JP3755238B2 - Material testing machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a material testing machine for measuring a load applied to a test piece, and more particularly to a material testing machine suitable for a compression test of a spring test piece.
[0002]
[Prior art]
By applying tensile force or compressive force to the test piece and analyzing the deformation amount of the test piece and the load applied to the test piece, the mechanical properties of the material can be examined. As a material testing machine capable of applying a tensile force or a compressive force to a test piece as described above, one having a mechanism for moving a crosshead linearly is known.
[0003]
FIG. 7 is a front view showing a material testing machine used for a spring compression test, for example. In FIG. 7, a pair of struts are erected on a fixed table 51 in a pair of left and right strut covers 52, and a cross yoke 53 is suspended above the struts. A pair of left and right screw rods (not shown) are erected between the fixed table 51 and the cross yoke 53, and a pair of nuts (not shown) provided on both sides of the cross head 55 are screwed to each screw rod. The cross head 55 is supported by the screw rod. A drive mechanism such as a motor is provided in the fixed table 51, and the screw rod is rotated by this drive mechanism to raise and lower the cross head 55.
[0004]
Upper and lower platens 57 and 58 are attached to the upper surface of the fixed table 51 and the lower surface of the crosshead 55, respectively, and a compression coil spring (not shown: The spring test piece is positioned) and the screw rod is rotated by the drive mechanism to lower the cross head 55. As a result, the space between the upper and lower platens 57 and 58 is narrowed and a compression load is applied to the spring test piece. The compressive load is measured by a load cell 59 attached to the upper part of the crosshead 55.
[0005]
[Problems to be solved by the invention]
In the material testing machine described above, a compression test is performed by holding a spring test piece between the upper and lower platens, but the end of the spring test piece does not contact the entire surface of the upper and lower platens, Because of partial contact, a force that is eccentric with respect to the load axis acts on the upper and lower platens to generate a bending moment. In addition, when the spring is compressed, a torsional force is generated due to the restoring force. However, due to the generation of such a torsional force and bending moment, the measurement result by the load cell includes an error, and accurate measurement cannot be performed.
[0006]
An object of the present invention is to provide a material testing machine capable of preventing the generation of bending moments and torsional forces even when a spring compression test is performed.
[0007]
[Means for Solving the Problems]
Referring to FIGS. 1 to 4 showing an embodiment, the invention of claim 1 includes a fixed table 1, two screw rods 4 standing on the fixed table 1, and screw rods 4. A crosshead 5 provided so as to be movable up and down, a lower platen 8 attached to the fixed table 1 via a lower attachment means 15, and upper attachment means 10, 11, to the crosshead 5 so as to face the lower platen 8 12 is applied to a material testing machine which includes an upper platen 7 attached via 12 and sandwiches a spring test piece between the upper platen 7 and the lower platen 8 and loads the spring test piece in the direction of the load axis G. The At least one of the upper mounting means 10, 11, 12 and the lower mounting means 15 is provided around the load axis G and at least three load cells 20 provided at substantially equal angular intervals around the load axis G. Rotation preventing means 21 for preventing rotation of the upper platen 7 and / or the lower platen 8 around the load axis G with respect to the crosshead 5 and / or the fixed table 1 , and crosses attached to both ends of the crosshead 5. Adjacent to each of the head guide 30 and the screw rod 4, the two columns 31 a and 31 b that are erected on the fixed table 1 and guide the cross head guide 30 are engaged with the two columns 31 a and 31 b. The above object is achieved by providing the reinforcing block 32 having the recesses 33a and 33b .
[0009]
In the section of the means for solving the above-described problems for explaining the configuration of the present invention, the drawings of the embodiments of the invention are used for easy understanding of the present invention. It is not limited.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 is a front view showing the configuration of a material testing machine according to the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1, FIG. 3 is a partial cross-sectional view seen from the direction of arrow A in FIG. FIG.
[0011]
As shown in FIG. 1, the material testing machine according to the present embodiment has a pair of struts (reference numerals 31 a and 31 b in FIG. 4) standing on a fixed table 1 in a pair of left and right strut covers 2. A cross yoke 3 is suspended from the upper part of the column. A pair of left and right screw rods (not shown) are erected between the fixed table 1 and the cross yoke 3, and a pair of nuts (not shown) provided on both sides of the cross head 5 are screwed to each screw rod. As a result, the crosshead 5 is supported by the screw rod. A motor (not shown) is provided in the fixed table 1, and the screw head is rotated by the driving force of the motor, and the crosshead 5 is moved up and down.
