JP7809977B2 - Material Testing Machine - Google Patents

Description

The present invention relates to a materials testing machine.

Conventionally, a material testing machine has been proposed that includes an elongation measuring device that measures the elongation between a pair of benchmark lines provided on a test piece by fixing a pair of arms to the pair of benchmark lines (Patent Document 1).
When a tensile test is performed, this elongation measuring device drives a pair of arms with a pair of pulse motors to position the pair of arms at any position between a pair of grippers.

Japanese Patent Application Laid-Open No. 2004-333382

However, the conventional extension measuring device described above has a problem in that the configuration of the drive system becomes complicated because the pair of arms is driven by a pair of pulse motors.
The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a materials testing machine that can appropriately change the positional relationship between a pair of grippers and a pair of arms with a simple configuration.

A first aspect of the present invention is a materials testing machine comprising: a loading mechanism that applies a test force to a test piece held at both ends by a pair of gripping tools; an elongation measuring device that fixes a pair of arms to a pair of benchmark lines on the test piece and measures the elongation between the pair of benchmark lines ; a test piece storage device that stores the test pieces; a transport device that removes the test pieces from the test piece storage device and hands them over to the loading mechanism; and a control device that acquires length information of the test pieces and drives an actuator based on the length information, in which the elongation measuring device comprises a positioning mechanism that pushes the pair of arms in conjunction with the movement of the loading mechanism and positions the pair of arms between the pair of gripping tools, the positioning mechanism comprises the actuator that adjusts the amount of pushing of the pair of arms in accordance with the length of the test piece , and the control device drives the actuator so that the test piece is pushed by a predetermined amount in accordance with the length of the test piece when it is handed over from the transport device to the loading mechanism .

According to the first aspect of the present invention, the positioning mechanism is equipped with an actuator that adjusts the amount of pushing of the pair of arms depending on the length of the test piece, making it possible to change the positional relationship between the pair of grippers and the pair of arms with a simple configuration.

FIG. 1 is a diagram of a material testing machine according to an embodiment. FIG. 2 is a side view showing the main parts of the elongation measuring device and the testing device. FIG. 2 is a perspective view showing the main parts of an elongation measuring device and a testing device. FIG. 1 is an explanatory diagram for testing a test piece. FIG. 5 is an explanatory diagram for testing a test piece shorter in length than the test piece described in FIGS. 2 and 4.

Embodiments of the present invention will be described below with reference to the drawings.

1. Embodiment
FIG. 1 is a diagram of a material testing machine 1 according to an embodiment.
The material testing machine 1, which is an example of the "material testing machine" of this embodiment, applies a test load as a test force to the test piece T, thereby measuring the tensile force and elongation of the test piece T.

The materials testing machine 1 includes a test specimen supply device 10, a testing device 30, a test specimen collection device 50, an elongation measurement device 70, and a control device 200.

The test piece supply device 10 includes a test piece storage device 12 that stores test pieces T on pallets 11, a measuring device 14 that measures the dimensions of the test pieces T, a transport table 13 to which the pallets 11 are transported from the test piece storage device 12, and a transport device 20 that transports the test pieces T from the pallets 11 supplied to the transport table 13 to the testing device 30.

The test specimen storage device 12 stores multiple pallets 11 containing test specimens T, for example, stacked one on top of the other.

The testing device 30 tests the test piece T by applying a test load to the test piece T supplied from the test piece supplying device 10 .
In this embodiment, the front-to-back direction FD (see FIGS. 2 and 3), the width direction SD, and the up-down direction TD are used with respect to the testing apparatus 30 shown in Fig. 1. The width direction SD is also referred to as the left-to-right direction.

The testing device 30 has a base 31. A table 32 is provided on top of the base 31. A pair of support columns 33 are provided on the table 32, extending vertically upward. A pair of support columns 33 are provided in the width direction SD of the testing device 30. A cross yoke 34 extending between the pair of support columns 33 is suspended above the support columns 33. A threaded rod (not shown) is provided inside the support column 33. The threaded rod is composed of a ball screw. Both ends of a crosshead 35 are connected to the threaded rod via nuts (not shown). The crosshead 35 rises and falls relative to the table 32 as the threaded rod rotates. The threaded rod is rotated by a motor (not shown).

