JP2008241530A - Stress test fixture and stress test method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stress test fixture for preventing a test piece from being buckled in a tensile and compression stress test, and a tensile and compression stress test method using it. <P>SOLUTION: In the stress test fixture provided with two flanges having respective recesses for holding an end of the test piece, the test piece is loaded with a compression stress or a tensile stress by applying the compression stress or the tensile stress to the test piece from one or both of the flanges, and at least two guide materials are installed in the direction parallel to the direction of the stress load applied to the test piece as to always match the direction of the stress load applied to the test piece with the longitudinal direction of the test piece during the stress test. The stress test method implements one or two or more compression tests or tensile tests for applying a distortion of 1.5% or more to the test piece. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stress test jig and a stress test method, and more particularly, to a metal material compression and tension test jig and a compression and tension test method.

  Since steel pipes for line pipes for transporting fluids such as oil and natural gas that are laid by reel purge are repeatedly subjected to tensile and compressive stresses, tensile and compressive strains caused by these stresses are applied. However, since such a metal material such as a steel pipe has a problem of mechanical performance after being imparted with tensile compressive strain, a test for applying repeated tensile compressive strain to a test piece is required.

  However, in a test in which repeated tensile and compressive strain is applied in the axial direction of a test piece cut out from such a metal material such as a steel pipe, the test piece is likely to buckle, and once per several tests. The fact is that buckling occurs at a rate. And every time buckling occurs, there is a problem that the test is forced to be interrupted.

  In addition, regarding the compression test of a metal material, as seen in Non-Patent Document 1, a standard is established in ASTM E9-89a.

  FIG. 1 is a side view showing an example of a stress test jig 1 used in a compression test of a metal material. The test piece P is held with both ends sandwiched between the upper and lower flanges 2a, 2b. The upper and lower flanges 2a and 2b are fixed to the fixing members 3a and 3b by bolts 4, respectively. Here, the upper fixing member 3a for fixing the upper flange 2a is movable in the vertical direction. A rod fixing hole 7 is formed in the upper part of the upper fixing member 3a and a female screw is cut.

  FIG. 2 is a side view showing a state in which the stress test jig 1 shown in FIG. 1 is attached to a tensile tester 5 capable of a compression test.

  When a compression test is performed using the stress test jig 1, the stress test jig 1 holding the test piece P is placed between the lower movable crosshead 9 and the base member 20 of the tensile tester 5. The test piece P held between the upper and lower flanges 2a, 2b is a rod 6 attached below the lower movable crosshead 9 via a movable upper fixing member 3a for fixing the upper flange 2a. By receiving the force downward, a compressive stress is applied vertically from the vertical direction along the axis. Note that a male screw is cut at the tip of the rod, and the rod is screwed into a rod fixing hole 7 formed in the upper portion of the upper fixing member 3a of the stress test jig 1.

  On the other hand, when performing the tensile test, the stress test jig 1 holding the test piece P is installed between the upper fixed crosshead 8 and the lower movable crosshead 9 of the tensile tester 5, and the test piece is tested. A tensile stress is applied to P vertically from the vertical direction along the axis.

  Patent Document 1 proposes a compression test jig for enabling a compression test of a metal material such as a thick steel plate using an existing tensile tester as it is. In order to convert the tensile stress applied by the tensile testing machine to the horizontal direction, a test piece is installed horizontally in a rockable rhomboid base frame, and this base frame is pulled outward in the vertical direction. By applying the stress, a compressive stress is applied to the horizontally installed test piece along the axis from the horizontal direction to the inward direction.

JP 2003-185545 A ASTM E9-89a (Reapproved 2000) “Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature” p. 110-118 (issued in 2000)

  As described above, in a test in which repeated tensile compression strain is applied in the axial direction of a test piece cut out from a metal material such as a steel pipe, the test piece is likely to buckle, and the test is interrupted each time. The problem of being driven into. In particular, the problem of buckling is significant in a stress test in which compression and tension are repeated.

  However, Non-Patent Document 1 only describes that the compressive stress F is applied from the vertical direction along the axis of the test piece P installed vertically, and the test cut out from the metal material. There is no description about the occurrence of buckling in a test piece made of a metal material in a test in which repeated tensile compression strain is applied to the piece.

