JPH049741A - Material tester - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] A. Industrial Application Field The present invention relates to a material testing machine for tensile testing steel pipes and other tubular specimens, and in particular enables automatic exchange of core metals inserted at both ends of the tubular specimen. Regarding the material testing machine.

B. Conventional technology When performing a tensile test on a steel pipe or other tubular test piece, a core bar selected by the operator according to the inner diameter of the test is placed inside the grip part of the test piece held by the grips of the tensile testing machine. , manually or by an automatic attachment/detachment device disclosed in Japanese Patent Application Laid-Open No. 63-275930.

C1 Problems to be Solved by the Invention However, in conventional material testing machines, the selection and replacement of the core metal that matches the inner diameter of the tubular test piece is performed manually, which makes the replacement work of the core metal complicated, making it difficult to perform tubular testing. Automation of tensile tests on pieces is difficult.

An object of the present invention is to provide a material testing machine that enables automatic replacement of a core metal applied to a tubular test piece.

The present invention will be explained in conjunction with FIGS. 1, 2, and 5, which are examples of means for solving problem D9. It is applied to a material testing machine in which both ends of the test piece are gripped by a pair of grips 18 provided on a load frame, and a tubular test piece TP is loaded by a load means 12.

The above purpose is to provide a core attachment/detachment means 20 for driving the core bar 30 along the load axis in order to insert and remove it from the tubular test piece TP, and a core metal installed in the load frame and communicating with the load axis. 30 passages 41 and an entrance/exit 511 of the core metal 30 that accommodates a plurality of types of core metals 30 with different diameters and communicates with the communication passage 41.
A core metal storage means 51 provided with C, and a core metal storage means 51
an indexing means 59 for indexing the cored metal 30 housed in the doorway 511C, and carrying the indexed cored metal 30 through the communication passage 41 to the load shaft center, and moving the cored metal 30 located at the load shaft center to the doorway 511C. This is achieved by providing a core metal loading/unloading means 63 for transporting the metal core to 511c.

E1 operation Among the plurality of core metals 30 in the core metal storage means 51, one suitable for the inner diameter of the tubular test piece TP to be tested is indexed by the indexing means 59 to the entrance/exit 511c. The indexed core metal 30 is fed by the core metal loading/unloading means 63 from its entrance/exit 511C through the communication passage 41 to the load shaft center. The core bar 30 that has been fed to the load axis is inserted into the tubular test piece TP in the non-grip state by the core bar attachment/detachment means 20. Thereafter, the test piece TP is gripped by the gripper] 8, and a tensile load is applied to the test piece TP by the loading means 12. After the test is completed, the core bar 30 can be pulled out from the tubular test piece 'rI) by the core bar attachment/detachment means 20.

After that, when testing tubular specimens TP with different diameters,
The used core metal 30 is transferred to the passage 41 by the core metal insertion/removal means 63. Return the core metal 30 to the storage means 51 through the entrance/exit 511c and have an outer diameter suitable for the diameter of the new test piece TP.
is selected, indexed by the indexing means 59, and the cored metal 30 can be carried into or out of the load axis in the same manner as described above, and the cored metal 30 can be inserted into and removed from the test piece TP. Therefore, the core bar 30 that matches the inner diameter of the tubular test piece TP can be automatically replaced.

Note that in the above sections D and E, figures of embodiments are used to make the explanation easier to understand, but the present invention is not limited to the embodiments.

F. Embodiment An embodiment of the present invention will be described based on FIGS. 1 to 5.

FIG. 3 is a diagram showing a core metal inserted into the end of a tubular test piece such as a steel pipe. The core bar 30 has a cylindrical main body part 31 having an outer diameter matching the inner diameter of the tubular test piece, and an engaging part 32 that engages with a core metal attachment/detachment mechanism formed at the lower end thereof. A flange-shaped stopper 33 is slidably attached to the core body 31 above the engaging portion 32 . The pad 33 has a sliding portion 33 that is engaged with and slides in a groove 41 of a guide member 4o, which will be described later, when the core bar 30 is mounted on the testing machine.
a and a notch 33 that engages and disengages a hooking fitting 651 to be described later.
b is provided. In addition, the pad 33 has a groove 41
It also has the function of being engaged with and restrained in the load axial direction, and latching the end face of the test piece when the core metal is pulled out.

