JPS604935B2 - Special atmosphere strength testing method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for testing the strength of a sample by applying a load in a special atmosphere such as a vacuum atmosphere, gas atmosphere, or molten metal atmosphere, without being affected by any external loads other than the sample. The present invention relates to a strength testing device capable of measuring real load.

In recent years, as the temperature of nuclear reactors such as high-temperature gas reactors and nuclear fusion reactors has increased, heat-resistant materials with excellent performance have become necessary as constituent materials for such high-temperature nuclear reactors.

Therefore, in order to appropriately select such materials, it is strongly desired to improve the accuracy and data reliability of high-temperature strength tests in special atmospheres such as vacuum and inert gas. Conventionally,
The load detection device for high temperature strength tests in special atmospheres is
As shown in Figures 1 to 3, the test piece 6 is
A load cell 4 is placed in the main body so as to be exposed to the atmosphere, and the load cell and the test piece are connected by a connecting rod 11 and a chuck 5, and a connecting rod A movable sealing structure is provided at the portion where the test piece passes through the sealed container to detect the load generated on the test piece.

The sealing structures of such conventional devices include the O-ring sealing structure shown in FIG. 1, the bellows sealing structure shown in FIG. 2, and the O-ring sealing structure at the bottom of the container 3 as shown in FIG. There are some combinations of a sealed structure and a bellows sealed structure at the top, but all of them have the disadvantage that external loads are applied slightly, making it impossible to obtain accurate detection values. That is, in the O-ring sealed structure (Fig. 1),
The friction between the connecting rod 11 and the O-ring 12 causes minute load changes irregularly, and this is combined with the load change occurring on the test piece and detected by the load meter, which has the disadvantage of causing errors. In addition, it is difficult to arrange the test piece 6 and the connecting rod 11 at the same position in the container 3, and if the load axis is bent, this will cause an error in the measured load. Further, in the bellows sealing structure (FIG. 2), since an integrated spring load is added as the bellows 13 expands and contracts, there is a drawback that correction is required. That is, Figure 4 shows the load in the case of a tensile test -
An example of an elongation curve is shown, and the chain line OD shown in the figure is the cumulative spring load that increases according to the amount of elongation of the bellows 13' alone. Curve OABCD is test piece 6
This is a load that is a combination of the bellows integrated spring load and the load that occurs in . In actual tests, data is obtained under such conditions. To correct this as a true load that occurs only on the test piece, the following must be done.

The true load (WE) at the elongation E point of the curve OABCD is WE=WE'-△WE, and the true load-elongation curve OA'B'C that was occurring on the test piece was calculated for all points on the curve OABCD for the first time. ′〇 is obtained.

Furthermore, in the O-ring bellows sealed structure (Fig. 3), it is difficult to align the center of the vacuum container 3 with the center of the connecting rod 11, which may cause the load axis to bend or cause damage to the test machine body. The mechanical vibration generated resonates with the bellows and is transmitted to the load system, and is detected as a composite load as in the case of FIG. 2. In addition, in an ultra-high temperature test using a small thin plate-shaped test piece, uneven deflection of the bellows B' or minute errors in the mounting position act as bending loads on the test piece in the unloaded state before the test. It was difficult to obtain normal test results. SUMMARY OF THE INVENTION An object of the present invention is to provide a strength testing device that eliminates the above-mentioned conventional drawbacks.

The device of the present invention is characterized in that it ensures hermeticity in an atmosphere-sealed container, such as a vacuum-sealed container, and that the load cell itself is also provided with a hermetic structure.

Hereinafter, the configuration of the apparatus of the present invention will be specifically explained using an example of a vacuum high-temperature tensile test apparatus using a confidential strain gauge type load cell as a load cell. FIG. 5 shows an apparatus for carrying out the present invention, in which the same parts as in FIGS. 1 to 3 are given the same reference numerals.

