JPS62113042A - Material tester - Google Patents

Abstract

PURPOSE:To prevent the application of biased load, by attaching a metal piece to both axial ends faces of sample piece to impart a compression or tension load to a sample piece by expanding or contracting the metal piece. CONSTITUTION:A metal piece 2 is attached to both end faces of a sample piece 1. These test piece 1, metal piece 2 are mounted into a frame 3 entirely firm. Here, when a part containing the metal piece 2 is heated with a heater/ cooler 4 up to T deg.C, the metal piece 2 thermally expands to make both end faces thereof adhere to the frame 3. Thereafter, as the metal piece 2 cools, adhesion effect between the metal piece 2 and the frame 3 increases to contract the metal piece 2. Thus, a tension stress works on the test piece 1. Then, when the metal piece 2 is heated with the unit 4 up to T2 deg.C (T2>T), a contraction stress works on the test piece 1 with thermal expansion of the metal piece 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a material testing device, and particularly to a material testing device suitable for tensile compression testing of brittle materials such as ceramics.

[Conventional technology]

Ceramics have advantages such as high strength and high corrosion resistance in high-temperature regions, light weight, and low coefficient of linear expansion and thermal conductivity, and have recently been used in various fields where these properties are required.

For example, it is effective and has great potential for application as a structural member such as a gas turbine, which is exposed to high temperatures and corrosive environments and is subject to high stress.

On the other hand, when ceramics are used under harsh conditions such as high temperatures, corrosive atmospheres, long-term constant stress, and repeated stress,
Its material properties change and it can fracture at relatively low stresses. Phenomena such as leap and fatigue are important factors in structural design and life prediction, and therefore, when using ceramics as a structural material, it is necessary to fully understand their characteristics.

However, it is only recently that ceramics have attracted attention as structural materials, and it cannot be said that methods for evaluating their characteristics have been established. In addition, conventional methods for evaluating the characteristics of metal materials cannot be applied directly to ceramics because they are brittle materials.

Mechanical testing methods for ceramics include tensile-compressive fatigue tests using round bar test pieces, cantilever bending tests using plate test pieces, and bioscillatory tests of 3-point bending and 4-point bending.
Although it is carried out at high temperatures up to around 300°C, bending fatigue tests are often carried out, and the reality is that tensile and compressive fatigue tests using round bar specimens are almost never carried out. It is.

In general, the strength of ceramics is controlled by surface and internal defects, so in conventional bending fatigue tests, it is important to accurately understand the behavior of internal defects. From the viewpoint of dependence, it is more desirable to perform a tension compression fatigue test, which is a test in a state closer to that of a practical member, than the above-mentioned bending fatigue test.

[Problem that the invention seeks to solve]

The biggest difference between ceramic materials and metal materials is
Its ductility is extremely poor.

Therefore, when performing tensile compression tests on ceramic materials, even if the central axis of the load shifts slightly, shearing force or bending stress is generated, which can result in fracture at low stress levels, or stress concentration at the specimen support. There is a problem of breakage, and true strength cannot often be measured.

In order to solve such problems, for example,
No. 13935, a test method has been proposed in which the shoulder of a test piece is engaged with a rod-shaped body to apply a load. Furthermore, there is a method shown in FIG. 2 in which a similar method is applied to a tensile compression test. In the figure, both ends of a test piece a made of ceramics are attached to a chuck body C via supports, and the end faces are supported by fasteners d fixed to the chuck body C. However, the chuck body C, which grips the test piece a in this manner, is connected to a rod e of an ordinary tension-compression autograph or a hydraulic servo fatigue testing machine, and is loaded with the rod e.

As a support for the above test piece, a fluid body of BN powder,
Various materials are used, such as aluminum foil or aluminum tubes that utilize plastic deformation, and rubber plates, and by inserting these between the test specimen and the chuck body, bending stress and shearing force are generated. can be prevented to some extent.

However, in order to prevent the occurrence of bending stress etc. in this way,
There is a problem in that during the test, the support must be moved and adjusted by trial and error, and this work takes a lot of time.

In addition, in a tension-compression test in which a tensile load and a compressive load are applied alternately, as the loading direction is repeatedly reversed, the support deforms plastically, creating a gap between the test specimen a and the stopper d. If the load is shifted from tension to compression in this state, there is a risk that the test piece will be damaged because an impact load will occur if the frequency is high.

An object of the present invention is to obtain a material testing device suitable for measuring the strength of brittle materials such as ceramics by preventing the occurrence of double bending stress and the like and suppressing the occurrence of impact loads.

[Means for solving problems]

41 The present invention provides a metal piece attached to both axial end faces of a test piece, a frame that restrains expansion and/or contraction of the test piece via this metal piece, and a frame that restrains expansion and/or contraction of the test piece through the metal piece.
and cooling means.