  Further, the compression test jig described in Patent Document 2 is for enabling a compression test of a metal material using a tensile tester, and for applying an outward tensile stress in the vertical direction in the horizontal direction. It is converted into a compressive stress in the direction, and the compressive stress is applied to the test piece installed horizontally from the horizontal direction inward along the axial center. And here, it is described that the crushed pieces can be prevented from scattering due to buckling of the test piece P and the like, and that a safe and efficient test operation can be realized. There is no mention of preventing bending itself.

  In view of such circumstances, the present invention provides a stress test jig capable of preventing the occurrence of buckling in a stress test in which compressive stress or tensile stress is applied to a test piece cut out from a metal material such as a steel pipe. An object of the present invention is to provide a stress test method using the stress test jig.

  As a result of various studies and experiments on the cause of buckling and its prevention method, the present inventors have obtained the following findings (a) to (f).

  (a) Buckling occurs because stress is applied in a direction different from the longitudinal direction of the test piece because play is provided when the test piece is attached to the stress test apparatus.

  (b) Therefore, in order to prevent the occurrence of buckling, it is conceivable to improve the machining accuracy of the test piece and reduce the play amount. However, the machining accuracy of the test piece is improved to the extent that buckling does not occur. It was difficult to do.

  (c) Next, with the idea that stress should not be applied in a direction different from the longitudinal direction of the test piece even if the play amount of the stress test apparatus is left as it is, As a result of further examination and experiment, if at least two guides are installed in parallel to the stress load direction on the test piece in the stress test jig incorporated in the stress test device, the direction is different from the longitudinal direction of the test piece. It has been found that since no stress is applied, the occurrence of buckling can be prevented.

  (d) That is, at least two guides are installed in parallel to the stress load direction on the test piece in a stress test jig having two flanges having recesses capable of holding the end of the test piece. It has been found that by holding the test piece between two flanges so that the stress load direction on the test piece and the longitudinal direction of the test piece always coincide during the stress test, the occurrence of buckling can be prevented. In addition, it is preferable to cut a female screw in the recessed part which can hold | maintain the edge part of a test piece, and to cut a male screw in the edge part of a test piece. The two flanges are preferably arranged in the vertical direction with respect to the test piece, but may be arranged in the horizontal direction. In addition, it is preferable to apply the stress to the test piece by moving the fixing members that respectively fix the two flanges. At this time, only one of the fixing members that fix the flange may be moved, or both of them may be moved. You may move it.

  (e) When such a stress test jig is used, a compressive stress and a tensile stress can be alternately applied to the test piece, so that repeated tensile and compressive strain can be applied to the test piece. Therefore, it is possible to perform a test in which repeated tensile and compressive strain is applied in the axial direction of a test piece cut out from a metal material such as a pipe material that is repeatedly subjected to tensile and compressive stress without causing buckling. This test can be applied to metal materials such as steel and aluminum. In addition, it is preferable that a test piece is made into a round bar shape, and the tensile compression strain can affix one or two or more strain gauges on the surface of a test piece.

  (f) Such a stress test jig can be incorporated into a tensile tester or a compression tester to perform a stress test, or can be incorporated into a fatigue tester to perform a stress test.

  The present invention has been completed based on such knowledge, and the gist thereof is the following (1) to (9) stress test jig and (10) to (11) stress test method. . Hereinafter, the present invention (1) to the present invention (11), respectively. The present invention (1) to the present invention (11) may be collectively referred to as the present invention.

  (1) It has two flanges with recesses that can hold the end of the test piece, and compressive or tensile stress is applied to the test piece from one or both of these flanges. A stress test jig for applying a compressive stress or a tensile stress, wherein at least two guide members are stress loaded on the test piece so that the stress load direction on the test piece and the test piece longitudinal direction always coincide during the stress test. A stress test jig characterized by being installed in parallel to a direction.

  (2) Test by having two flanges with recesses that can hold the end of the test piece and alternately applying compressive stress and tensile stress to the test piece from one or both of these flanges A jig for stress testing in which compressive stress and tensile stress are alternately applied to a piece, and at least two guide materials are tested so that the stress loading direction on the specimen and the longitudinal direction of the specimen always coincide during the stress test. A jig for stress testing, characterized in that the jig is installed in parallel to the direction of stress loading on the piece.

