JPH0646176B2 - Brittle materials High temperature impact fracture strength measurement method and equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for measuring the impact fracture strength of brittle materials at high temperatures and a measuring apparatus therefor.

[Prior Art] The impact destructive force test in the prior art is performed by a so-called three-point bending test in which both ends of a test piece are supported and an impact load is applied, or a cantilever bending test in which an impact load is applied to a cantilever. Has been.

[Problems to be Solved by the Invention] However, the three-point bending test and the cantilever bending test such as the impact fracture strength test of the prior art require the fulcrum member to have heat resistance when performed at high temperature. In addition, it is structurally inconvenient in the furnace, and the heat loss due to heat conduction from the test piece to the fulcrum member is large, so it is not suitable for measuring the brittle material impact fracture force meter at high temperature.

The present invention provides a method and apparatus suitable for measuring the impact fracture strength of brittle materials at such high temperatures.

[Means for Solving the Problems] In the present invention, two heat-resistant yarns for hanging a test piece are hung at intervals in a hollow hole of a high-temperature heating furnace in which a hollow hole is formed. Suspend one or both ends of the brittle material test piece, keep it heated to a predetermined temperature, hit the impact body against the brittle material test piece to apply impact force, destroy the brittle material test piece, and attach it to the impact body at that time The fracture strength of the brittle material is obtained from the measured signal of the strain gauge.

[Operation] When an impact body is struck against a brittle material test piece suspended by a heat-resistant thread and an impact force is applied, the heat-resistant thread is cut or loosened, and the brittle material test is performed under free terminal conditions. The piece is destroyed. At that time, a measurement signal is output from the strain gauge attached to the impact body, and the value of the high temperature impact fracture strength of the brittle material is obtained based on the measurement signal.

[Embodiment] An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an outline of a vertical apparatus according to the present invention for carrying out the method of the present invention.

A hollow hole 2 is formed in the infrared image furnace 1, and an upper part of the infrared image furnace 1 is covered with a heat insulating plate 3. In the heat insulating plate 3, a circular hole 4 is formed in the center at a position aligned with the hollow hole 2 and fine holes 5 and 5 are formed equidistantly on both sides thereof. That is,
The distance between the pores 5 and 5 is at least shorter than the diameter of the hollow hole 2.

Immediately above the circular hole 4 is an impact rod 6 that is slightly thinner than the diameter of the circular hole 4.
(For example, a steel rod) is suspended by the suspending thread 7. The hanging thread 7 connected to the upper end of the impact rod 6 is wound around the pulley 8 located above.

In this state, the hanging thread 7 is suddenly released, so that the impact rod 6 freely falls in the hollow hole 2 of the infrared image furnace 1 while passing through the circular hole 4.

Then, a strain gauge 9 is attached to an intermediate portion of the impact rod 6, and a measurement signal is sent to a microcomputer via a measuring device (not shown), for example, a D / A converter. Is a length above the strain gauge 9 so that the reflected wave from the upper end surface does not reach the strain gauge 9 before the destruction of the ceramic test piece T when the ceramic test piece T is dropped and impacted. Have enough.

A ceramic fiber thread whose upper end is fixed to the outside, that is, a heat resistant thread 10, 10 is inserted into the pores 5 and 5 and hung in the hollow hole 2 of the infrared image furnace 1.

FIG. 2 shows an overview of a horizontal device according to the invention for implementing the method of the invention.

A hollow hole 2 is formed horizontally in the infrared image furnace 1,
A side of the infrared image furnace 1 is covered with a heat insulating plate 3. Pores 5 and 5 are formed in the upper portion of the infrared image furnace 1 at appropriate intervals, and a hollow hole 2 is formed in the heat insulating plate 3 on one side.
A circular hole 4 is formed at the center of the.

The impact rod 6 (for example, steel rod), which is slightly thinner than the diameter of the circular hole 4,
Outside the furnace, it is supported by a guide support 11 so as to be in the same axis as the circular hole 4 and slidable in the horizontal axis direction, and is a hollow hole by a not shown punching device (for example, pneumatic device, electromagnetic device, spring device, etc.). It is designed to be launched within 2.

The other points are the same as those of the vertical type device.

A brittle material high temperature impact fracture strength measuring method according to an embodiment of the present invention will be described.

In the vertical device, first, the ceramic test piece T,
For example, both ends of a pressureless sintered silicon carbide test piece (if it is difficult to introduce a pre-crack, cut the broken part with a fine cutter) are attached to the lower ends of the heat-resistant threads 10 and 10, respectively, with heat-resistant adhesive. The ceramic test piece T is horizontally suspended in the hollow hole 2 of the infrared image furnace 1 by bonding with a chemical.

At that time, the fractured portion / notch portion of the ceramic test piece T (preferably the center in the length direction of the ceramic test piece)
Is located directly below the circular hole 4.

The impact rod 6 suspended by the suspending thread 7 is located above the circular hole 4, that is, the breaking point or notch of the ceramic test piece T, and has a predetermined drop height (from the upper surface of the ceramic test piece T at the lower end). Height). At that time, the height of the strain gauge 9 attached to the impact rod 6 from the heat insulating plate 3 is at least higher than the drop height, and the strain gauge 9 is always outside the furnace even when dropped.

Then, the ceramic test piece T is transferred to the infrared image furnace 1
Keep heating at the set temperature.

In this state, the hanging thread 7 is released, and the impact rod 6 is dropped toward the ceramics test piece T through the circular hole 4.
Then, when the falling impact rod 6 hits the ceramics test piece T, unlike the case where a static load is applied, the duration of the load acts as an impact load smaller than the lowest fixed cycle of bending vibration of the test piece T, A large elastic bending vibration occurs in the ceramic test piece T.

