Limit Load Solutions For Thick-walled Cylinders With Circumferential Constant-Depth Cracks Under Combined Pressure, Tension And Bending Loads

Cylinder is one of the most important element in constructing pressure vessels and pipes. The limit load of the cracked cylinder is a very important input in the structural integrity assessment for the pressure vessel and pipe by using R6typy procedure. Up to now, limit load solutions for thin-walled cylinders with circumferential cracks under combined loadings are well developed. However, the limit load solutions for thick-walled cylinders with circumferential cracks under combined loadings are still lacking. The purpose of this dissertation is to develop limit load solutions for thick-walled cylinders with a circumferential crack under combined internal pressure, axial tension and bending loadings. The main work of the researches and the conclusions are as follows,(1) Limit load solutions for thick-walled cylinders with circumferential cracks under combined internal pressure,axial tension and global bending loads are developed via the Mises yield criterion, considering axial stress distribution according to the neutral axis supposition, and considering both hoop stress and radial stress are constants.(2) Limit load analysis of elastic-perfectly-plastic finite element for thick-walled cylinders with various ratios of outer/internal radii of cylinders, crack depths(a/t=0.2,0.5,0.8), crack lengths(θ/π=0.2,0.8,1), loading ratios between internal pressure, axial tention and bending(γ=0.1,1,10,π=0.1,1,10).(3) The predictions are compared with the results of finite element analysis, the results show that the predictions using developed solutions are close to the finite element results and always conservative. The maxmum relevant error based on the finite element results for all cases studied in this work except long and deep cracks is about-20%, for the long and deep cracks the maxmum relevant error will above-20%but below-40%when1.2≤k≤2; but when k=3and internal pressure dominated loads the maximum relevant error above-25%but below-35%.(4) Comparing the predictions with the results of the finite element analysis.values of σθ and σ, are proposed in limit load analysis for thick-walled cylinder with circumferential crack.