JPH1123436A - Auxiliary jig for tensile strength measurement and tensile strength measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the accurate measurement of a test coupon even with high tensile strength by providing a protruded stripe on the surface of the side in contact with the test coupon in a direction orthogonal or approximately orthogonal in the tension direction. SOLUTION: In a measuring test of tensile strength, an adhesive agent such as an epoxy resin is poured into the tube of an auxiliary jig 41, and the end part of a rod 10 is inserted into the tube, sticked, and hardened. Then the part of the auxiliary jig 41 installed to the rod 10 is pressurized and deformed in advance so as to hold the test coupon tightly. Next, the auxiliary jig 41 is fixed to a gripper, and tensile strength is measured. During the test, as the rod 10 is tightly fixed to the auxiliary jig 41 by a protruded stripe 42 and the adhesive agent, and the auxiliary jig 41 is further deformed as the fastening pressure of the gripper is further increased and tightly holds the rod 10 by the protruded stripe 42 on the inner surface, it is possible to fix the rod 10 further tightly. Therefore, the rod 10 is never slipped from the auxiliary jig 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary jig used for measuring tensile strength and a method for measuring tensile strength, and is particularly useful for measuring a test material having high tensile strength.

[0002]

2. Description of the Related Art When measuring tensile strength, a tensile force is applied in the longitudinal direction by sandwiching both ends of a test material formed in a predetermined shape with a gripper, and while gradually increasing this tensile force, Is the tensile strength at the time of cutting.

[0003] In this test, generally, as the tensile force increases, the clamping pressure of the gripper against the test material increases. There is also a test method in which the tightening pressure is kept constant, but when measuring a high-tension test material by this method, the test material may come off from the gripper in the process of increasing the tensile force. . This is because the test material is fixed to the gripper by a manual force with a constant force, so the fixing force is weak, and when the test material has a high tension, a large tensile force exceeding the fixing force is applied. Therefore, as mentioned earlier, a method capable of gradually increasing the tightening pressure is exclusively used.

[0004] In recent years, improvements in FRP (fiber reinforced resin) and the like have progressed, and those having extremely high tensile strength have been developed. The use of such materials such as FRP for various applications is being studied, and for this use, it is necessary to measure the tensile strength in advance.

However, since the FRP and the like have a very high tensile strength as described above, accurate measurement of the tensile strength may not be possible even when the above-mentioned measuring method is adopted. That is, for example, although FRP has a very high strength in the fiber axis direction (which is the tensile direction at the time of the test), the strength in the direction perpendicular to the fiber axis direction is relatively weak, and therefore, is gripped by the gripper during the test. May be crushed and damaged. Both ends damaged in this way are cut before the center, and the true tensile strength cannot be measured. Therefore, a method has been proposed in which an auxiliary jig is attached to an end portion of a test material sandwiched between grips, and the above-described tightening pressure is buffered to protect the test material.

FIG. 4 is a perspective view showing a state in which a rod (test material) is attached to a conventional auxiliary jig (conventional example). The auxiliary jig 11 is composed of two iron plates 12 and screws 14, sandwiches the end of the rod 10 while injecting an adhesive 13 between the two iron plates 12, and holds the two iron plates 12 with the screws 14. Tightened and fixed. Note that an FRP plate may be used instead of the iron plate 12.

FIG. 5 is a perspective view showing an auxiliary jig used in a test method of an FRP rod according to ASTM D 3916 (conventional example). The auxiliary jig 21 is made of an aluminum alloy and includes a male member 22 having a projection 22a and a female member 23 having a hole 23a for inserting the projection 22a. Member 23
Rods (test materials) in the recesses 22b and 23b provided in
The male side member 22 and the female side member 23 are tightened and used.

FIG. 6 shows a conventional auxiliary jig 31 with a rod 10.
FIG. 7 is a perspective view showing a state where the camera is mounted (conventional example). The auxiliary jig 31 includes a cylindrical portion 32 and a wedge 33. The end of the rod 10 is inserted into the cylindrical portion 32, and the rod 10 is fixed to the cylindrical portion 32 by biting the wedge 33 from the rear end of the rod 10. I do. Since the pulling direction (the direction of arrow A) at the time of the test is opposite to the insertion side of the wedge 33, the wedge 33 does not come off during the tensile test. When the tensile strength is measured, the auxiliary jigs 11, 21 and 31 attached to the test material (rod 10) as described above are fixed to the above-mentioned gripper for the test.