In that case, the positions of both ends in the deformation of the ceramic test piece T first rise for a predetermined time t1 with the passage of time from the time when the impact rod 6 contacts the ceramic test piece T.
On the other hand, the ceramic test piece T is destroyed when the bending stress in the central portion reaches the resistance value peculiar to the material, and the elapsed time t2 from when the impact rod 6 was in contact with the ceramic test piece T until then was , Is shorter than the predetermined time t1. Therefore, the ceramic test piece T breaks at the breaking point / notch when the hanging thread 10 that suspends both ends of the ceramic test piece T is slackened, that is, when no force acts on the hanging thread 10.

Even if the suspension thread 10 is cut along with the fracture of the ceramic test piece T, the heat-resistant suspension thread 10 does not need a strength to support the load for breaking, and the ceramic test piece T
Since it is sufficient that the hanging thread 10 has a tensile strength enough to support its own weight, the resistance of the hanging thread 10 is smaller than that of the impact force. The effect of exerting a force on the ceramics test piece T is relatively small and is not a problem.

Also in the horizontal type device, the suspended state of the ceramics test piece T and the movement of the impact rod 6 are only different, and the others are the same as in the case of the vertical type device.

First, the ceramic test piece T and the heat-resistant yarn on both sides
The ceramic test piece T is hung vertically in the hollow hole 2 of the infrared image furnace 1 by adhering it to the lower ends of 10, 10 with a heat-resistant adhesive, and on the same axis as the circular hole 4, that is, the tip of the impact rod 6. The fractured portion / notched portion of the ceramics test piece T should be positioned so that

After that, the impact rod 6 is driven toward the ceramics test piece T through the circular hole 4 by a punching device (not shown), and an impact force is applied to the ceramics test piece T. The test piece T breaks at the breaking point / notch under the condition that both ends are free.

In either type of device, the measurement signal from the strain gauge 9 at the time of breaking the ceramic test piece T is converted into a breaking impact force or a dynamic stress intensity factor by the processing of the D / A converter and the microcomputer. It

Examples of brittle materials to be measured include rocks, concrete, plastics, and composite materials in addition to ceramics.

If this measurement is performed in vacuum, it can be used for testing carbon materials for nuclear reactors.

In particular, ceramics are used as members of turbochargers, internal combustion engines, etc., but since they are brittle materials, they have problems in impact strength and reliability against delayed fracture. Therefore, it is necessary to measure the fracture impact force at high temperature to derive the impact fracture toughness value at high temperature which is the usage state.

[Effect of the invention] Since the high temperature impact destructive force measurement according to the present invention does not use a fulcrum member, there is no heat loss due to heat conduction from the test piece to the fulcrum member, and the test piece is simply hung with a hanging thread. It is structurally simple, and when the test piece is broken, the hanging thread has already been cut or loosened, so that the end condition of free ends is satisfied and proper measurement is performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional perspective view of a vertical brittle material high temperature impact fracture strength measuring device according to the present invention, and FIG. 2 is a cross-sectional perspective view of a horizontal brittle material high temperature impact fracture force measuring device according to the present invention. 1: Infrared image furnace 2: Hollow hole 3: Heat insulating plate 4: Circular hole 5: Pore, 6: Impact rod 7: Hanging thread, 8: Pulley 9: Strain gauge, 10: Heat resistant thread 11: Guide Support, T: Test piece

Front page continuation (72) Inventor Shigeru Aoki 2-4302 Wakabadai, Asahi-ku, Yokohama-shi, Kanagawa Prefecture (72) Kikumoto Kikumoto 1-15-3 South East Coast, Chigasaki City, Kanagawa Prefecture

Claims (7)

[Claims] 1. A brittle material test piece is suspended at its end in a high-temperature heating furnace with a heat-resistant thread, heated and maintained at a predetermined temperature, and an impact body is abutted against the brittle material test piece to apply an impact force to the brittle material test piece. High temperature impact fracture force measurement method for brittle materials that destroys the test piece and obtains the impact fracture force of the brittle material from the measurement signal of the strain gauge attached to the impact body at that time 2. A brittle material test piece is hung at both ends in a horizontal state with a heat resistant thread, and an impact body is abutted against the brittle material test piece by dropping a rod-shaped impact resistant body in an upright state to exert an impact force. The method for measuring the high temperature impact fracture strength of brittle materials according to claim 1. 3. A brittle material high temperature impact fracture strength measuring method according to claim 1 or 2, wherein the brittle material is ceramics. 4. A brittle material high temperature impact fracture force measuring method according to claim 1, wherein an impact force is applied to a central portion of the test piece. 5. A high-temperature heating furnace having a hollow hole formed therein, and two heat-resistant yarns for suspending ends of brittle material test pieces suspended at intervals in the hollow hole and a strain gauge are attached, In addition, a brittle material high temperature impact fracture force measuring device composed of an impact body that applies an impact force to a brittle material test piece 6. The high-temperature heating furnace is upright, the impact body is upright, and the brittle material test piece is suspended by a suspending thread at an intermediate position between two heat-resistant suspending threads for suspending the end of the specimen. The brittle material high temperature impact fracture force measuring device according to claim 5, which is a rod-shaped body 7. The brittle material high-temperature impact fracture force measuring device according to claim 5, wherein the high-temperature heating furnace is in a horizontal state, and the impact body is a rod-shaped body that moves rapidly in an axial direction in a horizontal state.