The device according to the present invention includes a vacuum-sealed container mechanism that can be moved up and down and a load detection mechanism. The vacuum sealed container mechanism is
A heating section vacuum container 3 (hereinafter referred to as a container) that accommodates the test piece 6 and has an open top, and a load cell storage section 22 that accommodates the load cell 4.
and a sealing bellows 31 for coarse expansion and contraction. The lower part of the container 3 is fixed to a load transfer section 21 of the tester main body 2 (hereinafter referred to as the main body). The load cell storage part is a first cylinder 22a which is iron-fitted to a hole 2a provided in the main body 2 and whose upper end is fixed to the main body.
and a second cylinder 22b connected thereto.
The load cell 4 is fixed to the first cylinder 22a. One end of the bellows 31 is fixed to the second cylinder 22b, and the other end is fixed to the entrance edge of the vacuum container 3. Therefore, the insides of the container 3, the bellows 31, and the storage section 22 are kept airtight from the outside air and maintained in an optimal state, and the vertical movement of the load transfer section 21 is controlled by the bellows.
This is made possible by the expansion and contraction of the case 31, and therefore the container 3 can be raised and lowered. The load detection mechanism includes a load cell 4, a connecting rod 11 connected to the load cell, a joint 10 connecting the load cell and the connecting rod, an upper chuck 5 connecting the connecting rod and the test piece 6, and a test piece. It consists of a lower chuck 5 connecting the piece and the container 3. The upper chuck 5 is fixed to the connecting rod, and the lower chuck 5 extends integrally from the inner wall of the container. The test piece is detachably held by these pair of chucks 5. FIG. 6 shows the structure of the load cell 4, which includes a cylindrical main body 41 and a metal fitting 46 that is seated on a step provided inside the main body.

A circle 47 is provided between this metal fitting and the main body.
A load detection part support stand 44 is arranged on the metal fitting, and a load detection part 48 having a strain gauge 45 for load detection is provided on this. A shaft 42 extends from this load detection portion and is connected to the connecting rod through the joint. A closed bellows 43 for slight expansion and contraction is provided between the shaft 42 and the metal fitting 46, so that the space indicated by B is maintained in the same vacuum atmosphere as the inside of the vacuum-sealed container, and the space indicated by A is maintained at the same vacuum atmosphere as the inside of the vacuum sealed container. It is exposed to atmospheric pressure, and the detection element and strain gauge are located under this atmospheric pressure. That is, even when the load cell 4 is installed in a special environment, only the load detection section having the strain gauge 45 fixedly supported on the support base 44 is connected to the sealing bellows 4.
It is constructed with a bellows-sealed structure so that it is isolated by 3 and placed in an atmospheric environment. Next, the operation of the above device will be explained.

First, in order to confirm whether or not it was possible to eliminate the external load detection caused by a specimen other than the test piece being tested, which is the objective of the present invention, as a preliminary experiment, the load detection and measurement system was operated without connecting the test piece to the test section. Adjust to zero point, leave vacuum atmosphere 1×1 in this state
Maintain at 0-ITom.

The load detection mechanism indicated 11.0 (k9). This value does not change over time as long as the vacuum is maintained,
Average effective diameter of the sealing bellows for minute expansion and contraction in Figure 6 3
．． 7 (skin), the same cross-sectional area 11.04 (enemy) and atmospheric pressure of about 1.
This is tare due to the action of 0 (kg/). Although the load moving part of the testing machine body was moved up and down in this tare state of 11.0 (kg), the cumulative spring load of the bellows due to the elongation of the sealing bellow for rough expansion and contraction as shown in Figure 5 was not detected or measured at all. Ta. Next, in this experiment in which the test piece was incorporated, 1 × 10-
11 detected and measured at the initial stage after obtaining a vacuum below ITom
．． The tare of 0 (kg) could be removed by readjusting the load detection mechanism to zero, and preparations for this experiment were completed. Next, when performing a tensile test, for example, after gripping and fixing both ends of the sample 6 to a pair of chucks 5, 5a, and 5b, the load moving part 21 of the main body is moved downward to remove the container 3.
lower. As a result, the applied load on the test piece 6 is transmitted from the connecting rod 11 to the load cell 4 via the load detection mechanism and detected. In this device, since the vacuum sealing mechanism and the load detection mechanism of the container 3 are completely independent, the bellows cumulative spring load due to the extension of the bellows 31 is
It is not detected by the load cell 4 at all. On the other hand, load cell 4
Inside, the cumulative spring load of the sealing bellows 43 will affect the strain gauge due to the movement of the detection member 42, but the expansion and contraction in the bellows 43 is slight expansion and contraction, and therefore Since the cumulative spring load is also extremely small, its influence on the detection results is negligible and can be completely ignored. FIG. 7 and FIG. 8 are examples of load-elongation diagrams of a tensile test in a vacuum atmosphere according to the present invention.