[0012]
An upper platen 7 is fixed to the lower surface of the crosshead 5 via a load rod 10 and swash plates 11 and 12. Here, the swash plates 11 and 12 adjust the inclination of the lower surface of the upper platen 7 by rotating while sliding with each other. A joint 13 for attaching a grip for performing a tensile test is attached to the top of the crosshead 5. On the other hand, a lower platen 8 is fixed to the upper surface of the fixed table 1 via an attachment portion 15.
[0013]
As shown in FIGS. 2 and 3, the attachment portion 15 includes a substrate 17, load cells 20 </ b> A to 20 </ b> C (hereinafter referred to as load cells 20) disposed on the substrate 17 around the load axis G at equal angular intervals. And guide portions 21A to 21C (hereinafter referred to as guide portions 21) disposed at equal angular intervals between the load cells 20.
[0014]
The guide portion 21 is inserted into a hole 18 formed in the substrate 17, and is supported by the bearing holder 22, the stroke bearing 23 inserted in the bearing holder 22, and the stroke bearing 23 so as to be movable in the vertical direction in FIG. And a guide shaft 25 having a protrusion 26 formed at the upper end. On the other hand, the mounting seat 27 for mounting the lower platen 8 is formed with a hole 28 at a position corresponding to the guide portion 21, and the protruding portion 26 of the guide portion 21 is inserted into the hole 28 and fastened with a bolt. Thus, the lower platen 8 is attached to the attachment portion 15.
[0015]
Here, the three load cells 20 are arranged at substantially equal intervals around the load axis G for the following reason. That is, in the case where an eccentric load acts on the lower platen 8 like a compression coil spring, if a load cell is provided at the position of the load axis G, a bending moment is generated by the eccentric load, and the compressive load can be accurately measured. It becomes impossible. Therefore, by arranging the three load cells 20 around the load axis G and averaging the measurement results of the load cells 20, the influence of the bending moment due to the eccentric load can be reduced. It is possible to accurately measure the acting compressive load.
[0016]
As shown in FIG. 4, the crosshead 5 is screwed with the screw rod 4 and moves up and down by the rotation of the screw rod 4. A crosshead guide 30 is attached to the end of the crosshead 5, and the crosshead guide 30 is guided by columns 31 a and 31 b provided inside the column cover 2. The columns 31 a and 31 b are engaged with recesses 33 a and 33 b formed in the reinforcing block 32 provided in the column cover 2. As a result, even if a torsional force about the load axis G acts on the crosshead 5 during the test, the torsional force is received by the columns 31a and 31b and the reinforcing block 32. Never do.
[0017]
Next, the operation of the present embodiment will be described.
First, the crosshead 5 is raised and a compression coil spring test piece (hereinafter referred to as a spring test piece) is placed on the lower platen 8. Then, by rotating the screw rod 4 and lowering the cross head 5, a spring test piece is sandwiched between the upper platen 7 and the lower platen 8 to apply a compressive load to the spring test piece, and the load load is loaded into the load cell. Measured by 20.
[0018]
Here, the spring test piece is not in contact with the entire surface of the lower platen 8, but is in partial contact. For this reason, when a compressive load is applied to the spring test piece, a load eccentric from the load axis G acts on the lower platen 8 as shown in FIG. In the present embodiment, since the three load cells 20 are arranged at substantially equal angular intervals around the load axis G, even if an eccentric load is applied to the lower platen 8, the load measured by the load cell 20 is averaged. By doing so, the measurement result which removed the influence of the eccentric load can be obtained.
[0019]
Further, since the spring test piece is twisted by the action of the compressive load, the lower platen 8 tries to rotate around the load axis G by the torsional force of the compressed spring test piece, but the mounting seat for holding the lower platen 8 27, since the protruding portion 26 of the guide portion 21 is inserted into the hole 28, rotation around the load axis G is prevented. Therefore, the lower platen 8 does not rotate even when a torsional force is applied by the spring test piece.
[0020]
Further, the torsional force acts on the upper platen 7 as well as the lower platen 8, but the crosshead 5 to which the upper platen 7 is fixed is fixed at both ends of the crosshead guide 30 and the columns 31a and 31b regardless of the twisting direction. And since it is supported by the reinforcing block 32, a large torsional force can be borne by the columns 31a and 31b without making the columns 31a and 31b thick.
