JP7054433B2 - Material test equipment and material test method - Google Patents

Description

The present invention relates to a material test apparatus and a material test method for evaluating the strength characteristics of a material by applying a load to the test piece in a gas atmosphere.

When developing a new material, it is indispensable to evaluate the mechanical strength characteristics of the material, hypothesize and consider the mechanism by which the material leads to fracture, and then optimize the composition and structure. Examples of the strength property of the material include fatigue property, tensile property, bending property, torsional property, fatigue crack growth property, creep property, fracture toughness property, impact property and the like. These strength characteristics are not only the mechanical strength of the material itself, but also the environment in which the material is exposed, that is, cracks caused by various environments such as oxidizing atmosphere, sulfurization atmosphere, high temperature and high pressure, and extremely low temperature. Its characteristics are determined by the influence of generation and progress.

Among these environmental effects, it is known that particularly in the case of metal materials, the effect of oxidation due to the atmospheric atmosphere containing oxygen is large, and the effect of oxidation is remarkable in a high temperature environment. Therefore, in order to accurately evaluate the strength characteristics of a material in material development, it may be required to eliminate the influence of oxidation by oxygen and grasp and evaluate the strength characteristics of the material.

Conventionally, in a material test, in order to eliminate the influence of oxidation by the atmosphere and evaluate the strength characteristics, a test piece made of the material to be evaluated is stored in a container called a housing or a chamber (hereinafter referred to as a housing). It is installed and placed in a sealed state, and the inside of this housing is evacuated or an inert gas such as argon or nitrogen is supplied to create an inert atmosphere, and a load is applied to the test piece for testing. .. For example, as a material test in a high temperature atmosphere, Patent Document 1 describes a housing surrounding the test piece, a means for heating the inside of the housing, and an inert state in the housing in order to prevent oxidation of the test piece in the high temperature atmosphere. There is a description of a high temperature atmosphere material testing machine equipped with a means for supplying gas.

Japanese Unexamined Patent Publication No. 08-327519

In order to prevent the test piece from being oxidized by the surrounding atmosphere, the test piece is enclosed in a housing and sealed so as to block the test piece from the atmosphere containing oxygen, and as described above. It is necessary to evacuate the inside of the housing or, as shown in the testing machine of Patent Document 1, to eliminate the atmosphere inside the housing by supplying an inert gas into the housing. When the inside of the housing is evacuated to eliminate the atmosphere, it is necessary to ensure the airtightness of the housing in order to prevent the air from entering from the outside of the housing when the inside of the housing is evacuated. In order to ensure the airtightness of the housing, it is conceivable to use simple and inexpensive sealing means such as packing, O-ring, and bellows for the fitting portion and the sliding portion between the housing and the test device. However, in the case of a test in which the test environment is high temperature or the test time is long, the simple and inexpensive sealing means tends to cause deformation and deterioration due to heat, wear due to sliding, and the like. It is not easy to ensure airtightness because the air invades from outside the body. On the other hand, in order to ensure complete airtightness, a complicated, special and expensive sealed structure is required. When the inside of the housing is evacuated, it is necessary to install a special device such as a vacuum pump, but it is not economical to install a complicated and expensive sealing means in addition to this because the cost required for the material test increases.

In addition, when the atmosphere inside the housing is eliminated by supplying the inert gas into the housing, the inside of the housing is vacuum-sucked to discharge the air, and then the inert gas is supplied to replace the atmosphere, or the patent As shown in the testing machine of Document 1, the inert gas is supplied while discharging the atmosphere inside the housing. In either case, it is necessary to ensure the airtightness of the housing in the same way as when the inside of the housing is evacuated, and in order to ensure complete airtightness, a complicated, special and expensive sealing structure is required as described above. .. In addition, when the inert gas is supplied while discharging the atmosphere inside the housing, not only the closed structure but also the exhaust structure for discharging the atmosphere is required, and the test device becomes a more complicated structure.

In addition, in Patent Document 1, "when the inert gas is introduced into the heating furnace 1, the inert gas is eventually filled in the heating furnace 1, and all the residual gas in the heating furnace 1 is the heating furnace 1 and both. As described in the statement, "It is discharged from the gap between the rods 4 and 8 and the atmosphere inside the heating furnace 1 is only an inert gas." The structure is such that the atmosphere, which is the residual gas in the housing, is discharged from the gap in the fitting portion with the constituent members. From this description, it is considered that the sealed structure of Patent Document 1 is not a completely sealed structure that ensures complete airtightness, but a substantially sealed structure (hereinafter, may be referred to as a substantially sealed structure). In the case of a substantially sealed structure, the sealing means is simple and inexpensive, but the airtightness is insufficient and the oxygen concentration in the housing may increase and the oxidation of the test piece may not be suppressed. There is a risk that the oxygen concentration in the housing will fluctuate due to changes in air pressure, etc., and the degree of oxidation of the test piece will vary, making it impossible to obtain accurate test results.

