JP3944667B2 - Material testing machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a material testing machine, and more particularly to a material testing machine that detects an electrical load cell to detect a tensile load acting on a test piece when a tensile load is applied to the test piece.
[0002]
[Prior art]
In a material testing machine, in general, a moving member such as a cross head is disposed opposite to a fixed member such as a bed, and a test piece is mounted between them and the moving member is driven to load the test piece. Is granted. The load acting on the test piece is usually detected momentarily by an electric load cell. That is, for example, a load cell is fixed to a crosshead of a material testing machine, and a test piece mounting member such as a gripping tool is supported on a load sensitive portion of the load cell, and a load applied to the test piece by driving the crosshead is applied. The load cell is configured to act also on the load sensitive part, and configured to detect the load applied to the test piece every moment by the output of the load cell.
[0003]
In materials testing machine equipped with a load cell as described above, the mounting surface of the material testing machine of the load cell in the tensile load, i.e. the bearing surface of the load cell, a difference in deformation amount of the contact surface for the bearing surface of the load cell itself When it occurs, an error is included in the load measurement result at the time of loading and unloading due to a twist caused by friction at the interface. As countermeasures against this phenomenon, conventionally, by increasing the rigidity of the seating surface of the load cell, the respective distortions of the seating surface and the surface of the load cell itself in contact therewith are reduced, and the difference in deformation of the interface between them is reduced. Measures are taken to reduce the size.
[0004]
FIG. 3 is a diagram showing a material testing machine in which the above measures are taken, (A) is a front view of the main part, and (B) is an explanatory diagram of the mounting structure of the load cell 43 shown in the BB cross section. is there. In this conventional example, in the configuration in which the load cell 43 is attached to the cross head 42 that moves up and down by the rotation of the left and right screw rods 41a and 41b, and the gripping tool 44 is attached to the load sensitive portion on the lower surface of the load cell 43, the upper plate A through-hole H is formed in the upper plate 42a of the crosshead 42 formed by connecting the rib 42c with the lower plate 42b, and the load cell support member 45 is fixed to the upper surface of the lower plate 42b. By passing through the inner peripheral surface of the through hole H of the upper plate 42a in a non-contact manner and fixing the load cell 43 to the seat surface 45a formed on the upper end surface of the load cell support member 45, the cross The bending of the head 42 is reduced as much as possible to the seating surface 45a.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional measures for increasing the rigidity of the seat surface of the load cell as described above, not only a separate support member is required as the seat surface of the load cell, but also for attaching the support member to the cross head. There is a problem that complicated processing is required, the manufacturing process is complicated, and the cost is increased.
[0006]
An object of the present invention is to provide a material testing machine capable of mounting a load cell under a simple seating surface structure and performing high-precision tensile load measurement without adopting a complicated seating surface structure as in the prior art. There is to do.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the material testing machine of the present invention mounts a test piece between a fixed member and a moving member facing the fixed member, applies a tensile load to the test piece by driving the moving member, and applies the test piece to the test piece. In the material testing machine that detects the acting tensile load by the load cell held by the testing machine, a highly lubricious resin sheet is inserted between the load cell and the seating surface on the testing machine that holds the load cell. It is characterized by being.
[0008]
The present invention includes a seat surface for mounting the load cell, and take advantage of the lubricating function of high lubricating resin sheet to be interposed in the interface of the contact surface of the load cell relative to its seating surface, it contacts the seating surface and the seating surface It aims to achieve the intended purpose by making each deformation of the surface of the load cell independent.
[0009]
That is, by interposing a sheet of high-lubricity resin such as polytetrafluoroethylene (hereinafter referred to as PTFE) at the interface, a tensile load to be measured is applied to the load-sensitive portion of the load cell. Since the surface on the seating surface side and the load cell side can be deformed (moved) with little frictional resistance against the surface of the highly lubricious resin sheet, the high lubricity resin sheet On both sides, the seat surface side and the load cell side are smoothly and independently deformed independently of each other. Thereby, when the load applied to the test piece is changed, it is possible to prevent the occurrence of an error due to the difference in deformation amount between the load cell and its seating surface.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a front view of a material testing machine to which the present invention is applied, and FIG. 1B is an explanatory diagram of a mounting structure of a load cell 5 shown in an enlarged view of a main part in the BB cross section.
[0011]
Two vertical screw rods 2 a and 2 b are rotatably supported on the bed 1, and these drive mechanisms are held in the bed 1 while their upper ends are held by the cross yoke 11. (Not shown) provides rotation. Both ends of the crosshead 3 are supported on the screw rods 2a and 2b via nuts (not shown), and the crosshead 3 moves up and down by the rotational drive of the screw rods 2a and 2b. . A lower grip 4 a is attached to the center of the upper surface of the bed 1.
