JP2023037902A - material testing machine - Google Patents

Abstract

To provide a material testing machine that enables a highly reproducible test.SOLUTION: A material testing machine comprises a testing machine body that has first and second gripping tools for holding both end parts of a specimen, the material testing machine driving the first gripping tool to apply a test load to the specimen. The testing machine body includes a constraining mechanism on an outer peripheral part of the first gripping tool. The constraining mechanism includes a low friction part and makes the low friction part come into contact with the outer peripheral part of the first gripping tool, thus suppressing an axis displacement of the first gripping tool.SELECTED DRAWING: Figure 2

Description

The present invention relates to materials testing machines.

Conventionally, there is known a material testing machine provided with a pair of grips for gripping both ends of a test piece (see Patent Documents 1 and 2, for example).
In this type of testing, one jaw is driven to subject the specimen to a tensile or compressive test load.

JP 2020-94867 A JP 2004-191227 A

However, in conventional configurations, the axis of application of the test load can be offset with respect to the axis of the specimen when driving one of the jaws. If the working axis is misaligned, there is a problem that a test with good reproducibility becomes difficult.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a material testing machine capable of performing tests with good reproducibility.

The present invention is a material testing machine comprising a testing machine body having first and second grips for gripping both ends of a test piece, and driving the first grips to apply a test load to the test piece. The testing machine body includes a restraint mechanism on the outer circumference of the first grip, the restraint mechanism includes a low-friction portion, and the low-friction portion is arranged on the outer circumference of the first grip. The present invention relates to a material testing machine that suppresses axial misalignment of the first gripper by bringing it into contact with a part.

ADVANTAGE OF THE INVENTION According to this invention, the axis deviation of a 1st grip can be suppressed and a test with good reproducibility can be performed.

It is a figure which shows the structure of a material testing machine. It is a figure which shows the principal part of a testing machine main body. Figure 3 is an enlarged view of the first grapple of Figure 2; It is the figure seen in the arrow IV direction of FIG. Fig. 3 is a time-strain diagram;

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows the configuration of a material testing machine 1. As shown in FIG.
A material testing machine 1 includes a testing machine main body 2 . The testing machine main body 2 performs a material test by applying a load to a test object (for example, a test piece) TP.
The test piece TP is produced based on a predetermined standard.
TPs to be tested include various materials, parts or members of industrial products, and the like.

The testing machine main body 2 includes first and second grips 3 and 4 . The first and second grippers 3 and 4 grip both ends of the test piece TP.
The first gripper 3 comprises grip teeth 3a, 3b that open and close. The second gripper 4 comprises gripping teeth 4a, 4b that open and close.

A second grip 4 is fixed to the table 6 via a fixture 5 .
The first gripper 3 is driven by a loading mechanism.
The load mechanism may be a mechanical element such as a ball screw mechanism that converts an electrical signal into physical motion, or a hydraulic load mechanism.

After both ends of the test piece TP are gripped by the first and second grippers 3 and 4, when the first gripper 3 is driven, a test load is applied to the test piece TP.
For example, when the first gripper 3 is driven in a direction to pull the test piece TP, a tensile test load is applied to the test piece TP. When the first gripper 3 is driven in the direction of compressing the test piece TP, a compressive test load is applied to the test piece TP.

The testing machine main body 2 includes various sensors such as a load sensor that detects the test load applied to the test piece TP and a displacement sensor that detects the displacement of the test piece TP.

The material testing machine 1 has a control unit.
The control unit accepts user operations such as setting operations for various parameters such as test conditions for material tests, and execution instructions for material tests.
The control unit includes a display such as a display that displays various information.

The control unit has a function of transmitting and receiving signals to and from the testing machine body 2 .
The signals that are transmitted and received include a test load detection signal, a displacement detection signal of the test piece TP, a signal required for execution of the test program, and the like.

The control unit comprises a computer.
Computers include processors such as CPUs (Central Processing Units) and MPUs (Micro-Processing Units), memory devices such as ROMs (Read Only Memories) and RAMs (Random Access Memories), HDDs (Hard Disk Drives) and SSDs ( (Solid State Drive) and an interface circuit for connecting various peripheral devices.

The processor executes a material test program or the like stored in the memory device or storage device.