Further, in the test apparatus of Patent Document 1, it is described in paragraph 0020 that "it is desirable to continue the supply of the inert gas even during the test in order to prevent oxygen and the like from being mixed into the heating furnace 1." be. However, continuing the supply of the inert gas during the test is not only uneconomical because it consumes a large amount of the inert gas over a long period of time, and the test cost increases, but it is also inert. If the gas is discharged indoors, there are safety issues such as the danger of choking.

In view of the above-mentioned problems, an object of the present invention is a material test capable of suppressing an increase or fluctuation in oxygen concentration in a test atmosphere even with a simple structure, and evaluating strength characteristics in a gas atmosphere inexpensively and safely. To provide equipment and material test methods.

In order to achieve the above object, the present invention is configured as follows. That is, the material test apparatus of the present invention is a material test apparatus that applies a load to a test piece in a gas atmosphere, and includes a housing that surrounds the test piece, an exhaust means that exhausts the atmosphere inside the housing, and the above. According to the atmosphere gas supply means for supplying the atmosphere gas into the housing, the oxygen concentration measuring means for measuring the oxygen concentration of the atmosphere in the housing, and the oxygen concentration measured by the oxygen concentration measuring means, the inside of the housing is It has a control means for controlling the atmospheric gas supply means so as to have a predetermined oxygen concentration, and the exhaust means has an atmospheric discharge port fixed to the housing and an inverse arranged outside the housing. It is characterized by comprising a stop valve and a pipe extending from the air discharge port and connected to the check valve, and further extending from the check valve to communicate with the outside of the building and open to the atmosphere .

The material test apparatus of the present invention can be a material test apparatus for performing a high-temperature low-cycle fatigue test on a test piece by further providing a heating means for heating the test piece. Further, the material test apparatus of the present invention further includes a heating / cooling means for heating / cooling the test piece, and the cooling means constituting the heating / cooling means has a nozzle for blowing the atmospheric gas as a refrigerant onto the test piece. Therefore, it can be used as a material test device for performing a thermal fatigue test on a test piece.

The material test method of the present invention comprises a step of supplying atmospheric gas into a housing surrounding the test piece, discharging the air inside the housing to the outside of the housing, and replacing the inside of the housing with the atmospheric gas .
The test piece has a step of controlling the supply of the atmospheric gas while measuring the oxygen concentration in the housing , which is lowered by the replacement step, while maintaining the inside of the housing at a predetermined oxygen concentration. It is characterized by applying a load .

In the material test method of the present invention, the test can be performed by setting the oxygen concentration to an arbitrary concentration equal to or lower than the oxygen concentration in the atmosphere.

The material test method of the present invention further includes a step of heating the test piece, thereby holding the test piece at a predetermined test temperature and applying a tensile / compressive load to the test piece in a high-temperature low-cycle fatigue test. Can be. Further, the material test method of the present invention further includes a step of restraining the test piece and heating and cooling it, whereby the test piece is repeatedly subjected to temperature changes due to heating and cooling to cause thermal fatigue fracture. It can be a test .

According to the present invention, by providing the above-mentioned configuration, it is possible to suppress an increase or fluctuation in the oxygen concentration in the test atmosphere even with a simple structure, and to evaluate the strength characteristics in a gas atmosphere inexpensively and safely. It is possible to provide a material test device and a material test method that can be used.

It is a schematic block diagram of the material test apparatus which concerns on Embodiment 1 of this invention. It is sectional drawing of the heating and cooling coil of the material test apparatus which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. The present invention is not limited to the following embodiments.

(Embodiment 1)
In the first embodiment, among the material test apparatus and the material test method of the present invention, as an example of a test performed by heating a test piece, a test piece made of a metal material to be evaluated is brought to a constant temperature in a gas atmosphere. A high-temperature low-cycle fatigue test (LCF) that causes thermal fatigue fracture by repeatedly applying and removing strain to a test piece by holding it and applying a tensile / compressive load with a constant strain amplitude. The test apparatus to be performed and the test method thereof are exemplified.

FIG. 1 shows a schematic configuration diagram of the material test apparatus according to the first embodiment. In FIG. 1, the material test apparatus 1 is installed below a table 2, a plurality of columns 4 erected and fixed on the table 2, a crosshead 3 supported and fixed so as to be able to move up and down on the column 4, and a table 2. It is provided with a load-bearing means that operates by using an electric or hydraulic pump (not shown) as a drive source. A fixed rod 5 is fixed to the crosshead 3, an upper chuck 5a is attached to the tip of the fixed rod 5, and a load rod 6 penetrating the table 2 and extending upward is connected to the load loading means. A lower chuck 6a is attached to the tip of the load rod 6. Both ends of the test piece 10 are gripped and fixed by a pair of upper and lower chucks 5a and 6a, and are attached and held to the material testing machine 1.