[0012]
The cross head 3 has a structure in which an upper plate 3a and a lower plate 3b are integrated with each other by a rib 3c, and a load cell 5, a universal joint 6 and an upper grip 4b are attached to a central portion thereof. The load cell 5 is screwed to the upper surface of the upper plate 3a of the crosshead 3 around a through hole 3d formed through the upper plate 3a and the lower plate 3b of the crosshead 3 with the load sensitive portion 5a facing downward. . A PTFE sheet 7 is interposed between the cross head 3 and the seat surface 3e (the surface around the through hole 3d on the upper surface of the upper plate 3a).
[0013]
Load sensing portion 5a of the load cell 5 faces the inside hole 3 d, one end of the universal joint 6 to the load sensing portion 5a is fixed. The other end of the universal joint 6 is led to the lower side of the cross head 3 through the through hole 3 d, and upper jaws 4b are mounted therein.
[0014]
For example, when performing a tensile test using the above embodiment of the present invention, the screw heads 2a and 2b are driven with the test piece mounted between the upper and lower grippers 4a and 4b, and the crosshead 3 is moved. Raise. As a result, a tensile load is applied to the test piece, but the load acting on the test piece is transmitted to the load sensing portion 5a of the load cell 5 through the upper grip 4b and the universal joint 6 and detected.
[0015]
Now, during the above test, the load applied to the test piece also acts on the load cell 5 and the crosshead 3, and each of the loads causes a unique deformation. At this time, since the PTFE sheet 7 which is a highly-lubricating resin is interposed between the seating surface 3e of the crosshead 3 and the lower surface of the load cell 3 opposite to the seating surface 3e, these surfaces respectively correspond to the PTFE sheet 7. The lower surface of the load cell 5 and the seating surface 3e can be independently and smoothly deformed according to the load acting on each of them, and the difference in deformation amount between these two surfaces can be made freely. Even if there is, a load detection error caused by twisting or the like is prevented.
[0016]
Next, test results conducted to confirm the load detection error prevention effect of the PTFE sheet 7 will be described. For the experiment, the embodiment shown in FIG. 1 and a material testing machine having the same configuration as that of FIG. 1 except that the PTFE sheet 7 is not interposed as a comparative example are provided, and each of the load cells 5 has a capacity of 100 kN. In addition, the fixing bolt tightening force with respect to the crosshead 3 of the load cell 5 is made constant, and the tensile load on the test piece is changed by a known amount between 0 kN and 100 kN, and when the load (load gradually increases) and unloading (load gradually decreases) ) The output from the load cell 3 was read and the error contained therein was measured.
[0017]
FIG. 2 shows the result of repeating the above test three times and plotting the average value. In FIG. 2, (A) shows the test results of the embodiment of the present invention, and (B) shows the test results of the comparative example. As is apparent from FIG. 2, in the embodiment of the present invention, the load detection error is smaller than that in the comparative example, and it has been confirmed that the embodiment is particularly effective in eliminating the error during unloading.
[0018]
Here, PTFE sheet 7 in the above embodiments, be replaced by a sheet made of known high lubricity resins including other fluorine-based resin, Ru can be obtained the same effects as described above.
[0019]
【The invention's effect】
As described above, according to the present invention, when a load is applied to a test piece under a simple configuration in which a highly-lubricating resin sheet is interposed between the load cell and its seating surface, The seat surface is smoothly and independently deformed by the lubrication function of the highly lubricious resin sheet. Even if there is a difference between the amount of deformation of the load cell itself and the amount of deformation of the seat surface due to the load, the interface between the two In this case, the occurrence of a load detection error can be suppressed.
[Brief description of the drawings]
FIG. 1 (A) is a front view of a material testing machine to which the present invention is applied, and FIG. 1 (B) is an explanation of a mounting structure of a load cell 5 shown in an enlarged view of a main part in the BB cross section. FIG.
FIG. 2 is a graph showing experimental results for confirming the effect of suppressing the load detection error according to the embodiment of the present invention, and FIG. 2 (A) is a load detection error during loading and unloading according to the embodiment of the present invention. FIG. 2B is a graph showing the measurement results of the load detection error during loading and unloading in the same comparative example.
FIG. 3 is an explanatory diagram of an example of a conventional measure for preventing a load detection error caused by a difference in deformation amount of the seat surface of the load cell, and FIG. 3 (A) is a front view of the main part, FIG. (B) is explanatory drawing of the attachment structure of the load cell shown in the BB expanded cross section.
[Explanation of symbols]
1 bed 2a, 2b screw rod 3 crosshead 3d through hole 3e seating surface 4a, 4b gripping tool 5 load cell 6 universal joint 7 PTFE sheet

Claims (1)

Test pieces were mounted between the fixed member and the moving member facing thereto, thereby imparting a tensile load to the test piece by driving the movable member, every moment detected by the load cell held a tensile load acting on the test piece tester In the material testing machine, a high-lubricating resin sheet is inserted between the load cell and a seating surface on the testing machine holding the load cell.

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