[0021]
Furthermore, when a load acts in the direction of the load axis G due to the deformation of the spring test piece, the load cell 20 contracts and deforms in the axial direction via the mounting seat 27, and the guide shaft 25 of the guide portion 21 moves downward. Since 25 is supported by the stroke bearing 23 so as to be movable in the direction of the load axis G, the guide shaft 25 moves downward without being deformed. Therefore, the ratio that the sliding resistance when the guide shaft 25 descends is included as an error component in the load detected by the load cell 20 can be reduced, and the compressive load can be measured more accurately.
[0022]
In the above embodiment, the lower platen 8 is rotated by engaging the protrusion 26 of the guide portion 21 provided on the mounting portion 15 with the hole 28 of the mounting seat 27 fixed to the lower platen 8. On the contrary, as shown in FIG. 6, a bearing 40 may be provided instead of the guide portion 21, and the lower platen 8 may be supported rotatably without restricting the rotation. In this case, since it is not necessary to provide the crosshead guide 30, the main columns 31a and 31b, and the reinforcing block 32 for supporting both ends of the crosshead 5, the configuration of the testing machine can be simplified.
[0023]
In the above embodiment, three load cells 20 are provided around the load axis G, but four or more load cells 20 may be provided. In this case, the angular intervals of the load cells need to be substantially equal.
[0024]
Furthermore, in the said embodiment, although the three guide parts 21 are provided, you may provide one or two or more. In this case, it is desirable that the angular intervals of the guide portions are substantially equal.
[0025]
Furthermore, in the above embodiment, the lower platen 8 is fixed to the fixed table 1 by the attachment portion 15, but the upper platen 7 may be attached to the crosshead 5 by the attachment portion 15 similar to the above. Both the platen 7 and the lower platen 8 may be attached to the crosshead 5 and the fixed table 1 by the attachment portion 15.
[0026]
In the correspondence between the above embodiment and the claims, the attachment portion 15 constitutes the vertical attachment means, the guide portion 21 constitutes the rotation prevention means, and the bearing 40 constitutes the rotation holding means.
[0027]
【The invention's effect】
As described above in detail, according to the first aspect of the present invention, since at least three load cells are arranged at substantially equal angular intervals around the load axis, the upper portion of the spring test piece is compressed as in the case of compression. Even if an eccentric load acts on the platen or the lower platen, the load measured by the load cell can be averaged to remove the influence of the eccentric load and accurately measure the load acting on the spring test piece.
Also, the upper platen or the lower platen tries to rotate around the load axis due to the torsional force of the spring test piece, but the rotation is prevented by the rotation preventing means, so the upper platen or the lower platen does not rotate. .
Further, even if a torsional force about the load axis acts on the cross head during the test, the torsional force is not applied to the screw rod because the torsional force is received by the support column and the reinforcing block.
[Brief description of the drawings]
1 is a front view showing the configuration of a material testing machine according to the present embodiment. FIG. 2 is an enlarged cross-sectional view of the main part of FIG. 1. FIG. 3 is a partial cross-sectional view of FIG. Fig. 5 is a cross-sectional view taken along line II-II of Fig. 1. Fig. 5 is a view showing a screw test piece held on the lower platen. Front view showing the configuration of the material tester
DESCRIPTION OF SYMBOLS 1 Fixed table 2 Support | pillar 3 Cross yoke 4 Screw rod 5 Cross head 7 Upper platen 8 Lower platen 15 Mounting part 20 Load cell 21 Guide part 25 Guide shaft 27 Mounting seat 30 Crosshead guide 31a, 31b Post 32 Reinforcement block 40 Bearing

Claims (1)

A fixed table;
Two screw rods erected on the fixed table;
A crosshead provided on the screw rod so as to be movable up and down;
A lower platen attached to the fixed table via lower attachment means;
An upper platen mounted on the crosshead via upper mounting means so as to face the lower platen, and a spring test piece is sandwiched between the upper platen and the lower platen in the load axis direction. In a material testing machine for loading the spring test piece,
At least one of the upper mounting means and the lower mounting means is provided with at least three load cells provided at substantially equal angular intervals around the load axis;
A rotation preventing means provided around the load axis and preventing rotation of the upper platen and / or the lower platen with respect to the crosshead and / or the fixed table around the load axis ;
A crosshead guide attached to both ends of the crosshead;
Two struts standing on the fixed table adjacent to each of the screw rods and guiding the crosshead guide;
A material testing machine comprising a reinforcing block having a recess with which the two struts are engaged .

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