A load cell 36 is installed on the crosshead 35. A joint 37 is attached to the load cell 36. The joint 37 extends downward. An upper gripping tool 38 is connected to the lower end of the joint 37. A cylinder device (not shown) is attached to the upper gripping tool 38. When the cylinder device (not shown) is activated, the upper gripping tool 38 opens and closes in the width direction SD. The upper gripping tool 38 grips the upper end of the upright test specimen T. The test specimen T is positioned on the gripping center L of the upper gripping tool 38.

A lower gripping fixture 39 is positioned below the upper gripping fixture 38. The lower gripping fixture 39 is fixed to the upper surface of the table 32 via a joint 40. The lower gripping fixture 39 is configured similarly to the upper gripping fixture 38, except that it is configured vertically symmetrical to the upper gripping fixture 38. The lower gripping fixture 39 grips the lower end of the upright test specimen T. The test specimen T is positioned on the gripping center L of the lower gripping fixture 39.

With the test specimen T gripped by the upper gripping fixture 38 and the lower gripping fixture 39, the upper gripping fixture 38 moves up and down together with the crosshead 35. As a result, a test force is applied to the test specimen T gripped between the upper gripping fixture 38 and the lower gripping fixture 39. At this time, the load cell 36 measures the test force applied by the upper gripping fixture 38 via the joint 37. The measurement signal from the load cell 36 is input to the control device 200.

A test strip recovery device 50 is disposed to the right of the upper gripping tool 38 and the lower gripping tool 39. The test strip recovery device 50 recovers the test strip T from the testing device 30.
The test strip collection device 50 includes an upper collection device 51 provided in correspondence with the upper gripping tool 38, and a lower collection device 61 provided in correspondence with the lower gripping tool 39. The upper collection device 51 is fixed to the crosshead 35 and can be raised and lowered together with the crosshead 35. The lower collection device 61 is fixed to the upper surface of the table 32.

FIG. 2 is a side view showing the main parts of the elongation measuring device 70 and the testing device 30.
The material testing machine 1 includes an elongation measuring device 70 that measures the elongation of the test piece T when a test force is applied by the testing device 30. The elongation measuring device 70 of this embodiment is a contact-type extensometer that measures the elongation by contacting the test piece T with arms 80, 90.
The elongation measuring device 70 is disposed behind the crosshead 35 (the rear side of the paper in FIG. 1 ). The elongation measuring device 70 is fixed, for example, to the upper surface of the table 32 of the testing apparatus 30. The elongation measuring device 70 includes an exterior frame 71 extending in the up-down direction TD. A guide rod 72 is supported in front of the exterior frame 71. The guide rod 72 extends along the support columns 33 (see FIG. 1 ) of the testing apparatus 30. An upper arm 80 and a lower arm 90 are slidably supported on the guide rod 72. The upper arm 80 and the lower arm 90 are disposed between the upper grip 38 and the lower grip 39 of the testing apparatus 30.

A pair of pulleys 73A, 73B are rotatably supported inside the upper end of the exterior frame 71, corresponding to each arm 80, 90. Belts 75A, 75B, which serve as an example of a connecting member, are wound around each pulley 73A, 73B from above. One end of the belts 75A, 75B is connected to the arms 80, 90. Balancing weights 76A, 76B are suspended from the other ends of the belts 75A, 75B. The balancing weights 76A, 76B are set to weights corresponding to the weights of the corresponding arms 80, 90. The balancing weights 76A, 76B apply a force to the arms 80, 90 via the belts 75A, 75B to counteract the weights of the arms 80, 90. As a result, when an external force acts in the vertical direction TD, the arms 80, 90 are more likely to move in the vertical direction TD along the guide rod 72 in response to that external force.

Rotary encoders 74A and 74B are connected to pulleys 73A and 73B, respectively. Rotary encoders 74A and 74B detect the amount of rotation of pulleys 73A and 73B. When arms 80 and 90 move in the vertical direction TD, pulleys 73A and 73B rotate via belts 75A and 75B. Therefore, the amount of rotation of pulleys 73A and 73B is measured by rotary encoders 74A and 74B and input to control device 200, which can then measure the amount of movement of arms 80 and 90 based on the amount of rotation of pulleys 73A and 73B.

FIG. 3 is a perspective view showing the main parts of the elongation measuring device 70 and the testing device 30. As shown in FIG.
The upper arm 80 has a sliding portion 81 slidably supported on the guide rod 72. The sliding portion 81 is supported on the guide rod 72 via, for example, a linear bushing. A pair of clamping members 82 extending forward is supported on the sliding portion 81. The base ends of the clamping members 82 are supported rotatably about a hinge shaft (not shown) extending vertically, and the tip ends are configured to be openable and closable. A tension spring (elastic member) 83 is attached to the lower portions of the pair of clamping members 82 in a straddling manner. The tension spring 83 biases the clamping members 82 in the closing direction. Pressed rollers 84 are provided on the upper portions of the pair of clamping members 82. A cylinder mechanism 85 is arranged between the pressed rollers 84.

