JPH11237325A - Method and jig for testing material strength of pressure container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make estimable the material strength of a container with a dent and a scratch at the outer-periphery part in a cylindrical pressure container to receive an inner pressure. SOLUTION: A test piece 100 is prepared by partially cutting a cylindrical pressure container with a dented part 110 and a scratch 120 at the outer- periphery part, and the both edges are fixed to a testing tool 200. Positions P1 and P2 on the tool 200 being displaced for a center E1 of the test piece 100 are connected to a tensile testing machine and a pulling force F is applied. A pulling force σ and a bending moment M acts upon the test piece 100, and a pulling force and a bending moment being applied to the dented part of the pressure container are reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for testing the material strength of a steel pipe as a pressure vessel having dents and scratches.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view of a steel pipe 10 constituting a pressure vessel such as a gas supply pipe.
Shows a case in which dents and flaws occur in the outer peripheral portion S due to the action of.

In FIG. 10, it is assumed that a dent 20a is formed in the steel pipe 10, and a scratch 30a is formed in the center of the dent 20a. Since the internal pressure P acts on the steel pipe 10 as the pressure vessel, as shown in FIG. 3A, the internal pressure causes the bending moment M and the tensile stress σ in the direction for restoring the dent to act on the dent 20a. I do.

Due to the internal pressure, the deformation proceeds in the direction in which the dent portion is restored, and as shown in FIG. 1B, when the dent portion 20b is restored to a circular shape, only the tensile stress σ mainly surrounds the flaw 30b. Works. When the deformation further proceeds due to the internal pressure, as shown in (C), the dent portion is pushed outward from the outer peripheral portion of the steel pipe to form a projecting portion 20c. In this state, the bending moment M acts on the periphery of the scratch 30C together with the tensile stress σ, and finally, the scratch 30C expands and breaks.

[0005]

As described above, as a method for testing the material strength in the case where dents and scratches are present on the outer peripheral portion of a steel pipe as a pressure vessel, conventionally, an internal pressure is actually applied to the steel pipe. A test (burst test) was being performed. The pressure vessel with dents and scratches, with increasing internal pressure,
Then, the deformation progresses as shown and eventually breaks,
At this time, the pressure vessel is broken, and the fluid generating the internal pressure explosively scatters.

[0006] Therefore, this kind of pressure vessel strength testing equipment is large-scale, and it is necessary to prepare a pressure vessel for testing every time the conditions are changed. Was. The present invention uses a test piece made of the same material as a steel pipe, and simultaneously applies a desired bending moment and tensile stress to the test piece, thereby performing a burst test of the pressure vessel, thereby making the steel pipe due to dents and scratches. The present invention provides a test method and an apparatus for performing a strength test.

[0007]

SUMMARY OF THE INVENTION A method of testing the material strength of a portion of a steel pipe which is a cylindrical pressure vessel having a dent and a flaw in an outer peripheral portion of the steel pipe according to the present invention comprises: A step of cutting out the test piece as a long test piece, a step of holding both ends of the long test piece by a tensile tester through a jig, and applying a tensile stress to the test piece by the tensile tester, The method includes a step of applying a bending stress in a direction in which the concave portion restores the cylindrical shape.

[0008] A test jig for testing the material strength of a portion having dents and scratches on the outer peripheral portion of a steel pipe, which is a cylindrical pressure vessel of the present invention, using a tensile tester, comprises: A groove into which a test piece formed by cutting out as a long object in the circumferential direction is inserted, means for fixing the test piece inserted into the groove, and means for connecting the test jig to a tensile tester, The means for connecting the test jig to the tensile tester
The line of action of the tensile force given by the tensile tester is arranged so as to be deviated from the center line of the groove holding the test piece.

Further, the means for connecting the test piece to the tensile tester is a plurality of through holes with which the tips of the hooks of the tensile tester are engaged. On the other hand, they are displaced by different distances in a direction perpendicular to the axis of the groove.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are explanatory views showing a method of preparing a test piece used for a strength test according to the present invention. First, a part 50 of a steel pipe to be subjected to a strength test is cut out,
Desired indentation by the tool T ₁ using a pressing machine 60
To form Then, a test piece 100 is prepared by cutting out a steel pipe including the dent portion 60.

FIG. 3 is a plan view of the prepared test piece, and FIG.
FIG. 5 is a front view, and FIG. 5 is a sectional view showing the shape and size of a flaw formed by machining a dent. The test piece 100 is a long member having a dent 110 and a scratch 120 at the center, and flat portions 120 are provided at both ends. Sheet thickness t
Prepared 12.7 mm. The flat portion 120 has a mounting hole 140 for mounting the test piece 100 to a tester.
Is provided.

[0012] The shape and size of the flaw provided in the dent portion are as follows.
It is desirable that the steel pipe to be tested approximates the actual damage. FIG. 5A shows a case where a scratch 120a having a width of 0.2 mm and a depth of 3.8 mm is provided.
(B) has a width of 3 mm and a depth of 3.8 mm,
A scratch 120b having a bottom surface in an arc shape with a radius of 1.5 mm was prepared.