[0009]

However, recently, F
Improvements in RP have been further advanced, and new materials have been developed. For example, CFRP (carbon fiber reinforced resin) and GFRP (glass fiber reinforced resin) have been developed with further improved tensile strength. Even when the test was performed using the auxiliary jigs of Examples 1 to 4, there were cases where accurate measured values could not be obtained. The reason for this is that the test material comes off from the auxiliary jig during the test. If the test material comes off before cutting the test material, the tensile strength cannot be measured naturally.
Even if it does not come off, if the test material is displaced from the auxiliary jig, the tensile strength cannot be measured accurately.

[0010] This is because the auxiliary jigs of the above-mentioned conventional examples have insufficient fixing force to the test material. On the other hand, those having a high clamping pressure as in the conventional method using no auxiliary jig are used. However, the test material is damaged at the tightened portion, which also makes it impossible to measure accurately.

[0011] In addition to the above problems, since it is expected that materials having higher tensile strength will be developed in the future, the development of a technique that can accurately measure even a member having extremely high tensile strength will be developed. It is hoped that it will advance.

Therefore, in the present invention, the tensile strength is measured so that the test material does not come off or slip off from the auxiliary jig, and the end of the gripped test material is not crushed and broken. It is an object to provide an auxiliary jig for use and a method for measuring tensile strength.

[0013]

According to the present invention, there is provided an auxiliary jig for measuring tensile strength for holding an end portion of a test material under pressure, wherein the auxiliary jig has a surface in a tensile direction which is in contact with the test material. The gist of the present invention is that a ridge is provided in a direction orthogonal or substantially orthogonal to.

By providing the ridges as described above, the frictional resistance between the auxiliary jig and the test material increases, and the test material does not shift from the auxiliary jig. In addition, the auxiliary jig is appropriately deformed as the clamping pressure of the grip increases,
Increase the holding force of the test material. Therefore, as the tensile force increases, the test material will be held more strongly with it, and the test material will not shift from the auxiliary jig,
Therefore, there is no escape. On the other hand, since the clamping pressure of the gripper is relieved by the auxiliary jig, the gripped end of the test material does not break.

In the present invention, the material of the auxiliary jig is not particularly limited, but is preferably made of metal. The metal material is not too soft and not too hard and has an appropriate toughness, so that it is appropriately deformed by increasing the tightening pressure to strongly hold the test material while protecting the test material from the tightening pressure. As the metal used for the auxiliary jig,
Suitable materials include iron, copper, aluminum and the like, and alloys thereof (iron alloy, copper alloy, aluminum alloy, etc.). The thickness of the metal auxiliary jig is preferably about 0.3 to 1.5 mm.

As a material for the auxiliary jig, a synthetic resin or the like can be used in addition to the metal described above. For example, a thermoplastic resin or a thermosetting resin can be used. That is, any material may be used as long as the same effect as that of the above-described metal can be obtained. In the case of the above synthetic resin, it is preferable to use a fiber reinforced type reinforced with glass fiber, carbon fiber, or the like because the strength is improved.

When the material of the auxiliary jig is a metal, a thermoplastic resin, a thermosetting resin, or the like, a manufacturing method is as follows.
Cutting, casting, compression molding, injection molding, pultrusion molding and the like can be mentioned. At this time, the auxiliary jig may be manufactured using a shape such that a convex pattern is provided on the contact side surface of the auxiliary jig, or a mold having no convex pattern may be used. The ridges may be formed by post-processing.

Further, in the present invention, the auxiliary jig has a cylindrical shape, an inner surface of the cylinder is a surface on a contact side with the test material, and the protruding line is a spiral line along the inner surface of the tube. Preferably, there is.

