JP7557139B2 - Rotating bending fatigue testing equipment that enables high cycle fatigue testing in a high pressure hydrogen environment - Google Patents

Description

The present invention relates to a rotating bending fatigue testing device that enables high cycle fatigue testing of metal materials such as steel in a high pressure hydrogen gas environment.

In recent years, in order to prevent global warming, there has been active development of electric vehicles that do not emit carbon dioxide while driving, vehicles that use fuel cells, and hybrid and plug-in hybrid vehicles that can significantly reduce carbon dioxide emissions, in place of vehicles that use gasoline-fueled reciprocating engines. Of these, fuel cell vehicles are being actively developed as vehicles that can prevent future global warming, as they do not emit any carbon dioxide while driving.

However, because fuel cell vehicles use hydrogen as fuel and tanks filled with hydrogen under high pressure, it is essential to develop steel materials whose mechanical properties do not deteriorate significantly even in a hydrogen environment for use in parts that come into contact with high-pressure hydrogen gas, such as pipe fittings and valves. In particular, to ensure long-term use, there is a strong demand for the development of fatigue testing equipment capable of high-cycle fatigue testing. In other words, because hydrogen has long been known as an element that significantly affects the deterioration of the mechanical properties of steel, it is essential to develop steel materials that are less affected by hydrogen and that have excellent properties even in a high-pressure hydrogen environment.

A conventionally known means for testing and measuring the mechanical properties of metallic materials in a high-pressure hydrogen environment is a test device in which a moving rod connected to a hydraulic servo fatigue testing machine is inserted into a high-pressure test vessel filled with high-pressure hydrogen gas. In this device, the load generated by the hydraulic servo is transmitted to the test piece in the test vessel via the moving rod, and the device is capable of conducting tensile tests and axial load type fatigue tests of metallic materials in the test vessel, and is commercially available (see, for example, Non-Patent Documents 1 and 2).

Saburo Matsuoka, Hisao Matsunaga, Junichiro Yamabe, Shigeru Hamada, Takashi Iijima, "Proposal of various strength characteristics and design guidelines of low alloy steels SCM435 and SNCM439 in 115 MPa hydrogen gas", Transactions of the Japan Society of Mechanical Engineers, Vol. 83, No. 854 (2017). Kazumasa Kubota, "Introduction of material testing equipment in high pressure hydrogen environment", Aichi Steel Technical Report Vol. 36, No. 1 (2020).

In the above test equipment, a moving rod is inserted into a test vessel filled with high-pressure hydrogen gas. The moving rod moves relative to the test vessel as a load is applied and removed from the test specimen. To balance the displacement of the moving rod and the containment of high-pressure hydrogen gas inside the test vessel, a lip seal made of a material such as fluororesin is provided at the position where the rod penetrates the test vessel. The seal completely seals the gap between the moving rod and the test vessel, allowing the moving rod to move without leaking hydrogen gas, and transmitting the test stress to the test specimen inside the test vessel.

The test equipment described in the above literature can be used to perform slow strain rate tensile (SSRT) tests, low cycle fatigue tests, fatigue crack growth tests, etc., but the number of times that a load is applied to the test piece, i.e. the number of times that the moving rod is moved, is relatively small. For such tests that require a relatively small number of tests, the tests can be performed without any problems by periodically replacing the lip seal during maintenance of the testing equipment.

However, the above-mentioned conventional techniques have the following problems.
High-pressure hydrogen parts for fuel cell vehicles and the like need to be designed on the assumption that they will be subjected to repeated stresses at high cycles, and it is of course essential to understand the fatigue characteristics in the high-cycle range in a high-pressure hydrogen environment. However, while the above-mentioned conventional testing equipment can perform tests with a relatively small number of repetitions without any problems, when attempting to perform high-cycle fatigue tests, the current seal life is not sufficient to withstand such high cycles, and it becomes difficult to maintain the hydrogen pressure inside the container, making the test difficult.