In order to evaluate the fatigue life of the test piece 10 at a high temperature, the test piece 10 is heated and held by the heating means 71 and subjected to the test. The heating means 71 includes a ring-shaped heating coil 72 shown in FIG. 1, a high-frequency induction heating device (not shown), a temperature control device, and a temperature sensor.

The heating coil 72 is installed so as to surround the outer periphery of the test piece 10, is connected to a high frequency induction heating device, and a high frequency current is passed from the high frequency induction heating device to the heating coil 72 to induce and heat the test piece 10. The high frequency induction heating device is connected to a heating coil 72 at one end and a temperature control device (not shown) at the other end, and the temperature control device is connected to a temperature sensor (not shown) attached to the surface of the test piece 10. The temperature control device controls the high frequency current from the high frequency induction heating device that energizes the heating coil 72 based on the predetermined temperature preset in the temperature control device and the measured temperature of the temperature sensor, and determines the test piece 10. Heat and maintain at the test temperature of (for example, 900 ° C.). The heating means of the test piece 10 is not limited to induction heating, and resistance heating or infrared heating may be used as other heating means. In addition to the above, the material test apparatus 1 is provided with a load cell for measuring the load acting on the test piece 10, a displacement meter for measuring the strain generated on the test piece 10, and the like so that the strength characteristics can be measured. ..

The material test apparatus 1 of the first embodiment is a high-temperature low-cycle fatigue test apparatus having a conventionally known configuration such as the load-bearing means and the heating means 71 described above. Further, the material test apparatus 1 of the first embodiment has a housing 11, an exhaust means 21, an atmospheric gas supply means 31, an oxygen concentration measuring means, which surrounds and stores the test piece 10 and the like, as a configuration characterized by the present invention. By providing the 41 and the control means 51, a high temperature and low cycle fatigue test in a gas atmosphere is possible.

That is, the material test apparatus 1 is connected to a housing 11 that surrounds and stores the test piece 10, an exhaust means 21 that is connected to the housing 11 and exhausts the air inside the housing 11, and a housing that is connected to the housing 11. An atmosphere gas supply means 31 that supplies an atmosphere gas into the body 11, an oxygen concentration measuring means 41 that consists of an oxygen concentration meter installed in the housing 11 and measuring the oxygen concentration of the atmosphere in the housing 11, and an oxygen concentration measurement. It has a control means 51 for controlling the atmosphere gas supply means 31 so that the inside of the housing 11 has a predetermined oxygen concentration according to the oxygen concentration measured by the means 41.

The outer peripheral wall of the housing 11 is penetrated by a plurality of columns 4, a fixing rod 5, and a load rod 6 constituting the material test device 1. The outer peripheral wall of the housing 11 and the fitting portions of the plurality of columns 4, the fixing rod 5, and the load rod 6 penetrating the outer wall thereof are sealed by packing or the like and supplied into the housing 11 described later. It has a sealed structure that does not leak atmospheric gas to the outside and maintains an airtight state so that the atmosphere does not enter the housing 11 from the outside of the housing 11. The housing 11 does not have to be in a completely airtight state, and is a substantially airtight structure having an atmosphere adjusting ability capable of replacing the inside of the housing 11 with an atmospheric gas to maintain a weak positive pressure. good. By configuring the housing 11 with a substantially sealed structure composed of simple and inexpensive sealing means, the cost required for the material test can be saved. In the first embodiment, a mode in which a plurality of columns 4, a fixing rod 5, and a load rod 6 penetrate the housing 11 is shown, but this is only an example, for example, the volume of the housing 11 is made smaller. Then, the housing 11 may be penetrated only by the fixed rod 5 and the load rod 6, or the housing 11 may be further reduced in volume so that only the chucks 5a and 6a penetrate the housing 11. good.

In order to create a gas atmosphere inside the housing 11, the housing 11 is provided with an exhaust means 21 via the atmosphere discharge port 22 and an atmosphere gas supply means 31 via the gas supply port 32, respectively.

The exhaust means 21 has an air discharge port 22 fixed to the housing 11, a check valve 23 arranged downstream of the air discharge port 22, and a pipe extending downstream from the check valve 23, and the pipe is outside the building. Communicate with. The atmosphere gas supply means 31 has a gas supply port 32 fixed to the housing 11, a flow rate control valve 33 arranged upstream of the gas supply port 32, and a pipe extending upstream from the flow rate control valve 33. It communicates with an inert gas source 34 accommodating nitrogen, and the inert gas can be supplied into the housing 11 by opening the flow rate control valve 33. As the inert gas source 34, argon, carbon dioxide gas, helium or the like can be used in addition to nitrogen. Specifically, as the inert gas source 34, a gas gas cylinder or a liquefied gas cylinder can be used.

