JPH02311739A - Fatigue tester for shape memory alloy - Google Patents

Abstract

PURPOSE:To make it possible to perform a fatigue test under the environment close to an actually operating environment and to inspect many pieces of shape memory alloy at the same time by changing external stress, and imparting temperature change. CONSTITUTION:When a sample S is immersed into cooling water by the rotation of a rotary body 1, the sample S is cooled rapidly and transformed into a martensite phase (M phase). Since the sample in M phase is readily deformed, the sample S is contracted by the compressing force of a pushing spring. The length of the sample S is elongated and shortened by the repetition of heating and cooling. The operation is converted into the angular change of a rotary shaft 16 of a rotary potentiometer 15 through an extending lever 18 and a linking arm 17. Finally, said operation is detected as the change in resistance value of the potentiometer 15. The level of the cooling water 2 is monitored with a level sensor 36. When the level is lowered, a solenoid valve 32 is automatically opened, and water is supplied. Thus the water level is kept constant. Therefore, the sample after the end of the test is not left alone for a long time, and the deterioration of the sample can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fatigue testing machine for shape memory alloys, and more specifically, it is capable of testing the fatigue degree of shape memory alloys in a state similar to the actual usage environment, and is capable of testing a large number of shapes. The present invention relates to a fatigue testing machine for shape memory alloys that can simultaneously test shape memory alloys and perform repeated tests a huge number of times in a short period of time.

[Conventional technology]

As the scope of use of shape memory alloys expands, there is a demand for the development of a property testing machine for shape memory alloys, and in particular, the development of a fatigue testing machine that can test the deterioration of memory performance during repeated use, that is, the degree of fatigue. is desperately needed. Since shape memory alloy itself is a comparatively rare material, the development of testing machines is still immature, and at this stage, the only fatigue testing machine for shape memory alloys is one that stretches the shape memory alloy at a constant temperature, compresses it, and expands and contracts it. Alternatively, the actual situation is that a constant load is applied to the shape memory alloy, and the shape memory alloy in that state is heated and cooled to expand and contract.

[Problem to be solved by the invention]

However, when shape memory alloys are used as actuators, as symbolized by their use as opening/closing means for dampers, etc., they are usually used in environments where load changes and temperature changes occur simultaneously. Conventional testing machines in which one of the load and temperature is fixedly set have a problem in that they cannot test the degree of fatigue in accordance with the actual usage environment. In addition, conventional fatigue testing machines cannot test many shape memory alloys at the same time, and it takes a long time to repeatedly test tens of thousands to hundreds of thousands of times. There was a problem in that it was not possible to measure the fatigue level of memory alloys. Furthermore, with conventional fatigue testing machines, it was not possible to continuously measure the internal stress for recovery during the elongation process (hereinafter referred to as recovery stress), and it was not possible to understand the recovery characteristics of shape memory alloys in detail. .

The present invention was made in view of the current situation, and it enables fatigue testing in an environment similar to the actual usage environment by applying temperature changes while changing external stress, and also enables fatigue testing in an environment similar to the actual usage environment. Shape memory allows alloys to be inspected at the same time, repeated tests tens to hundreds of thousands of times can be conducted in a short period of time, and changes in recovery stress can be continuously measured. The purpose is to provide a fatigue testing machine for alloys.

[Means to solve problems]

The shape memory alloy fatigue tester according to the present invention has achieved the above-mentioned problems. The shape memory alloy fatigue tester according to the present invention holds a shape memory alloy formed into a coil shape so that it can expand and contract, and applies an external stress whose magnitude is known to the shape memory alloy. A holding mechanism is constituted by fixedly or removably associated with an external stress applying means capable of acting in the direction of expansion and contraction of the memory alloy, and furthermore, a means for measuring the expansion and contraction distance of the shape memory alloy is provided in the holding mechanism to form a unit test unit. A rotating body is constructed in which a plurality of unit test units are arranged radially around the outer periphery, and the rotating body is positioned between a heating means and a cooling means that are spaced apart, and each test unit is located on the surface of the rotating body. The gist is that the device is configured to rotate and move between the heating means and the cooling means.

