KR20080102790A - Fatigue tester for pipe material - Google Patents

Fatigue tester for pipe material Download PDF

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Publication number
KR20080102790A
KR20080102790A KR1020070049683A KR20070049683A KR20080102790A KR 20080102790 A KR20080102790 A KR 20080102790A KR 1020070049683 A KR1020070049683 A KR 1020070049683A KR 20070049683 A KR20070049683 A KR 20070049683A KR 20080102790 A KR20080102790 A KR 20080102790A
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KR
South Korea
Prior art keywords
pipe material
fatigue
pipe
block
specimen
Prior art date
Application number
KR1020070049683A
Other languages
Korean (ko)
Inventor
김대용
Original Assignee
현대자동차주식회사
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Application filed by 현대자동차주식회사 filed Critical 현대자동차주식회사
Priority to KR1020070049683A priority Critical patent/KR20080102790A/en
Publication of KR20080102790A publication Critical patent/KR20080102790A/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0073—Fatigue
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/026—Specifications of the specimen
    • G01N2203/0296—Welds

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

Fatigue test equipment for pipe is provided to produce the high quality pipe with durability more than the proper strength and fatigue property and pipe welding condition by analyzing the fatigue property of pipes according to steel type. Fatigue test equipment for pipe comprises an upper grip part(14) of movable side and lower grip part(15) of fixed side which moves with the power supplied from a driving unit, a pipe specimen(10) having certain diameter, thickness and length and a welding unit formed on one side in the longitudinal direction, upper blocks(11) for tightening specimen, which are attached to the upper and lower grip parts with the pipe specimen interposed, lower auxiliary blocks(12) which are installed at upper and lower sides in the pipe specimen to face the upper blocks, and a fixing unit(13) for fixing the upper block, the pipe specimen and the lower auxiliary block.

Description

Fatigue tester for pipe material {Fatigue Tester for Pipe Material}

Figure 1a is a front view showing the structure of a mechanism for fixing the pipe material in the pipe material fatigue test apparatus according to an embodiment of the present invention,

1B is a side view of FIG. 1A,

2 is a configuration diagram showing an example of a method of fastening a pipe member and a fixing block in a mechanism for fixing a pipe member according to the present invention;

3A and 3C are schematic views showing a method of fixing a pipe member for a fatigue test of the pipe member according to the present invention;

Figure 4 is a graph showing the fatigue test results using the pipe fatigue test apparatus according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: pipe material specimen 11: upper block for specimen fastening

12: lower auxiliary block for fastening the specimen 13: fixing means

14: upper grip portion 15: lower grip portion

16: welded part 17: incision part

The present invention relates to a fatigue property evaluation apparatus for performing the evaluation of the fatigue properties of the pipe material, and more particularly, fatigue properties in the circumferential direction of the pipe material with a means for evaluating the fatigue properties of the pipe material in the pipe material state By precisely evaluating the fatigue properties of the pipe material and welded parts as well, the fatigue properties of the pipe material are analyzed in advance, and the welding conditions of high-quality pipe materials and pipe materials requiring durability and fatigue properties above the appropriate fatigue strength are required. An apparatus for evaluating fatigue properties of pipes capable of producing

Current challenges in the automotive industry include shorter development periods, cost reductions, and lighter weights. In the early stages of vehicle development, vehicle durability verification through durability analysis is essential.

In addition, as a challenge for improving the durability analysis technology, it is difficult to predict the quantitative durability life due to the lack of reliability of the durability analysis technology, and in particular, it is difficult to predict the durability life due to the lack of accurate tensile and fatigue characteristic data of the material. The evaluation of the mechanical properties (tensile and fatigue properties) of the metal material should be preceded.

On the other hand, a real machine or structure is subjected to repeated stresses or deformations rather than a simple load, causing a failure, this failure caused by repeated loads or vibrations is called fatigue failure.

Fatigue failure usually occurs after long periods of use in a stress state that is lower than the stress required for fracture under simple loading.

Fatigue is a breakdown that occurs frequently in automobiles, and because it suddenly occurs without any major deformation without special warning, it can be said that it is of destructive importance.

Therefore, in order to apply a material as a part material, a test for predicting the life to fatigue failure is essential.

In general, the pipe material is produced by processing the pipe in the form of a pipe through a pipe forming process, such as roll forming from the plate and then finished by welding and directly processed into a pipe material through a process such as extrusion.

After that, in order to improve the mechanical properties of the pipe material, an appropriate heat treatment process may be added to the material or a process including plastic processing such as stretching may be added.