In this embodiment, the first gripper 3 is driven by a hydraulic load mechanism 7 .
A material testing machine 1 is a tensile testing machine that measures the elastic modulus of a test piece TP.
The test piece TP is made of resin or metal.

The load mechanism 7 includes a cylinder 8 , a piston 9 slidable inside the cylinder 8 , and a piston rod 10 fixed to the piston 9 .
A first oil passage 11 is connected to the first chamber 8 a of the cylinder 8 .
A hydraulic pump 12 and a pressure accumulation type accumulator 13 filled with nitrogen gas are connected to the first oil passage 11 .

A second oil passage 14 is connected to the second chamber 8 b of the cylinder 8 .
A high-speed servo valve 15 is connected to the second oil passage 14 .
The high speed servo valve 15 is connected to the buffer tank 16 and the buffer tank 16 is connected to the main tank 17 .
A displacement detection mechanism 18 that is resistant to vibrations and shocks is arranged above the cylinder 8 .
The displacement detection mechanism 18 is a capacitive displacement detector using the piston rod 10 as an electrode. It is possible to control the speed of the piston rod 10 by controlling the high-speed servo valve 15 based on the output of the displacement detection mechanism 18 .

A run-up mechanism 20 suitable for high-speed tensile tests is connected to the lower end of the piston rod 10 . A first gripper 3 is connected to the run-up mechanism 20 .
The run-up mechanism 20 includes a bar-shaped inner rod 21 and a cylindrical outer rod 22 .
Outer rod 22 is fixed to the lower end of piston rod 10 .

FIG. 2 is a diagram showing the essential parts of the testing machine main body 2. As shown in FIG. FIG. 3 is an enlarged view of the first gripper 3 of FIG.
The first grip 3 includes a grip main body 35 and a grip 31 screwed to the outer peripheral portion of the grip main body 35 .
A tooth press screw 33 is screwed into the inner peripheral portion of the grip 31 . A hexagonal hole 33a (see FIG. 3) is provided at the upper end of the tooth pressing screw 33. As shown in FIG. A pair of grip teeth 3 a and 3 b are held between the tooth pressing screw 33 and the grip 31 .
The gripper main body 35 is screwed to the lower end of the inner rod 21 by the connector 23 .
Above the grip 31, the displacement sensor (displacement meter) 51 for detecting the displacement of the test piece TP is arranged. The displacement sensor 51 includes a pipe 52 made of a conductor and a coil 53 wound around a thin rod-shaped magnetic body.

The second grip 4 includes, as shown in FIG. 2, a grip main body 45 and a grip 46 screwed onto the outer peripheral portion of the grip main body 45 .
A pair of grip teeth 4 a and 4 b are held between the grip 46 and the grip body 45 .
The gripper main body 45 is fixed to the table 6 by the fixture 5 .
The fixture 5 incorporates the load sensor (load cell) 61 for detecting the test load applied to the test piece TP.

As shown in Figures 1 or 2, the piston rod 10 and the outer rod 22 are hollow. An inner rod 21 is arranged inside the piston rod 10 and the outer rod 22 .
The inner rod 21 is vertically slidable in the hollow of each rod 10 , 22 .
A tapered portion 22a that narrows downward is formed in the lower region of the outer rod 22 . A tapered portion 21 a that widens upward is formed in the upper region of the inner rod 21 .

When the piston rod 10 rises to a predetermined position, the tapered portion 22a of the outer rod 22 and the tapered portion 21a of the inner rod 21 are engaged.
In the ascending process of the piston rod 10, the interval until the tapered portion 22a of the outer rod 22 and the tapered portion 21a of the inner rod 21 engage with each other is defined as an approach interval L. As shown in FIG.

In this embodiment, a restraining mechanism 25 is arranged on the outer peripheral portion of the first gripper 3 .
The restraint mechanism 25 is arranged on the outer circumference of the grip 31 of the first gripper 3 .
The grip 31 has a straight portion 31a in its lower region. The restraint mechanism 25 is arranged on the outer peripheral portion of the straight portion 31 a of the grip 31 . The restraint mechanism 25 contacts the outer surface of the straight portion 31a to restrain the movement of the grip 31 in directions other than the axial direction, thereby suppressing axial displacement of the grip 31. As shown in FIG.
The restraint mechanism 25 holds the grip 31 of the first grip 3 so that the axis of the grip 31 of the first grip 3 does not deviate in the front, rear, left, and right directions (radial direction of the grip 31) when the inner rod 21 slides in the vertical direction.