As a holding mechanism, a coiled shape memory alloy is inserted into a longitudinally movable slide rod, and one end of the shape memory alloy is fixed or locked to the slide rod, so that the moving distance of the slide rod is controlled by the shape memory alloy. It is preferable to use a device that corresponds to the expansion/contraction distance of the slide rod and is associated with an external stress applying means that can move the slide rod.

Further, as the external stress applying means, a coil spring having a known spring constant is used, and one end of the coil spring is fixed or locked to the slide rod and inserted into a position adjacent to the shape memory alloy on the slide rod. It is considered that the elastic restoring force of

In addition, as the means for measuring the extension/contraction distance, a rotary potentiometer is arranged near the base end of the slide rod, and a connecting arm is fixed to the rotating shaft of the rotary potentiometer, and the tip of the connecting arm is slid through an extending rod. A method is adopted in which a slide rod is pivoted at the base end and the horizontal movement distance of the slide rod is replaced by the rotation angle of a rotary potentiometer.

As the heating means and the cooling means, it is possible to bring a liquid or gas set at a high or low temperature into contact with the shape memory alloy, but it is preferable to use a hot air blower as the heating means and use cooling water as the cooling means.

Furthermore, it is desirable to use antifreeze as the cooling water to avoid freezing.

Furthermore, it is preferable that a drain pipe equipped with a solenoid valve is attached to the water tank, and when the rotation of the rotating body is completed, the solenoid valve is opened to drain the cooling water.

[Effect]

A shape memory alloy fatigue test using a shape memory alloy fatigue tester having such a configuration is performed as follows. First, a plurality of coiled shape memory alloys having a predetermined length memorizing the original shape to serve as a sample are prepared, and these are placed radially around the surface of the rotating body. Attachment to the surface of the rotating body is performed using a holding mechanism provided radially around the surface of the rotating body. That is, each sample is held by a holding mechanism in a state where it can be expanded and contracted in the length direction, and an external stress applying means is associated with the sample to apply external stress in the direction of expansion and contraction of the sample. A test unit is constructed in which a means for measuring the expansion/contraction distance is associated with the test unit. Using the same procedure, samples are set in each holding mechanism provided around the outer periphery of the rotating body to complete all unit test units.

When the setting of the sample on the rotating body is completed as described above, the rotating body is rotated at a constant speed. Since heating means and cooling means are spaced apart from each other at the top and bottom of the rotating body, when the rotating body rotates, the sample is repeatedly heated and cooled in accordance with the rotational speed of the rotating body. Become. When the sample is heated, it becomes the matrix austenite phase (P phase), and when it is cooled, it becomes the martensitic phase (M phase), but because the sample is subjected to external stress, the M The phase sample will be deformed in the direction of the external stress. That is, when the external stress is a pushing force, it will contract, and on the other hand, when the external stress is a tensile force, it will be expanded.

Next, the sample is moved to a position where it is exposed to the heating means by the rotation of the rotating body, and the sample becomes P phase by being heated and instantly restores to the memorized shape. The degree of fatigue of the shape memory alloy is measured by performing such deformation and restoring operations, that is, expansion and contraction, of the sample tens of thousands to hundreds of thousands of times, and measuring the deformation and restoring characteristics during the process of this repeated test. It is something.

The expansion/contraction movement of the sample is constantly monitored by the expansion/contraction distance measuring means, and since the external stress loading means is of a known magnitude, the deformation characteristics of the sample in response to the magnitude of external stress can be easily monitored. Characteristics during restoration performed against external stress can be continuously known.

When a holding mechanism is used in which the sample is inserted into a slide rod with one end fixed or locked to the slide rod, and an external stress applying means for sliding the slide rod is associated. The distance of expansion and contraction of the sample can be measured by the distance traveled by the slide rod.