The pitch of the spiral strip is not particularly limited, and may be appropriately adjusted in consideration of the material of the test piece, the expected strength, and the like. The formation of the spiral strip may be performed by post-processing using a die or the like on the cylinder having no convex strip, and the present invention is not limited to such post-processing. As a matter of course, it is also possible to use a cylinder which has been previously manufactured so as to have a ridge.

In the tensile strength measuring method according to the present invention, the tensile strength test is performed by holding an end portion of the test material under pressure on an auxiliary jig for measuring tensile strength and deforming the auxiliary jig. And As described above, when the auxiliary jig is deformed, the force for holding the test material is improved, and the test material does not come off during the test. In addition, in the present invention, it is preferable to conduct a tensile strength test in a state where an adhesive is interposed between the contact surface of the auxiliary jig for measuring tensile strength and the test material.

By interposing the adhesive in the auxiliary jig as described above, the fixing force of the auxiliary jig to the test material can be further increased, and the displacement of the test material during the test can be further reduced. It can be further prevented.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an auxiliary jig for measuring tensile strength according to the present invention will be specifically described with reference to the drawings showing embodiments, but the present invention is not limited to the illustrated examples. However, the present invention can be appropriately modified and implemented within a range that can be adapted to the gist of the preceding and following descriptions, and all of them are included in the technical scope of the present invention.

FIG. 1 is a perspective view showing a state in which a test material (rod 10) is attached to an auxiliary jig for measuring tensile strength according to Embodiment 1 of the present invention. The auxiliary jig 41 is made of iron,
Has moderate toughness. The auxiliary jig 41 has a cylindrical shape so that the rod 10 can be inserted into the cylinder. On the inner surface of the cylinder of the auxiliary jig 41 that comes into contact with the rod 10, a spiral ridge 42 is provided along the inner surface of the cylinder. The convex shape is substantially orthogonal to the tension direction, and the pitch interval of the spiral ridge 42 is 1.33 to 1.4.
mm, and the ridge 42 can be easily formed by tapping with a tap. Instead of the spiral ridge, several annular ridges may be used.

At the time of the tensile strength measurement test, an adhesive such as an epoxy resin is poured into the cylinder of the auxiliary jig 41,
The end of the rod 10 is inserted into the cylinder to be fixed and hardened. Needless to say, the type of the adhesive is not limited, and any adhesive may be used as long as the adhesive can exhibit sufficient strength.

Then, the auxiliary jig 41 attached to the rod 10 is deformed by applying pressure in advance, so that the test material is strongly held. Next, the auxiliary jig 41 is fixed to a gripper (such as a chuck), and the tensile strength is measured. The tension is applied in the direction of arrow A in the figure.

During the test, the rod 10 is firmly fixed to the auxiliary jig 41 by the ridge 42 and the adhesive, and as the clamping pressure of the gripper increases, the auxiliary jig 41 becomes more rigid. The rod 1 is deformed by the ridge 42 on the inner surface.
By pressing down on 0, it can be fixed more firmly. Therefore, the rod 10 does not shift from the auxiliary jig 41.

On the other hand, even if the rod 10 is made of a material that is weak in the direction perpendicular to the fiber axis direction, such as CFRP, the clamping pressure of the gripper is not directly transmitted to the rod 10, but is buffered by the auxiliary jig 41 (weaker). Will be transmitted)
It does not reach the point where the rod 10 is crushed and broken.

That is, the auxiliary jig 41 exhibits both an effect as an anchor for firmly fixing the rod 10 to the auxiliary jig 41 and an effect as a cushion for protecting the rod 10 from the force of the gripper.

Therefore, the rod portion to be cut by applying tension during the test is, for example, the center portion, and is not cut at the mounting portion of the rod 10. Since this is a cut purely by tension, it can be read as an accurate value of tensile strength.

It should be noted that the auxiliary jig 41 may be immediately fixed to the gripper without previously deforming the auxiliary jig 41 as described above. In this case, the auxiliary jig 41 is fixed by the clamping pressure of the gripper.
1 deforms and firmly fixes the rod 10.