The restraint mechanism 25 includes a linear bushing 26 and a support member 27 that supports the linear bushing 26 . The linear bushing 26 is an example of a low friction portion.
The support member 27 is configured in a gate shape.
The support member 27 includes a pair of struts 28 and a support block 29 connecting upper parts of the pair of struts 28 .
Therefore, the linear bushing 26 can be supported in a well-balanced manner from both sides of the linear bushing 26 while ensuring workability.

The support block 29 is formed with an opening 29a as shown in FIG. The opening 29a has a stepped portion 29b at the top. The upper end of the linear bushing 26 is fitted into the opening 29a from below until it contacts the stepped portion 29b.

The linear bushing 26 has an inner diameter matching the outer diameter of the straight portion 31 a of the grip 31 . In other words, the outer diameter of the straight portion 31 a is formed to match the inner diameter of the linear bushing 26 . The straight portion 31a has a right cylindrical shape extending in the direction of the axis L0.
The linear bushing 26 includes an outer cylinder 26a, a retainer 26b, a seal 26c, and a plurality of steel balls 26d held by the retainer 26b.
The steel ball 26d contacts the outer surface of the straight portion 31a of the grip 31, and when the grip 31 moves vertically, the steel ball 26d rolls with low friction.

In the present embodiment, since the restraint mechanism 25 includes the linear bushing 26, compared to the case where a member such as the linear bushing 26 is provided on the side of the first gripper 3 for suppressing axial misalignment, the first The structure of the grip 3 is simplified, and the weight of the first grip 3 is reduced. In particular, the grip 31 is a member that holds the grip teeth 3a and 3b, and is constrained by the linear bushing 26 without interposing any other member on the outer peripheral portion of the grip 31. Simplified.
Therefore, when the outer rod 22 moves in the run-up section L of the high-speed tensile test and engages with the inner rod 21, the first gripper 3 moves at high speed together with the piston 9 and the tensile load is applied to the test piece TP. Even when the force acts, the restraining mechanism 25 can restrain the lightened first gripper 3 with high precision, and the axial displacement of the first gripper 3 can be effectively suppressed. Therefore, in elastic modulus measurement, the linear bushing 26 of the restraint mechanism 25 effectively suppresses axial misalignment at the beginning of the test when the tensile load begins to act on the test piece TP.

FIG. 4 is a view of FIG. 2 viewed in the IV direction.
A stopper 30 is screwed to the lower portion of the opening 29a. The stopper 30 includes a first stopper 30a and a second stopper 30b, as shown in FIG.
The opening 30a1 of the first stopper 30a is formed to have a smaller diameter than the outer diameter of the grip 31, and holds the grip 31. As shown in FIG. The opening 30b1 of the second stopper 30b is formed to have a larger diameter than the outer diameter of the grip 31 and holds the linear bushing 26. As shown in FIG.

The linear bushing 26 can be held in the opening 29a of the support block 29 by the first stopper 30a and the second stopper 30b. Also, the first grip 3 can be held in the opening 29a of the support block 29 by the first stopper 30a.
In this embodiment, when pulling out the first grip 3 below the support block 29, it can be pulled out simply by removing the first stopper 30a.
At this time, the linear bushing 26 can be kept in the opening 29a of the support block 29 unless the second stopper 30b is removed.

Long holes (not shown) extending in the vertical direction are formed in the pair of pillars 28, and a support block 29 is fastened by inserting a bolt 41 into the long holes. Therefore, the height (position in the axial direction) of the support block 29 can be easily adjusted within the range of the length of the slot.
In this embodiment, the position of the support block 29 can be adjusted according to the length of the test piece TP.
A pair of posts 28 are fixed to the table 6 to which the second gripper 4 is fixed.
In this embodiment, when the first gripping tool 3 is installed, the pair of supports 28 are fixed to the table 6 . 2 and the gripping tool 4 can be easily aligned. That is, it is possible to easily suppress axial deviation of the first gripper 3 with respect to the second gripper 4 .