Furthermore, when a coil spring with a known spring constant is used as the external stress loading means, the external stress exerted on the coil spring sample can be determined by the length of extension of the coil spring, and the length of extension of the coil spring is determined by the distance traveled by the slide rod. Therefore, by measuring the moving distance of the slide rod, the amount of external stress can be measured at the same time as the distance of expansion and contraction of the sample.

Further, when a rotary potentiometer connected to the end of the slide rod via a connecting arm and an extension rod is used as the extension/contraction distance measuring means, the extension/contraction distance is converted into a rotation angle and then taken out as an electrical signal. Therefore, by inputting this electrical signal into a computer via an analog-to-digital conversion mechanism and processing it, it becomes possible to automatically and accurately record and analyze various characteristics of the sample, including the degree of fatigue, without requiring human intervention. A fully automated testing machine is provided.

When a hot air blower that can vary the hot air temperature, air volume, and blowing angle is used as the heating means, it becomes possible to change the heating conditions as appropriate, and a variety of test environments can be realized.

Furthermore, when antifreeze is used as the cooling water, the temperature of the cooling water can be lowered to below zero degrees Celsius, making rapid cooling possible.

Furthermore, if the drain pipe is equipped with a solenoid valve that opens at the same time as the rotation of the rotating body finishes and drains the cooling water, the sample will not be immersed in the cooling water for a long time after the test is completed.
The characteristics of the sample do not deteriorate after the test is finished.

〔Example〕

Next, details of the present invention will be explained based on illustrated embodiments.

FIG. 1 schematically shows the overall configuration of an embodiment of a shape memory alloy fatigue testing machine according to the present invention. In this example, a rotating body 1 is constructed in which a plurality of shape memory alloys S (hereinafter referred to as samples S) to be tested are arranged around the outer periphery, and a cooling water 2 as a cooling means is provided in the lower part of the rotating body 1. Arrange the filled aquarium 3,
On the other hand, a hot air blower 4 as a heating means is disposed above the rotating body, and the sample S is configured to be exposed alternately to cooling water and hot air by rotating the rotating body 1. . The rotating body 1 is constructed by inserting a rotating shaft 6 into a parallel disk 5.5, and a plurality of test units U are provided around the outer periphery of the disk 5. In the illustrated example, there are six sample placement positions, but this number is arbitrary. The driving force of the motor 9 for rotating the rotating body is transmitted to the rotating shaft 6 of the rotating body 1 via the pulley 7.7 and the transmission belt 8.The motor 9 for rotating the rotating body 9 is capable of rotating at a constant speed. One that can continuously vary the rotational speed is used.

The mechanism around the sample provided around the outer periphery of the rotating body is shown in FIG. That is, a base plate 10 is constructed across both opposing discs 5, 5, and two support plates 12a are provided with insertion holes 1.1a and 1.1a and llb formed at appropriate intermediate positions of the base plate 10,
12b are erected at a certain distance apart, and a slide rod 13 that is movable in the length direction is inserted into the insertion holes 11a and llb. A locking ring 14 that extends the slide rod 13 in the length direction is fixed at approximately the middle position of the slide rod 13, and an extended sample S is inserted between one support plate 12a and the locking ring 14. A compression spring B is inserted between the other support plate 12b and the locking ring 14. The push spring B is used to compress and deform the sample by applying external stress to the sample S.
The length and elastic repulsion force are set so that when the sample S becomes the M phase, the locking ring 14 is pressed and moved to the left in the figure to compress the sample S. Further, as the push spring B, a spring constant whose spring constant is known is used, and the magnitude of the external stress due to the push spring B can be known by measuring the amount of expansion/contraction displacement of the push spring B.

In the figure, reference numeral 15 denotes a rotary potentiometer attached near the outer periphery of the rotary plate 5. A connecting arm 17 is fixed to the rotary shaft 16, and one end of the connecting arm 17 is connected to the slide rod 13. An extending rod 18 is pivotally attached to the base end, converts the horizontal movement of the slide rod 13 into rotational movement, and detects the angular displacement amount as a resistance change.