The cylinder mechanism 85 is composed of an air cylinder. The cylinder mechanism 85 has a conical rod tip 85A. When the rod tip 85A enters between the pressed rollers 84, it pushes the clamping members 82 apart against the elastic force of the tension spring 83, causing them to open. When the rod tip 85A retreats from between the pressed rollers 84, the elastic force of the tension spring 83 causes the clamping members 82 to close. When the clamping members 82 are closed by the cylinder mechanism 85, the upper arm 80 clamps the test piece T and fixes it to the test piece T.
In this embodiment, the upper arm 80 is formed with a plate-shaped pressure receiving portion 86 (see FIG. 2).

The lower arm 90 is configured to be substantially symmetrical in the vertical direction to the upper arm 80. In detail, the lower arm 90 has members 91 to 95 that correspond to the members 81 to 85 of the upper arm 80.
The lower arm 90 is also formed with a detachable portion 92A having a downwardly recessed detachable hole. A collar 96 extending in the up-down direction TD is detachably supported by the detachable portion 92A. The collar 96 is a rod configured to have a length corresponding to the gauge length λ1, λ2 of the test strip T (see FIGS. 4 and 5). The upper arm 80 abuts against the top surface of the collar 96, thereby maintaining the gauge length λ1, λ2 between the upper arm 80 and the lower arm 90.

In this embodiment, multiple collars 96 of different lengths corresponding to the length of the test strip T are prepared, and the collars 96 are selectively used. This allows the spacing between the upper arm 80 and the lower arm 90 to be set to the specified gauge length λ1, λ2.

A stopper 77 is fixed to the lower part of the guide rod 72. The stopper 77 has a clamp structure. By clamping the guide rod 72, the stopper 77 fixes the guide rod 72 at a predetermined height. The predetermined height corresponds to the height of the lower gripping tool 39. The upper surface of the stopper 77 comes into contact with the lower arm 90, restricting the downward movement of the lower arm 90. The stopper 77 sets the lower limit position of the lower arm 90.

A plate-shaped adjuster 78 having a predetermined thickness is removably supported on the upper surface of the stopper 77. The adjuster 78 is formed, for example, in a roughly C-shaped plate shape that fits onto the guide rod 72. The adjuster 78 fits onto the guide rod 72 and is supported on the upper surface of the stopper 77. As a result, the upper surface of the stopper 77 is raised by the thickness of the adjuster 78. In other words, the adjuster 78 is a member that variably adjusts the lower limit position of the lower arm 90 set by the stopper 77.

In this embodiment, a plurality of adjusters 78 of different heights are prepared corresponding to the distances D1, D2 (see FIGS. 4 and 5) between the lower marked line M2 of the test piece T and the lower gripping tool 39, and the adjusters 78 are selectively used. Note that the phrase "selectively disposing the adjuster 78 relative to the stopper 77" is used to mean a case where the adjuster 78 is not disposed relative to the stopper 77. This makes it easier to adjust the lower limit position of the lower arm 90 compared to the case where the stopper 77 is unclamped and clamped to adjust the position of the stopper 77 relative to the lower gripping tool 39.
The stopper 77 and the adjuster 78 constitute a stopper mechanism 79 of the lower arm 90 of this embodiment.

As shown in FIGS. 2 and 3, a positioning mechanism 100 is provided on the crosshead (load mechanism) 35 located above the upper arm 80 .
The positioning mechanism 100 has a connecting frame 101 connected to the crosshead 35. The connecting frame 101 is in the form of a bent plate extending downward from the crosshead 35. A triangular plate-shaped rib 101A is supported on the connecting frame 101. The rib 101A ensures the rigidity of the bent plate-shaped connecting frame 101. An actuator 102 is supported on the lower end of the connecting frame 101.

In this embodiment, the actuator 102 is configured as an air cylinder. The actuator 102 includes a cylinder portion 102A and a rod portion 102B that is supported so as to be extendable and contractible in the vertical direction TD relative to the cylinder portion 102A.