The oxygen concentration measuring means 41 is provided inside the housing 11 to measure and detect the oxygen concentration in the housing 11, and outputs the measurement result to the control means 51. As the oxygen concentration measuring means 41, a detecting means such as an oxygen concentration meter or an oxygen sensor can be adopted. The control means 51 is connected to the flow rate control valve 33 on the flow path of the atmospheric gas supply means 31 and the oxygen concentration measuring means 41. The control means 51 controls the flow rate of the atmospheric gas supply means 31 based on the oxygen concentration setting function for presetting the oxygen concentration in the housing 11 prior to the material test and the oxygen concentration measured by the oxygen concentration measuring means 41. The valve 33 is provided with a function of outputting a valve open / close signal. Then, the control means 51 controls the atmospheric gas supply means 31 according to the oxygen concentration measured by the oxygen concentration measuring means 41, that is, controls the opening and closing of the flow rate control valve 33, thereby charging the atmospheric gas at a desired flow rate. It is supplied into the body 11 and maintained so that the inside of the housing 11 has a predetermined oxygen concentration.

Next, a material test method using the material test apparatus 1 of the first embodiment will be described. After fixing the test piece 10 to the material test device 1 configured as described above by the chucks 5a and 6a, the test piece 10 is surrounded by the housing 11. Next, the heating means 71 is operated to heat and hold the test piece 10 to a predetermined test temperature by the heating coil 72. On the other hand, while the atmospheric gas supply means 31 supplies nitrogen as an atmospheric gas into the housing 11, the exhaust means 21 discharges the atmosphere inside the housing 11 to the outside. At this time, the excess nitrogen supplied from the atmospheric and atmospheric gas supply means 31 in the housing 11 is discharged from the atmospheric discharge port 22 of the exhaust means 21, and the inside of the housing 11 is from nitrogen from the atmosphere containing oxygen. It is replaced with an atmosphere mainly composed of inert gas. That is, in the material test method of the first embodiment, the atmosphere in the housing 11 is replaced by discharging the atmosphere while supplying the atmosphere gas into the housing 11 surrounding the test piece 10.

More specifically, the replacement of the atmosphere in the housing 11 is described by opening the flow control valve 33 of the atmosphere gas supply means 31 and sending the nitrogen discharged from the inert gas source 34 into the housing 11 from the gas supply port 32. .. With the supply of nitrogen, the atmosphere inside the housing 11 is discharged to the outside of the building via the atmosphere discharge port 22 and the check valve 23 arranged downstream thereof, and the oxygen concentration in the housing 11 decreases. go. Here, the air discharged from the housing 11 to the outside of the building does not flow back into the housing 11 by the check valve 23. The oxygen concentration measuring means 41 measures the oxygen concentration in the housing 11 at any time, and outputs the measurement result to the control means 51. The control means 51 outputs a signal to close the valve to the flow control valve 33 when the oxygen concentration measured by the oxygen concentration measuring means 41 reaches a predetermined oxygen concentration set in advance, and the flow control valve 33 closes the valve. Stop the supply of oxygen.

The order of heating the test piece 10 by the heating coil 72 and replacing the atmosphere in the housing 11 is in no particular order, and both may be performed at the same time, or either one may be performed in advance. .. From the viewpoint of suppressing slight oxidation of the test piece 10 at the initial stage of the start of the test, it is preferable to heat the test piece 10 by the heating coil 72 after replacing the atmosphere in the housing 11 in advance.

As described above, by substituting the inside of the housing 11 with nitrogen from the atmosphere, the test piece 10 is surrounded by a gas atmosphere having a predetermined oxygen concentration, and even in a material test in which the test piece 10 is heated to a high temperature, the test piece 10 is used. Since the oxidation of 10 is suppressed, a material test excluding the influence of oxidation becomes possible.

Next, a load-bearing means (not shown) is operated on the test piece 10 which is placed in a gas atmosphere having a predetermined oxygen concentration and is heated and held at a predetermined test temperature, and is connected to the load-bearing means. A high-temperature low-cycle fatigue test is performed by repeatedly applying a required tensile / compressive load to the test piece 10 via the loaded load rod 6.

Here, the operation and operation of the material test apparatus 1 under test will be described. In the material test method of the first embodiment, the test is performed while maintaining the inside of the housing 11 at a predetermined oxygen concentration by controlling the supply of atmospheric gas while measuring the oxygen concentration in the housing 11 at any time. Since the housing 11 of the material test device 1 has a substantially sealed structure, a small amount of the housing 11 present in the fitting portion between the outer peripheral wall of the housing 11 and the constituent members of the material test device 1 such as the load rod 6 during the test. While the atmospheric gas inside the housing 11 leaks through the gap, the atmosphere may enter from the outside of the housing 11 and the oxygen concentration may increase or fluctuate. However, according to the material test method of the first embodiment, it is possible to suppress an increase or fluctuation in the oxygen concentration in the housing 11 during the test.