Next, the high-speed tensile test will be explained.
A test strip TP is held between the first and second grippers 3,4.
When holding the test piece TP in the first gripper 3, first, referring to FIGS. A tool is inserted into the hexagonal hole 33a of and rotated.

When the tooth press screw 33 is retracted, the pair of grip teeth 3a, 3b are released. In this state, the test piece TP is inserted between the grip teeth 3a and 3b.
When the tooth pressing screw 33 is advanced, the tooth pressing screw 33 and the grip 31 cooperate to hold the test piece TP between the pair of grip teeth 3a and 3b.
Next, the grip body 35 and the grip 31 are connected.

In the second grip 4, when the grip 46 is rotated in the loosening direction, the pair of grip teeth 4a, 4b are released.
In this state, the test piece TP is inserted between the grip teeth 4a and 4b.
When the grip 46 is rotated in the opposite direction, the test piece TP is held between the pair of grip teeth 4a and 4b. The first gripper 3 and the second gripper 4 are arranged on the axis L0 (see FIG. 1), and the test piece TP is held on the axis L0.

As shown in FIG. 1 , the hydraulic pump 12 is driven while both ends of the test piece TP are gripped by the first and second grippers 3 and 4 .
When the hydraulic pump 12 is driven, pressure is accumulated in the accumulator 13 .
In this state, when an open signal is output to the high-speed servo valve 15, the high-speed servo valve 15 opens, and the hydraulic pressure accumulated in the accumulator 13 causes the piston 9 to rise at high speed.
The speed of piston 9 is controlled by high speed servo valve 15 .

The piston 9 rises in the run-up section L until the tapered portion 22a of the outer rod 22 engages the tapered portion 21a of the inner rod 21 until reaching a predetermined high speed.
When the tapered portion 21a and the tapered portion 22a are engaged with each other, the piston 9 rises due to the high initial velocity obtained in the run-up section L, and a high-speed tensile load is applied to the test piece TP.

When a high-speed tensile load is applied, the test piece TP elongates, and the first gripper 3 moves upward according to the elongation of the test piece TP.
At this time, the displacement meter 51 detects the elongation of the test piece TP. Also, when a high-speed tensile load is applied, the load cell 61 detects the test load. Detection signals detected by the displacement meter 51 and the load cell 61 are output to the control unit.
The elastic modulus of the test piece TP is calculated from the elongation of the test piece TP measured by the displacement meter 51 and the test load detected by the load cell 61 .

The run-up mechanism 20 has a gap between the inner rod 21 and the outer rod 22 .
When a high-speed tensile load is applied, due to the gap, the inner rod 21 of the run-up mechanism 20 is subjected to a force that causes an axial shift.

In this embodiment, since the restraint mechanism 25 is arranged on the outer peripheral portion of the grip 31 of the first grip 3, the axis of the grip 31 shifts in the front, back, left, and right directions when the inner rod 21 slides in the vertical direction. Therefore, the first gripper 3 is prevented from being misaligned.

In the present embodiment, the linear bushing 26 holds the outer peripheral portion of the grip 31 to reduce sliding resistance with the grip 31 while keeping the position of the test axis constant. The linear bushing 26 makes it possible to restrain movement in directions other than the axial direction, and the sliding resistance is also reduced, so that the effect on the test results of the high-speed tensile test can be reduced.

FIG. 5 is a time-strain diagram.
A high-speed tensile test was performed by attaching strain gauges 62 and 63 (see FIG. 2) to both surfaces (first surface TP1 and second surface TP2) of the test piece TP. The length of the test piece TP is 30 [mm]. Moreover, the set speed of the high-speed tensile test is 3 [m/s]. In FIG. 5, the horizontal axis indicates time, and the vertical axis indicates strain on each plane TP1 and TP2. In FIG. 5, the solid line indicates the distortion of the first plane TP1, and the dashed line indicates the distortion of the second plane TP2.

A significant difference was observed between the outputs of the strain gauges 62 and 63 when the restraint mechanism 25 was not provided on the outer circumference of the first gripper 3 (not shown). The reason for the difference in output is that the inner rod 21 is slightly off-axis.

