Steel structure safe fracture toughness determination method and steel structure design safety checking method

A technology of fracture toughness and determination method, applied in the direction of applying stable tension/pressure to test the strength of materials, etc., can solve the problems of poor engineering practicability, long test period of strain fracture toughness, cumbersome test process, etc., to prevent excessive plasticity. Deformation failure, safe fracture toughness is accurate and reliable, and the realization process is simple and fast.

Inactive Publication Date: 2015-07-29
BC P INC CHINA NAT PETROLEUM CORP
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  • Abstract
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AI Technical Summary

Problems solved by technology

The high-tonnage testing machine is expensive, and even if a high-tonnage testing machine is available, it may not be possible to prepare a sample that meets the size requirements, so that the measurement of the plane strain fracture toughness of the material cannot be carried out, and thus the safety of the steel structure cannot be determined. Fracture toughness, poor engineering practicability
At the same time, the test cycle for determining the plane strain fracture toughness of the material is relatively long, and the test process is relatively cumbersome.
In addition, the above method of determining the safe fracture toughness of steel structures only considers the fracture failure mode, but does not consider the plastic deformation failure mode controlled by strength factors, which is not conservative enough in engineering applications

Method used

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  • Steel structure safe fracture toughness determination method and steel structure design safety checking method
  • Steel structure safe fracture toughness determination method and steel structure design safety checking method
  • Steel structure safe fracture toughness determination method and steel structure design safety checking method

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Embodiment 1

[0040] The embodiment of the present invention provides a method for determining the safe fracture toughness of steel structures, see figure 1 , methods include:

[0041] Step 101: Test the yield strength σ of the material used in the steel structure y and tensile strength σ u .

[0042] Specifically, the yield strength σ of materials used in steel structures can be tested by uniaxial tensile testing y and tensile strength σ u .

[0043] Further, a universal material testing machine can be used to test the yield strength and tensile strength of the materials used in the steel structure.

[0044] Wherein, the steel structure may be a steel plate, section steel or steel pipe, etc.

[0045] Step 102: According to the formula L r =σ ref / σ y Calculate the load ratio L of the steel structure when the crack reaches the maximum allowable size under the design condition r .

[0046] Among them, σ ref It is the reference stress when the crack reaches the maximum allowable s...

Embodiment 2

[0052] The embodiment of the present invention provides a method for determining the safe fracture toughness of steel structures, see figure 2 , methods include:

[0053] Step 201: Test the yield strength σ of the material used in the steel structure y and tensile strength σ u .

[0054] Among them, the yield strength σ y and tensile strength σ u It can be measured by ordinary uniaxial tensile test, and can be tested by universal material testing machine (or electronic universal material testing machine).

[0055] In this embodiment, before step 201 , samples of materials used in steel structures are obtained. The test specimen is usually an ordinary tensile test specimen.

[0056] Step 202: Determine the reference stress σ when the crack reaches the maximum allowable size in the steel structure under design conditions ref .

[0057] In practical applications, you can refer to relevant standards in the field (such as API579-1-2007), manuals or literature to select the...

Embodiment 3

[0086] The embodiment of the present invention provides a safety check method for steel structure design, see image 3 , the method includes:

[0087] Step 301: Test the yield strength σ of the material used in the steel structure y and tensile strength σ u .

[0088] Wherein, the steel structure may be a steel plate, section steel or steel pipe, etc.

[0089] Step 302: According to the formula L r =σ ref / σ y Calculate the load ratio L of the steel structure when the crack reaches the maximum allowable size under the design condition r .

[0090] Among them, σ ref It is the reference stress when the crack reaches the maximum allowable size of the steel structure under the design condition.

[0091] Step 303: When the load ratio L r meet L r ≤(σ y +σ u ) / (2·σ y ), according to the formula K r =(1-0.14L r 2 )[0.3+0.7exp(-0.65L r 6 )] Calculate the safe fracture ratio K of the steel structure when the crack reaches the maximum allowable size under the design c...

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Abstract

The invention discloses a steel structure safe fracture toughness determination method and a steel structure design safety checking method, and belongs to the technical field of test of mechanical performances of a material. The steel structure safe fracture toughness determination method comprises the following steps: testing the yield strength sigma y and the tensile strength sigma u of the material of a steel structure; calculating the load ratio Lr of the steel structure with the crack reaching an allowed maximum size under design conditions according to a formula of Lr=sigma ref/sigma y, wherein the sigma ref is the reference stress when the crack reaches the allowed maximum size; calculating the safe fracture ratio Kr of the steel structure according to a formula of Kr=(1-0.14Lr<2>)[0.3+0.7exp(-0.65Lr<6>)] when the load ratio is not greater than (sigma y + sigma u)/(2.sigma y); and calculating the safe fracture toughness Ks according to a formula of Ks=KI/Kr, wherein KI is the crack tip stress strength factor of the crack reaching the allowed maximum size. The steel structure safe fracture toughness determination method avoids the problems of high cost and long time brought by special condition requirements for determining the plane strain fracture toughness of the material, is simple and fast to realize by determining the safe fracture toughness through testing the yield strength and the tensile strength of the material, and is in favor of realizing engineering application.

Description

technical field [0001] The invention relates to the technical field of material mechanical performance testing, in particular to a method for determining the safe fracture toughness of steel structures and a method for checking the safety of steel structure designs. Background technique [0002] The materials used in the steel structure will inevitably initiate cracks due to the environment and load during the service process. The brittle expansion of this crack will lead to the sudden failure of the steel structure, resulting in significant economic losses and even personal injuries. Therefore, the influence of crack defects must be fully considered in the design process of steel structures. [0003] Studies have shown that the brittle growth of cracks is related to the stress-strain state at the crack tip, and the thickness of the member wall made of the material used in the steel structure has a great influence on the stress-strain state at the crack tip. When the thickn...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08
Inventor 王海涛陈宏远吉玲康张广利池强黄呈帅张伟卫齐丽华王鹏
Owner BC P INC CHINA NAT PETROLEUM CORP
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