A pressing mechanism (shock absorbing member) 104 is connected to the rod portion 102B via a connecting plate 103 in the form of a bent plate.
The pressing mechanism 104 descends integrally with the crosshead 35 and presses the pressure receiving portion 86 of the upper arm 80 downward when it comes into contact with the pressure receiving portion 86. In this embodiment, the pressing mechanism 104 is configured by an air cylinder. The pressing mechanism 104 includes a cylinder portion 104A fixed to the connecting plate 103, a rod portion 104B supported so as to be extendable and contractible in the up-down direction TD relative to the cylinder portion 104A, and a pressing element 104C supported at the lower end of the rod portion 104B. The lower end of the pressing element 104C is positioned below the upper gripping tool 38.

The pressing mechanism 104 holds the rod portion 104B with a force smaller than the force with which the actuator 102 holds the rod portion 102B. The pressing mechanism 104 functions as a buffer mechanism.

As shown in FIG. 1, the materials testing machine 1 is equipped with a control device 200 that controls each part of the materials testing machine 1. The control device 200 is connected to the materials testing machine 1 so that it can send and receive signals to and from the materials testing machine 1. The signals received by the control device 200 include measurement signals output by the load cell 36, measurement signals output by the rotary encoders 74A and 74B, and other appropriate signals required for control and testing. The signals sent by the control device 200 include control signals for the test piece supply device 10, control signals for the cylinder devices (not shown) of the grippers 38 and 39, control signals for the motor of the threaded rod (not shown), control signals for the recovery devices 51 and 61, control signals for the cylinder device (not shown) of the actuator 102, and other appropriate signals required for control and testing.

The control device 200 includes a computer that includes a processor such as a CPU (Central Processing Unit) or MPU (Micro-Processing Unit), a memory device such as a ROM (Read Only Memory) or RAM (Random Access Memory), a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive), and an interface circuit for connecting the control device 200 and various peripheral devices. The processor executes control programs stored in the memory device or storage device to realize the various functions of the materials testing machine 1.

The control device 200 stores length information for each test strip T. Here, if each pallet 11 contains test strips T of the same standard and the standard of the test strips T varies for each pallet 11, the length of the test strip T may be stored for each pallet 11. Before starting the test, the operator can input the length of each test strip T into the control device 200, causing the control device 200 to store it.

The control device 200 acquires these descent amounts and pushing amounts based on, for example, reference information corresponding to the length of the test piece. Then, when the test piece T is transferred from the transport device 20 to the upper gripping tool 38, the control device 200 lowers the crosshead 35 by an amount corresponding to the length of the test piece T. Furthermore, when the test piece T is transferred from the transport device 20 to the upper gripping tool 38, the control device 200 controls the actuator 102 to perform pushing amounts U1 and U2 (see FIGS. 4 and 5) corresponding to the length of the test piece T. Instead of the length of the test piece T, the descent amounts and pushing amounts of the test piece T may be stored.
In the elongation measuring device 70, before the start of the test, the adjuster 78 is selectively disposed in the stopper mechanism 79. Also, a collar 96 is selectively attached to the lower arm 90.

Fig. 4 is an explanatory diagram for testing a test piece T. Fig. 5 is an explanatory diagram for testing a test piece T that is shorter in length than the test piece T described in Figs. 2 and 4.
The operation of the embodiment will be described with reference to FIGS.
When a predetermined operation to start the test is input, in the test piece supply device 10, the transport device 20 uses the suction pad 29 supported by the pivoting arm 26 (see Figure 1) to pick up and hold the test pieces T one by one from the pallet 11, and as shown in Figure 2, supplies the test pieces T to the upper gripper 38 of the testing device 30 and has them gripped by the upper gripper 38.

Next, the crosshead 35 is lowered, moving the upper grip 38 holding the test specimen T toward the lower grip 39. As the crosshead 35 descends, the connecting frame 101, actuator 102, and pressing mechanism 104 that make up the positioning mechanism 100 descend together, until the pressing mechanism 104 abuts against the upper arm 80. As the crosshead 35 continues to descend after the pressing mechanism 104 abuts against the upper arm 80, the upper arm 80 begins to descend and abuts against the collar 96. As the crosshead 35 continues to descend, the upper arm 80 begins to press down on the lower arm 90 via the collar 96, and the lower arm 90 begins to descend together with the upper arm 80. The crosshead 35 then descends a predetermined distance and stops, and the test specimen T enters the lower grip 39, which then grips the test specimen T, as shown in Figure 4. The lower arm 90 stops when it hits the stopper mechanism 79.