As is clear from these figures, it can be seen that the cumulative spring load ΔW (external load) in FIG. 4 has been completely removed. It is also clear that material-specific phenomena are clearly detected, and that even after the specimen breaks, it completely returns to the zero point of readjustment and does not require any external load correction. The test conditions in FIG. 7 were as follows. Maximum vacuum level: 5×
10-5Ton test temperature: 1000℃, material: pure molybdenum polycrystalline material, plate-shaped test piece (parallel length: 3 x 4, cross-sectional area: 4
．． 0 machine), tensile speed: 0.2 ribs/min. In addition, in Fig. 8, a serration phenomenon appears as a phenomenon peculiar to the material, but in the conventional O-ring sealing structure method, this phenomenon is combined with the load change due to friction between the connecting rod and the O-ring. It is impossible to separate only the serration phenomenon, and analysis of the data itself is impossible.

The test conditions in FIG. 8 were as follows. Maximum vacuum level: 5×1-5Ton, test temperature: 700m, material: Inconel 625, rod-shaped test piece (parallel part 3mm, cross-sectional area 7mm)
．． 07 candles), tensile speed: 0.2 skin/min. If the above load detection mechanism is installed below the load transfer part and the load transfer part is moved downward, compression and bending tests will be performed, and if the load transfer part is repeatedly moved up and down by a certain amount, tension and compression tests will be performed. This is a fatigue test.

Similarly, changes in the type and installation position of the load cell, changes in the installation position of the sealing bellows for rough expansion and contraction, changes in the installation method and installation position of the heating furnace, and creep tests and creep rupture tests It is possible to faithfully and reliably obtain test results for the load that occurs on the sample itself under single load conditions, and to conduct strength tests in special atmospheres. FIG. 9 shows a compression test device according to another embodiment of the present invention, which is formed in the opposite shape to the above-described tensile test device, and has a load cell 71.
A compression mold is used for this, and the test piece 6 is held between test picks 72 fixed to the ends of the connecting rods.

In this compression testing apparatus, the compressive load of the test piece is transferred to the lower connecting rod 73 by moving the load moving part 21 downward.
However, the amount of contraction generated in the test piece due to the compression load is absorbed by the contraction of the bellows 74, and is not applied to the compression platform other than the load system. Incidentally, a bending test can also be performed by replacing the test jig 72 with a bending test tool. Furthermore, the load cell is a tension compression type and the jig is structured so that the connection with the test piece maintains rigidity under repeated tension and compression loads (e.g. screwed together), making it possible to use it as a tension compression fatigue testing device in special atmospheres. Become.
In addition, as shown in FIG. 10, a heavy flywheel 75 and a load control device 76
By providing a load detection mechanism with
Detection and measurement can be carried out continuously for 4 hours or over a long period of time, so that only the true load can be detected and measured during creep tests, creep rupture tests, relaxation tests, etc. Next, a strength test using the apparatus of the present invention using an inert gas atmosphere (He, N2, Ar) will be described.

Heat-resistant materials used in multi-purpose high-temperature gas-cooled nuclear reactors and the like are subjected to various stresses in a flowing He gas atmosphere at high temperature and pressure.

Materials used in such environments are determined by the temperature of the atmosphere,
Depends on impurities (oxygen, carbon, hydrogen, water), pressure, etc. Diffusion of oxygen, carbon atoms, etc. and steam corrosion reactions have a great effect on long-term integrity. Therefore, strength testing of such materials should be conducted in a He gas atmosphere that is controlled as much as the practical atmosphere to ensure that changes in the state of the material itself that occur during the test due to the influence of He gas are obtained. is important. In addition, in high-temperature strength tests of materials, if the alloy composition of the material being tested contains a solid component with a higher vapor pressure than the base metal, this component may cause evaporation at the high test temperature. .