This pipe material varies not only in the material from which it is manufactured, but also in the manufacturing process and the welding conditions.

Among them, the fatigue property is a characteristic that directly affects the durability of the product. The fatigue property is tested and analyzed, which is an important factor in making a durable product.

Conventionally, in order to evaluate the fatigue properties of the pipe material, a fatigue test is performed by fabricating a specimen from a state before the pipe material is manufactured, that is, a plate material during the pipe forming process or a casting material during the extrusion process. The fatigue properties of the pipe material were tracked, or some parts of the manufactured pipe material were cut to make the plate shape close to the fatigue test.

Alternatively, there is a method of obtaining fatigue properties for the pipe member by fixing it in the uniaxial direction and giving a tensile load or a torsional load in the axial direction.

However, when the fatigue test is carried out in the state before the pipe material is manufactured, the resulting compressive properties may be helpful for comparing fatigue properties related to the material composition between the materials. Hardening, softening, etc. cannot be judged based on the change of structure, and in particular, evaluation of a weld cannot be obtained.

 In addition, it can be evaluated when a part of the manufactured pipe material is cut to produce a plate shape close to the plate type, but the method of fabricating a plate type by cutting a part from the pipe material is not easy. In addition, in particular, in the case of a welded part, the range thereof is very small, so that it is not easy to produce a plate, and thus, a fatigue test cannot be performed.

The present invention has been made in view of the above, and is provided with a means capable of applying a load in the circumferential direction of a cylindrical pipe material in a pipe material state, so that the fatigue test of the pipe material can be performed, and thus the base material portion of the pipe material, in particular, Accurate fatigue properties of welded parts can be obtained, and from these properties, fatigue properties of steel pipes used in various industries, including the automotive industry, are known and analyzed. It is an object of the present invention to provide an apparatus for evaluating fatigue properties of a pipe material capable of producing pipe materials and welding conditions of pipe materials.

The present invention for achieving the above object in the fatigue property evaluation apparatus of the pipe material,

An upper grip part on the movable side and a lower grip part on the fixed side that are driven by power from the driving means; Welded portion is formed in the longitudinal direction on one side, the pipe material specimen having a constant diameter, thickness and length; A sample fastening upper block attached to the upper and lower grip portions with the pipe material specimen interposed therebetween; A lower auxiliary block installed in close contact with an upper block on upper and lower inner surfaces of the pipe material specimen; And fixing means for fixing the upper block, the pipe material specimen and the lower auxiliary block, wherein the pipe material specimen is tightly fixed to the upper block and the lower auxiliary block by using the fixing means. And it is characterized in that the fatigue property of the weld portion is evaluated.

In a preferred embodiment, the pipe material specimen is characterized in that the welded portion and the opposite side of the pipe material specimen is tightly fixed by the upper block and the lower auxiliary block when the fatigue property of the base material is evaluated.

In a more preferred embodiment, when the pipe material specimen is evaluated for the fatigue properties of the welded portion, the welded portion and the opposite side of the piped specimen are positioned vertically in the upper block and the lower sub-block, and the upper and lower portions are the upper block and the lower sub-block. It is characterized in that the tightly fixed by.

In addition, the base material on the opposite side of the weld is characterized in that the incision is formed for more accurate fatigue properties of the weld.

In addition, the length of the pipe member is characterized in that 1.0 to 2.0 times the diameter.

In addition, the thickness of the pipe member is characterized in that 0 to 0.5 times the radius.

In addition, the fixing means is a bolt and nut, the bolt penetrates the upper block, the pipe material specimen and the lower auxiliary block, it is characterized in that the pipe member is fastened in the circumferential direction is fastened with the nut.

In addition, the upper block is characterized in that the inner surface is in the form of a flat plate in contact with the outer surface of the pipe material specimen.

In addition, the lower auxiliary block is characterized in that the semi-circular shape so as to contact with the inner surface of the pipe material specimen.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a pipe member fixing device which is mounted on a fatigue tester for testing fatigue characteristics by applying an axial load so that a load can be applied in a circumferential direction to a pipe specimen.

1A is a front view showing the structure of a mechanism for fixing a pipe member in a pipe fatigue test apparatus according to an embodiment of the present invention, Figure 1b is a side view of Figure 1a.

The apparatus shown in FIGS. 1A and 1B is fastened to a normal fatigue tester fixture body (not shown) for performing a general fatigue test. Here, the method of operating the upper and lower grip portions to apply the load to the pipe material specimens may be adopted without particular limitation as long as it is a method commonly known in the art.