FIG. 1(a) is a front view of the material testing machine, and FIG. 1(b) is a plan view thereof.

This material testing machine consists of a testing machine main body MTM equipped with an automatic core metal insertion/removal mechanism, and an automatic transfer device ATD that selectively transfers a core metal matching the inner diameter of a tubular test piece to the core metal automatic insertion/removal mechanism. It consists of

A ram cylinder 12 is installed at the center of the bed 11, and a pair of vertical columns 13 are installed at diagonal corners.
has been erected. A pair of columns 15 are erected on a table 14 fixed to the upper part of the rams 1 and 2a, on a diagonal line different from that of the screw column 13. An upper crosshead 16 is horizontally suspended and fixed to the upper ends of the pair of columns 15, and a lower crosshead 17 is provided inside the pair of threaded columns 13 and is screwed together with a pair of nuts to be described later. The upper crosshead 16 is moved by the table 14. due to the expansion and contraction of the ram cylinder 12. It can move up and down together with the support column 15, and the lower crosshead 17 can move up and down by rotating a nut. In addition, the upper and lower crossheads 16.1
7 has a built-in hydraulic upper grip 18tJ and a lower grip 18L (representatively indicated by reference numeral 18), and both ends of the test piece TP are provided with upper and lower grips 18U.
.

18L respectively. Further, an upper core metal attachment/detaching mechanism 20U is installed on the upper surface of the upper crosshead 1-6, and a lower core metal attachment/detachment mechanism 2OL is installed on the lower surface of the lower crosshead 17 coaxially with the load axis X. These core metal attachment/detachment mechanisms are represented by the reference numeral 2o.

Next, the structure of the lower crosshead 17 will be explained with reference to FIG.

FIG. 2(a) is a partially cutaway front view of the lower crosshead 17, and FIG. 2(b) is a plan view of FIG. 2(a). crosshead 17
3 includes a pair of left and right support blocks 171 that are screwed together and supported by the threaded column 13, and a center block 172 that is sandwiched between the left and right support blocks 171 and screwed with bolts 173.
It is divided. The bolt 173 is attached to the support block 171
Four wires are provided in each row on both left and right ends of the outer surface of the wire to resist the bending moment that occurs in the plane of the paper in FIG. 2(a) when a load is applied. Furthermore, a protrusion 17 is provided on the inner surface of the support block 1'71.
1A is provided protrudingly, and a recess 172A is provided on the outer surface of the central block 172, and the protrusion 171A is fitted into the recess 172A to maintain shearing force in the load axial direction.

A rotary nut 71 is rotatably installed on the support block 171, and a gear 72 is fixed to the lower end surface of the rotary nut 71. The gear 72 is connected via an idle gear 73 to the output shaft of a hydraulic motor (not shown) built into the crosshead 17, and the hydraulic motor drives the rotary wheel 1-71 to rotate and move the crosshead 17 up and down.

74 is a backlash removal device installed on the top surface of the crosshead 17. This backlash removal device W74
is an annular metal fitting 7 screwed onto the upper surface of the support block 171.
41, and a spring reaction force support nut 742 which is screwed onto the spring pillar 13 and housed inside the annular metal fitting 741 with a gap between the upper end surface of the rotating nut 1-71 and which is screwed into the open upper end of the annular metal fitting 741. cup member 743 and cup member 743
and the reaction force support nut 742.
44, and a spring 745 interposed between the spring receiver 744 and the cup member 743, and the spring force of the spring 745 constantly urges the crosshead 17 in the -L direction to connect the rotating nut 71 and the spring post. 13 backlash has been removed.

Further, the support block 171 is also penetrated with a hole 171B through which the support column 15 passes in parallel to the axis of the rotating nut 7.

On the other hand, a recess 172B is formed in the center of the upper surface of the central block 172 and opens in the front-rear direction of the test machine.
A hydraulic horizontal opening/closing grip 18L for gripping the lower end of the tubular test piece TP from the left and right sides is built into the opposing side surfaces of the test piece 2B. The hydraulic horizontal opening/closing type grip 18L has a pair of hydraulic cylinders 180 that extend and contract oppositely across the load axis.

