JPS60196643A - Strength measuring method of brittle material - Google Patents

Abstract

PURPOSE:To measure the static tensile strength characteristic accurately and simply, by applying stress to a body under test comprising a brittle material such as ceramics through a supporting member, in hich deformation is yielded by the stress. CONSTITUTION:A load converter 3 is fixed to an upper cross head 2A of a tensile tester 1. A universal joint 4 is attached to the load converter 3. A pair of rods 5A and 5B is connected to the universal joint 4 and a moving cross head 2B by pins 6A and 6B. A test piece is supported by holding tools 7A and 7B, which are connected to the rods 5A and 5B by pins 8A and 8B. A V-shaped groove 71A of a pair of the holding tools 7A is line-contacted with a supporting member 9, which comprises a round pipe, whose elastic constant is lower than that of the test piece 10 and plastic deformation ability is large, e.g., a aluminum round pipe. Thus the initial deformation can be made adequate. Since the bending stress, which is applied on the test piece 10 by the initial deformation of the supporting member, can be absorbed, troublesome breakdown of the test piece 10 can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for measuring the strength of brittle materials such as ceramics.

Technical background of the invention and its problems) In recent years, the need for fine ceramics such as silicon nitride and alumina as structural materials for various energy devices including automobile engine parts has increased, and their practical use on an industrial basis is progressing.

Therefore, in order to do this, it is important to know the basic properties of materials, such as tensile strength, from a design perspective.
It is also very similar to Ichikawa in terms of its origin from the wood. however,
Ceramics, which are brittle materials, do not undergo plastic deformation, so in tensile tests, for example, there may be eccentric loads due to mismatch between the central axis of the specimen being tested and the central axis of the testing machine, or the relationship between the specimen and the gripping jig. It has been difficult to accurately measure tensile strength, etc. because the test pieces tend to crack or break due to concentrated loads that tend to occur at the contact areas.

Purpose of the Invention) The present invention provides a method that can easily and accurately measure the strength of brittle materials such as ceramics.

(Summary of the Invention) The present invention is characterized in that when stress is applied to a brittle (four-stone) specimen such as ceramics for strength measurement, the stress is applied via a support member that is deformed by the stress. Due to the brittleness of ceramics, methods for measuring their strength have been limited, but the method of the present invention makes it possible to easily and accurately measure the tensile strength, etc. of ceramics.The supporting member applies stress to the specimen. It is better to use a support member that deforms appropriately and does not cause damage to the specimen.In particular, it is preferable to use a material that alleviates the bending stress that is applied to the specimen at the initial stage of applying the Ω load.For this reason, the supporting member should be more elastic than the specimen. A material having a low constant and excellent plastic deformability is effective.For example, a material made of soft metal such as aluminum is preferable.Furthermore, a material having a space inside, such as a tubular body, does not result in appropriate deformation. The method of the present invention is particularly effective when the stress is along the axial direction of the specimen, such as in a tensile test.

A tensile test apparatus suitable for carrying out the method of the present invention is shown in Figure 1.
゛. In Figure 1, the tensile test (1 is the tensile test device 1)
Load transducer 3 fixed to fixed crosshead 2△ on top of
A pair of upper and lower rods 5△, 5B are connected to the universal joins 1 to 4 attached to ( ) and the movable cross head 2B installed at the lower part ( ) with pins 6△, 6B, and the lower rod 5 Pins 8△, 8B are installed at the lower and upper ends of each of △, 5B so as to be substantially perpendicular to the joining pins 6△, 6B.
A clamping tool 7△ that supports the test piece.

It has a structure in which a pair of upper and lower 7Bs are joined. Universal join 1~ and joint IA3fi with orthogonal hinge pins
Therefore, the center line of the test piece can always align with the gravity axis as the load is applied. In addition, the eccentricity of the load can be suppressed by making the upper and lower parts as long as possible. Figure 2 shows an enlarged view of the clamping tool part.

In FIG. 2, the pair of clamping tools 7Δ are arranged in a V-shaped groove 71A so as to be in line contact with a supporting member 9°9 made of, for example, an aluminum circular tube, which has a lower elastic constant than the test piece 10 and a greater plastic deformability. , 71A are installed. The test specimen 10 is placed in line contact with the support member 9.9. In this way, by bringing the test piece into line contact with the supporting member, the initial deformation can be made appropriate.
What can you do? This support member 9.9 gradually undergoes plastic deformation as the load increases during the tensile test, and the contact area with the test piece 10 increases accordingly, resulting in a good and stable contact state. In particular, by structuring the support means for the test piece 10 as described above, it is possible to absorb the bending stress applied to the test piece 10 due to the initial deformation of the support part (A) without pinching the test piece 10. Therefore, inconvenient destruction of the test piece 10 can be prevented.Furthermore, the supporting members 9,
Since the load capacity of the test piece 9 can be increased or decreased by selecting an appropriate material and form depending on the material of the test piece, it is possible to prevent the test piece 10 from breaking at the clamped portion, which has conventionally occurred.

