JPH03200046A - Repetitive fatigue testing device - Google Patents

Abstract

PURPOSE:To stabilize testing conditions by crimping a test piece between a lifting rod and supporting rod which are held on the same axial line by a holding cylinder, imparting the oscillations of an oscillation diaphragm via the lifting rod to the test piece, and thereby generating curvature strains in the test piece. CONSTITUTION:The lifting rod 13 and the supporting rod 22 are disposed on the same axial line and both ends thereof are positioned in a testing position T. Both ends of the test piece P are supported by supporting ends 15, 15 and a pressing end 23 is pressed to the central upper surface thereof. Alternating voltages of a prescribed frequency are impressed from an AC power source to electrostrictive element layers 5a, 5b. Strains are generated in the element layers 5a, 5b in this way and the oscillation diaphragm 3 oscillates curvaturely. The lifting rod 13 moves upward and downward and the impulsive dynamic loads corresponding to the impressed frequency are periodically imparted via the supporting ends 15, 15 to both ends of the test piece P, by which the fatigue by the curvature strains are accumulated until finally the test piece causes a failure. This bending stress is occasionally read from a load cell 21. The time, impressed voltages, number of pulses, etc., to the failure are measured, by which the strength, such as transverse rapture strength, of the test piece P is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cyclic fatigue testing device for testing the fatigue strength of ceramic test pieces and the like.

[Prior art] For cyclic fatigue testing of ceramic and ink test pieces, one side is held at two points, the other side is held at the center, and a dynamic load is applied from the negative side by a three-point bending test. There is a method to measure the degree of bending fatigue of a sample.

Conventionally, in the cyclic fatigue testing apparatus used in this method, a mechanical linear reciprocating mechanism such as a piston or cylinder is used as an impact source, and a dynamic load is applied from one side of the test piece.

However, with such a conventional configuration, it is troublesome to adjust and change the driving force, it is not possible to generate a high frequency driving force, and furthermore, it generates a large driving noise, and furthermore, it is caused by mechanical friction. There were drawbacks such as severe wear and tear and difficulty in keeping test conditions constant.

Therefore, as shown in FIG. 2, a diaphragm a having an electrostrictive element layer C disposed on at least one surface of a curved plate is supported at one end or both ends on a base d, and furthermore, the diaphragm a is Attach the holding member e of the test piece p to the curved surface of the
A test piece holding member e has been proposed that includes a test piece suppressing end f that holds the test piece p between them (Japanese Patent Application No. 62-250208).

In this configuration, when an alternating voltage of a predetermined frequency is applied to the front and back electrodes of the electrostrictive element layer C, a bending vibration is generated in the curved plate. And along with this.

The holding member e supported by the curved surface of the diaphragm a vibrates. Therefore, the specimen p, whose negative side is supported by the holding member e and the other side is held by the suppressing end f, is subjected to a sinusoidal or pulse-like dynamic load based on a predetermined frequency due to the vibration of the holding member e. This eventually leads to damage. At this time, by measuring the speed at which damage occurs and the frequency of dynamic loads,
The strength of the test piece can be detected.

Therefore, with this configuration, by appropriately selecting the alternating voltage applied to the electrostrictive element layer C, the repetitive stress and period can be adjusted, and various test conditions can be set at will. Moreover, unlike conventional means of applying a dynamic load using a mechanical linear reciprocating drive mechanism, this method has the advantage of generating less noise and less wear and tear due to mechanical friction, and making it easier to maintain the same test conditions.

[Problems to be Solved by the Invention] With this configuration, when testing the strength of the test piece p in a high-temperature atmosphere of several hundred degrees, it is necessary to house the test piece in a high-temperature furnace. However, with the conventional configuration described above, it is impossible to store only the test piece in the high-temperature furnace.
The entire system is to be housed, but since each part is exposed to high temperatures, each component must be made of heat-resistant material, and the diaphragm may not produce stable output due to the effects of high-temperature creep, etc. do not have.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cyclic fatigue testing apparatus that can house only a test piece in a high-temperature furnace and can impart stable bending strain to the test piece.

Means for Solving Problem E] The present invention provides a method for supporting a diaphragm having an electrostrictive element layer on at least one surface of a curved plate at one end or both ends thereof on a base; The lower end of the lifting rod is fixed to the movable surface to form a movable part, and holding cylinders are placed above and below the test area on the same axis.
Insert the lifting rod into the lower holding cylinder.

It is inserted into the upper holding cylinder, which is a support rod whose upper end is held on the fixed side, so as to face the test site, which is the end of the lifting rod and the support rod, and one of the rod ends is brought into contact with the periphery of the test piece, The test piece is held by bringing the other rod end into contact with the center of the test piece, and the diaphragm is moved by applying an alternating voltage to the electrostrictive element layer to continuously apply bending strain to the test piece. It is characterized by the fact that it is made to do so.

f action] The test piece is held between the lifting rod and the support rod, and by applying an alternating voltage of a predetermined frequency to the electrostrictive element layer, the lifting rod is vibrated up and down, and the vibration causes the test piece on the support end to , given a curved deformation.

In this repeated fatigue test, since the test site is located at a distance from the diaphragm, it is possible to accommodate only the test site in the high-temperature furnace.

Moreover, since each rod is held on the same axis by the guide cylinder, stable bending strain is imparted to the test piece even by the separation operation.

[Example] An embodiment of the invention will be described with reference to FIG.

Reference numeral 1 denotes a base, and a bimorph-structured diaphragm 3 serving as an impact source is supported at one end of the base 1.