This phenomenon causes compositional changes and cross-sectional bond reductions in the material being tested, making it impossible to obtain normal test results. Therefore, in high-temperature strength tests of such materials, He,
By filling in an inert gas such as Ar or N2 at a predetermined pressure, evaporation of material components can be prevented and normal test results can be obtained. Moreover, the strength test in Na and NaK atmospheres is as follows. Heat-resistant materials used as constituent materials of fast breeder reactors, etc. are used in environments where molten metals such as Na or NaK flow at high temperatures as reactor coolants, and some of the reactor constituent materials are used as reactor coolants at high temperatures. flowing N
It is subjected to various stresses while immersed in molten metal such as a or NaK.

Materials used in such environments are
Impurities (oxygen, carbon,
Oxidation by nitrogen, carbonization, etc., or corrosion by other factors causes phenomena such as changes in the composition of the material surface, grain boundary corrosion, and oxide formation, which have a large effect on the desired strength. In order to obtain strength under such conditions, high-temperature strength tests are conducted in an atmosphere of molten metal such as Na or NaK under various conditions. This test must be conducted with the heating section located outside the sealed container because molten metals such as Na and NaK are good electrical conductors. According to the present invention, by converting the non-negligible external load that occurs with the movement of the bellows for coarse expansion and contraction into the movement of the bellows for fine expansion and contraction,
Since the strength of the sample can be tested under extremely small conditions, the influence of external loads can be completely ignored, and there is no need for correction, and highly accurate detection results without synthetic loads can be obtained. Obtainable.

Furthermore, by appropriately changing the position of the load cell, the position of the bellows, the installation means of the heating furnace, etc., the present invention can be applied to a wide range of strength tests including fatigue tests, bending tests, etc.

[Brief explanation of the drawing]

1 to 3 are longitudinal sectional views showing the configuration of a conventional strength testing device, FIG. 4 is a load-elongation diagram of the conventional device, and FIG. 5 is one implementation of the strength testing device according to the present invention. FIG. 6 is a vertical cross-sectional view showing one embodiment of a load cell used in the strength testing device of the present invention, and FIGS. 7 and 8 show the load obtained by the device of the present invention. Stretch line diagram, No. 9
Figures 1 and 10 are longitudinal sectional views showing other embodiments of the strength testing device according to the present invention. 2: Testing machine main body, 3: Heat sealed container, 4: Load cell, 5:
Chuck, 6: Sample, 11: Connecting rod, 21: Load moving part, 31: Bellows for coarse expansion and contraction, 43: Bellows for fine expansion and contraction. Figure 'Figure 2 Figure 3 Figure 4 Figure 5 Figure 0 Figure ? Figure '0 Figure 7 Figure 0

Claims (1)

[Claims] 1. A load detection element (strain gauge) section is installed in the atmosphere, and a load transmission system of a sealed strain gauge type load cell extending from the detection element section is located in a sealed container in a special atmosphere. , one end of the test piece located in the sealed container in the special atmosphere and forming a part of the sealed container structure is connected to the load transmission system, and the other end is connected to the load system of the testing machine main body, and the test piece is A strength testing method in a special atmosphere that makes it possible to detect and measure only the load generated by a piece. 2. The method according to claim 1, wherein the special atmosphere is a vacuum atmosphere. 3. The method of claim 1, wherein said special atmosphere is an inert gas such as helium, argon or nitrogen. 4. The method of claim 1, wherein said special atmosphere is a liquid metal such as sodium or sodium potassium. 5. A test body with a built-in sealed structure in which the load detection element is placed in the atmosphere and most of the load transmission system other than the engagement end that engages with the load detection element is placed in a special atmosphere. A sealed strain gauge type load cell that is tightly fitted and fixed in the storage part of the load cell, a connecting rod having a sample chuck at the tip and the other end connected to the load transmission system of the load cell, and the connecting rod being inserted into the load cell. The sample chuck, which is fixed to the load transfer part of the main body of the tester and which forms a pair, is provided inside with another sample chuck which has an opening that allows the sample chuck to be assembled on a straight line aligned with the sample chuck of the connecting rod. A heat-sealed container that can be moved toward and away from the container; and a retractable tubular container that airtightly connects the load cell storage section and the opening of the sealed container so as to cover the periphery of a connecting rod inserted into the sealed container. A special atmosphere strength testing device characterized by comprising a connecting part.