JPH07119679B2 - Cyclic fatigue test equipment - Google Patents

Description

The present invention relates to a cyclic fatigue test apparatus for inspecting bending fatigue of ceramic samples and the like.

<Prior Art> In a cyclic fatigue test of a ceramic sample or the like, one side is held at two points, the other side is held at the center, and a bending fatigue test of the sample is performed by a three-point bending test in which a dynamic load is applied from one side. There is a means to measure the degree.

<Problems to be Solved by the Invention> In this three-point bending test, it is conceivable to use expansion / contraction drive of the piezoelectric laminate as a drive source.

Further, in such a configuration that the sample is displaced by the expansion and contraction of the piezoelectric laminate a, and the one shown in FIG. 5 can be proposed in order to give the sample a large displacement. This is because one end of each of the armature pieces b, b is supported on both sides of the frame c by an axis d, d, respectively, and both armatures b, b are laid across the upper surfaces of the piezoelectric laminated bodies a, a. The pressing edges e, e protruding upward from the other end are used as the sample w.
Then, the lower surface thereof is connected between the axes d, d and the pressing edges e, e and the center of the working end of the piezoelectric laminate a, a via fulcrums f, f. Thus, the sample w is supported by the pressing edges e, e, and the center of the upper surface of the sample w is supported by the fulcrum g between the pressing edges e, e, thereby supporting three points. Then, by the extension action of the piezoelectric laminates a, a, the pressing edges e, e of the extension pieces b, b are moved upward about the axes d, d of the frame c. , A displacement larger than the displacement of the piezoelectric laminated body a on the pressing edges e, e is generated at the peripheral edge of the sample w.

By the way, in such a configuration, two piezoelectric laminates a,
Since it is necessary to provide a and a bayonet movement piece b, b, the device becomes complicated and large. In addition, between the shaft d and the pressing edge e, a pawl piece b
Since the fulcrum f of the piezoelectric laminate a is arranged,
The length from the supporting part to the pressing edge e is at least the axis d
To the fulcrum f at the center of the piezoelectric laminated body a. Therefore, the entire length of the armature piece b becomes large, and accordingly, it is necessary to make it thicker in order to improve its rigidity, and the resonance frequency is lowered. Then, in order to adapt to the resonance frequency, it is necessary to lower the frequency of the voltage applied to the piezoelectric laminate, the frequency applied per unit time decreases, and the time to fatigue failure increases.

It is an object of the present invention to provide a cyclic fatigue test apparatus capable of achieving the action of magnifying the displacement without lowering the resonance frequency of the coil piece.

<Means for Solving Problems> In the present invention, a piezoelectric laminate serving as a drive source is formed into a cylindrical shape, a supporting rod is inserted in the center thereof, and a pair of pressing edges for supporting a sample are provided at both end edges of an upper surface. , Is fixed to the upper end of the support rod at the central portion, which is formed so as to be point-symmetric with respect to the center, the lower surface, inward than both pressing edges, In addition, two contact points that are point-symmetric with respect to the center are in contact with the working end of the piezoelectric laminate, and further, the contact end that contacts the center of the upper surface of the sample is provided on the bayonet movement piece. It is a cyclic fatigue test device characterized by.

<Operation> When an alternating voltage is applied to the piezoelectric laminate, the bayonet movement piece
It is pushed up by the pair of contact ridges and moves around the fixed part of the support rod as a fulcrum, and the pair of pressing edges rises. As a result, since the center of the upper surface of the sample is supported by the abutting edge, the peripheral edge is pushed up by the pressing edge pair and curved.

In such an operation, if the distance from the fixed portion of the support rod to the contact portion of the bayonet movement piece is x, the distance from the fixed portion to the contact edge is y, and the displacement of the working end of the piezoelectric laminate is h. The displacement H of the contact edge is h × y / x. Since the distance x is smaller than the distance y, the displacement H of the contact edge is increased by y / x as compared with the displacement h of the working end of the piezoelectric laminate.

Further, in such a structure, the sample is strained by the single piezoelectric laminated body. Compared with the structure of FIG. 5, if the piezoelectric laminated body of the same diameter is used, the pressure edge pair The problem can be reduced to half or less, and the size can be reduced. With this, the distance y of the bayonet armature piece can be shortened, and can be made thinner than the armature piece b in FIG.

<Embodiment> An embodiment of the present invention will be described with reference to FIG.

On the base 1, a cylindrical piezoelectric layered body 2 for applying a dynamic impact to the sample w is erected. A support rod 3 is erected on the base 1 so as to pass through the center of the piezoelectric laminate 2. The piezoelectric laminated body 2 has a known structure in which a large number of annular piezoelectric element plates 4 are electrically parallel to each other and laminated, and the maximum displacement is generated at the upper end thereof.

A bayonet movement piece 5 is fixed to the support rod 3 by a male screw 6 and a nut. This bayonet movement piece 5 has a thin wall 7 at the center of the mounting portion, becomes thicker toward the outside, and is pushed upward so that the outermost edge thereof is point-symmetric with respect to the pressing edges 9, 9. It's rushing. Further, contact projections 8,8 mounted on the working end of the piezoelectric laminate 2 are projected on the lower surface of the bayonet movement piece 5 so as to be point-symmetrical with respect to the center inside the pressing edges 9,9. Is made.

The sample w is mounted on the pressing edges 9, 9, and the contact end 10 is pressed against the center of the sample w from above.

In the above structure, when an alternating voltage is applied to the piezoelectric laminate 2, the piezoelectric laminate 2 expands and contracts. At this time, the bayonet movement piece 5 is in contact with the piezoelectric laminated body 2 by the contact ridges 8 and 8. Therefore, as the piezoelectric laminated body 2 extends, the male screw 6 of the support rod 3 to which the nut is screwed is attached. With the fulcrum as a fulcrum, the thin wall 7 bends and the pressing edges 9 and 9 rise. Thus, the center of the upper surface of the sample w is
Since it is held by the abutting edge 10, its peripheral edge moves upward.