This hydraulic cylinder 180 has hydraulic cylinder bores 81 bored from the left and right side end surfaces of the center block 172,
The piston 182 is slidably inserted into the bore 81 from the left and right open ends and the piston rod 184 at the tip protrudes into the recess 172B, and the hydraulic cylinder 180 fitted into the open end of the bore 181 is used for sealing. The inner surface of each support block 171 is placed against the left and right end surfaces of the center block 172 and screwed with bolts 173, thereby making the bore 181 oil-tight.

A pair of gripping teeth 185 attached to the tip of each piston rod 184 are configured to be openable and closable within the recess 172B.

Further, a through hole 172C is formed in the center bottom of the recess 172B coaxially with the load axis X, and the sleeve 25 is fitted into the through hole 172C.

A lower mandrel attachment/detachment mechanism 2OL for inserting and removing the mandrel 30 from the lower end of the tubular test piece TP is provided on the lower surface of the central block 172 coaxially with the through hole 172C. This core metal attachment machine side 20 has a load axis X on the bottom of the central protrusion 172.
A hydraulic cylinder consists of a cylinder tube 21 fixed coaxially with the cylinder tube 21, a piston 22 sliding inside the cylinder tube 21, and a piston rod 24 connected to the piston 22 via a compression spring with a tightening nut 23. . The protruding end side of the piston rod 24 has a through hole 172C.
A groove 24a having a convex cross section is formed in the upper end surface of the sleeve 25 provided in the sleeve 25 so as to be slidable in the vertical direction.

In addition, the recess 1 extending in the front-rear direction of the central block 172
At the bottom of 72B, a guide member 40 for engaging and disengaging the core metal 30 from the core metal attachment/detachment mechanism 20 is installed. The upper part of the guide member 40 has a groove 41 for guiding the stopper 33 of the cored metal 30 by its sliding part 33a, and an engaging part 3 of the cored metal 30.
A groove 42 for guiding the lower core metal attachment/detachment mechanism 2OL is formed on the back surface of the central portion of the guide member 40 so that the tip of the piston rod 24 of the lower core metal attachment/detachment mechanism 2OL can be accommodated therein.

On the other hand, as shown in FIG. 1, the upper crosshead 16 is supported by left and right support blocks 161 fixed to the tops of the pair of pillars 15 and sandwiched between the left and right support blocks 161 by a total of 16 bolts. The support block 161 also has a through hole for the screw column 13. Further, like the lower crosshead 17, the support block 161 and the center block 162 are fitted in a concave-convex manner on their contact surfaces, and this concave-convex fit holds the shearing force in the direction of the load axis, and the bending moment due to the load is 16 in total. Sharing with the book bolt.

Furthermore, a recess 162B is formed in the center of the lower surface of the center block 162 in the front-back direction of the center block 162, and a hydraulic upper grip 18U that opens and closes left and right across this recess 162B is built in. An upper core metal attachment/detachment mechanism 20U is installed coaxially with the load axis X. The structures of the hydraulic upper grip 18U and the upper mandrel attachment/detachment mechanism 20U are exactly the same as the hydraulic opening/closing type grip 18L and the lower mandrel attachment/detachment mechanism 2OL built into the lower crosshead 17, and a description thereof will be omitted.

Next, FIG. 1 shows the configuration of the automatic core metal transfer device ATD.

FIG. 3 and FIG. 4 will be explained.

Core metal automatic transfer device jiiATD has upper crosshead 16
an upper core metal stocker 51U located on the back of the lower cross rad 17 and arranged parallel and horizontal thereto; and a lower core metal stocker 51 located on the back of the lower cross rad 17 and arranged parallel and horizontal thereto.
It is equipped with L. Here, since the upper core metal stocker 51U and the lower core metal stocker 51L have the same structure, the structure will be described using the representative symbol 51. In the following description, when distinguishing between upper and lower parts, the upper member is marked with U, and the lower member is marked with -.

The core metal stocker 51 has a rail 511 having a cross-sectional structure as shown in FIG.
The upper and lower rails 511U and 511L are connected by a plurality of connecting members 53 between them. Also, rail 511
A plurality of guide grooves 511a, each of which is slidably engaged with a plurality of pads 33, are formed over the entire length of the inner surface of the guide grooves 511a. Furthermore, a guide groove 511b, in which the engaging portion 32 of the core metal 30 is slidably engaged, is formed over the entire length on the opposing inner surfaces of the rail 511. Note that the upper core metal 30U and the lower core metal 30L are supported by respective stockers 510.51L in a vertically inverted state with respect to each other, as shown in FIG.

