JP2001255249A - Chuck of tensile tester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life chuck capable of executing a tensile test by gripping directly a high-strength steel bar. SOLUTION: The end part of a grip piece 15 inserted into a groove formed on a grip holder 14 is locked by a presser plate 16, and cushioning material 17 is inserted between the grip piece 15 and the presser plate 16. The grip piece 15 comprises high speed steel having HRC 60 or more, and the grip holder 14 comprises heat treated alloy steel having HRC 45-58.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chuck for a tensile tester for gripping a test piece in a tensile test, and more particularly to a chuck suitable for a high-strength material such as a PC steel rod or a spring steel wire. It is.

[0002]

2. Description of the Related Art In general, the mechanical strength of a material is measured using a tensile tester as shown in FIG. This tester measures the tensile strength by gripping and pulling a test piece P with a chuck 10 as shown in FIG. 1 provided at a portion indicated by A in FIG.

As shown in FIG. 4, a conventional chuck grips a test piece by holding a grip piece 14 having serrations 15a cut into a grip holder 14, as shown in FIG.
A grip fixed by the holding plate 16 is used.
Conventionally, a carbon steel material is used for the grip piece and the grip holder.

[0004]

However, when a tensile test is performed on a high-strength steel rod having a hardness of HRC45 or more, such as a PC steel rod, using a conventional commercially available chuck, the serrations 15a of the grip piece 15 shown in FIG. Wear is significant, 1
After two tests, it could not be used. Therefore, it was practically difficult to perform a tensile test on such a high-strength steel rod by directly gripping the test piece.

[0005] Further, the grip holder for holding the grip piece also cracked as shown in FIG. 5 during the test, and was broken in about four months of use. Further, the pressing plate 16 'of the grip piece 15 in FIG. 4 also has a service life similar to that of the grip holder because the contact surface with the grip piece 15 is deformed by the impact.

Accordingly, an object of the present invention is to provide a chuck for a tensile tester having a long life, which can solve the above-mentioned drawbacks and can perform a tensile test by directly gripping even a high-strength steel rod.

[0007]

To achieve the above object, a chuck of a tensile tester according to the present invention comprises a grip piece for gripping a test piece and a buffer piece placed on a grip holder for holding the grip piece. Is held.

As a method for loading the cushioning material, a groove is provided in the grip holder so as to extend the test piece in the pulling direction of the test piece and into which the grip piece is inserted, and the end of the grip piece inserted in the groove in the pulling direction is provided. Preferably, the portion is locked by a holding plate attached to an end of the grip holder in the pulling direction, and a cushioning material is inserted between the grip piece and the holding plate.

In other words, by doing so, the shock applied to the holding plate when the test piece breaks in the tensile test is absorbed by the cushioning material, so that the deformation of the contact surface between the holding plate and the grip piece is reduced. Thus, the life of the grip holder and the holding plate can be extended.

It is preferable that the grip piece for gripping the test piece is made of high-speed steel heat-treated to a hardness of HRC 60 or more in order to reduce the wear of serrations of the grip piece and extend the life. Is preferably made of an alloy steel heat-treated to HRC 45 to 58 in order to increase the impact resistance of the grip holder and reduce cracking. This hardness is more desirably HRC 50-53.

It is desirable that the width of at least one side of the edge of the groove into which the grip piece of the grip holder is inserted be at least 2.5 times the thickness of the grip piece in order to reduce cracking. More preferably, it is three times or more. In order to prevent cracking as shown in FIG. 5, it is desirable to increase the width t of the edge of the groove into which the grip piece is inserted, but in many cases, this width cannot be increased due to the structure of the machine. The present inventors have found that if the width of the edge is at least 2.5 times the thickness of the grip piece, cracks can be greatly reduced. The expansion of the groove at the edge is desirable on both sides, but the effect can be improved on one side.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to one embodiment shown in the drawings. 1 is a sectional view of a chuck according to an embodiment of the present invention, FIG. 2 is an exploded view of the grip, FIG. 3 is an overall view of a tensile tester used in the embodiment of the present invention, and FIG. 4 is a perspective view of a conventional grip.

First, the tensile tester shown in FIG. 3 will be briefly described. The tensile tester 1 comprises an upper saddle 3 supported by two columns 2 and a lower saddle which slides up and down the columns 2 by a hydraulic cylinder 5. 4, the test piece P is gripped by chucks 10 provided on the upper and lower saddles 3, 4, and the lower saddle is moved by the hydraulic cylinder 5 so that the test piece P
Is pulled to break, and the breaking load is displayed on the dial 6. The present invention relates to a chuck 10 for holding the test piece.

As shown in detail in FIG.
It comprises a chuck frame 11 and a chuck piece 12 fixed to the upper and lower saddles 3 and 4, respectively, and a grip 13 for holding a test piece.

The chuck frame 11 includes upper and lower saddles 3 and 4
And a groove having a tapered surface 11a inside is provided. The chuck piece 12 holding the grip 13 is inserted into this groove, and the tapered surface 11 supports the outer tapered surface 12 a of the chuck piece 12.

