltage setting device 22 Comparator p Test piece

Claims (1)

[Claims] 1. A vibrating plate having an electrostrictive element layer disposed on at least one surface of a curved plate, holding one or both ends of the vibrating plate on a base, and further mounting a sample holding member on the moving surface of the vibrating plate. Mounting, a load cell for sandwiching a test piece with the holding member is provided on the sample holding member, and an alternating voltage of a predetermined frequency is applied to the electrostrictive element layer to cause bending vibration in the diaphragm. In the fatigue test equipment, the maximum strain signal value from the load cell was compared with the preset predetermined strain signal value, and if it was less than this, the alternating voltage value applied to the electrostrictive element layer was increased. A cyclic fatigue test apparatus comprising a voltage control means.