At this time, in the elongation measuring device 70, the positions of the upper arm 80 and the lower arm 90 coincide with the positions of the marked lines M1, M2 of the test piece T, and the clamping members 82 of the upper arm 80 and the clamping members 92 of the lower arm 90 are closed to fix the test piece T at equal positions above and below the center position M0 of the pair of gripping tools 38, 39. This enables the arms 80, 90 to follow the marked lines M1, M2 in accordance with the elongation of the test piece T.
In addition, since the pressing mechanism 104 functions as a buffer mechanism, even if the lower arm 90 abuts against the stopper mechanism 79 and the crosshead 35 stops descending, excessive pressing on the upper arm 80, etc. is prevented.
In the elongation measuring device 70, the upper arm 80 and the lower arm 90 can be moved and positioned to the marked lines M1 and M2 by utilizing the movement of the crosshead 35 of the testing device 30.

Figure 5 is an explanatory diagram of the case where a test piece T having a length shorter than that of the test piece T described in Figures 2 and 4 is tested. When the length of the test piece T is short, the distance L2 between the pair of grips 38, 39 becomes shorter than the distance L1 shown in Figure 4. Also, the distance λ2 between the gauge lines of the test piece T becomes shorter than the distance λ1 between the gauge lines shown in Figure 4, and the distance between the pair of arms 80, 90 becomes shorter.
In this embodiment, the positioning mechanism 100 includes an actuator 102, and the amount of pressing of the pair of arms 80, 90 is adjusted by the positioning mechanism 100 in accordance with the length of the test piece T. Specifically, the position of the presser 104C of the pressing mechanism 104 is adjusted to a distance U2 from the upper gripping tool 39. At this time, an adjuster 78 is selectively disposed in the stopper mechanism 79. In addition, a collar 96 is selectively attached to the lower arm 90.

As a result, when the crosshead 35 descends by a predetermined amount according to the length of the test piece T, the elongation measuring device 70 can move the upper arm 80 and the lower arm 90 to different positions relative to the grippers 38, 39 to align them with the marked lines M1, M2 that are different from those of the long test piece T. Therefore, the upper arm 80 and the lower arm 90 can be fixed to the marked lines M1, M2 of a short length.
Therefore, in this embodiment, the positioning mechanism 100 is equipped with an actuator 102 that adjusts the amount of pushing of the pair of arms 80, 90 according to the length of the test piece T, so that the configuration of the elongation measuring device 70 is simplified, and the positional relationship between the pair of gripping devices 38, 39 and the pair of arms 80, 90 can be changed with this simple configuration.

When a test force is applied to the test piece T, the pressing mechanism 104 retracts the rod portion 104B to separate the presser 104C from the pressure receiving portion 86 of the upper arm 80. This allows the presser 104C to be in a state where it does not restrain the upper arm 80 when the test force is applied.
Then, the crosshead 35 rises, and the upper gripping tool 38 moves away from the lower gripping tool 39, thereby applying a tensile load to the test piece T. Accordingly, the test piece T is pulled by the upper gripping tool 38 and extends upward. At this time, the lower arm 90 moves upward following the movement of the marked line M2 and moves away from the stopper mechanism 79. Furthermore, the upper arm 80 moves upward following the movement of the marked line M1 and moves away from the collar 96. The pressing mechanism 104 rises together with the crosshead 35. In the materials testing machine 1, the tensile load of the test piece T is measured, and the elongation of the test piece T is measured from the fluctuation of the distance between the arms 80 and 90 during the test.
2, the stopper mechanism 79, the lower arm 90, the upper arm 80, and the pressing mechanism 104 move away from each other in the vertical direction TD, and the upper arm 80 and the lower arm 90 return to positions where they can be pressed by the positioning mechanism 100. In the pressing mechanism 104, the retracted rod portion 104B is extended, and the pressing element 104C is returned to a position for pressing the upper arm 80.

2. Modifications
The above-described embodiment merely exemplifies one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.

In the above-described embodiment, the actuator 102 is configured as an air cylinder, and the rod portion 102B can be switched between two positions, but it may also be configured to be adjustable to any position. For example, the actuator 102 may be configured as an electric cylinder, and may be configured to be adjustable to any desired amount of thrust.

In the above-described embodiment, a pressing mechanism 104 was provided, but the upper arm 80 may also be pressed directly by the rod portion 102B of the actuator 102.