The grip 13 is held in a recess provided on the inner surface of the chuck piece 12. As shown in detail in FIG. 2, the grip 13 includes a grip holder 14, a grip piece 15, a pressing plate 16, and a cushioning material 17.

The grip piece 15 has inclined surfaces 15 on both sides.
The serration 15a is formed in a trapezoidal cross-section plate shape having a cross section b and crossed at an angle of 60 degrees on the top surface of the trapezoid.

The grip holder 14 has a dead end groove 14a extending in the pulling direction. The side surface of the groove 14a has a taper that fits with the inclined surface 15b of the trapezoidal cross section of the grip piece 15, and the grip piece 15 is inserted and held in this groove.

On the end face of the grip holder 14 opposite to the end of the groove, a holding plate 16 is provided with a screw 1 via a cushioning material 17.
8 attached. Thereby, the grip holder 14
Of the grip piece 15 inserted into the groove 14a, the inclined surfaces on both sides are held by the inclined surfaces on the side of the groove 14a, and both ends are provided with the pressing plate 16 with the dead end of the groove 14a and the cushioning material 17 interposed therebetween.
And is mounted on the grip holder.

With the above structure, when the chuck frame 11 is moved upward in the drawing with the test piece P interposed between the grip pieces 15 shown in FIG. 1, the tapered surface 11 of the chuck frame 11 and the tapered surface 12a of the chuck piece 12 Slides, the space between the grip pieces 15 becomes narrow, and the test piece P is securely held.

In the conventional grip, the cushioning material is not used for the holding plate as in the present invention, and the grip piece is mounted by directly contacting the holding plate with the holding plate. According to the present invention, by providing a cushioning material between the holding plate and the grip piece, the shock during the tensile test is absorbed to prevent deformation of the holding plate, thereby extending the life of the holding plate.

(Embodiment) In this embodiment, the dimensions of the grip holder 14 are 90 mm wide × 100 mm long × 40 m thick.
m, and the dimensions of the grip piece 15 were 50 mm wide × 85 mm long × 10 mm thick. The grip holder 14 used was SCM435 of chromium molybdenum steel heat-treated to the hardness of HRC40. Also, the grip piece 15 uses SKH51 heat-treated to HRC63,
Urethane rubber was used as a cushioning material.

The width t of the edge of the groove into which the grip piece of the grip holder shown in FIG. 2 is inserted has been increased from about 10 mm to 30 mm on one side. As a result, the width of the conventional grip piece was 1 time,
Doubled.

As a result, the life of the grip piece is extended from one or two times to about one month in the past, so that a tensile test can be performed by directly gripping a high-strength PC steel rod or the like, which has been difficult in the past. As a result, the production cost of the test piece can be reduced and the tensile test can be performed efficiently. In addition, the life of the grip holder and the holding plate can be extended to two years or more from the conventional four months. As a result, a significant improvement in work efficiency and cost reduction was achieved.

In this embodiment, the grip holder is SC
Although M435 was used, other alloy steels may be used.
Although SKH51 was used as the grip piece, other high-speed steel or die steel may be used. Although urethane rubber was used as the cushioning material, other elastic materials such as high-strength synthetic rubber can also be used.

[0026]

As described above, according to the chuck of the tensile tester of the present invention, it is possible to perform a tensile test on a high-strength PC steel bar or the like, which has conventionally been difficult to directly grip and test. Therefore, the production of the test piece was simplified, and the efficiency of the test operation was improved. In addition, the life of the grip holder, grip piece, etc. has been greatly improved, which has made it possible to reduce costs.

[Brief description of the drawings]

FIG. 1 is a sectional view of a chuck of a tensile tester according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the grip according to the embodiment of the present invention.

FIG. 3 is an overall view of a tensile tester used in Examples of the present invention.

FIG. 4 is a perspective view of a conventional grip.

FIG. 5 is a view for explaining the state of occurrence of cracks in a conventional grip holder.

[Explanation of symbols]

1 tensile tester, 2 columns, 3 upper saddle, 4 lower saddle, 5 hydraulic cylinder, 6 dial, 10 grip, 11 chuck frame, 12 chuck piece,
13 grip, 14 grip holder, 15 grip piece, 16 holding plate, 17 urethane rubber (buffer), 18 bolt, P test piece

Claims (5)

[Claims] 1. A chuck for a tensile tester, wherein a gripping member is held on a grip piece for gripping a test piece and a grip holder for holding the grip piece. 2. The grip holder is provided with a groove extending in the pulling direction of the test piece to insert the grip piece, and the end of the grip piece inserted in the groove in the pulling direction is pulled by the grip holder. The chuck according to claim 1, wherein the chuck is locked by a holding plate attached to the end in the direction, and a cushioning material is inserted between the grip piece and the holding plate. 3. The grip piece for gripping the test piece is HR
The chuck according to claim 1, wherein the chuck is made of a high-speed steel heat-treated to a hardness of C60 or more. 4. The chuck according to claim 1, wherein the grip holder for holding the grip piece is made of an alloy steel heat-treated to HRC 45 to 58. 5. The grip holder according to claim 2, wherein the width of at least one side of the edge of the groove into which the grip piece of the grip holder is inserted is at least 2.5 times the thickness of the grip piece. The chuck of the tensile tester described.