In addition to the number of repetitions, the test frequency also has to be set at around 1 Hz at most, as the durability of the sealing material means that the test frequency cannot be increased. At this test frequency, a fatigue test with 10 million repetitions, which is generally considered to be the fatigue limit, would take a significant amount of time, so there was a strong demand for the development of a test device capable of high-cycle fatigue testing at a high test frequency.

The present invention was made to solve the above problems, and aims to propose a new fatigue testing device that can perform fatigue testing of metal materials in a high-pressure hydrogen environment at high speeds for fatigue characteristics not only in the low-cycle region where the number of stress repetitions is low, but also in the high-cycle region where the number of repetitions is 10 million or more.

In order to solve the above problems, the present invention has been devised to provide a rotating bending fatigue testing apparatus that enables high-cycle fatigue testing in a high-pressure hydrogen environment. A rod-shaped test specimen is placed in a test vessel filled with high-pressure hydrogen and is rotatably fixed. The test specimen is configured to be rotated while being subjected to a constant bending moment by applying a load in the vertical downward direction of the test specimen. The rotating force to the test specimen is transmitted by a magnet drive using a magnet drive system, and the magnet drive and the test specimen are connected by an extendable rotating shaft with universal joints at both ends.

Conventional fatigue testing equipment requires a rod to be inserted into a test vessel filled with high-pressure hydrogen, and the rod moves in and out of the vessel. This requires the installation of a dynamic seal at the interface between the rod and the test vessel to prevent leakage of high-pressure hydrogen, but the short lifespan of this seal makes it impossible to perform high-cycle fatigue testing. In addition, the movement of the rod in and out places a limit on how high the test frequency can be increased, which is also an issue when it comes to efficiently performing high-cycle fatigue testing. Therefore, in this invention, the method of applying the external force has been changed to a rotational test method (applied from a conventional rotating bending fatigue test device) that makes it easier to increase the test speed, and instead of directly penetrating the rotating shaft itself that applies the rotational motion into the test vessel wall, a test piece integrated with the rotating shaft is placed inside the test vessel, the end of the rotating shaft is contained in a holder (hereinafter referred to as the inner holder), and the inner holder is connected so that it is completely fixed to the test vessel and becomes part of the test vessel wall, a magnet is fixed to the end of the rotating shaft contained in the inner holder, and a magnet placed in the outer holder on the outside is rotated to rotate the test piece without contact using magnetic force. A structure has been devised to rotate the test piece attached to the rotating shaft by using a magnet drive method.

As a result, the inner holder is completely fixed to the test vessel, so there is no need to install dynamic seals as in conventional testing equipment, there is no need to worry about the seal's lifespan, there is no need to worry about high-pressure hydrogen gas leaks, and the test is performed using a rotational motion that makes it easy to increase the test frequency, so we have succeeded in efficiently conducting high-cycle fatigue tests in a high-pressure hydrogen environment in a short amount of time.

1 is a side view for explaining an embodiment of a rotating bending fatigue testing device according to the present invention. FIG. FIG. 2 is an enlarged view of a magnet drive portion of FIG. 1 .

The following describes an embodiment of the rotating bending fatigue testing device of the present invention, which enables high-cycle fatigue testing in a high-pressure hydrogen environment.

(Test vessel)
The test vessel is a vessel for placing a test piece for a rotating bending fatigue test in a high-pressure hydrogen gas atmosphere during the rotating bending fatigue test.
In a low-pressure hydrogen gas atmosphere, the seal problem in an axial load type fatigue testing machine is minor compared to a high-pressure hydrogen gas atmosphere. Conventional seals to prevent leakage of high-pressure hydrogen gas become a significant problem when the hydrogen gas pressure is 10 MPa or more. On the other hand, fuel cell vehicles use high-pressure hydrogen gas of 70 MPa, so it is necessary to enable fatigue testing when the high-pressure hydrogen gas pressure is 70 MPa or more. However, as described above, the present invention uses a magnet drive system to rotate the test piece and does not require leakage prevention by dynamic seals, so there is no need to worry about leakage even at pressures of 70 MPa or more, and it is possible to perform high-cycle fatigue testing with a number of repetitions of 10 million or more.