That is, the oxygen concentration measuring means 41 measures and detects the oxygen concentration in the housing 11 at any time during the test. When the oxygen concentration in the housing 11 exceeds the predetermined oxygen concentration set by the control means 51 due to the atmosphere invading from the outside of the housing 11, the control means 51 outputs a signal for opening the flow rate control valve 33 to control the flow rate. The valve 33 opens the valve and supplies nitrogen from the inert gas source 34 into the housing 11. Atmospheric gas in the housing 11 that is surplus due to the supply of nitrogen is discharged from the atmospheric exhaust port 22 of the exhaust means 21, passes through the check valve 23, and passes through the piping of the exhaust means 21 to the atmosphere outside the building. Be released. Then, when the oxygen concentration in the housing 11 becomes equal to or lower than the predetermined oxygen concentration due to the supply of nitrogen from the atmosphere gas supply means 31, the flow rate control valve 33 closes and the supply of nitrogen is stopped.

In this way, by interlocking the oxygen concentration measuring means 41, the control means 51, and the flow rate control valve 33, the supply of nitrogen is controlled while measuring the oxygen concentration in the housing 11 at any time, so that the outer wall of the housing 11 can be contacted. Atmosphere invades into the housing 11 due to the gap between the fitting portion of the material test device 1 and the fitting portion, or due to the deterioration of the sealing means of the material test device 1 over time or the change in atmospheric pressure, and the housing during the test. It suppresses the rise and fluctuation of the oxygen concentration in the body 11. This makes it possible to eliminate the influence of oxidation by oxygen and grasp and evaluate the strength characteristics of the material.

Further, according to the material test apparatus 1 of the first embodiment, the cost required for the material test can be suppressed. Since the material test device 1 does not require the installation of a special device such as a vacuum pump or complicated and expensive sealing means, the equipment cost of the device itself can be suppressed. Further, as described above, according to the material test method of the first embodiment, since the supply of nitrogen is controlled according to the oxygen concentration in the housing 11, the amount of expensive inert gas used can be saved. That is, the fatigue test is a test method in which the supply of the inert gas is continued even during the test in order to prevent oxygen from entering the test atmosphere, as in the test method using the test device of Patent Document 1 which has been known conventionally. When the test time is long, a large amount of inert gas is consumed. On the other hand, according to the material test method of the first embodiment, it is necessary to suppress the increase in oxygen concentration due to the atmosphere invading the housing 11 instead of continuously supplying the inert gas during the test. Only nitrogen is supplied into the housing 11. Therefore, even if the test time is long as in the fatigue test, a small amount of nitrogen is supplied to the housing 11, so that the running cost can be suppressed. As described above, in the material test apparatus 1 and the material test method of the first embodiment, both the equipment cost and the running cost can be suppressed, so that the test cost can be reduced.

Further, according to the material test apparatus 1 of the first embodiment, it is safe because the piping of the exhaust means 21 communicates with the outside of the building. That is, excess atmospheric gas is discharged from the housing 11 to the outside of the housing 11 according to the amount of nitrogen supplied into the housing 11 in order to maintain a predetermined oxygen concentration. At that time, most of the exhausted atmospheric gas is discharged to the outside of the housing 11 via the exhaust means 21, not the gap between the outer peripheral wall of the housing 11 and the fitting portion of the component of the material test device 1. Will be done. This is because when comparing the flow path resistance of the gap with the flow path resistance of the piping of the exhaust means 21, the latter is much smaller than the former, so that the atmospheric gas is discharged via the exhaust means 21 which is easier to flow. Because. In the material test apparatus 1 of the first embodiment, since the exhaust means 21 including the pipe communicating with the outside of the building is provided, the amount of nitrogen leaking from the inside of the housing 11 through the gap is extremely small. Since the inside of the building such as the room where the material test apparatus 1 is installed is not filled, the risk of suffocation is low and safety problems can be avoided.

In addition, according to the material test method of the first embodiment, it is possible to perform a material test excluding the influence of oxidation due to an atmospheric atmosphere containing oxygen, while the inside of the housing 11 is provided with a control means 51 having an oxygen concentration setting function. By arbitrarily setting the oxygen concentration of, the material test can be carried out in a desired oxidizing gas atmosphere. This has the effect of being able to evaluate the strength characteristics of the material used in a gas atmosphere having an oxygen concentration (about 21%) or less in the atmosphere and having a specific oxygen concentration.