The present invention provides a pipe material fixing device that allows the pipe material specimen 10 to be properly fixed during a fatigue test.

This pipe material fixing device is a means to properly test the pipe material when the fatigue load is periodically applied to the pipe material specimen (10), can be used in combination as it is simply without changing the structure of the existing fatigue tester It is supposed to be.

The pipe material fixing device includes two pairs of specimen fastening upper blocks 11 and specimen lower fastening blocks 12 that can closely support a portion of the outer surface and the inner surface of the pipe material specimen 10, and each It consists of a fixing means 13 which can fix a pair of blocks and pipe material.

To this end, the upper block 11 and the lower auxiliary block for fastening the specimen on the outer side and the inner side of the upper and lower portions of the pipe member 10 are arranged side by side with the pipe member 10 between. The pipe material specimen 10 is fixed by the fixing means 13 for fastening and connecting the upper block 11 and the lower auxiliary block 12 to the pipe material.

Fixing means 13 for fastening the upper block 11 and the lower auxiliary block 12 is preferably using a bolt and a nut. In order to fasten using this, a hole having a diameter of a bolt is drilled in a state in which the upper block 11 and the lower auxiliary block 12 for fastening the specimen between the outer side and the inner side and the pipe member are in a straight line. Inserted into the upper block (11) and fastened by fixing with a nut on the inner side lower auxiliary block (12).

The upper block 11 fixed to the outer surface of the pipe member is preferably rectangular in shape so as to be tangent to the contact surface of the pipe member, and the lower auxiliary block 12 fixed to the inner surface of the pipe member has a curvature of the inner diameter of the pipe member. Smaller semicircular blocks are preferred.

The semi-circular block gives a position that can be securely fastened while being in close contact with a point of the inner surface of the pipe material.

The fixing device of the pipe member is provided with an upper grip portion 14 which can be fastened to the upper grip of a normal fatigue tester and a lower grip part 15 which can be fastened to the lower grip, and is mounted to the fatigue tester.

Typically, a tester facility for performing a fatigue test is provided with an upper grip portion 14 and a lower grip portion 15 to hold both ends of the fixing device according to an embodiment of the present invention from above and below.

At this time, the upper grip portion 14 is a movable side to receive power from a driving means (not shown) like a normal fatigue tester, the lower grip portion 15 is a fixed side.

Here, the method of operating the upper and lower grip parts 14 and 15 to apply a load can be adopted without particular limitation as long as it is a method commonly known in the art.

When applying a load in a fatigue tester, it is common to apply a repeated tensile compressive load several times to tens of thousands periodically at a speed of 10 Hz to 100 Hz.

When the fatigue test of the pipe material using the fixing device of the present invention is carried out, the length of the pipe material is suitable 1.0 ~ 2.0 times the diameter, the thickness of the pipe material is preferably 0.5 times or less of the pipe radius.

2a to 2c show a method of fastening a pipe member to the fixing device of the present invention. Here, the same reference numerals as in the above-described drawings indicate the same members having the same function.

According to the case of evaluating the fatigue property of the pipe base material or the case of evaluating the fatigue property of the welded part 16, it is fastened by changing the position.

In the case of evaluating the fatigue properties of the base material, as shown in FIG. 2A, it is most preferable to position the weld 16 to be in close contact with the upper block 11 and the lower auxiliary block 12, and to evaluate the fatigue properties of the weld 16. In this case, as shown in FIG. 2B, the upper block 11 or the lower auxiliary block 12 is preferably positioned at 90 degrees.

In the present fatigue test apparatus, the portion indicated by the circle in FIG. 2A is subjected to the tensile-compression load due to the cyclic load, and the physical properties of the portion indicated by the circle are represented by the fatigue properties. Therefore, in order to evaluate the physical properties of the welded portion, it is preferable that the welded portion is located at a portion indicated by a circle.

In addition, in order to evaluate the fatigue property of the welded portion more precisely, as shown in FIG. 2C, the cutout portion 17 is formed in advance in the base material in the opposite direction of the welded portion, and then the pipe material specimen 10 is mounted on the fixing device and the test is performed.

Because the load is mainly applied to the circular part during repeated loading, it is preferable to cut and test the opposite base material part to obtain only the properties of the weld.