As shown in the figure, the diaphragm 3 includes electrostrictive element layers 5a and 5b provided with electrodes on the front and back surfaces of a rectangular curved plate 4 on the upper and lower surfaces thereof. These electrostrictive element layers 5a and 5b are polarized in opposite directions, and their outer electrodes are connected to an AC power source, and their inner electrodes are connected to ground through the curved plate 4. When one side expands due to voltage application, the other side expands. is wired so that it contracts.

One end side of the curved plate 4 is supported on the base 1 by a bolt 7 via a spacer 8. Further, a weight 9 is fixed to the other end of the curved plate 4. Instead of this weight 9, the other edge may be fixed to the base l side to support the diaphragm 3 at both ends.

A lower end of an elevating rod 13 made of a heat-resistant material such as ceramic is fixed on the emotional surface in the middle of the diaphragm 3 . The upper end of this lifting rod 13 is a wide support part 14, on the upper surface of which a rod-shaped support end 15.15 made of a wear-resistant material is arranged.

On the other hand, a support rod 2 made of a heat-resistant material such as ceramic is connected to the machine frame 20a on the fixed side via a load cell 21.
2 is suspended. A rod-shaped pressing end 23 is disposed at the lower end of this support rod 22 between it and the test piece p, as will be described later.

Further, the holding cylinders 24 and 25 are held on the same axis by the machine frame 20b above and below the test site T. The lifting rod 13 is inserted into the lower holding cylinder 24 from above and its lower end is fixed to the diaphragm 3 side, so that the supporting part 14 is arranged at the testing site T. A bearing 26 may be disposed within the holding cylinder 24 to allow the lifting rod 13 to move up and down smoothly. Further, the support rod 22 is inserted into the upper holding cylinder 25 in advance.

Therefore, the lifting rod 13. A support rod 22 is disposed on the same axis, and both ends thereof are located at the test site T, and the test piece p
Both ends are supported by supporting ends 15.15, and the pressing end 23 is brought into contact with the upper center surface of the supporting end 15.15. A high-temperature furnace 30 is provided at this test site T, if desired. At this time, since the diaphragm 3, load cell 21, etc. are separated from the test site T by the elongated lifting rod 13 and the support rod 22, the high temperature furnace 30 can be placed without any trouble. can be placed in a high-temperature atmosphere, and the fatigue characteristics of the test portion T in the high-temperature atmosphere can be detected.

The operation of the above configuration will be explained.

An alternating voltage having a predetermined frequency and having an alternating current wave such as a pulse wave, a sine wave, or a triangular wave is applied from an alternating current power source to the electrostrictive element layers 5a and 5b. This causes strain in the electrostrictive element layers 5a and 5b, and the diaphragm 3 vibrates in a curved manner. And the lifting rod 13
moves up and down, and the test piece p is periodically applied with a pulse-like dynamic load corresponding to the applied frequency via the support ends 15 and 15 on both sides, fatigue due to bending strain accumulates, and eventually breaks. It will be reached. This bending stress is read from the load cell 21 at any time.

Therefore, the time and applied voltage that lead to such damage.

By measuring the number of pulses, etc., it becomes possible to measure the strength, such as the transverse rupture strength, of the test piece p.

In the above configuration, the lower end of the support rod 22 is made wide to support both sides of the test piece p, and the lifting rod 13
The test piece p may be supported at three points so that the upper end of the test piece p contacts the center of the test piece p.

In addition, although the present invention is particularly useful for three-point bending tests, it is also applicable to test modes in which the entire periphery of the test piece p is held by a support edge and the pressing end is brought into contact with the center of the test piece p. obtain.

[Effects of the Invention] As described above, the present invention provides the lifting rods 13. The test piece p is held between the support rods 22 and the vibration of the diaphragm 3 is transferred to the lifting rod 13.
Since the test piece p is applied to the test piece p through the duct to cause a bending strain, the test part T can be set at a position away from the lifting rod 13 etc., and only the test piece p is stored in the high temperature furnace 30. In addition, the lifting rod 13,
Since the holding tubes 24 are held on the same axis, they can always apply a load in a predetermined direction to the test piece p, and therefore the strain mode remains constant even if they are in separate positions, and stable bending strain is always applied. This has excellent effects, such as stabilization of test conditions and therefore being optimal for fatigue tests at high temperatures.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of an embodiment of the present invention, and FIG. 2 is a schematic side view of a conventional configuration. ■... Base 3... Vibration plate 4... Curved plates 5a, 5b... Electrostrictive element layer 13... Lifting rod 14... - Support portion 15.15... Support end 21... ...Load cell 22...Support rod 24.25...Holding cylinder 30...High temperature furnace p...Test piece T...Test part No.

Claims (1)

[Claims] A diaphragm having an electrostrictive element layer disposed on at least one surface of the diaphragm is supported at one end or both ends on a base, and furthermore, an elevating rod is mounted on the curving surface of the diaphragm. In addition to fixing the lower end, holding cylinders are placed above and below the test site on the same axis.
Insert the lifting rod into the lower holding cylinder, insert the support rod whose upper end is held on the fixed side into the upper holding cylinder, so that the ends of the lifting rod and the support rod face the test site, and The rod end is brought into contact with the periphery of the test piece, and the other rod end is brought into contact with the center of the test piece to sandwich the test piece, and the diaphragm is flexed by applying an alternating voltage to the electrostrictive element layer. A cyclic fatigue testing device characterized in that a bending strain is continuously applied to a test piece by bending the test piece.