Further, a regulating plate 19 is provided at a predetermined distance from the tip of the slide rod 13 for regulating excessive movement of the slide rod 13, and prevents mechanical stress from being applied to the rotary potentiometer 15. There is.

The method for setting the sample S shown in Fig. 4 is to compress and deform the sample S whose elongated state has been memorized using a push spring B, and then heat the compressed and deformed sample S to instantly elongate it and return it to its original state. This tester is used to measure the deformation characteristics and restoration characteristics when the sample is restored to its memorized shape. It is also possible to detect the deformation characteristics and restoration characteristics of a sample when the sample is instantaneously restored and shrunk by heating. This situation is, for example, shown in Figure 5 (
As shown in b), a sample S with a compressed shape memorized is placed between the support plate 12a and the locking ring 14, and the support plate 1
2b and the locking ring 14 is a tension spring B in an extended state.
', one end of the sample S and one end of the tension spring B' are fixed to the locking ring 14, and the sample S is expanded by the contraction force of the tension spring B'. Also, Figure 5 (b)
As shown in FIG. 2, it is also possible to apply a tensile force to the sample S by attaching a locking plate 20 to the tip of the slide rod 13 and disposing a pressure spring B between the locking plate 20 and the support plate 12b.

Furthermore, although not shown, it is also possible to exclude the compression spring and measure the deformation characteristics and restoring characteristics of the sample in an unloaded state.

In addition, as the external stress applying means, other means may be adopted as long as the size thereof is known. For example, it is also possible to arrange an electromagnet close to the tip of the slide rod to magnetically attract the slide rod. .

As shown in FIG. 6, as a means for measuring the moving distance of the slide rod 13, a differential transformer 21 is disposed on the base end side of the slide rod 13, and a core 2 of the differential transformer 21 is disposed on the base end side of the slide rod 13.
2 can also be directly moved and measured by reciprocating movement of the slide rod 13.

The unit test units U configured in this way are arranged radially around the outer periphery of the rotating body at equal intervals, making it possible to simultaneously measure a large number of samples.

A lead wire 23 for deriving an output signal from the rotary potentiometer 15 is led out into the rotary shaft 6 or along the surface of the rotary shaft 6 to the end of the rotary shaft, and is led out to the outside of the rotary body via a slip ring 24.

The hot air blower placed above the rotating body is one that has enough heat to instantly restore the deformed sample; in this example, the heat generated by the built-in heater 25 and the blower 2 are
6, the amount of air blown can be individually controlled. or,
The installation position and blowing angle of the blowing port 27 are adjusted so that the hot air sent out is blown directly onto the entire sample S.

In FIG. 1, the air outlet 27 is placed above the sample for convenience of notation in the drawing, but in reality it is set at the same height as the sample S, and the air outlet 27 is placed at the same height as the sample S. It is set so that it can be attached.

The cooling means is constructed by immersing a cooling body 29 led out from an immersion type cooler 28 into a water tank filled with cooling water 2 to a certain height. It is preferable to use antifreeze as the cooling water 2, and in this way, it is also possible to set the cooling water temperature to below zero degrees Celsius. The cooling water 2 is filled to a height where the sample S located at the bottom of the rotating body is completely submerged, and this height is constantly monitored by a level sensor 30 for detecting the water level provided on the inner peripheral wall of the water tank 3. There is. When the water level drops, the solenoid valve 32 of the water supply pipe 31 is opened to supply water, and the water level is automatically restored to a predetermined level.

Further, the water tank 3 is provided with a drain pipe 34 to which a solenoid valve 33 is attached, and the solenoid valve 33 is opened at the same time as the rotating body 1 stops rotating, so that the cooling water 2 in the water tank is drained. By doing this, it is possible to avoid the situation where the sample is immersed in cooling water for a long time after the test is completed.
Deterioration of the characteristics of the sample after the test can be prevented.

Further, a rotating blade 35 of an agitator configured by attaching a motor 36 to a rotating blade 35 is positioned in the water tank.
It is designed to rotate appropriately to even out the temperature distribution of the cooling water.

