CN-122020896-A - Method for evaluating stress intensity factor distribution of crack front edge of pressure vessel connecting pipe

CN122020896ACN 122020896 ACN122020896 ACN 122020896ACN-122020896-A

Abstract

The invention relates to an evaluation method for stress intensity factor distribution of a crack front edge of a pressure vessel connecting pipe, and belongs to the field of evaluation of structural integrity of pressure vessels. The method comprises the steps of carrying out finite element analysis of the pressure vessel pipe joint cracks with different sizes, constructing a correction factor database of the front edge of the pressure vessel pipe joint cracks, establishing a weight function equation suitable for the pressure vessel pipe joint cracks, and evaluating stress intensity factor distribution of the front edge of the pressure vessel pipe joint cracks under complex stress conditions. The invention provides a stress intensity factor distribution evaluation method suitable for the crack front edge of a pressure vessel connecting pipe with a wide size range under a complex load condition, which is coupled with a finite element analysis result and a weight function theory, and can avoid the problems of large-scale fracture mechanics numerical simulation, convergence misjudgment and the like, and effectively improve the structural integrity evaluation precision and efficiency of the pressure vessel connecting pipe with the crack.

Inventors

LU KAI
WU ZIQIANG
LI XUESEN
Xiao Chenxu
SHEN HAO
WANG DONG

Assignees

福州大学

Dates

Publication Date: 20260512
Application Date: 20260127

Claims (10)

1. A method of evaluating a crack front stress intensity factor profile of a pressure vessel nozzle, comprising: finite element analysis is carried out on the connecting pipe cracks of the pressure vessels with different sizes; Constructing a correction factor database of the crack leading edge of the pressure vessel based on the finite element analysis result; Based on the correction factor database, establishing a weight function equation of the pressure vessel for taking over the crack; Inputting the size of the pressure vessel takeover to be evaluated and the size of the crack of the pressure vessel takeover to be evaluated, and evaluating the stress intensity factor distribution of the front edge of the crack of the pressure vessel takeover under the complex stress condition acting on the crack surface of the pressure vessel takeover to be evaluated based on a correction factor database and a weight function equation.
2. The method for evaluating the stress intensity factor distribution of the leading edge of the crack of the pressure vessel adapter according to claim 1, wherein the finite element analysis is carried out on the crack of the pressure vessel adapter with different sizes, and the method specifically comprises the following steps: Setting the size of a pressure vessel connecting pipe and the size of a crack of the pressure vessel connecting pipe; Setting material properties of the pressure vessel; Setting an action stress on a crack surface of the connecting pipe of the pressure vessel; Based on the setting conditions, a three-dimensional model of the connecting pipe of the pressure vessel with the cracks is established, and finite element analysis is carried out on the cracks of the connecting pipes of the pressure vessels with different sizes.
3. The method for evaluating the stress intensity factor distribution of the leading edge of the crack of the pressure vessel adapter according to claim 2, wherein the finite element analysis is performed on the cracks of the pressure vessel adapter with different sizes based on the linear elastic fracture mechanics theory.
4. The method for evaluating the stress intensity factor distribution of the crack front of the pressure vessel pipe according to claim 1, wherein the step of constructing a correction factor database of the crack front of the pressure vessel pipe based on the finite element analysis result specifically comprises the following steps: based on the finite element analysis result, calculating J integral of the crack front of the pressure vessel; Calculating reference fracture parameter distribution data of the crack front of the pressure vessel pipe based on J integral; And carrying out dimensionless treatment on the reference fracture parameter distribution data, and constructing a correction factor database of the crack leading edge of the pressure vessel.
5. The method for evaluating the stress intensity factor distribution of the crack front of the pressure vessel nozzle according to claim 4, wherein the J integral of the crack front of the pressure vessel nozzle is calculated by using a contour integration method.
6. The method for evaluating the stress intensity factor distribution of the leading edge of the crack of the pressure vessel pipe according to claim 1, wherein the step of establishing a weight function equation of the crack of the pressure vessel pipe based on the correction factor database comprises the following steps: solving a weight coefficient in the three-dimensional crack general weight function based on the correction factor database; And establishing a weight function equation of the pressure vessel for taking over the crack based on the solved weight coefficient.
7. The method for evaluating the distribution of stress intensity factors of the leading edge of a crack in a pressure vessel nozzle according to claim 6, wherein the weight coefficients in the three-dimensional general weight function of the crack are solved by weight function theory.
8. The method for evaluating the stress intensity factor distribution of the leading edge of the crack of the pressure vessel takeover according to claim 1, wherein the method for evaluating the stress intensity factor distribution of the leading edge of the crack of the pressure vessel takeover under the complex stress condition acting on the crack surface of the pressure vessel takeover to be evaluated based on the correction factor database and the weight function equation comprises the following steps: Determining the size of a pressure vessel nipple to be evaluated the size of the crack of the pressure vessel adapter to be evaluated; determining complex stress conditions acting on the crack surface of the pressure vessel connecting pipe to be evaluated; Calculating the correction factor of the front edge of the take-over crack of the pressure vessel to be evaluated by interpolation based on the take-over size of the pressure vessel to be evaluated and the size of the take-over crack of the pressure vessel to be evaluated by combining a correction factor database; Substituting the calculated correction factors into a weight function equation of the pressure vessel pipe crack to obtain a weight function of the pressure vessel pipe crack to be evaluated; And evaluating the stress intensity factor distribution of the front edge of the pressure vessel connecting pipe crack under the complex stress condition based on the complex stress condition acting on the crack surface of the pressure vessel connecting pipe to be evaluated and the calculated weight function of the crack of the pressure vessel connecting pipe to be evaluated.
9. An evaluation system for the distribution of stress intensity factors at the leading edge of a crack in a pressure vessel, comprising a memory, a processor and computer program instructions stored on the memory and executable by the processor, which, when executed by the processor, are capable of carrying out the steps of the method according to any one of claims 1-8.
10. A computer readable storage medium having stored thereon computer program instructions executable by a processor, which when executed by the processor are capable of carrying out the steps of the method according to any one of claims 1-8.