The material used for the test vessel is preferably high-strength SUH660, which is less susceptible to embrittlement caused by hydrogen gas, and in order to keep the wall thickness necessary for safely filling the vessel with high-pressure hydrogen as thin as possible and to reduce the vessel's mass.

(Rotational power source)
In the rotating bending fatigue test apparatus of the present invention, the motor that starts the magnet drive and rotates the test piece is a motor placed outside the test vessel. The motor used is preferably an explosion-proof motor from the viewpoint of preventing accidents, and is preferably inverter-controllable to control the fatigue test frequency. It is preferable to optimize the number of poles of the motor and provide a reduction gear as necessary so that the rotation speed of the magnet drive can be variably controlled. This makes it possible to make the motor variably controllable, for example, to 600 to 2000 rpm.

(Magnetic drive)
This is a part for transmitting the torque of the rotary power source to the inside of the high pressure test vessel without using dynamic seals, and it transmits the torque to the rotating shaft that is installed in the inner holder and directly connected to the test piece by using magnets. This part was previously used as a stirrer.

Since high-pressure hydrogen gas is used in the present invention, it is desirable to use SUH660 as the material for the inner circumference holder of the magnet drive, which comes into direct contact with the high-pressure gas, just like the test vessel.

In addition, to ensure the test frequency, it is preferable to use a transmission method between the motor (the rotary power source) and the magnet drive that does not change the rotation speed due to slippage of a timing belt, etc.

However, if the rotation speed of the magnet drive is made too slow, it will be close to the resonant frequency of the rotating bending fatigue test mechanism, which is inconvenient as it will cause unintended stress in the test piece. Also, if it is made too fast, the heat generated by the eddy currents generated by the rotation of the magnetic field will increase, making it difficult to configure the test device, so the rotation speed of the magnet drive is preferably in the range of 600 to 2000 rpm.

(Coupling mechanism)
This part is connected to the same rotating shaft housed within the inner holder of the magnet drive that protrudes into the high-pressure test vessel, and is used to transmit rotational force to the test piece.

The coupling mechanism can be realized, for example, by making the tip of the rotating shaft inside the inner circumference holder of the magnet drive into a spline shape and making the coupling side into a shape that receives the spline groove.

(Telescopic shaft and universal joint)
This is a part that transmits rotational force to the test specimen while absorbing changes in angle and length between the rotating shaft of the magnet drive received by the coupling and the rotating shaft of the test specimen. By arranging two universal joints in a row on both ends of the extendable rotating shaft, it is possible to cancel out irregularities in angular velocity.
That is, due to the effect of the bending moment load from the weight, the distance between the tip of the rotating shaft of the magnet drive and the test piece changes, and the mounting angle of the telescopic shaft connecting them also changes. At this time, the change in distance can be absorbed by the telescopic shaft, but the change in angle brings about the effect that the rotation speed of the motor is not directly transmitted to the test piece (irregularity of angular velocity).

In this invention, two universal joints are placed on both ends of the telescopic shaft, and the two universal joints are connected so that the effects on the angular velocity generated by each of them cancel each other out, so that the rotational speed of the motor is almost the same as the rotational speed of the test piece. In this case, it is more preferable to select two universal joints with the same specifications, as this will more reliably cancel out the effects of the angular velocity.

In the present invention, a load is applied vertically downwards using a weight to apply a bending moment to the test piece, but when determining the fatigue limit at 10 million repetitions, the size of the weight must be changed and the load must be tested under multiple conditions. It is assumed that the angle of the telescopic shaft changes when a bending moment is applied to the test piece, but by using two universal joints at both ends of the telescopic shaft as described above, it is possible to perform testing at a stable test speed regardless of the angle of the telescopic shaft. Note that parts with two identical universal joints connected to both ends of the telescopic shaft are commercially available, so they can be used.