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

(Section 1)
One embodiment of a materials testing machine comprises a loading mechanism that applies a test force to a test piece held at both ends by a pair of gripping devices, and an elongation measuring device that fixes a pair of arms to a pair of marking lines on the test piece and measures the elongation between the pair of marking lines.The elongation measuring device may comprise a positioning mechanism that pushes the pair of arms in conjunction with the movement of the loading mechanism and positions the pair of arms between the pair of gripping devices, and the positioning mechanism may comprise an actuator that adjusts the amount of pushing of the pair of arms depending on the length of the test piece.

In the materials testing machine described in paragraph 1, the positioning mechanism is equipped with an actuator that adjusts the amount of pushing of the pair of arms depending on the length of the test piece, so the positional relationship between the pair of grippers and the pair of arms can be changed with a simple configuration.

(Section 2)
In the material testing machine described in paragraph 1, the positioning mechanism may include a connecting frame connected to the loading mechanism, the actuator supported by the connecting frame, and an impact absorbing member connected to the actuator.

The material testing machine described in paragraph 2 can cushion the impact on the arm caused by contact with the actuator.

(Section 3)
In the material testing machine described in paragraph 1 or 2, the pushing amount of the pair of arms may be adjusted so that the center position between the pair of arms coincides with the center position between the pair of benchmark lines of the test piece.

The material testing machine described in paragraph 3 allows the arm to be fixed to the test piece in a balanced manner.

(Section 4)
The material testing machine described in any one of paragraphs 1 to 3 may be provided with a test piece storage device that stores the test piece, a transport device that removes the test piece from the test piece storage device and transfers the test piece to the loading mechanism, and a control device that acquires length information of the test piece and drives the actuator based on the length information.

The material testing machine described in paragraph 4 allows for automated actuator control, making it easy to measure the elongation of test pieces of different lengths.

(Section 5)
In the material testing machine described in any one of paragraphs 1 to 4, when the positioning mechanism positions the pair of arms between the pair of grippers, it may move the upper gripper of the pair of grippers toward the lower gripper.

The material testing machine described in paragraph 5 allows the arm to be moved in the direction of gravity for positioning.

The material testing machine described in paragraph 5 may also be provided with a test piece storage device that stores the test pieces, and a transport device that removes the test pieces stored in the test piece storage device and transports the test pieces to the upper grip of the loading mechanism.
According to this material testing machine, the pair of arms can be positioned by utilizing the movement of the loading mechanism at the start of the test.

1 Material testing machine 12 Test piece storage device 20 Conveying device 35 Crosshead (loading mechanism)
38 Upper gripping tool
39 Lower gripping tool
70 Extension measuring device 80 Upper arm 90 Lower arm 100 Positioning mechanism 101 Connecting frame 102 Actuator 104 Pressing mechanism (shock absorbing member)
M0 Center position between marked lines M1, M2 Marked lines T Test piece U1, U2 Push amount

Claims (5)

A materials testing machine comprising: a loading mechanism that applies a test force to a test piece gripped at both ends by a pair of gripping tools; an elongation measuring device that fixes a pair of arms to a pair of benchmark lines provided on the test piece and measures the elongation between the pair of benchmark lines; a test piece storage device that stores the test piece; a transport device that removes the test piece from the test piece storage device and transfers the test piece to the loading mechanism; and a control device that acquires length information of the test piece and drives an actuator based on the length information ,
the elongation measuring device includes a positioning mechanism that pushes and moves the pair of arms in conjunction with the movement of the load mechanism and positions the pair of arms between the pair of gripping tools;
the positioning mechanism includes the actuator that adjusts the pushing amount of the pair of arms in accordance with the length of the test piece ;
The control device drives the actuator so that a predetermined pushing amount corresponding to the length of the test piece is applied when the test piece is transferred from the transport device to the loading mechanism . a pallet for accommodating the test strips;
the test strip storage device is capable of storing a plurality of the pallets;
2. The materials testing machine according to claim 1, wherein the control device stores the length information for each of the pallets and drives the actuator based on the length information for each of the pallets. 3. The materials testing machine according to claim 1, wherein the positioning mechanism comprises a connecting frame connected to the load mechanism, the actuator supported by the connecting frame, and an impact absorbing member connected to the actuator. 4. The materials testing machine according to claim 1, wherein the actuator adjusts the amount of pushing of the pair of arms so that a center position between the pair of arms coincides with a center position between a pair of benchmark lines on the test piece. A materials testing machine according to any one of claims 1 to 4, wherein the positioning mechanism moves the upper grip of the pair of grips toward the lower grip when positioning the pair of arms between the pair of grips.