Interaction Of Stress Intensity Factor With Multiple Cracks In Inner Surface Of Nuclear Pipelines

Nuclear pipeline safety assessment has been the important application part of the fracture mechanics and reliability. With the aging of nuclear and nuclear accident occurs again, the reliability of the life of nuclear pipeline safety becomes more important. In the past, a single crack problem was considered on the assessment of nuclear piping, and multiple cracks phenomenon, as a part of fracture mechanics, is not perfect. To improve the content of fracture mechanics, and to improve the multiple cracks research and the reliability of nuclear piping evaluation, this paper focus on the effect of multiple cracks nuclear piping stress intensity factor of the actual variation, and a "leak before break" technique (LBB) measures for improvement was suggested. Thus, the multiple crack problems of research is enriched, multi-crack problem solving accuracy is improved and nuclear pipeline assessment methods is improved.In fact, the crack shape and the distance between the cracks play the significant role of the stress intensity factor when multiple cracks exist. Therefore, the same pipe material, the same pipe size, the same level of stress and stress are set to in the finite element solution process.Firstly, methods based on the finite element model of the cracked nuclear pipeline in ABAQUS software are used to analyze and to select the more appropriate method for solving the stress intensity factor. And it is proved that the node displacement extrapolation method is the most precise solution method of the stress intensity factor of this kind of crack.In addition, in order to study the multiple cracks variation of the stress intensity factor, crack groups are combined with variables cracks with the crack spacing, crack depth ratio, the crack length ratios as the single-factor. The single cracks those groups refer to are solved in ABAQUS software.Besides, the stress intensity factor of each groups are solved in ABAQUS software. And calculate the effect factor of each single factor when multiple cracks exist. Equations, with each single factor as the self-variables and with stress intensity factor coefficients as dependent variable, are deserved by curver fitting.Finally, the results of the previous multi-core crack pipe stress intensity factor theory are applied to the "leak before break" technique (LBB), which proposes the improved method of assessment of nuclear piping.The purpose of this paper is to improve the safe operation of nuclear facilities, and to provide a theoretical basis on the pipeline capacity.