In the above example, the adhesive is used when attaching the auxiliary jig to the test material. However, the auxiliary jig may be attached without using the adhesive. When the adhesive is used, the inner surface of the auxiliary jig 41 (the ridge 4
2 and its valley portion) and the rod 10 (test material) are interposed between the rods and the rods (test material), so that the rods 10 and the rods 10 are more strongly fixed. Therefore, it is more preferable to use an adhesive.

FIGS. 2 and 3 are perspective views showing a state where a rod 10 is attached to an auxiliary jig for measuring tensile strength according to Examples 2 and 3 of the present invention. The auxiliary jig 51 (Example 2) shown in FIG. 2 does not form a ridge on the entire inner surface of the auxiliary jig 41, but has a spiral ridge 52 along the inner surface of the cylinder only at both ends thereof.
a, 52b. The auxiliary jig 61 (Example 3) shown in FIG. 3 has a spiral ridge 62 provided only at one end of the auxiliary jig.

The rod 10 can be firmly fixed in the same manner as in the first embodiment even if the protrusion is partially provided in this manner, and the rod 10 is prevented from being displaced from the auxiliary jig 41. it can.

The auxiliary jig may be made of copper.
As described above, it is deformed moderately by the clamping pressure of the gripper,
Improves the holding force of the rod (test material) and prevents the rod from shifting from the auxiliary jig.

The thickness of the auxiliary jig is not particularly limited. However, when the tensile strength is measured by a normal tensile tester, the thickness is preferably 0.3 to 1.3 mm for iron. Preferably it is 0.3 to 1.0 mm. In the case of copper, the material is softer than iron.
5 mm is preferred. If the thickness is more than 1.3 mm for iron and 1.5 mm for copper, it hardly deforms even when the clamping pressure of the gripper is increased, and the holding force on the test material does not increase, so the test material is displaced. On the other hand, iron:
If the thickness is smaller than 0.3 mm and copper: 0.7 mm, the test material cannot be protected from the clamping pressure of the gripper.

The auxiliary jig is not limited to the integral cylindrical type as in the above embodiment, but may be a cylindrical member divided into two in the longitudinal direction, or a test material made of two plate members. In any case, a strong fixing force can be obtained by the ridges.

In addition, the ridges are not limited to the ridges formed in the substantially orthogonal direction by spirally cutting as described above, but may be formed in the orthogonal direction.
The shape of the test material is not limited to the rod shape described above, and the auxiliary jig according to the present invention can be used when measuring a test material having another shape such as a plate-like test material.

<Experiment 1> As an example of the present invention, an auxiliary jig 51 of Example 2 shown in FIG. 2 was used. The auxiliary jig 51 is provided with a ridge provided by threading a steel cylinder with a tap, and the pitch of the ridge is 1.33 mm.

While inserting the end of the test material (rod 10) into the auxiliary jig 51, an amine-curable epoxy resin is interposed in the auxiliary jig 51, and these are adhered to each other. Test machine: Shimadzu Autograph AD25TD manufactured by Shimadzu Corporation.

On the other hand, as a comparative example, a cylindrical iron auxiliary jig having no convex line formed on the inner surface side was used, and the auxiliary jig was inserted into the auxiliary jig in the same manner as described above. These are adhered to each other with an amine-curable epoxy resin interposed in the fixture, and a tensile strength test (tensile tester: Shimadzu Autograph AD25
TD Shimadzu Corporation). Various CFRP rods were used as the test materials. The measurement results are shown in Table 1 below.

[0041]

[Table 1]

In the comparative example, the rod was shifted from the auxiliary jig. On the other hand, in the example of the present invention, accurate measurement could be performed without the rod being displaced from the auxiliary jig. In the comparative example, since the measurement was shifted as described above, the measurement result was slightly low as shown in Table 1 above, and the measurement could not be performed accurately.

<Experiment 2> In this experiment 2, the auxiliary jig 51 was not interposed between the auxiliary jig 51 and the test material.
The test material was attached as it was, and a tensile strength test was performed.
As the auxiliary jig, a steel cylinder which was threaded with a tap and provided with ridges as in Example 2 shown in FIG. 2 was used. The pitch of the ridges is 1.33 mm. Various GFRP rods were used as test materials. The measurement results are shown in Table 2 below.