  (3) The stress test jig according to (1) or (2) above, wherein two flanges are arranged above and below the test piece.

  (4) One or both of the fixing members that fix the flange are movable, and compressive stress or tensile stress is applied to the test piece by applying stress to the fixing member. 3) The stress test jig according to any one of the above.

  (5) The stress according to (4) above, wherein the recess capable of holding the end of the test piece is internally threaded, and the end of the test piece is externally threaded. Test jig.

  (6) The stress test jig according to any one of (1) to (5) above, wherein the test piece is a material cut out from a pipe material.

  (7) The stress test jig according to any one of (1) to (6) above, which is used in a tensile tester.

  (8) The stress test jig according to any one of (1) to (6) above, which is used in a compression tester.

  (9) The stress test jig according to any one of (1) to (6) above, which is used in a fatigue tester.

  (10) Using the stress test jig of any of (1) to (9) above, perform a compression test or a tensile test that imparts a strain of 1.5% or more to the test piece once or twice or more. A stress test method characterized by the above.

  (11) Using the stress test jig of any of (1) to (9) above, repeat the compression test and the tensile test that give a strain of 1.5% or more to the test piece once or twice or more A stress test method characterized by the above.

  According to the stress test jig according to the present invention, it is possible to prevent the occurrence of buckling in a stress test in which a compressive stress or a tensile stress is applied to a test piece cut out from a metal material such as a steel pipe, and to repeat the test piece. It is also possible to impart tensile compression strain.

  Hereinafter, the present invention will be described with reference to the drawings. The present invention is not limited to the following examples.

  FIG. 3 is a side view showing an example of a stress test jig according to the present invention. The upper and lower flanges 2a and 2b each have a recess 12 that can hold the end of the test piece P, and the end of the test piece P is screwed and held in the upper and lower flanges 2a and 2b, respectively. . The test piece P has male screws 15 cut at both ends, and a female screw 16 cuts in the recess 12 of the flange. The upper and lower flanges 2a, 2b are fixed to the fixing members 3a, 3b by bolts 4, respectively. A rod fixing hole 7 is formed in the upper portion of the upper fixing member 3a and a female screw is cut. The upper fixing member 3a for fixing the upper flange 2a is movable in the vertical direction, but the upper fixing member 3a has two holes 11, and the guide 10 is provided vertically in each hole 11. It is arranged to penetrate in the direction.

  The test piece is a material cut out from a steel pipe for pipeline into a round bar shape (parallel portion diameter 20 mm, parallel portion length 40 mm), and two strain gauges (not shown) are provided on the surface of the test piece P. It is affixed. Further, although two guide materials are used in the stress test jig here, the number of guide materials is not limited to two, and even if there are three or four or more, the stress load direction and test on the test piece during the stress test are performed. Since the longitudinal directions of the pieces can always coincide with each other, the occurrence of buckling can be prevented.

  FIG. 4 is a side view showing a state in which the stress test jig 1 shown in FIG. 3 is attached to a tensile tester 5 that can also perform a compression test.

  When a compression test is performed using the stress test jig 1, the stress test jig 1 holding the test piece P is placed between the lower movable crosshead 9 and the base member 20 of the tensile tester 5. The test piece P held between the upper and lower flanges 2a, 2b is a rod 6 attached below the lower movable crosshead 9 via a movable upper fixing member 3a for fixing the upper flange 2a. By receiving the force downward, a compressive stress is applied vertically from the vertical direction along the axis. Note that a male screw is cut at the tip of the rod, and the rod is screwed into a rod fixing hole 7 formed in the upper portion of the upper fixing member 3a of the stress test jig 1. When compressive stress is applied vertically from the vertical direction along the axis of the test piece P, the upper fixing member 3a is provided with two guides 10 penetrating in the vertical direction. When the member 3a is moved downward, no stress is applied in a direction different from the longitudinal direction of the test piece, so that it is possible to reliably apply a compressive stress in the same direction as the axis of the test piece and Occurrence can be prevented.