Feed screws 55 are arranged in parallel over almost the entire length of the core metal stocker 51, and both ends of these feed screws 55 are
It is rotatably supported by a bracket 56 fixed to each stocker.

A pair of core metal feed fittings 57 are screwed into each feed screw 55 in a non-rotating state, as shown in FIG. 11 (a).

As shown in (b) and FIG. 4, the upper core metal stocker 5
10 and the pads 33 of the upper and lower core metals arranged in a row in the lower core metal stocker 51L are held from both left and right ends.

In addition, at the left end of the upper and lower core metal stockers 51U and 51L,
As shown in FIG. 1(a), a motor 59 for moving the core metal is installed by a support member 58 horizontally fixed between the two, and is installed on the rotating shaft of this motor 59, or installed on the timing pulley 60 and each feed screw 55. A timing belt 62 is wound between the timing pulleys 61.

On the side wall of the lower crosshead side of the lower rail 511L,
As shown in FIG. 5(a), an opening 511c for inserting and removing the core metal is formed corresponding to the recess 172B, and this opening 511
In c, a guide groove 511 continuous to the guide groove 41 of the guide member 40 is shown.
d is formed.

Furthermore, the guide groove 511a and the core metal guide groove 42 on the side of the central block 172B are connected to each other by the transfer core guide groove 511.
e is formed.

On the other hand, the lower crosshead 17 of the side wall of the rail 511
On the opposite side, there is an opening 511 as shown in FIG.
An air cylinder 63 for loading and unloading the core metal is supported by a bracket 64 opposite to c. This air cylinder 6
A hooking device 65 is attached to the piston rod 63a of No. 3.

As shown in FIG. 5(b), the hooking device 65 includes a pair of hooks 651 that are symmetrically attached to the tip of the piston rod 63a, a spring 652 that biases the hooks 651 in the expansion direction, and a spring 652 that biases the hooks 651 in the expansion direction. 65] and a mini air cylinder 653 for opening and closing operations. The tip of the hooking device 65 engages and disengages from the notch 33b of the stopper 33 shown in FIG.

In addition, the upper crosshead 16 and the upper core metal stocker 51U
The structure of the automatic loading and unloading mechanism for the cored metal 30 between the lower crosshead 17 and the lower cored metal stocker 51L is the same as that between the lower crosshead 17 and the lower cored metal stocker 51L, so a description of its configuration will be omitted.

Next, the operation will be explained.

First, adjust the upper and lower core bars 30 to match the inner diameter of the tubular test piece TP.
This section describes the case where ``are automatically selected and replaced''.

First, the lower crosshead 17 is screwed onto the threaded column 13.
Rotate the inner rotating nut 71 to remove the lower crosshead 17.
Adjust the position.

After selecting the tubular test piece TP, the core metal feed motor 59 is started to rotate each feed screw 55. Each core metal feed fitting 5
7 move in the same direction at the same speed, the padding metal 3 is placed inside the upper core metal stocker 51U and the lower core metal stocker 51L.
The core metal row group accommodated through 3 moves along the guide grooves 511a and 511b of the respective core metal stockers. Then, when the core metal 30 having a diameter matching the inner diameter of the selected tubular test piece TP is positioned in the core metal insertion/removal opening 511c, the motor 59 stops. Thereafter, the upper and lower core metal insertion/removal air cylinders 63 move forward, so that the tip of the hook 651 in the closed state of the mini air cylinder 653 is inserted into the selected notch 33b of the upper and lower pads 33. .

When the air cylinder 63 moves further forward in this state, the stopper 33 of the selected cored metal 30 moves into the cored metal guide groove 511.
e and into the upper and lower crossheads 16, 17 through openings 511c. The extruded pad 33 and the core metal 30 supported by these are attached to the guide member 4
Upper and lower grips 18.1 along the guide grooves 41.42 of 0
It is sent between the grip teeth 185 of No. 9. In other words, core metal 3
0 is carried to the load axis. At this time, the upper and lower core metals 30
As shown in FIG. 2(a), each engaging portion 32 is a convex groove 24. of the piston rod 24 constituting the core metal attachment/detachment mechanism 20.
engaged with a.

When the core metal 30 has been carried into each crosshead 16, 17, the air cylinder 63 is retracted and the bow hanging device 65 is retracted.