The control signals for controlling the hot air blower 4, rotary body rotation motor 9, and injection type cooler 28 are provided by an analog-to-digital converter (A/D C0NVER) as shown in Fig. 3.
The output signal from the rotary potentiometer 15 derived via the slip ring 24 is also controlled by the computer 37 via the analog/digital converter.
7 and is subjected to arithmetic processing. The amount of heat blown by the hot air blower 4, the cooling capacity of the input cooler 28, and the rotation speed of the motor 9 for rotating the rotating body can be freely controlled by operating a control knob on a control panel (not shown) connected to the computer 37. It is configured to be continuously variable, making it possible to realize a wide variety of test environments.

In this embodiment, the hot air blower 4 operates at room temperature to 150 degrees Celsius.
The type of cooler 28 that can blow hot air within the temperature range of -20°C to +3°C is used.
Using something that can be changed within the range of 0°C,
In addition, the motor 9 for rotating the rotating body rotates the rotating body 1 at 0 per minute.
A device that can rotate within a range of 20 times to 20 times is used.

Further, the output signals of each rotary potentiometer 15, 15, . The characteristic data obtained in this way is displayed on the display 3, and a hard copy is made as appropriate by the printer 39 or block 40, and the test data is stored on the floppy disk 41 together with the test environment data. .

The operating mode of this testing machine with such a configuration is as follows. First, each sample S is set in a sample holding mechanism provided around the outer periphery of the rotating body, and then cooling water is supplied to a predetermined height in the water tank, and the injection type cooler 28 is operated to supply the cooling water 2.
lower the temperature.

Next, while rotating the rotating body 1, the hot air blower 4 is activated to blow hot air onto the sample. The sample then begins to expand and contract repeatedly while rotating between the hot air and cooling water.

Details of the expansion and contraction movement of the sample are shown in FIG. FIG. 7(a) shows the state immediately after heating, where the sample is in the parent austenite phase (P phase) and has restored its memorized shape against the pressing force of the compression spring B. In the restored state, the sample is strong and difficult to deform, so the sample S does not shrink even when pressed by the push spring.

When the sample S is immersed in the cooling water 2 due to the rotation of the rotating body 1, the sample S is rapidly cooled and turns into a martensite phase (M phase). Since the sample in the M phase is easily deformed, the pressure of the push spring B is The sample S contracts due to the pressure.

This state is shown in FIG. 7(b). In this way, the length of the sample expands and contracts through repeated heating and cooling.
This expansion/contraction movement is converted into an angle change of the rotating shaft 16 of the rotary potentiometer 15 via the extending rod 18 and the connecting arm 17, and is finally detected as a change in the resistance value of the rotary potentiometer 15.

The resistance value changes detected in this way are processed by the computer 37, and continuous data on the deformation characteristics and restoring characteristics of the sample is collected.

Since the spring constant of the pressing spring B used as the external stress applying means is known, its pressing force can be directly calculated from the moving distance of the slide rod 13. Therefore, by simply detecting the resistance value of the rotary potentiometer 15, it is possible to measure the magnitude of external stress as well as the deformation characteristics and restoring characteristics with respect to the external stress. Then, the expansion and contraction motion of the sample is repeated tens of thousands to hundreds of thousands of times, and the deterioration of characteristics during this repetitive process is measured.

The water level of the cooling water 2 is constantly monitored by the level sensor 30, so when the water level drops, the solenoid valve 32 automatically opens to supply water, and the water level is always maintained constant, ensuring that the sample does not enter the cooling water. Ensures immersion. or,
When the test is completed, this state is automatically detected and the solenoid valve 33 is opened to drain the cooling water. By doing this, the sample will not be left in the cooling water for a long time after the test is completed, and deterioration of the sample can be prevented.

