Welding Residual Stresses And Holes On Q235 Steel Study On The Influence Of Crack Propagation

Welding is a manufacturing process of joining alloy metal or other thermoplastic materials by heating,high temperature or high pressure.Residual stress would inevitably appear in the welding process,which may have a certain impact on the mechanical properties of components,and structural parts may appear defects such as round holes or inclusions in the production and use process.As a result,it affects the crack propagation path.Therefore,on the basis of systematically analyzing the welding residual stress,it is of great significance to study the influence of defects on the crack propagation path of steel structures under low cycle fatigue.Based on the non-linear finite element analysis,the butt welding process of Q235 steel plate is simulated by SYSWELD.The temperature field and stress field produced in the welding process are studied,and the residual stress of welded plate is measured by X-ray diffraction method.The simulation results are compared with the actual measurement results,and the two results are in good agreement,which verifies the feasibility of the finite element simulation analysis.The fatigue life of butt plate members is studied by applying low-cycle reciprocating loads.The test results show that the greater the residual stress of welded parts,the less the fatigue cycles of specimens,and the welding residual stress has adverse effects on the fatigue life of structural parts.By introducing the concept of crack deflection coefficient,the influence of circular hole defects on the deflection degree of crack propagation is quantitatively described.Using ABAQUS simulation software,the crack propagation process is simulated based on the extended finite element method(XFEM).The experimental results are compared with the simulation results to verify the accuracy of the extended finite element method.The results show that when the angle θ between the circular hole and the crack tip is 45°,the crack deflection coefficient reaches the maximum value.The crack deflection coefficient increases with the increase of the radius R of the circular hole and decreases with the increase of the distance L between the circular hole and the extension line of the crack tip.Under the combined action of R and L,L is the dominant factor affecting crack deflection coefficient.