Figure 3 shows the results of the fatigue test using a fatigue tester equipped with a pipe member circumferential fixing mechanism of the present invention, as shown, it can be obtained a reliable result for the fatigue properties of the pipe member in the circumferential direction.

Fatigue test can be equipped with the apparatus of the present invention to a general MTS company or INSTRON company fatigue test equipment as a hydraulic fatigue test equipment, for the embodiment of the present invention was used MTS equipment.

In Figure 3 Relative Force is the fatigue strength value relative to the tensile strength of the pipe material, Cycle Number to Failure is the number of fatigue life at a given load, showing a similar tendency to the results showing the general fatigue strength.

As described above, the fatigue test on the pipe specimen 10 can be effectively performed using the rolling prevention mechanism in the circumferential direction of the pipe member provided in the present invention. Rather, there is an advantage in that the circumferential fatigue properties of the welded portion 16 can be accurately obtained.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to these embodiments, and has been claimed by those of ordinary skill in the art to which the invention pertains. It includes all the various forms of embodiments that can be implemented without departing from the spirit.

As described above, according to the fatigue property evaluation apparatus of the pipe material according to the present invention, it can be fixed in the circumferential direction of the pipe material during the fatigue test to obtain the exact fatigue properties of the pipe material, and to develop the pipe material or design the pipe material manufacturing process It provides the fatigue properties of reliable pipe materials as required.

In addition, the fatigue properties of the welded portion of the pipe material, where durability quality is important, enable the design of welding conditions in the welding process.

Claims (7)

In the fatigue property evaluation apparatus of the pipe material, An upper grip portion 14 on the movable side and a lower grip portion 15 on the fixed side that are moved by receiving power from the drive means; Welded portion 16 is formed on one side in the longitudinal direction, the pipe member 10 having a constant diameter, thickness and length; A sample fastening upper block 11 attached to the upper and lower grip portions with the pipe material specimen therebetween; A lower auxiliary block 12 installed in close contact with an upper block on upper and lower inner surfaces of the pipe material specimen; And Fixing means (13) for fixing the upper block, the pipe material specimen and the lower auxiliary block; The pipe material specimen is configured to include, and the fatigue property evaluation device of the pipe material, characterized in that the upper and lower portions are tightly fixed to the upper block and the lower sub-block using the fixing means to evaluate the fatigue properties of the base material and the weld. The method according to claim 1, When the pipe material specimen is evaluated for the fatigue property of the base material, the welded portion of the pipe material and the opposite side is fixed to the pipe material fatigue characterized in that the upper block and the lower auxiliary block is fixed tightly. The method according to claim 1, When the pipe material specimen is evaluated for the fatigue property of the welded part, the welded part and the opposite side of the pipe material specimen are positioned vertically in the upper block and the lower sub-block, and the upper and lower parts are tightly fixed by the upper block and the lower sub-block. Fatigue property evaluation apparatus of the pipe material characterized by the above-mentioned. The method according to claim 3, Apparatus for evaluating the fatigue properties of the pipe material, characterized in that the cutout portion (17) is formed in the base material on the opposite side of the weld portion for more precise fatigue property evaluation of the weld. The method according to any one of claims 1 to 4, The fixing means is a bolt and a nut, the bolt penetrates the upper block, the pipe material specimen and the lower auxiliary block, is fastened with the nut, the pipe material fatigue device characterized in that the pipe material is fastened in the circumferential direction . The method according to claim 5, The upper block is a fatigue material evaluation apparatus of the pipe material, characterized in that the inner surface is in contact with the outer surface of the pipe material specimen in the form of a flat contact. The method according to claim 6, The lower auxiliary block is a fatigue property evaluation device of the pipe material, characterized in that the semi-circular shape so as to be in contact with the inner surface of the pipe material specimen.
KR1020070049683A 2007-05-22 2007-05-22 Fatigue tester for pipe material KR20080102790A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104535417A (en) * 2014-12-01 2015-04-22 芜湖恒美电热器具有限公司 Apparatus for detecting welding performance of steel pipe
KR20210061812A (en) * 2019-11-20 2021-05-28 조선대학교산학협력단 ring specimen for deformation and damage behavior analysis of elbow pipe by cyclic load, testing method using the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104535417A (en) * 2014-12-01 2015-04-22 芜湖恒美电热器具有限公司 Apparatus for detecting welding performance of steel pipe
KR20210061812A (en) * 2019-11-20 2021-05-28 조선대학교산학협력단 ring specimen for deformation and damage behavior analysis of elbow pipe by cyclic load, testing method using the same

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