FIGS. 6 and 7 show a test piece 100 according to the present invention.
It is explanatory drawing which shows the test method of. Both ends of the test piece 100 are inserted into the grooves 210 of the jig 200, and are fixed to the jig 200 using the mounting holes 140. In this state, the tensile tester to which the jig 200 is attached is operated, and the two jigs are pulled by the force F in a direction away from each other. At this time, while the axis E ₁ through two middle jig 200 axis E ₂ and test strip 100 in the initial state connecting the point P _1, P ₂ of the force exerted on it is displaced by a distance G ₁ is there. Then, when the jig 200 is pulled by the force F, the bending moment M and the tensile stress σ act on the test piece 100 at the same time.

Therefore, the tensile force F and the axial distance G ₁
By appropriately selecting the above, mechanical conditions similar to the bending moment M and the tensile stress σ when the internal pressure P acts on the steel pipe having the dents and scratches described with reference to FIG. 10 can be given to the test piece.

FIG. 7 shows a state in which the tensile force F applied by the test device increases and the test piece 100 is bent by the bending moment M in the direction in which the dent portion 110 decreases. This state corresponds to FIG. 10B, and only the tensile stress σ mainly acts on the test piece 100.

Further, when the tensile force F increases, the tensile stress concentrates on the flaw 120, and the test piece 100 is finally broken. By measuring the tensile force applied to the test piece and the deformation of each part of the test piece during this time, the strength of the pressure vessel having the dent and the flaw can be estimated.

FIG. 8 is a plan view of a jig used in the test method of the present invention. The jig 200 is made of a steel plate having a large thickness dimension, and has a rectangular planar shape. A slit 2 for inserting a test piece close to one of the side walls 206 on the short side.
10 are provided. A hole 220 penetrating this slit 210 is formed from the side wall 206 of the jig 200, and the test piece 1
The pin 230 penetrating through the hole 140 of 00 is inserted,
The test piece 100 is connected to a jig 200. Jig 200
Has a plurality of holes arranged on an axis parallel to the axis of the hole 220 along a long side wall 204 opposite to the long side wall 202 where the slit 210 is provided.

In the illustrated embodiment, four holes 24 are provided.
0, 241, 242, and 243 are provided. First hole 2
The center of 40 is disposed at the same position as the distance L ₁ from the short side wall 206 of the jig 200 to the center of the slit 210. Distance L ₂ from the side wall 206 to the center of the second hole 241, a distance L ₃ to the center of the third hole 242, the distance L ₄ to the center of the fourth hole 243, to be applied to each test piece It is set according to the amount of bending moment M.

[0019]

As described above, according to the method for testing the material strength of a steel pipe as a pressure vessel according to the present invention, a test piece having a dent and a flaw on the surface of a pipe body is prepared, and the bending moment and the A test for material strength is performed while simultaneously applying a tensile stress. Based on the test results, the strength of the tubular pressure vessel having dents and scratches can be estimated.

Further, according to the test apparatus of the present invention, it is possible to apply a bending moment together with a tensile stress to a test piece by using a tensile tester for a material. Since the amount of the bending moment to be applied can also be easily adjusted, the strength test of the steel pipe, which is a pressure vessel having dents and scratches, can be efficiently performed.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method for producing a test piece.

FIG. 2 is an explanatory view showing a method for producing a test piece.

FIG. 3 is a plan view of a test piece.

FIG. 4 is a front view of a test piece.

FIG. 5 is a cross-sectional view of a dent wound.

FIG. 6 is an explanatory diagram showing a test method.

FIG. 7 is an explanatory view showing a test method.

FIG. 8 is a plan view of a test jig.

FIG. 9 is a sectional view of a steel pipe constituting the pressure vessel.

FIG. 10 is an explanatory view showing dents and scratches of a steel pipe.

[Explanation of symbols]

 Reference Signs List 50 pressure vessel 100 test piece 110 dent 120 scratch 200 test jig 210 groove 230 pin 240-243 connection hole to tensile tester

Claims (3)

[Claims] 1. A method for testing the material strength of a portion of a steel pipe which is a cylindrical pressure vessel having dents and scratches on an outer peripheral portion, wherein the steel pipe is formed as a test piece that is long in the circumferential direction around the dents and scratches. The step of cutting out, the step of gripping both ends of a long test piece with a tensile tester through a jig, and the application of tensile stress to the test piece by a tensile tester, and the concave part of the test piece having a cylindrical shape Applying a bending stress in a direction to restore the material strength of the pressure vessel. 2. A test jig for testing the material strength of a portion having a dent and a flaw on an outer peripheral portion of a steel pipe as a cylindrical pressure vessel, using a tensile tester, wherein the steel pipe has a circumference centered on the dent and flaw. A groove into which a test piece cut and formed as a long object in a direction is inserted, a means for fixing the test piece inserted into the groove, and a means for connecting a test jig to a tensile tester; Means for connecting the jig to the tensile tester is to determine the material strength of the pressure vessel in which the line of action of the tensile force given by the tensile tester is offset from the center line of the groove for gripping the test piece. Test jig. 3. The means for coupling a test specimen to a tensile tester comprises:
A plurality of through holes with which hook tips of a tensile tester are engaged, wherein the plurality of through holes are displaced from the groove into which the test piece is inserted by different distances in a direction perpendicular to the axis of the groove. 3. The test jig for material strength of a pressure vessel according to claim 2, wherein the test jig is arranged in a manner to be arranged in a manner as described above.