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Method for measuring fracture toughness of pipeline steel by using unilateral notched tensile test

A fracture toughness and tensile test technology, applied in the direction of applying stable tension/pressure to test the strength of materials, can solve the problems of small range of measurement results and insufficient assessment of fracture toughness of pipeline steel

Active Publication Date: 2014-02-26
BC P INC CHINA NAT PETROLEUM CORP +1
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a method for measuring the fracture toughness of pipeline steel by using a unilateral notch tensile test, by using tensile samples to measure the fracture toughness of pipeline steel, to overcome the traditional technology using three-point bending Defects in which test and compact tensile specimens result in a range of measurements that is too small to assess the fracture toughness of pipeline steels

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  • Method for measuring fracture toughness of pipeline steel by using unilateral notched tensile test
  • Method for measuring fracture toughness of pipeline steel by using unilateral notched tensile test
  • Method for measuring fracture toughness of pipeline steel by using unilateral notched tensile test

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example 1

[0054] Example 1: Prepare a tensile sample (SENT sample) for a pipeline steel with a yield ratio of 0.85 and a thickness B of 5mm. The sample size refers to the attached figure 2 , the width of the sample is W=0.75t, the processing of the sample crack can be divided into wire cutting and fatigue prefabrication, and the fatigue crack of 2mm size is prefabricated according to the ASTM1820 standard. The prefabricated fatigue cracked sample is loaded on the MTS tensile machine. The sample is clamped vertically. The entire loading process is carried out at room temperature to reduce the influence of temperature. The loading method is displacement control, and the rate is 2mm. / min, each group of samples must be stretched at least six times in different degrees, and at least three samples should be loaded beyond the highest load point to ensure that the crack growth is 0.5mm. After the loading process of the tensile specimen is finished, the crack growth amount Δa is measured by th...

example 2

[0055] Example 2: Prepare a tensile sample (SENT sample) for a pipeline steel with a yield ratio of 0.85 and a thickness B of 6mm. The sample size refers to the attached figure 2 , the width of the sample is W=0.75t, the processing of the sample crack can be divided into wire cutting and fatigue prefabrication, and the fatigue crack of 2mm size is prefabricated according to the ASTM1820 standard. The prefabricated fatigue cracked sample is loaded on the MTS tensile machine. The sample is clamped vertically. The entire loading process is carried out at room temperature to reduce the influence of temperature. The loading method is displacement control, and the rate is 1mm. / min, each group of samples must be stretched at least six times in different degrees, and at least three samples should be loaded beyond the highest load point to ensure that the crack growth is between 1mm. After the loading process of the tensile specimen is finished, the amount of crack growth is measured...

example 3

[0056] Example 3: Prepare a tensile sample (SENT sample) for a pipeline steel with a yield ratio of 0.90 and a thickness B of 5mm. The sample size refers to the attached figure 2 , the width of the sample is W=0.70t, the processing of the sample crack can be divided into wire cutting and fatigue prefabrication, and the fatigue crack of 2mm size is prefabricated according to the ASTM1820 standard. The prefabricated fatigue cracked sample is loaded on the MTS tensile machine. The sample is clamped vertically. The entire loading process is carried out at room temperature to reduce the influence of temperature. The loading method is displacement control, and the rate is 2mm. / min, each group of samples must be stretched at least six times to different degrees, and at least three samples should be loaded beyond the highest load point to ensure that the crack growth is between 0.2mm. At the end of the loading process of the tensile sample, the amount of crack growth is measured by ...

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Abstract

The invention discloses a method for measuring fracture toughness of pipeline steel by using a unilateral notched tensile test. The method is characterized by comprising the steps of preparing a unilateral notched tensile test sample; prefabricating a tensile sample crack by wire-electrode cutting and fatigue crack growth rate test method; calculating crack growth amount according to the tensile sample cracks; and acquiring J integration and stress intensity factor K for characterizing the fracture toughness of the pipeline steel by drawing a J-R curve for characterizing crack resistance of the crack growth. The method measures the fracture toughness of the pipeline steel by using tensile samples (SENT samples), overcomes the defects that the scope of measurement results of tensile samples (SENT samples) by a conventional technology is so small that the fracture toughness of the pipeline steel can not be evaluated; the crack toughness value of the tensile samples (SENT samples) can be more reasonable; waste of test for pipeline steel materials can be prevented; and the method has the advantages of high measurement accuracy.

Description

technical field [0001] The invention belongs to the technical field of fracture toughness measurement, in particular to a method for measuring the fracture toughness of pipeline steel by means of a single-side notch tensile test. Background technique [0002] With the improvement of the strength level of pipeline steel, the requirements for toughness are getting higher and higher. In addition, the service environment of pipeline steel is very harsh, which increases the probability of cracks. Safe operation is of great significance. [0003] The traditional technique uses three-point bending test (SENB) and compact tensile test specimen (CT), both of which are deeply cracked specimens with crack size (a 0 ) to the specimen width (w) is between 0.45-0.55, and the crack tip is highly constrained, so the range of fracture toughness values ​​measured by the test is too small to evaluate the fracture toughness of pipeline steel, although it is beneficial Safety assessment of eng...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08
Inventor 李洋程鹏明刘刚张伟卫李鹤李炎华黄呈帅王海涛吉玲康池强
Owner BC P INC CHINA NAT PETROLEUM CORP
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