For example, exhaust system parts such as a turbine housing of a turbocharger (supercharger) attached to an automobile engine are exposed to oxidative exhaust gas at a high temperature. The temperature and composition of the exhaust gas emitted from the combustion chamber of an automobile engine differ depending on the type of engine such as a gasoline engine or diesel engine and the unique combustion characteristics of each engine, and these differences are the differences in the exhaust system parts. It has a great influence on heat resistance, durability, etc. The degree of oxidation of the exhaust gas is largely determined by the temperature of the exhaust gas and the oxygen concentration in the exhaust gas. The oxygen concentration (capacity ratio of oxygen content) in the exhaust gas is, for example, about 0.01 to 5% for a gasoline engine and about 5 to 21% for a diesel engine.

It is necessary to evaluate the strength characteristics of the materials constituting the exhaust system parts by setting the test atmosphere so that the conditions are the same as the temperature and oxygen concentration of the exhaust gas discharged from the actual engine. According to the material test method of the first embodiment, the gas atmosphere in the housing 11 is set to an arbitrary and predetermined oxygen concentration, and the material test is performed while suppressing the rise and fluctuation of the gas atmosphere and maintaining the stability. Is possible. That is, in the material test method of the first embodiment, the test can be performed by setting the oxygen concentration to an arbitrary concentration equal to or lower than the oxygen concentration in the atmosphere.

As described above, by providing the configuration shown in the first embodiment, the material test apparatus and the material test method of the present invention surround the test piece even if the apparatus has a simple structure including a substantially sealed structure. It is possible to perform a high-temperature low-cycle fatigue test in a gas atmosphere inexpensively and safely while suppressing an increase or fluctuation in the oxygen concentration in the test atmosphere and maintaining a predetermined oxygen concentration in a stable manner.

(Embodiment 2)
In the first embodiment, the fatigue test under a constant high temperature is exemplified, but in the second embodiment, the temperature fluctuation test, that is, the thermal fatigue life test is exemplified. In the second embodiment, among the material test apparatus and the material test method of the present invention, as an example of a test performed by heating and cooling the test piece, the test piece made of the metal material to be evaluated is restrained in a gas atmosphere. By repeatedly applying the temperature amplitude (temperature change) due to heating and cooling, the expansion and contraction associated with heating and cooling are mechanically restrained, causing thermal stress (thermal strain) in the test piece and causing thermal fatigue fracture. It exemplifies a test apparatus for performing a life test (TMF: Thermo-Mechanical Fatigue) and a test method thereof.

The material test apparatus of the second embodiment has the same table, column, and cloth as the first embodiment except that the atmospheric gas is used as a refrigerant for cooling the test piece in the heating and cooling means described later. It is a thermal fatigue test apparatus equipped with a conventionally known configuration such as a chuck for gripping and fixing a head and a test piece, and a heating / cooling means capable of repeatedly applying thermal stress (heat strain) to the test piece. The load applied to the test piece in the second embodiment is given by the thermal stress generated by the heating / cooling means described later instead of the load-loading means in the first embodiment. Similar to the first embodiment, the material test apparatus according to the second embodiment has a characteristic structure of the present invention, such as a housing for surrounding and storing a test piece and the like, an exhaust means, an atmospheric gas supply means, and an oxygen concentration. By providing a measuring means and a controlling means, it is possible to perform a thermal fatigue life test in a gas atmosphere.

FIG. 2 shows a cross-sectional view of a heating / cooling coil 82 constituting the heating / cooling means 81 of the material test apparatus according to the second embodiment. In FIG. 2, the test piece 10 is held and held by a pair of upper and lower chucks (not shown) at both ends thereof, attached to and held by a material tester, and is supported by a ring-shaped heating / cooling coil 82 installed so as to surround the outer periphery thereof. Besieged.

In order to evaluate the thermal fatigue life of the test piece 10, the test piece 10 is subjected to a heating and cooling cooling cycle by a heating and cooling means 81 including a heating and cooling means including a heating and cooling coil 82 and subjected to a test. To.

As shown in FIG. 2, the heating / cooling coil 82 has a double pipe structure in which two square pipes are arranged inside and outside, and the square pipe on the outer peripheral side has a cooling for cooling the heating / cooling coil 82 itself. A water passage 83 for circulating water is formed, and a gas passage 84 for circulating a cooling gas, which is a refrigerant for cooling the test piece 10, is formed in the square pipe on the inner peripheral side. A large number of nozzles 84a are formed on the inner peripheral surface of the heating / cooling coil 82 in the circumferential direction, and the test piece 10 heated by blowing cooling gas from each of the nozzles 84a toward the surface of the test piece 10 is cooled. can do.