In order to operate the universal joint so as to compensate for the irregularity in angular velocity as much as possible, it is desirable to position the driven side rotating shaft of the magnet drive so that there is no horizontal deviation from the position of the test specimen drive side rotating shaft, and to position it higher than the test specimen drive side rotating shaft in the vertical direction, so that even if the test specimen drive side rotating shaft is displaced by the load of the weight, the position of the universal joint connected to the test specimen drive side rotating shaft will not be higher than the position of the other universal joint on the driven side rotating shaft of the magnet drive. Although it is difficult to completely eliminate the irregularity in angular velocity, this makes it possible to reduce problems such as vibrations associated with rotation to a level that does not cause problems in experiments.

(torque limiter)
It is a mechanism that is placed on the drive side of the test specimen (between the tip of the driven side rotating shaft of the magnet drive and the drive side rotating shaft of the test specimen) to prevent the rotational force from being transmitted to the test specimen side in order to protect the high pressure test vessel when excessive torque is generated. If an excessive torque is applied for some reason, such as if some kind of failure occurs in the rotating bending fatigue test unit, it may lead to an unexpected serious failure, so it is preferable to have a structure that does not apply a torque greater than a certain level to the test specimen side.

In addition to using a general mechanical torque limiter, a torque limiter function can be achieved with a simple structure in which a set screw is screwed into the side of the drive side rotating shaft of the test specimen, and the side of the rotating shaft that is tightened by the set screw undergoes plastic deformation to release excessive torque, as the torque limiter function can be achieved.

(weight)
In the test device of the present invention, a weight is used to apply a bending moment by four-point bending to a rotor consisting of a test piece and a test piece rotation shaft, and to generate a tensile and compressive test stress in the test piece. The use of this weight itself is exactly the same as in known rotating bending fatigue test devices, and is not particularly new.

However, in the present invention, as described above, the test must be performed with not only the test specimen but also the weight housed in the test vessel filled with high-pressure hydrogen. Therefore, if the test vessel is to be made smaller, there is not enough space, and it is necessary to make it easy to insert and remove the weight from the test vessel before and after the test. Therefore, by, for example, providing a plastic wheel on the bottom of the weight, it can be made easier to insert and remove the weight from the test vessel. During the test, the weight is naturally suspended from the shaft connected to the test specimen, but if the test specimen breaks, it will fall. In this case, providing a plastic wheel can prevent the entire weight from directly hitting the test vessel and damaging the vessel.

(Positioning pins and wheels for moving the fixed base)
By providing two or more positioning pins at the inner wall end of the test vessel on the side having the magnet drive, and by drilling positioning holes on the inner wall end side of the fixed base that receives the fatigue test mechanism when inserting the test piece rotating bending fatigue test mechanism into the test vessel, the rotating bending fatigue test mechanism can be guided to a predetermined position with respect to the test vessel. This facilitates positioning for joining the driven side rotating shaft of the magnet drive arranged in the test vessel and the coupling of the rotating bending fatigue test mechanism when inserting the fatigue test mechanism, and also plays a role in canceling the counter torque against the rotation of the coupling.

When inserting this fatigue testing mechanism, by providing wheels not only on the weight mentioned above but also on the bottom of the fixed base that supports the fatigue testing mechanism, it is possible to easily perform operations such as removing and attaching the test piece and replacing the weight, in addition to disconnecting the coupling.

(Specimen drive side rotation axis and specimen driven side rotation axis)
It is a part that extends the length of the test specimen, thereby shortening the length of the test specimen. In some ways, it can also be said to be a part that makes it easier to machine the test specimen when manufacturing it.