When the restraint mechanism 25 is provided on the outer circumference of the first gripper 3, as shown in FIG. It changes from 0 to strain ε1. The outputs of the strain gauges 62 and 63 are almost the same, and no difference is recognized in the outputs.
In the present embodiment, axial deviation of the first gripper 3 can be suppressed.
In addition, the time T0 is the time when a predetermined time has passed since the start of the high-speed tensile test. Time T1 is the time when the outer rod 22 and the inner rod 21 of the run-up mechanism 20 are engaged, and is the time when the tensile load starts to act on the test piece TP. Time T2 is the time at which the test piece TP was broken.

Also, in the material testing machine 1, a high-speed tensile test for measuring the elastic modulus of the test piece TP was performed. In this high-speed tensile test, 10 test pieces TP made according to certain standards were used. In this case, when the restraint mechanism 25 was not provided in the material testing machine 1, the calculated coefficient of variation of the elastic modulus of the test piece TP was 2% to 3%. The coefficient of variation of elastic modulus was improved to about 1%.
In this embodiment, a test with good reproducibility is possible.

[2. Modification]
The above-described embodiment is merely an example of one aspect of the present invention, and can be arbitrarily modified and applied without departing from the scope of the present invention.

In the above-described embodiment, the first gripper 3 is connected to the lower end of the piston rod 10 via the run-up mechanism 20 suitable for high-speed tensile tests, and the restraint mechanism 25 is attached to the outer peripheral portion of the first gripper 3. has been described, the present invention is not limited to this configuration.
For example, the first gripper 3 is directly connected to the lower end of the piston rod 10 without connecting the run-up mechanism 20, and the restraint mechanism 25 is attached to the outer peripheral portion of the directly connected first gripper 3. It is good also as a structure to arrange|position. Also in the testing machine main body 2 that uses a load mechanism using a mechanical element such as a ball screw mechanism instead of the hydraulic load mechanism 7 described above, the restraint mechanism 25 is arranged on the outer peripheral portion of the first gripper 3. It is good also as a structure which carries out.

In the above-described embodiment, the configuration in which the linear bushing 26 of the restraining mechanism 25 is arranged on the outer circumference of the first gripper 3 has been described. can be placed in the department.
In this case, the inner rod 21 to which the first gripper 3 is connected can be restrained from moving in directions other than the axial direction, thereby suppressing axial displacement of the first gripper 3 and enabling tests with good reproducibility. can be

Although the configuration of the linear bushing 26 has been described as an example of the low-friction portion in the above-described embodiment, the low-friction portion is not limited to the linear bushing 26 . For example, the low-friction portions may be linear guides arranged at equal intervals in the circumferential direction of the outer peripheral portions of the first gripper 3 and the inner rod 21 . As the low-friction portion, it is sufficient that the outer peripheral portion of the first gripper 3 or the outer peripheral portion of the inner rod 21 can be restrained by reducing the sliding resistance to the extent that the reproducibility of the test is not affected.

It will be appreciated by those skilled in the art that the exemplary embodiments and variations described above are specific examples of the following aspects.

(Section 1)
A material testing machine according to one aspect includes a testing machine body having first and second grips that grip both ends of a test piece, and drives the first grips to apply a test load to the test piece. The testing machine body includes a restraint mechanism on the outer peripheral portion of the first gripper, the restraint mechanism includes a low friction portion, and the low friction portion is connected to the first may be brought into contact with the outer peripheral portion of the first grip to suppress axial misalignment of the first grip.

According to the material testing machine described in item 1, it is possible to suppress axial deviation of the first gripper, and to enable a test with good reproducibility.

(Section 2)
In the material testing machine according to item 1, the first grip includes a grip main body and a grip screwed to the outer peripheral portion of the grip main body, and the restraint mechanism comprises the grip. It may be arranged on the outer periphery.

According to the material testing machine described in paragraph 2, since the restraint mechanism can directly contact the grip, the first grip is lightened in construction, and compared to the case where the weight is not lightened, the first The grip can be constrained with high accuracy.

In the material testing machine according to item 2, the grip may have a straight portion, and the straight portion may have an outer diameter that matches the inner diameter of the low friction portion.
According to this, while the sliding resistance is reduced by the low-friction portion, axial deviation of the first grip can be suppressed with high accuracy.

