Numerical Simulation Of Stress Field At Oblique Crack Tip Of The Pressure Pipeline

Pressure pipeline safety assessment can be carried out by fracture mechanics, which is the international development trend of the pipeline safety assessment. Since the late seventies, theory and applications of fracture mechanics have been developed rapidly. However, in the engineering practice, fracture parameters which you can directly refer to are still few when safety assessment is executed in structures with some cracks. Based on fracture mechanics and FEM, a finite element model of pressure pipeline containing oblique cracks is built by ANSYS finite element analysis software. Through calculation, values of the stress intensity factor K are obtained under different elastic conditions(different crack geometries, material properties and loading conditions, etc.), and they can be converted to correction factor F which is more applicable in engineering practice. Then the expression of F can be achieved by fitting. The stress field near the tip of oblique crack is analyzed, and by comparing results, influencing factors of stress field and strain field near the tip of oblique crack are discussed.The main contents of this thesis are as follows:1. The use of pressure pipeline in our country is briefly introduced, the methods and development of fracture mechanics at current stage are studied and analyzed and provide a basis for fracture analysis of pressure pipeline.2. A finite element model of the cracked plates by ANSYS is established, and it demonstrates the feasibility and accuracy by adopting this model and SHELL63 element and it lays the foundation of subsequent research work.3. A finite element model of pressure pipeline with axial crack by ANSYS is built; the value of KI is obtained under conditions of internal pressure loads and linear elasticity. Finite element results are extracted with parameters of wall thickness, pipe diameter, and the crack length respectively, and curves with those parameters and stress intensity factor are plotted.4. A finite element model of pressure pipeline with oblique crack by ANSYS is set up; the values of KI and KII are acquired under conditions of internal pressure loads and linear elasticity. Through changing parameters of material properties, geometries, loading conditions etc., the evolution of SIF under different influencing factors is drawn, and results are analyzed and discussed.