[0044]

[Table 2]

In the comparative example, the rod came off the auxiliary jig, and the tensile strength could not be measured. On the other hand, in the example of the present invention, the rod was not displaced from the auxiliary jig, and did not come off.

<Experiment 3> A cylindrical auxiliary jig made of copper and having a ridge in the cylinder, one having no ridge,
Alternatively, for an auxiliary jig having a cylindrical shape made of iron and having a ridge in the cylinder, an experiment was conducted to examine a limit at which the tensile strength can be accurately measured (hereinafter sometimes referred to as a measurement limit). The auxiliary jig had a thickness of 1 mm and a pitch of the ridge of 1.3 mm. At the time of the experiment, after injecting the adhesive into the auxiliary jig, insert the rod and fix it,
A tensile strength test was performed.

As a result, a copper auxiliary jig having no ridges can be used.
Has a measurement limit of 80-100 kgf / mm ^Two Despite the degree
However, with a copper auxiliary jig having a ridge, the measurement limit is 140
~ 160kgf / mm^Two Had improved to a degree. Also has ridges
With iron auxiliary jigs, the measurement limit is 180-200kgf / mm
^Two The degree was high.

Therefore, it can be seen that the copper auxiliary jig and the iron auxiliary jig having the convex strip can accurately measure even if the test material has a high strength. Further, it can be seen that, in the case of an iron auxiliary jig having convex ridges, the tensile strength can be accurately measured even with a very high-strength test material such as CFRP. In addition, it has been confirmed that the aluminum auxiliary jig having the ridge has almost the same measurement limit as that of the copper auxiliary jig, and the aluminum auxiliary jig (with the ridge) has a high strength test material. Can be measured.

In a tensile strength test using an auxiliary jig having a ridge, the measurement limit was examined for the case where an adhesive was used and for the case where an adhesive was not used. Showed the limits. Therefore, when an adhesive is used in addition to the provision of the ridge on the auxiliary jig, a very high-strength test material can be measured.

[0050]

In the auxiliary jig for measuring tensile strength according to the present invention, the test material does not shift from the auxiliary jig during the test, and the gripped portion of the test material is crushed and broken. Never do. Therefore, even when a test material having a high tensile strength is measured, the tensile strength can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state where an auxiliary jig for measuring tensile strength according to a first embodiment of the present invention is attached to a rod.

FIG. 2 is a perspective view showing a state where an auxiliary jig for measuring tensile strength according to a second embodiment of the present invention is attached to a rod.

FIG. 3 is a perspective view showing a state where an auxiliary jig for measuring tensile strength according to a third embodiment of the present invention is attached to a rod.

FIG. 4 is a perspective view showing a state where an auxiliary jig according to a conventional example is attached to a rod.

FIG. 5 is a perspective view showing an auxiliary jig according to a conventional example.

FIG. 6 is a perspective view showing a state where a rod is attached to an auxiliary treatment according to a conventional example.

[Explanation of symbols]

 Reference Signs 10 Rod 11, 21, 31, 41, 51, 61 Auxiliary jig 42, 52a, 52b, 62

Claims (4)

[Claims] 1. An auxiliary jig for measuring tensile strength for pressurizing and holding an end of a test material, wherein the auxiliary jig is orthogonal or substantially orthogonal to a surface on a contact side of the auxiliary jig with the test material. An auxiliary jig for measuring tensile strength, characterized in that a ridge is provided in a direction. 2. The auxiliary jig has a cylindrical shape, an inner surface of the tube is a surface on a contact side with the test material, and the convex line is a spiral line along the inner surface of the tube. Auxiliary jig for measuring tensile strength according to 1. 3. An auxiliary jig for measuring tensile strength according to claim 1 or 2, wherein an end of the test material is pressed and held, and the auxiliary jig is deformed to perform a tensile strength test. Tensile strength measurement method. 4. The tensile strength measuring method according to claim 3, wherein a tensile strength test is performed with an adhesive interposed between a contact surface of the auxiliary jig for measuring tensile strength and the test material.