Boundary Element Method Simulation Of Fatigue Crack Propagation On Engineering

General engineering structure will produce mini crack and cranny inevitable during theprocess of manufacturing and using in local area. These mini crack will gradually propagateunder the action of fatigue loads,stress corrosion or creep, and eventually lead to the failuredue to fracture.Boundary element method (BEM) was applied the to simulate the propagation crack of2-D crack with Fortran program. The advantage of BEM was made full use during thesimulation process, and quadratic elements were meshed on boundary, one-quarter singularelements were meshed nearby crack tip to simulate singularity of crack tip. Displacementinterpolation method was applied to calculate the stress intensity factor, and the direction ofmixed mode crack propagation was predicted by the greatest tangential tensile stress rule. Themesh nearby crack would be divided automatic when crack propagated. Compared to finiteelement method, it greatly reduced the difficulty and work of meshing.Two simple examples were applied to calculated stress intensity factor for checking thevalidity of program. They were compared with the results calculated by ANSYS and stressintensity factor manual, meanwhile analyzing the influence of mesh size nearby the crack tipto results. On base of the above work, marine star ring was choose to simulate and distinguishcrack propagation track under different backup ratio.The stress intensity factor of Simple symmetry structure was calculated by Fortranprogram. Finite big body with nonpenerative cravk was taken as a model, the results werecompared with that calculated by meshless Galerkin method and stress intensity factor manual.At the sametime, some degradation units were proposed to solve the problem of the singularelement integral in BEM. The precision of two kinds degradation units was compared. At last,the main error source of BEM was analyzed.