(Section 3)
In the material testing machine according to item 1 or 2, the restraint mechanism includes a support member, and the support member fixes the low-friction portion to a table that fixes the second grip. good.

According to the material testing machine described in item 3, the restraint mechanism is integrated with the second gripper, and the position at which the first gripper is restrained can be easily aligned with the position of the second gripper.

(Section 4)
In the material testing machine according to item 3, the support member may be of a portal type.

According to the material testing machine described in item 4, it is possible to support the low-friction portion from both sides in a well-balanced manner while ensuring workability.

(Section 5)
In the material testing machine according to item 3 or 4, the support member includes a support column and a support block that supports the restraint mechanism, and the support block has an adjustable support position relative to the support column. may be configured.

According to the material testing machine described in item 5, the position of the low friction portion can be adjusted according to the axial length of the test piece.

(Section 6)
In the material testing machine according to any one of items 1 to 5, the testing machine body may include a run-up mechanism for high-speed tensile testing.

According to the material testing machine described in item 6, when the run-up mechanism for a high-speed tensile test that tends to cause misalignment is provided, the misalignment of the axis of the first grip can be suitably suppressed, and the reproducibility is good. testing can be made possible.

(Section 7)
In the material testing machine according to any one of items 1 to 6, the low-friction portion may be a linear bush provided with a plurality of steel balls.

According to the material testing machine described in item 7, it is possible to suppress axial deviation of the first gripper with a simple configuration, and to enable a test with good reproducibility.

(Section 8)
A material testing machine according to one aspect includes a testing machine body having first and second grips that grip both ends of a test piece, and drives the first grips to apply a test load to the test piece. A material testing machine that applies a The restraint mechanism may include a low-friction portion, and the low-friction portion may be brought into contact with an outer peripheral portion of the inner rod to suppress axial deviation of the inner rod.

According to the material testing machine described in item 8, since the inner rod to which the first grip is connected can be restrained from moving in directions other than the axial direction, the axial deviation of the inner rod can be suppressed, and the first grip can be prevented from moving. Axial misalignment can also be suppressed, enabling a test with good reproducibility.

REFERENCE SIGNS LIST 1 material testing machine 2 testing machine body 3 first grip 4 second grip 6 table 20 run-up mechanism 21 inner rod 25 restraint mechanism 26 linear bush (low friction portion)
26d steel ball 27 support member 28 strut 29 support block 31 grip 35 grip main body TP test piece

Claims (8)

A material testing machine comprising a testing machine body having first and second grips that grip both ends of a test piece, and driving the first grips to apply a test load to the test piece,
The testing machine main body includes a restraint mechanism on the outer peripheral portion of the first grip,
The restraint mechanism includes a low-friction portion, and contacts the low-friction portion with the outer peripheral portion of the first gripper to suppress axial deviation of the first gripper. The first grip includes a grip main body and a grip screwed to the outer peripheral portion of the grip main body,
A materials testing machine as set forth in claim 1, wherein said restraint mechanism is located on the outer periphery of said grip. The restraint mechanism comprises a support member,
3. A material testing machine according to claim 1 or 2, wherein said support member is fixed to a table fixing said second gripper. 4. The material testing machine according to claim 3, wherein the support member is of a portal type. The support member includes a support post and a support block that supports the restraint mechanism,
5. The material testing machine according to claim 3, wherein said support block is configured such that a support position with respect to said strut is adjustable. The material testing machine according to any one of claims 1 to 5, wherein the testing machine main body includes a run-up mechanism for high-speed tensile testing. The material testing machine according to any one of claims 1 to 6, wherein the low friction portion is a linear bushing having a plurality of steel balls. A material testing machine comprising a testing machine body having first and second grips that grip both ends of a test piece, and driving the first grips to apply a test load to the test piece,
The testing machine body includes a run-up mechanism for high-speed tensile testing having an inner rod to which the first grip is connected,
A restraint mechanism is provided on the outer periphery of the inner rod,
The restraint mechanism includes a low-friction portion, and contacts the low-friction portion with the outer peripheral portion of the inner rod to suppress axial deviation of the inner rod.

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