Next, the hydraulic cylinders 21 constituting the upper and lower cored metal attachment/detachment mechanisms 20 move backward to retract the respective cored metals 30 into the central blocks 162B, 172B. In this state, the tubular test piece TP is loaded between the upper crosshead 16 and the lower crosshead 17 by a robot (not shown) or the like.

Next, the hydraulic cylinder 21 is moved forward to remove the upper and lower core metals 3.
0 into both ends of the tubular test piece TP, and the inserted portion of the core metal is gripped by the upper and lower grips 18, 1.9.

Then, when pressure oil is supplied to the ram cylinder 12, the ram cylinder 12 extends and the table 14. The rest 15 and the upper crosshead 16 rise together. Thereby, a tensile load is applied to the tubular test piece, and the tubular test piece TP can be subjected to a tensile test.

After the test is completed, the tubular test piece TP is released from the upper and lower grips 18, and then the piston rod 24 of the upper and lower core metal attachment/detachment mechanism 20 is removed.
When contracted, the pads 33 are fitted into the guide member 40 and are not moved immediately in the direction of the load axis, so the lower and upper end surfaces of the tubular test piece TP abut and are latched to each pad 33, The core bar 30 is pulled out from the tubular test piece TP.

In addition, when replacing the core metal with a core metal of a different diameter due to a change in the tubular test piece TP, do the following: With the hook fitting 651 contracted, extend the air cylinder 63 for loading and unloading the core metal, Insert the metal fitting 651 into the notch 33b of the pad 30. Next, use the mini air cylinder 652 to
1 is opened to engage the stopper 30, and the air cylinder 63
Shrink the used core metal and return it to its original position on the stocker. Thereafter, another core metal may be indexed to a position corresponding to the air cylinder 63 and fed into the corresponding position of the crosshead in the same manner as described above.

As described above, in this embodiment, a plurality of core metals with different diameters are stored in a line in a horizontally arranged stocker corresponding to the upper and lower crossheads, and the upper and lower core metal groups are While moving in the horizontal direction, select a core metal with a diameter that matches the tubular test specimen, and use an air cylinder and hooking device to transfer it to the grips of the upper and lower crossheads or return it from the grips to the stocker. In addition, since the core metal transferred to the grip part can be inserted and removed from the tubular test piece using the attachment/detachment mechanism,
It is possible to automatically select the core metal that matches the inner diameter of the tubular test piece and insert it into and remove it from the test piece.As a result, it is possible to automatically select the core metal that matches the inner diameter of the tubular test piece, and to automatically insert and remove the core metal into the test piece. This makes it possible to perform bow tension tests on test pieces.

In addition, a flange-shaped butt is slidably attached to the outer periphery of the core, and the movement of this buck in the direction of the load axis is restrained by a crosshead, so the outer diameter of the core is different. Also, the end face of the tubular test piece is always latched with a stopper, allowing the core to be pulled out reliably.

Therefore, there is no need to change the position of the stopper using a pair of cylinders as in the prior art according to the outer diameter of the core metal, and the core metal attachment/detaching mechanism is simplified and costs can be reduced.

Furthermore, as in this embodiment, by making the crosshead into three parts, the bores of the hydraulic cylinders are formed facing each other from the left and right sides of the center block.

Since the hydraulic cylinder can be constructed by inserting a piston there, there is no problem with the built-in hydraulic cylinder due to the left and right threaded columns or columns as in the past. Furthermore, there is no initial compressive force acting on the test piece TP unlike in the case of using a wedge-type grip.

Furthermore, unlike the use of hydraulic opening/closing grips externally attached to the crosshead, the central portion of the crosshead can be used effectively, eliminating waste.

6 and 7 show other embodiments of the core metal stocker of the present invention.

In this embodiment, the stocker main body 8 is located between a guide rail 80 that is composed of a pair of side walls that are spaced apart from each other by a predetermined distance and arranged in parallel.
1 is slidably supported in the longitudinal direction of the guide rail. In the stocker main body 81, a plurality of core metal storage sections 82 are formed at equal intervals by cutting out concave shapes separated by a foot, and each of the core metal storage sections 82 accommodates various types of core metal 30 having different diameters. .

Further, the engagement portion 32 of the core metal 30 is provided on the upper bottom surface of each storage portion 82.
A groove 83 in which the metal core 30 is slidably engaged is formed in the thickness direction of the stocker body 81, and a groove 84 in which the pad 33 of the core metal 30 is slidably engaged is formed on the inner surface of the storage portion 82. It is formed in the thickness direction.