Then, the sample w is fatigued by being subjected to a dynamic load many times, and is eventually broken.

In such an operation, as shown in FIG. 3, the distance x from the male screw 6 of the support rod 3 to the contact protrusion 8 is smaller than the distance y from the male screw 6 to the pressing edges 9, 9. , And the displacement of the piezoelectric laminate 2 is h, the displacement H of the contact edge is h × y /
x, which will be expanded by y / x.

Further, in such a configuration, by the single piezoelectric laminate 2,
The sample w is distorted. As compared with the configuration of FIG. 5, if the piezoelectric laminate having the same diameter is used, the pressing edge is
The interval of 9,9 can be reduced to less than half, and the size can be reduced. With this, the distance y of the fluid armature piece can be shortened, and it can be made thinner than the armature piece b of FIG. The frequency does not decrease.

FIG. 4 shows a second embodiment of the present invention.

Similar to the first embodiment, the base 20 is provided with a cylindrical piezoelectric laminate 21 for applying a dynamic load to the sample w, and an annular connecting fitting 22 is fixed to the upper surface thereof. Also, the piezoelectric laminate
A male screw 24 is formed on the upper end of the support rod 23 that is fixed to the base 20 by being inserted through the nut 21, and a nut screwed to the male screw 24.
A disc spring 26 is arranged between 25 and the connecting fitting 22, and a preload is applied to the piezoelectric laminate 21 by the disc spring 26. Further, L-shaped support pieces 27, 27 are projectingly provided on the connecting fitting 22, and the contact ends 28, 28 projecting upward from the inner ends thereof are located as close to the center of the support rod 23 as possible.

Further, a bayonet movement piece 30 is attached to the upper end of the support rod 23, and a bolt portion 32 formed below the center of the thin portion 31 is screwed to support the lower surface in contact with the contact ends 28, 28. is doing. And the pressing edge 3 protruding from the peripheral edge of the bay moving piece 30
The sample w is mounted on the surfaces 33 and 33, and the contact end 34 is brought into contact with the center of the sample w.

In such a configuration, when an alternating voltage of a predetermined frequency having an alternating current wave such as a pulse wave, a sine wave, and a triangular wave is applied to the piezoelectric laminate 21, the piezoelectric laminate 21 causes the disc spring 26 to move on the basis of the alternating wave. It expands and contracts against the pressure and the sample w
A periodic dynamic pressure is applied around the.

Since the distance x from the bolt portion 32 to the contact ends 28, 28 is smaller than the distance y from the bolt portion 32 to the pressing edges 33, 33, the lever edge action of the fluid armature piece 30 causes the pressing edges 33, 33 to move. The displacement H is a value obtained by magnifying the displacement h of the piezoelectric laminate 21 by y / x times, and the sample w is given a large bending strain and eventually broken.

In addition, although the present invention is particularly useful for a three-point bending test,
It is also applicable to a test mode in which the entire circumference of the sample w is held by a supporting edge, and the pressing end is brought into contact with the center of the sample w.

<Effects of the Invention> As described above, the present invention is to apply a dynamic load to a sample w such as a ceramic by a piezoelectric laminated body, wherein the piezoelectric laminated body has a cylindrical shape, and a supporting rod inserted through the center thereof. , Y / x described above, in which the pressing edge that supports the center of the bayonet movement piece and is in contact with the sample w is located outside the contact portion with the piezoelectric laminate.
Is increased to increase the displacement h of the piezoelectric laminate. Therefore, as shown in FIG. 5, unlike the structure in which each pressing edge is displaced by two piezoelectric laminated bodies, a single piezoelectric laminated body and a wobbling piece distort the sample. Therefore, the interval between the pair of pressing edges can be reduced to half or less, the configuration is simplified, and the size can be reduced.
In addition, along with this, it is possible to reduce the length of the bayonet movement piece,
The thickness can be reduced as compared with the case piece b shown in FIG. As a result, there is an excellent effect that the amount of displacement can be increased while maintaining a high frequency repetitive impact without increasing the resonance frequency, and the fatigue speed of the sample w can be increased.

[Brief description of drawings]

The attached drawings show an embodiment of the present invention, FIG. 1 is a side view of the first embodiment, FIG. 2 is a plan view showing the contact end 10 and the sample w removed, and FIG. FIG. 4 is an enlarged view of the main part showing the operation of the piece 5, and FIG. 4 is a side view of the second embodiment. FIG. 5 is a side view of the main part of the conventional device. 2; Piezoelectric laminate, 5; Bay movement piece, 6; Bolt, 8,8; Contact protrusion, 9,9; Pressing edge, 10; Contact end, 21; Piezoelectric laminate, 28, 28; Contact Edge, 30; Bay movement piece, 32; Bolt part, 33, 33; Push edge, 3
4; abutting end

Claims (1)

[Claims] 1. A piezoelectric laminate serving as a drive source is formed into a cylindrical shape, a supporting rod is inserted through the center of the piezoelectric laminate, and a pair of pressing edges for supporting the sample are provided on both edges of the upper surface in point symmetry with respect to the center. The bayonet movement piece is formed so that it is fixed to the upper end of the support rod at its central portion, and the lower surface is inward of both pressing edges and point-symmetric with respect to the center. A repetitive fatigue test apparatus comprising: an abutting end that is in contact with the working end of the piezoelectric laminate at two points, and that is in contact with the center of the upper surface of the sample on the movable armature piece.