The inventors initially considered lengthening the test piece and integrating it with the rotating shaft to eliminate the joint and reduce the size of the rotating bending fatigue test mechanism. However, they changed their mind because such a long test piece could not be machined with precision and the cost of machining the test piece would be excessively expensive. Instead, they decided to shorten the test piece and provide a rotating shaft to extend the length of the test piece, similar to a typical rotating bending fatigue tester.

High workability is required in terms of concentricity, coaxiality, etc., so that the test piece does not rotate and vibrate abnormally during testing. In a rotating bending fatigue test, the test piece and the rotating shaft rotate at high speed, so JIS Z2274 (1978) "Rotating bending fatigue test method for metallic materials" requires that the runout of the center of the parallel part of the test piece be within 0.05 mm when the test piece is attached. For this reason, a collet chuck is generally used to attach the test piece to a rotating bending fatigue tester, and it is preferable to use a collet chuck in the present invention as well.

(Test Piece)
In this device, the test piece length can be adjusted by the above-mentioned test piece drive side rotating shaft and test piece driven side rotating shaft, so it is possible to use a JIS No. 1 test piece, which is a test shape described in JIS Z2274 (1978) "Rotating bending fatigue test method for metallic materials", which is the JIS standard for conventional rotating bending fatigue test devices, and which has been widely used in the past, and which has a gripping part φ12 mm, parallel part φ8 mm, and parallel part length of about 20 mm, which is common in tests in air. This makes it easy to compare and consider the data of rotating bending fatigue tests that have been accumulated in the past, since it is possible to test with the same test piece shape.

(Wedge parts to prevent resonance at start-up)
The rotating shaft of the test piece of the rotating bending fatigue test device of the present invention is restrained for positioning the rotating shaft at the test piece drive side rotating shaft 14 (see FIG. 1 described later). Although the horizontal displacement is restrained, the vertical direction is not restrained because the test piece is subjected to a bending moment in the vertical direction and deformed. Therefore, when the device is started and the test piece starts to rotate, excessive vibrations may occur in the vertical direction when passing through the resonance frequency. Therefore, it is preferable to fill the gap on the ground side by inserting a wedge-shaped part, such as a counter, into the gap on the ground side of the part that displaces to the top side when the test piece breaks at the end position of the test piece driven side rotating shaft 16 (see FIG. 1 described later), thereby restricting the displacement of the rotating shaft to the ground side at resonance and making the amplitudes of the vibrations on the top side and the bottom side when resonance is about to occur mismatch, thereby suppressing the occurrence of resonant vibration at startup.

Below, we will explain examples to clarify the effects obtained by the fatigue testing device of the present invention, which performs rotating bending fatigue testing in a high-pressure hydrogen gas environment.

FIG. 1 is a side view of a rotating bending fatigue testing device according to an embodiment of the present invention, and FIG.
Reference numeral 1 denotes a motor, which rotates the outer peripheral holder 41 of the magnet drive via a timing belt 2, rotates the magnet drive driven side rotating shaft 45 arranged in the inner peripheral holder 47 by magnetic force, and rotates the test piece 15 connected to the test piece drive side rotating shaft 14. The magnet drive 4, which rotates the magnet drive driven side rotating shaft 45 arranged in the inner peripheral holder 47 by magnetic force, is a general part that has been commercially available as an agitator for a long time, and is not particularly new as a single unit. In this embodiment, an agitator manufactured by Nitto High Pressure Co., Ltd. is used. The detailed structure of the magnet drive will be described later. In this invention, since high-pressure hydrogen is handled, and safety is emphasized, the motor 1 is a motor with excellent explosion-proof performance.

8 is a test vessel, which is connected to a hydrogen gas cylinder and a booster (not shown) so that hydrogen gas pressurized by the booster can be supplied from the hydrogen gas cylinder and filled into the vessel, and the vessel is structured to be able to hold high-pressure hydrogen for a long period of time. In particular, since the present invention requires that fatigue testing be possible in a high-pressure hydrogen environment of 70 MPa or more, the vessel is designed to be able to be filled with high-pressure hydrogen up to 99 MPa using the booster. Furthermore, since hydrogen causes the embrittlement of steel, the test vessel 8 of the present invention is manufactured using SUH660, a type of steel that is less susceptible to embrittlement problems and has excellent strength.