The heating means is composed of a heating / cooling coil 82, a conventionally known high-frequency induction heating device, a temperature control device, a temperature sensor, and a cold water supply device (which are not shown), and a high-frequency current is applied from the high-frequency induction heating device to the heating / cooling coil 82. The test piece 10 is heated and held at a predetermined test temperature (for example, 1000 ° C.), and cooling water is flowed from the cold water supply device to the water passage 83 of the heating / cooling coil 82 to allow the heating / cooling coil 82 itself. Prevents melting damage.

The cooling means is composed of a heating / cooling coil 82, a conventionally known cold air supply device (not shown), a temperature adjusting device, and a temperature sensor, and a cooling gas as a refrigerant is flowed through a gas passage 84 of the heating / cooling coil 82 from a nozzle 84a. This is ejected to cool the test piece 10 to a predetermined test temperature (for example, 150 ° C.) (and further maintain the test temperature as necessary). Here, the temperature adjusting device and the temperature sensor do not need to be individually provided in the heating means and the cooling means, and may be shared.

The cold air supply device communicates with an inert gas source accommodating nitrogen via a flow rate control valve (not shown) upstream of the gas passage 84 of the heating / cooling coil 82, and opens and closes the flow rate control valve to serve as cooling gas. Controls the ejection and stopping of the gas.

In the material test apparatus of the second embodiment, in addition to the same configuration as that of the first embodiment, the atmosphere gas is supplied into the housing to replace the atmosphere and maintain the oxygen concentration to a predetermined value. The atmospheric gas supplied into the housing is used as a cooling gas for cooling the heated test piece. The inert gas source may be individually provided or shared by the atmosphere gas supply means for replacing the atmosphere in the housing and the cooling means for cooling the test piece.

Next, a material test method using the material test apparatus of the second embodiment will be described. Also in the second embodiment, the test piece 10 is fixed and restrained by the chuck to the material test apparatus configured in the same manner as the first embodiment, and then the test piece 10 is surrounded by the housing. Next, while supplying nitrogen as an atmospheric gas into the housing by means of an atmospheric gas supply means, an exhaust means, an oxygen concentration measuring means, and a control means, the air inside the housing is discharged and the inside of the housing is replaced with an atmosphere having a predetermined oxygen concentration. do.

Next, by repeating the heating step and the cooling step by the heating / cooling means 81, a cooling / heating cycle is applied to the test piece 10 in the restrained state. In the heating step, a heating means is operated to apply a high-frequency current from the high-frequency induction heating device to the heating / cooling coil 82 to heat and hold the test piece 10 to a predetermined test temperature. In order to prevent the heating / cooling coil 82 from being melted, the cooling water is always circulated from the cold water supply device to the water passage 83 in the heating / cooling coil 82 during the test.

In the cooling step, the energization of the high frequency current to the heating / cooling coil 82 is stopped, and the cooling means is operated to transfer nitrogen as a cooling gas from the inert gas source of the cold air supply device to the gas passage 84 in the heating / cooling coil 82. While circulating, nitrogen is blown from the nozzle 84a toward the surface of the test piece 10 to cool the test piece 10 to a predetermined test temperature.

The temperature control of heating and cooling of the test piece 10 in the heating step and the cooling step is based on the temperature pattern of heating and cooling preset in the temperature control device and the measured temperature of the temperature sensor attached to the surface of the test piece 10. The temperature during heating is controlled by controlling the high-frequency current from the high-frequency induction heating device that energizes the heating / cooling coil 82, while the opening degree of the flow control valve of the cold air supply device is controlled to control the nozzle of the heating / cooling coil 82. This is done by controlling the cooling temperature by adjusting the amount of cooling gas sprayed from 84a. By such temperature control of heating and cooling, the test piece 10 can be subjected to a cooling / heating cycle with an arbitrary temperature amplitude (for example, 150 ° C. to 1000 ° C.).

In the material test method of the second embodiment, the nitrogen supplied as a cooling gas for cooling the test piece 10 may be excessive to keep the gas atmosphere in the housing constant, and lowers the oxygen concentration in the housing. May act to cause. When the oxygen concentration decreases, it is conceivable to supply oxygen into the housing because the desired test cannot be performed when the test is performed by setting the oxygen concentration to an arbitrary concentration. As the oxygen supply means, an oxygen supply source for accommodating oxygen or the atmosphere may be communicated through a flow control valve on the flow path of the atmosphere gas supply means or the cooling means for cooling the test piece, or these means. Separately, an oxygen supply port may be provided in the housing, and the oxygen supply port, the flow control valve, and the oxygen supply source may be communicated with each other by a pipe. The flow rate control valve on the flow path of the oxygen supply means is connected to the control means, and the flow rate control valve of the oxygen supply means is controlled according to the oxygen concentration in the housing to bring oxygen or the atmosphere of a desired flow rate into the housing. Supply. As a result, even if nitrogen is supplied for cooling the test piece 10, the inside of the housing is maintained at a predetermined oxygen concentration.