FIG. 3 shows a test piece for tensile testing suitable for the method of the present invention. The portion 11 of the test piece in contact with the support member is formed approximately at right angles to the central axis, and the width becomes narrower toward the center. When using a brittle material such as ceramics, it is preferable to reduce the thickness of the central part of the test piece and make it a 414-piece structure in which the test piece breaks at the central part.

(Example of the Invention) When a tensile test was conducted using three silicon nitride test pieces (shown in FIG. 3) using the tensile test device 6 shown in FIG. The test piece broke almost at the center, and there was no breakage at the sandwiched part. Similarly, J5 was tested on three specimens of the shape shown in Figure 3 with no reduction in the thickness direction, but the results were the same as above.
I got some great results. However, in the test piece shown in FIG. 3, the fracture location is more reliably constant, and it is considered that highly accurate measurement is possible.

In the above tensile test, as a tensile load is applied by the tensile testing machine 1, the support member 9 formed of a metal circular tube is plastically deformed as the load increases, and the test piece 1
0 and the clamping portion of the clamping tool 7 increases, and a good and stable contact state can be obtained. FIG. 4 schematically shows the deformation behavior of the support member based on a load-displacement curve showing the behavior of the tensile load detected by the load converter 3 at this time and the displacement between the fixed and moving crossheads.

As shown in Figure 4, the deformation behavior of the support member is normal.

It can be divided into areas I and H.

In the early area construction, the rate of increase (slope of the curve) of the load P against the displacement δ decreases as δ, and in this area, if there is a difference in the load applied to the upper or lower support member, the displacement increases. It is relaxed as δ increases. In this area■,
Due to the load P, the curve applied to the test piece relaxes and absorbs the stress, and has the effect of stabilizing the load state after J-measuring.1
An almost linear relationship is established between the displacement δ and the displacement δ, and the upper R ratio of the load P to the displacement δ takes the minimum value in this area. -C The deformation of the supporting member progresses most gracefully, increasing the contact area between the test piece and the clamping tool, and forming a good contact state. In region ■, the slope of the curve increases, contrary to region ■, so there is a possibility that the bending stress will be further expanded for some reason, and this is the region where the support member will begin to fail. . In view of the above, it is preferable that the supporting member be determined so that the fracture of the test sample C occurs in the middle to the latter half of the region (C) according to the predicted tensile strength of the test C method.

When using a silicon nitride specimen with a plate thickness of 3 ml, the support part is - (outer diameter 9 +u+++, length dimension iQ+nu+
When using an aluminum circular tube of about 100 mL, the above-mentioned region 1 could be stably achieved.

Effects of the Invention) According to the method of the present invention, when testing the strength of brittle materials such as ceramics that are hardly accompanied by plastic deformation at the time of fracture, the clamping 'eA'C' test does not result in starvation and the bending stress component is reduced. It can be said that the occurrence of 4M
It is possible to measure the basic static tensile strength characteristics with good viscosity when planning the strength of brittle materials such as ceramics with high Ml sensitivity.

[Brief explanation of drawings]

Figure 1 is a front view of a tensile test device to which the method of the present invention is applied, and Figure 2 is a tensile test! FIG. 3 is an enlarged view of the portion holding the test piece in the li position, FIG. 3 is a view showing an example of the testing machine used in the present invention, and FIG. 4 is a schematic diagram showing the deformation behavior of the support portion 44 used in the method of the present invention. This is a graph showing the 1...Tensile test device 3...Load converter 4...Universal joint 7A, 713 ・ ・ ・ (Fire holding V↓9...
Supporting member 10...Test piece representative Burialist side Ken Ken f(i (IJ or 1 person)
Figure 1 Figure 2 Figure 3 (a) I (b) Figure 4 Displacement J

Claims (4)

[Claims] (1) A method for measuring the strength of a brittle material, characterized in that when stress is applied to a specimen made of a brittle material, the stress is applied via a support member that is deformed by the stress. (2) A method for measuring the strength of a brittle material according to claim 1, which is a brittle material. (3) The method for measuring the strength of a brittle material according to claim 1, wherein the supporting member has a lower elastic constant than the specimen and is more plastically deformable. (4) The IJ method for measuring the strength of a brittle material according to claim 3, wherein the support member is formed of a soft metal. (5) The method for measuring the strength of a brittle material according to claim 1, wherein the stress is along the axial direction of the specimen.