Furthermore, on the right side of the drawing of the test vessel 8, an openable test vessel opening/closing opening 10 is provided, which allows the test specimen 15, weight 7, etc. to be easily pulled out together with the fixed base 12 onto a stand (not shown) or placed into the test vessel. In particular, to complete an S-N diagram through fatigue testing, it is necessary to repeat tests at various stresses, and therefore it is necessary to change the weight 7 to one with a different mass and replace the test specimen 15 with a new one each time a test is completed, and this has been devised to make this work easy. Specifically, the test specimen 15, etc. are placed on the fixed base 12, and fixed base moving wheels 13 are attached to the bottom of the fixed base 12, so that they can be easily pulled out onto the stand (not shown) on the right side or placed into it. During testing, the weight 7 is also suspended to apply a bending moment to the test specimen 15. When the test specimen reaches the end of its life and breaks, it will fall to the ground. To prevent this, plastic wheels 11 are attached to the test container to prevent damage to the container when it falls, and to make it easy to move it on and off the stand.

When the test specimen 15, weight 7, etc. are pulled out to replace the test specimen and weight, and then returned to the test vessel 8, they must be returned to the exact same position as before they were pulled out in order to align with the tip position (driven tip 46) of the driven side rotating shaft 45 of the magnet drive. Therefore, two positioning pins 3 are attached to the opposite side of the test vessel opening/closing port 10 of the test vessel 8, and two positioning holes (not shown) are drilled in the side of the fixed base 12 on the side of the positioning pins to match the positions. When the fixed base 12 is moved into the test vessel 8 together with the test specimen 15 and weight 7, the positioning pins 3 can be easily inserted into these holes.

In other words, the position of the coupling part 5 relative to the positioning hole is fixed by a bearing fixed on the fixed base 12 (not shown), so by returning the fixed base 12 so that it is inserted into the positioning pin 3, the coupling part 5 can be easily aligned with the tip 46 of the driven side rotating shaft of the magnet drive.

The test piece 15 can be fixed by a collet chuck, and the test piece drive side rotating shaft 14 and the test piece driven side rotating shaft 16 are connected to both sides of the chuck. A counter 9 is attached to the tip of the test piece driven side rotating shaft 16 on the test container opening/closing port 10 side, which can display the cumulative number of rotations according to the number of rotations of the rotating shaft, and a wedge part (not shown) for preventing resonance is inserted below it, as described above, to prevent resonance at start-up. A universal joint 61 is attached to the tip of the test piece drive side rotating shaft 14, which is connected to the spline-molded driven side rotating shaft tip 46 of the magnet drive via the telescopic shaft 6, the other universal joint 61, and the coupling part 5, so that the test piece 15 can be rotated by the rotation of the motor 1 via the magnet drive 4.

Here, the position of the driven side rotating shaft 45 of the magnet drive that passes through the test vessel 8 is completely fixed, whereas the test piece 15 is loaded with a bending moment by the weight 7 during the test, and due to factors such as the mass of the weight 7, not only does it no longer position itself on the extension of the axis of the driven side rotating shaft 45 of the magnet drive, but the amount of deviation also changes. Therefore, since it is necessary to absorb this deviation while suppressing the irregularity of the angular velocity, two universal joints 61 of the same specifications that have an extendable shaft 6 and are arranged to cancel the irregularity of the angular velocity are provided at both ends of the extendable shaft 6.