As described above, the shape memory alloy fatigue tester according to the present invention can test a large number of samples at the same time, and can perform expansion and contraction tests while applying external stress to the sample, so it can be used in the actual usage environment. This makes it possible to carry out fatigue tests in a timely manner. In addition, the structure is such that a rotating body surrounding the sample is rotated between hot air and cooling water, and the expansion/contraction cycle of the sample can be easily performed by controlling the rotation speed of the rotating body, so the expansion/contraction cycle can be changed. It is easy to carry out the test, and it is also easy to shorten the expansion/contraction cycle, so the time required for repeated tests can be significantly shortened. Furthermore, when the coil spring is removed, fatigue tests can be performed in a no-load state, making it possible to perform both load and no-load tests with a single device.

In this embodiment, a hot air blower is used as the heating means and cooling water is used as the cooling means, but it is also possible to use hot water as the heating means and a cold air blower as the cooling means.

It is also possible to use a hot air blower as the heating means and a cold air blower as the cooling means. In this way, when a blower is used as both the heating means and the cooling means, the sample does not get wet unlike when cooling water or hot water is used, and the sample can always be kept in a dry state. The influence of this can be eliminated as much as possible, and since there is no need for drying, the rotation speed of the rotating body can also be increased.

〔Effect of the invention〕

The shape memory alloy fatigue tester according to the present invention is provided with an external stress loading means that can fixedly or removably apply an external stress whose magnitude is known to the shape memory alloy formed into a coil shape. The holding mechanism is provided with an expansion/contraction distance measuring means for measuring the expansion/contraction distance of the shape memory alloy to form a unit test unit, and a plurality of unit test units are arranged radially around the outer circumference of the unit test unit. The rotating body is configured to rotate and move between the heating means and the cooling means, which are spaced apart, so that it is possible to test a large number of samples at the same time, and to perform a huge number of repeated tests in a short period of time. be able to. Furthermore, since the apparatus of the present invention can measure the deformation characteristics and restoring characteristics when external stress is applied to the sample, fatigue tests can be conducted under an environment that more closely resembles the environment in which the sample will actually be used. Further, when the external stress applying means is removed, a characteristic test can be performed under no load, and a single device can perform both a load test and a no-load test, making it highly versatile.

In addition, as a sample holding mechanism, a coiled sample was inserted into a slide rod, the distance of expansion and contraction of the sample corresponded to the distance of movement of the slide rod, and an external stress applying means was associated with the slide rod. In some cases, the sample can be easily held and the distance of expansion and contraction of the sample can be measured by the moving distance of the slide rod, making it easy to measure the distance of expansion and contraction of the sample.

When a coil spring with a known spring constant inserted through the slide rod is used as the external stress loading means, the magnitude of the external stress can be measured by the distance traveled by the slide rod, which simplifies the configuration of the test unit. .

Furthermore, when a rotary potentiometer is used as a means for measuring the stretching distance, the stretching motion of the sample is replaced by a rotating motion, and ultimately it can be detected as a resistance value change, so computer processing of the obtained data is easy. It becomes easier.

When a hot air blower is used as the heating means and a water tank filled with cooling water is used as the cooling means, the heating means and the cooling means can be placed apart in the height direction, and there is relatively little heat exchange between the two means. Since the two means can be arranged in close proximity to each other, it is possible to downsize the entire device.

Furthermore, when using a hot air blower that can vary the hot air temperature, air volume, and blowing angle, it is possible to vary the heating conditions over a wide range, and when antifreeze is used as the cooling water, the temperature of the cooling water can be kept below zero degrees Celsius. It is also possible to implement a wide variety of test environments.

In addition, if a drain pipe with a solenoid valve is installed in the water tank, and the opening and closing of the solenoid valve is related to the control mechanism of the rotating body, and the cooling water is drained at the same time as the rotation stops, the sample will remain in the cooling water for a long time after the test is completed. Since the sample is not in an immersed state, it is possible to prevent the characteristics of the sample from deteriorating after the test is completed. Furthermore, after the test is completed, there is no characteristic deterioration even if left for a long time, and since there is no need to remove the sample immediately after the test, it is possible to provide a fully automated testing machine that does not require researchers to be present during the test. .