  On the other hand, when performing the tensile test, the stress test jig 1 holding the test piece P is installed between the upper fixed crosshead 8 and the lower movable crosshead 9 of the tensile tester 5, and the test piece is tested. A tensile stress is applied to P vertically from the vertical direction along the axis. Also at this time, since the two guides 10 are vertically disposed in the upper fixing member 3a, the tensile stress is reliably applied in the same direction as the axis of the test piece during the tensile test. can do.

  Here, the stress test jig is incorporated into a tensile tester or a fatigue tester to perform a compression tensile test. However, the stress test can be performed even when incorporated into a compression tester.

  Next, an experiment for applying repeated tensile compression strain was performed. When the test piece as described above is held in the stress test jig shown in FIG. 3 and attached to a fatigue tester (not shown), the test piece is subjected to repeated tensile compression strain up to ± 3%. The result of measuring the SS curve (Stress Strain Curve) is shown in FIG. The number of repetitions was four. As a result, no sudden decrease in stress and strain was observed, so that it was confirmed that there was no occurrence of buckling even when repeated tensile and compressive strains were applied, and that a tensile and compressive test could be performed.

  In addition, the test piece can be not only a material cut out from the tube material but also a material cut out from a metal material such as a steel plate, a steel bar or a wire, and the two flanges of the stress test jig are horizontal to the test piece. You may arrange in the direction. The stress on the test piece may be applied by moving both of the fixing members that fix the flange.

  According to the present invention, it is possible to prevent occurrence of buckling in a stress test in which compressive stress or tensile stress is applied to a test piece cut out from a metal material such as a steel pipe, and to provide a desired number of repeated tensile compressive strains. A compression test can be performed.

It is a side view which shows an example of the stress test jig | tool 1 used in the compression test of a metal material. It is a side view which shows the condition which attached the stress test jig | tool 1 shown by FIG. 1 to the tension test machine 5 which can also perform a compression test. It is a side view which shows an example of the stress test jig | tool concerning this invention. It is a side view which shows the condition which attached the stress test jig | tool 1 shown by FIG. 3 to the tensile testing machine 5 which can also perform a compression test. The SS curve when repeatedly applying compressive tensile strain is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stress test jig 2a, 2b Flange 3a, 3b Fixing member 4 Bolt 5 Tensile tester 6 Rod 7 Rod fixing hole 8 Fixed crosshead 9 Movable crosshead 10 Guide 11 Hole 12 Recessed part 15 Male screw 16 Female screw 20 Base member P Test piece

Claims (11)

  It has two flanges with recesses that can hold the ends of the specimen, and compressive stress or tensile stress is applied to the specimen by applying compressive stress or tensile stress to the specimen from one or both of these flanges. A stress test jig for applying a tensile stress, wherein at least two guide members are parallel to the stress load direction with respect to the test piece so that the stress load direction with respect to the test piece always coincides with the test piece longitudinal direction during the stress test. A jig for stress testing, characterized by being installed in   It has two flanges with recesses that can hold the end of the test piece, and compresses the test piece by alternately applying compressive stress and tensile stress to the test piece from one or both of these flanges A stress test jig for alternately applying stress and tensile stress, wherein at least two guide members are stresses on the test piece so that the stress loading direction on the test piece and the test piece longitudinal direction always coincide during the stress test. A stress test jig characterized by being installed in parallel to a load direction.   The stress test jig according to claim 1, wherein two flanges are arranged above and below the test piece.   One or both of the fixing members for fixing the flange are movable, and compressive stress or tensile stress is applied to the test piece by applying stress to the fixing member. The jig for stress tests described in 1.   5. The stress test according to claim 4, wherein the recess capable of holding the end of the test piece is internally threaded, and the end of the test piece is externally threaded. jig.   The stress test jig according to any one of claims 1 to 5, wherein the test piece is a material cut out from a pipe material.   The stress test jig according to claim 1, wherein the stress test jig is used in a tensile tester.   The stress test jig according to claim 1, wherein the stress test jig is used in a compression tester.   The stress test jig according to claim 1, wherein the stress test jig is used in a fatigue testing machine.   Using the stress test jig according to any one of claims 1 to 9, a compression test or a tensile test for imparting a strain of 1.5% or more to the test piece is performed once or twice or more. Stress test method.   Using the stress test jig according to any one of claims 1 to 9, a compression test and a tensile test for imparting a strain of 1.5% or more to a test piece are repeated once or twice or more. Stress test method.

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