[For production]

In the present invention, metal pieces are attached to both axial end faces of a test piece, the whole is housed in a strong frame, and the metal pieces are expanded or contracted to apply a compressive or tensile load to the test piece. External heating and cooling are used to expand and contract the metal piece. In other words, if the linear expansion coefficient of the metal piece is α, the Guyang's modulus is E, the temperature when the test piece is mounted is T/, and the temperature during heating or cooling is T, then the stress acting on the test piece is σ
σ=Eα(T-T'), and by controlling the temperature of the metal piece, the direction and magnitude of the applied load can be arbitrarily set.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which metal pieces 2 are attached to both end faces of a test piece, and the entire test piece 1 and metal piece 2 are housed in a strong frame 3. It is mounted on. A heating/cooling device 4 made of a stainless steel tube for passing a refrigerant, a heater for heating, etc., is installed on the outside of the frame 3 at a point corresponding to the metal piece 2. . Further, guides 5 are formed at both ends of the test piece 1 so as to be in sliding contact with the inner wall of the frame 3. On the other hand, a heating and cooling device 4 is provided on the inner wall of the test piece 1. In order to reduce the thermal influence caused by heat, a heat shielding plate 6 having a hole for slidably supporting the test piece 1 is fixed in the center. A monitor connected to the monitor device 7 was installed at a portion of the test piece 1 that was appropriately spaced from the 4I section.
E sensor I3 is attached.

The metal piece 2 is generally bonded to the test No. 11, and there are various known bonding methods such as Dowa-SL bonding system, solid phase-solid phase system, and solid phase-liquid phase system. Among these, the in-phase-vapor phase bonding method has excellent heat resistance. In order to apply a tensile load to the test piece 1, it is necessary to adhere the metal piece 2 to the frame 3 side as well, but the adhesion between the metal piece 2 and the frame 3 is performed as part of the test as described below. be able to.

Further, it is desirable that the material of the metal piece 2 has a large coefficient of thermal expansion, but it may be made of an appropriate material depending on the temperature difference to be applied.

In the above configuration, stress is applied to the test piece 1 in the following manner.

First, a test piece 1 with metal pieces 2 glued to both end faces is mounted on the probe 3, the part containing the metal pieces 2 is heated to a high temperature (T°C), and at this temperature one of the above-mentioned The metal piece 2 is glued to the frame 3 by a method.

At this time, the heating temperature T'C is a temperature at which the metal piece 2 thermally expands and both end surfaces are sufficiently bonded to the frame 3.

After the bonding is completed, when the metal piece 2 is cooled down to 71'C by the cooling part of the heating/cooling device 4, the adhesion effect between the bonded part of the metal piece 2 and the frame 3 increases as it cools, and the metal piece 2 In order to contract, a tensile stress expressed by the following equation acts on the test piece 1.

σT−Eα(T−T□) (]) Here, α is the linear expansion coefficient of the metal piece 2, and E is also Young's modulus.

Next, when the metal piece 2 is heated by the heating and cooling device 4,
The stress acting on the test piece becomes zero at T°C, and if it is heated to a temperature exceeding this temperature T2°C, the stress on test piece 1 becomes σ2-I3α(T2-T)...expressed as ■ due to the thermal expansion of metal piece 2. Compressive stress will be applied.

By repeating the cycle to a constant heat 1 as described above, a tensile load and a compressive load can be repeatedly applied to the test piece 1. The magnitude of the load at this time is ■,■
As is clear from the equation, it depends on the physical property values of the metal piece 2 and the heating temperature, so it can be changed freely by changing these. Furthermore, detection of cracks during the test can be monitored by a monitor device 8 using an AE sensor 7 protected by a heat shield plate 6.

〔Effect of the invention〕

As described above, according to the present invention, a load is not applied unbalancedly due to mechanical error, and therefore stress concentration and bending stress are prevented from occurring. Furthermore, even when the load is reversed from tension to compression, no impact load is generated at all, so the present invention is extremely excellent as a testing device for brittle materials such as ceramics.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a material testing device according to an embodiment of the present invention, and FIG. 2 is a sectional view showing an outline of a conventional material testing device. 1... Test piece, 2... Metal piece, 3... Frame,
4...Heating/cooling device, 5...Guide, 6...Heat shielding plate, 7...Monitor device, 8...AE sensor representative Patent attorney Noriyuki Chika Yudo Hirofumi Mitsumata Figure 1 Figure 2

Claims (3)

[Claims] (1) A metal piece attached to both axial end faces of a test piece, a frame that restrains expansion and/or contraction of the test piece via this metal piece, and heating and/or cooling of the metal piece. A material testing device comprising means. (2) The material testing device according to claim 1, wherein the metal piece is bonded to the test piece and the frame. (3) A material testing device according to claim 1 or 2, wherein an AE sensor is attached to the test piece.