A feed screw 85 is arranged in parallel on the upper surface side of the stocker main body 81, and both ends of the feed screw 85 are rotatably supported by a support member 86. A NAND member 87 screwed onto the feed dog 85 is connected to the stocker main body 81. Also, feed 8
A timing pulley 88 is fixed to one end of the motor 5, and rotation is transmitted to the timing pulley 88 from a motor via a timing belt 89, as in FIG.

In the core metal stocker having the above configuration, when the feed screw 85 is rotated to the left or right, the stocker body 81 moves in the direction of the arrow in FIG. Inlet/outlet opening 80a formed at 80
Find out. In this opening 80a, as in the case shown in FIG. 5(a), an air cylinder for feeding the core metal and a central block of the crosshead are arranged, and the expansion and contraction of the air cylinder allows the core metal to be moved in the same manner as in the above embodiment. Automatic loading and unloading is possible.

In addition, in the configuration of the above embodiment, the core metal stocker 51
is the core metal storage means, the motor 59 is the indexing means, the air cylinder 63 is the core metal insertion/removal means, and the guide groove 4],
, 42 constitute a communication passage, the ram cylinder 12 constitutes a load means, and the upper and lower crossheads 16 and 17 and the columns 13 and 1.5 constitute a load frame, respectively.

The automatic core transfer device, core attachment/detachment mechanism, grip, testing machine main body, and other structures in the present invention are not limited to the embodiments.

G1 Detailed explanation of the invention According to the present invention, various core metals with different diameters are held in the housing means, and one of the core metals in the housing means is placed opposite to the passageway leading to the load axis. At the same time, the indexed core can be carried in and out through a passage between the load shaft core and the entrance and exit, and the core can be inserted into and removed from the tubular test piece using the core attachment/detachment means. With this configuration, it is possible to automatically replace the core metal that matches the inner diameter of the tubular test piece, and it is possible to easily realize full automation of material testing including replacement of the core metal.

[Brief explanation of drawings]

FIG. 1(a) is a front view of a material testing machine showing one embodiment of the present invention, FIG. 1(b) is a plan view of a portion along 1-1 m in FIG. 1(a), and FIG. 2(a) is a 2(b) is a plan view of the lower crosshead, FIG. 3 is a perspective view of the metal core, and FIG. 4 is an enlarged view of the portion along line IV-IV in FIG. 1(a). 5(a) is a plan view of the core metal loading/unloading mechanism, FIG. 5(b) is an enlarged plan view of the hook part in FIG. 5(a), and FIG. 6 is a plan view of the stocker of the present invention. FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6. FIG. 12 Nilam cylinder 13: Threaded column 15: Support column 17: Lower crosshead 18L: Lower grip 20L: Upper core metal attachment/detachment mechanism 31: Core metal body 33: Buttons 4.1, 42: Guide groove 51L: Lower core metal stocker 57: Feeding metal fitting 63: Air cylinder 651: Hooking metal fitting MTM: Material testing machine main body 16 Two upper cross heads 18U Two upper grips 20U: Upper core metal attachment/detachment mechanism 30: Core metal 32: Engagement part 40: Guide member 51U: Upper part Core metal stocker 55: Feed screw 59: Motor 65: Hooking device TP: Tubular test piece ATD: Core metal automatic transfer device Patent applicant Shimadzu Corporation

Claims (1)

[Claims] Both ends of the tubular test piece into which the core metal has been inserted are held by a pair of grips provided on the loading frame, and the tubular test piece is inserted into and removed from the tubular test piece in a material testing machine that loads the tubular test piece with a loading means. Therefore, there is provided a core metal attachment/detachment means for driving the core metal along the load axis, a core metal passage provided in the load frame and communicating with the load axis, and a core metal passage that accommodates a plurality of types of core metals with different diameters and communicates with each other. a core metal storage means provided with an entrance/exit for the core metal that communicates with the passage; an indexing means for indexing the core metal accommodated in the core metal storage means with respect to the entrance/exit; A material testing machine characterized by comprising a core metal loading/unloading means for transporting the core metal located at the load shaft center to the load shaft core and transporting the core metal located at the load shaft core to the entrance/exit.