As described above, by substituting the inside of the housing with nitrogen from the atmosphere, the test piece 10 is surrounded by a gas atmosphere having a predetermined oxygen concentration, and when the heated test piece 10 is cooled, the atmosphere containing oxygen is removed. Since nitrogen similar to that of atmospheric gas is sprayed onto the test piece 10 as a refrigerant instead of using it as a refrigerant, oxidation of the test piece 10 is suppressed even in a material test in which the test piece 10 is heated and cooled. Material testing that eliminates the effects of oxidation is possible.

Next, the heating / cooling means 81 is operated on the test piece 10 which is placed in a gas atmosphere having a predetermined oxygen concentration and is in a restrained state, and is heated by the heating / cooling coil 82 and the cooling gas from the nozzle 84a. The cooling and heating cycle by spraying is repeated. A thermal fatigue test is performed by repeatedly applying a thermal stress associated with the temperature amplitude to the test piece 10 by this thermal cycle to apply a load.

As described above, by providing the configuration shown in the second embodiment, the material test apparatus and the material test method of the present invention surround the test piece even if the apparatus has a simple structure including a substantially sealed structure. It is possible to perform a thermal fatigue test in a gas atmosphere inexpensively and safely while suppressing an increase or fluctuation in the oxygen concentration in the test atmosphere and maintaining a predetermined oxygen concentration in a stable manner.

In the above-described first and second embodiments, the high-temperature low-cycle fatigue test in which the test piece is heated (the first embodiment) and the thermal fatigue test in which the test piece is heated and cooled (the second embodiment) have been described as fatigue tests. The material test apparatus and material test method according to the present invention are not limited to these, and by appropriately changing the configuration of the load-bearing means, the mounting jig for the test piece, etc., or the temperature of the test environment such as high temperature, normal temperature, and below freezing point, etc. Needless to say, it can be applied to material tests such as tensile test, compression test, bending test, torsion test, impact test, and creep test. For example, if the load-bearing means is configured to be able to continuously apply a load to the test piece for a long time, a creep test at a high temperature can be performed. As described above, according to the material test apparatus and the material test method of the present invention, it can be applied to various material tests, and the strength characteristics in a gas atmosphere excluding the influence of oxidation can be measured.

1: Material test equipment 2: Table 3: Crosshead 4: Column 5: Fixed rod 6: Load rod 5a, 6a: Chuck 10: Test piece 11: Housing 21: Exhaust means 22: Atmospheric discharge port 23: Check valve 31: Atmospheric gas supply means 32: Gas supply port 33: Flow control valve 34: Inert gas source 41: Oxygen concentration measuring means 51: Control means 71: Heating means 72: Heating coil 81: Heating and cooling means 82: Heating and cooling coil 83: Water passage 84: Gas passage 84a: Nozzle

Claims (6)

A material tester that applies a load to a test piece in a gas atmosphere.
The housing that surrounds the test piece and
Exhaust means for exhausting the atmosphere inside the housing and
Atmospheric gas supply means for supplying atmospheric gas into the housing and
An oxygen concentration measuring means for measuring the oxygen concentration of the atmosphere in the housing,
It has a control means for controlling the atmospheric gas supply means so that the inside of the housing has a predetermined oxygen concentration according to the oxygen concentration measured by the oxygen concentration measuring means.
The exhaust means is
The atmospheric exhaust port fixed to the housing and
A check valve located on the outside of the housing and
It consists of a pipe that extends from the air discharge port and connects to the check valve, and further extends from the check valve to communicate with the outside of the building and open to the atmosphere.
A material testing device characterized by that. The material test apparatus according to claim 1, further comprising a heating means for heating the test piece. The material test apparatus further includes a heating / cooling means for heating / cooling the test piece, and the cooling means constituting the heating / cooling means has a nozzle for blowing the atmospheric gas as a refrigerant onto the test piece. The material test equipment described in. A step of supplying atmospheric gas into the housing surrounding the test piece, discharging the air inside the housing to the outside of the housing, and replacing the inside of the housing with the atmospheric gas .
It has a step of controlling the supply of the atmospheric gas while measuring the oxygen concentration in the housing , which is lowered by the replacement step, at any time.
A material test method comprising applying a load to the test piece while maintaining the inside of the housing at a predetermined oxygen concentration. The material test method further comprises a step of heating the test piece, and is a high-temperature low-cycle fatigue test in which the test piece is held at a predetermined test temperature and a tensile / compressive load is applied to the test piece. Item 4. The material test method according to Item 4. The material test method further includes a step of restraining the test piece and heating and cooling it, and is a thermal fatigue life test in which the test piece is repeatedly subjected to temperature changes due to heating and cooling to cause thermal fatigue failure. The material test method according to 4 .

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