[Brief explanation of drawings]

FIG. 1 is a front view schematically showing the overall configuration of an embodiment of a shape memory alloy fatigue testing machine according to the present invention, FIG. 2 is a side view of a rotating body in the embodiment, and FIG. An explanatory diagram showing the control system, FIG. 4 is an enlarged explanatory diagram showing the test unit in the same embodiment, FIGS. A) and (B) are enlarged explanatory diagrams showing the movement of the test unit. S: sample, U: unit test unit, B: push spring, B': tension spring, rotating body,
2: Cooling water, 3: Water tank, 4: Hot air blower, 5: Disc,
6: Rotating shaft, 7: Pulley, 8: Transmission belt, 9: Rotating body rotation motor, 10: Base plate, lla, llb: Through hole, 1
2a, 12b: support plate, 13 varnished rod,
14: Locking ring, 15: Rotating potentiometer, 16: Rotating shaft, 17: Connection arm, 18: Extension rod, 19: Regulation plate, 20: Locking plate, 2
1: Differential transformer, 22: Core, 23: Lead wire, 24 Nisslip ring, 25: Built-in motor,
26: Blower, 27: Air outlet, 28: Inlet type cooler, 29: Cooling body, 30 Nilevel sensor, 31: Water supply pipe, 32: Solenoid valve, 33:
Solenoid valve, 34: Drain pipe, 35: Rotating vane, 36
: Motor, 37: Computer, 38: Display, 39 Nibinter, 40 Niblock-14
1: Floppy disk. Patent applicant Osaka Science and Technology Center Figure 6 (a) Figure 4 Figure 5 (a)

Claims (1)

[Claims] 1) Holding a shape memory alloy formed into a coil shape so that it can expand and contract, and applying an external stress whose magnitude is known to the shape memory alloy in the direction of expansion and contraction of the shape memory alloy. A holding mechanism is constructed by fixedly or removably associating an external stress applying means that can be applied, and a shape memory alloy expansion/contraction distance measuring means is attached to the holding mechanism to form a unit test unit. A plurality of rotating bodies are arranged radially around the outer periphery, and the rotating bodies are positioned between a heating means and a cooling means that are spaced apart, and each test unit located on the surface of the rotating body rotates between the heating means and the cooling means. Shape memory alloy fatigue testing machine configured to move. 2) Insert a coiled shape memory alloy into a longitudinally movable slide rod, fix or lock one end of the shape memory alloy to the slide rod, and calculate the expansion and contraction distance of the shape memory alloy by the moving distance of the slide rod. The shape memory alloy fatigue structure according to claim 1, wherein the holding mechanism is constructed by associating the slide rod with an external stress applying means capable of moving the slide rod in the longitudinal direction. testing machine. 3) A coil spring with a known spring constant is inserted into a position adjacent to the shape memory alloy on the slide rod with one end fixed or locked to the slide rod, and the elastic restoring force of the coil spring is applied to an external stress. A shape memory alloy fatigue testing machine according to claim 2, which is used as a means. 4) As an expansion/contraction distance measuring means, a rotary potentiometer is arranged near the base end of the slide rod, and the tip of a connecting arm fixed to the rotating shaft of the rotary potentiometer is connected to the base end of the slide rod through an extending rod. A shape memory alloy fatigue testing machine according to claim 2 or 3, which uses a shape memory alloy fatigue testing machine that is pivotally connected to the body. 5) Shape memory alloy fatigue according to claim 1, 2, 3 or 4, wherein a hot air blower is used as a heating means and a water tank filled with cooling water is used as a cooling means. testing machine. 6) The shape memory alloy fatigue testing machine according to claim 5, wherein the hot air blower is one that can vary the hot air temperature, air volume, and blowing angle. 7) The shape memory alloy fatigue tester according to claim 5, wherein antifreeze is used as the cooling water. 8) A drain pipe for draining cooling water is provided in the water tank, and the drain pipe is provided with an electromagnetic valve that opens the valve and discharges the cooling water when the rotation of the rotating body is completed. The shape memory alloy fatigue tester according to item 5.