Study On The Influence Of Welding Residual Stress On The Ultimate Strength Of Structures

Ultimate strength is an important aspect of hull strength,welding residual stress has an important effect on the ultimate strength of the structure.At present,the welding residual stress models commonly used in structural design and strength checking are based on the research of welded structures of ordinary steel and some high strength steel of average thickness.With the development of large-scale ships,the application of thick plates and high-strength steel in ship structure design is more and more common.For this kind of structures,domestic and overseas scholars have carried out many welding numerical simulations and experimental researches from the perspective of process mechanics,but the researches on the effect of welding defects on the strength of the structure are rare.In view of the above problems,this paper carried out a research on welding residual stress and its effect on structural ultimate strength.The main contents of this paper are as follows:1)Based on the thermal-elasto-plastic finite element analysis theory,the welding heat source model,element types and constraints are analyzed,and full coupling method and sequential coupling method for welding numerical simulation are established.On top of this,a welding simulation method based on shell-solid mixed element model is proposed.The calculation results show that compared with the solid element model and the shell element model,the shell-solid mixed element model not only ensures the calculation accuracy but also effectively improves the calculation efficiency.2)Based on the numerical simulation method of shell-solid mixed element model for the welding process,numerical simulations of butt welding and fillet welding of hull structures are carried out.The effects of variation in plate thickness and material yield limit on the level and distribution of residual stresses in welding are analyzed.Based on this,the commonly used welding residual stress model is modified to meet the needs of thick plate and high-strength steel welded structure design and strength assessment3)Based on the modified simplified model of welding residual stress accounting for the plate thickness and material yield stress corrections,and by applying the nonlinear finite element method,an analytical method for ultimate strength of hull structures was established The calculation of the ultimate strength of stiffened plates with different material yield limits,stiffener forms(Flat-bar,Angle-bar and Tee-bar)and sizes is carried out.The effects of residual stress and material yield limit on the ultimate strength of stiffened plates with different slenderness ratios are systematically analyzed.