Description

Method for evaluating stress intensity factor distribution of crack front edge of pressure vessel connecting pipe Technical Field The invention belongs to the field of evaluation of structural integrity of pressure-bearing containers, and particularly relates to an evaluation method of stress intensity factor distribution of a crack front edge of a pressure container connecting pipe. Background In practical engineering applications, the pressure vessel needs to be connected with other structural members to jointly realize the whole function. In a plurality of connection parts of the pressure vessel, the geometry of the connection pipe area is complex, and more remarkable stress concentration can be generated under the action of pressure, so that cracks are promoted to initiate or expand. In order to ensure the service safety of the in-service pressure vessel nipple, the stress intensity factor of the nipple area crack needs to be calculated so as to carry out the structural integrity assessment of the pressure vessel nipple. Currently, the cracks considered in the joint area of the pressure vessel are mainly quarter-circular surface cracks, and the technical specifications (such as the eleventh volume of the American boiler and pressure vessel specifications and the safety evaluation specification of nuclear power equipment of the Japanese society of machinery) of the cracks are given an empirical formula for calculating the stress intensity factor of the deepest point of the cracks. However, in recent years, the research finds that the empirical formula in the specification is established based on a two-dimensional finite element analysis method, and the influence of the three-dimensional structure sizes of different takeover tubes in actual engineering is not considered, so that the method is difficult to widely apply. Meanwhile, the stress intensity factor of the deepest point of the crack of the pressure vessel connecting pipe is generally lower than that of other positions of the front edge of the crack, and the structural integrity of the in-service pressure vessel connecting pipe is assessed by using an empirical formula in the specification, so that an unsatisfied assessment result can be brought, and the service safety of the pressure vessel connecting pipe is affected. Thus, there is a need to develop methods that can scientifically evaluate the stress intensity factor profile of the leading edge of a pressure vessel nozzle. Disclosure of Invention The invention aims to provide an evaluation method for the stress intensity factor distribution of the crack front edge of a pressure vessel connecting pipe, In order to achieve the purpose, the technical scheme of the invention is that the method for evaluating the stress intensity factor distribution of the crack front edge of the pressure vessel connecting pipe comprises the following steps: finite element analysis is carried out on the connecting pipe cracks of the pressure vessels with different sizes; Constructing a correction factor database of the crack leading edge of the pressure vessel based on the finite element analysis result; Based on the correction factor database, establishing a weight function equation of the pressure vessel for taking over the crack; Inputting the size of the pressure vessel takeover to be evaluated and the size of the crack of the pressure vessel takeover to be evaluated, and evaluating the stress intensity factor distribution of the front edge of the crack of the pressure vessel takeover under the complex stress condition acting on the crack surface of the pressure vessel takeover to be evaluated based on a correction factor database and a weight function equation. Further, the finite element analysis is carried out on the connecting pipe cracks of the pressure vessels with different sizes, and the method specifically comprises the following steps: Setting the size of a pressure vessel connecting pipe and the size of a crack of the pressure vessel connecting pipe; Setting material properties of the pressure vessel; Setting an action stress on a crack surface of the connecting pipe of the pressure vessel; Based on the setting conditions, a three-dimensional model of the connecting pipe of the pressure vessel with the cracks is established, and finite element analysis is carried out on the cracks of the connecting pipes of the pressure vessels with different sizes. Further, finite element analysis is performed on the pressure vessel connecting pipe cracks with different sizes based on the theory of linear elastic fracture mechanics. Further, based on the finite element analysis result, a correction factor database of the crack front of the pressure vessel is constructed, and the correction factor database specifically comprises: based on the finite element analysis result, calculating J integral of the crack front of the pressure vessel; Calculating reference fracture parameter distribution data of the crack front of