Next, the magnet drive 4 will be described with reference to FIG.
The magnet drive 4 has two holders, an outer holder 41 which is rotated by a timing belt 2 connected to the motor 1, and an inner holder 47 which is rotatably connected to the outer holder 41 via an outer bearing 42. An outer magnet 49 is fixed inside the outer holder 41, and a driven-side rotating shaft 45 of the magnet drive is fixed inside the inner holder 47 via an inner bearing 48. The inner magnet 44 fixed to the driven-side rotating shaft of the magnet drive and the outer magnet 49 are fixed so that their magnetic poles face each other to generate a magnetic force that attracts them to each other, and the rotation of the outer holder 41 imparts a rotational force to the driven-side rotating shaft 45 of the magnet drive. Therefore, when the motor 1 rotates, the outer holder 41 rotates due to the rotation of the timing belt 2, and the driven-side rotating shaft 45 of the magnet drive can be rotated. A splined tip portion (tip portion 46 of the driven side rotating shaft of the magnet drive) is provided at the tip of the driven side rotating shaft 45 of the magnet drive rotated in this manner, so that a rotational force can be transmitted to the test piece 15 via the coupling portion 5, universal joint 6, and test piece drive side rotating shaft 14.

The joint between the universal joint 61 on the right side of Figure 1 and the test specimen drive side rotating shaft 14 has an additional structure in which a set screw (not shown) is screwed into the side to join them. If excessive torque is applied, the tip of the set screw will plastically deform, preventing excessive load from being placed on the testing machine.

The inner holder 47 must be non-magnetic, and since its interior is filled with high-pressure hydrogen just like the test vessel 8, SUH660 is used, which is non-magnetic just like the test vessel 8, has excellent hydrogen embrittlement properties, and is strong.

Next, the effects of this embodiment will be described.
In the rotating bending fatigue testing apparatus of the present invention, the inner circumferential holder 47 is fixed so as to be part of the wall of the test vessel 8. However, unlike the moving rod of the conventional apparatus, it is fixed in a completely fixed state relative to the test vessel 8, and therefore it is not necessary to prevent leakage of high-pressure gas by dynamic sealing as in the conventional apparatus. Therefore, high-cycle fatigue tests of 10 million or more cycles in a high-pressure hydrogen environment can be performed without any problem. This makes it possible to efficiently determine the maximum stress (endurance limit) at which a specimen does not break after 10 million or more cycles in a high-pressure hydrogen environment, which can greatly contribute to the development of high-strength steels for high-pressure hydrogen.

1: Motor, 2: Timing belt, 3: Positioning pin, 4: Magnet drive, 5: Coupling, 6: Telescopic shaft, 7: Weight, 8 Test container, 9: Counter, 10: Test container opening and closing, 11: Wheel, 12: Fixed base, 13: Wheel for moving the fixed base, 14: Rotating shaft on the drive side of the test specimen, 15: Test specimen, 16: Rotating shaft on the driven side of the test specimen, 41: Outer holder, 42: Outer bearing, 44: Inner magnet, 45: Driven rotating shaft of the magnet drive, 46: Tip of the driven rotating shaft of the magnet drive, 47: Inner holder, 48: Inner bearing, 49: Outer magnet, 61: Universal joint

Claims (2)

A fatigue testing apparatus capable of performing a test to evaluate fatigue characteristics in a high-pressure hydrogen environment in a test vessel filled with high-pressure hydrogen,
a rod-shaped test piece disposed in the container is rotatably fixed, and a load is applied in a vertical downward direction of the test piece, thereby allowing the test piece to rotate while applying a bending moment to the test piece;
A rotating bending fatigue testing device that enables high-cycle fatigue testing in a high-pressure hydrogen environment, characterized in that the rotational force to the test piece is transmitted by a magnet drive using a magnet drive system, and the magnet drive and the test piece are connected by an expandable rotating shaft with universal joints at both ends. The rotating bending fatigue testing device described in claim 1, which enables high cycle fatigue testing in a high pressure hydrogen environment, is characterized in that it has a torque limiter mechanism on the drive side of the test piece that can cut off the torque load when a large torque load is applied.

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