Design And Development Of Weld Fatigue Analysis Based On SiPESC

Structural fatigue refers to the phenomenon that after a period of time under the action of alternating loads,a small crack is formed in the local high-stress area of the structure,and the crack gradual propagation until it breaks.Fatigue failure is characterized by sudden occurrence in time and locality in location,so fatigue failure often occurs without any visible signs and is prone to accidents.Welding structure is a kind of economic and efficient structure connection method,the welding of pressure vessels under cyclic loading are especially vulnerable to fatigue damage.In general,the static strength of welds itself is not lower than the parent metal,but due to the existence of stress concentration,residual stress and welding defects,welded structure under dynamic load capacity is far lower than the parent metal,it is welded structure fatigue weak links,and is one difficulty in fatigue analysis.Compared with the traditional welding structure fatigue assessment method,the structural stress method has the characteristics of small SN curve dispersion and mesh insensitive,and has been included in ASME code.In this paper,the fatigue analysis module of welded structure is developed on SiPESC platform by using the structural stress method,and the correctness of the program is verified by the example.Firstly,the basic theory of structural fatigue including SN curve,time series load spectrum,rain flow counting method and fatigue damage accumulation is introduced in this parper.On the basis of this,a special structure of structural fatigue,welding structure,is introduced emphatically.In this paper,we choose the most advantageous structural stress method among several welding fatigue assessment methods,and its basic theory and formula are introduced,and then,general fatigue analysis is developed in this paper based on SiPESC platform module,program is capable of metal fatigue analysis and weld fatigue analysis parameter definition,the rain flow counts method,SN material parameter,Minner fatigue damage accumulation,single channel and multi-channel load history definition,mean stress correction and other general fatigue analysis function,lays a foundation for the subsequent welding fatigue assessment of structural stress method.Furthermore,this paper develops a structural stress menthod welding fatigue assessment module on the SiPESC platform,which can support the definition of welding seam of mixed shell or solid elements with the same order and freedom degree,and it can support the functions of automatic ordering of node and elements at the welding line.Finally,the developed program is confirmed by example,also,the functions and results are compared with the foreign commercial fatigue software.The program developed in this paper has the necessary functions of general fatigue analysis,and the developed fatigue analysis module of structural stress method can basically meet the actual engineering requirements after the comparison with foreign commercial software.The program is compared with the results of the foreign commercial software,and the results are proved to be accurate.Other subsequent algorithms and functions can be added dynamically in the SiPESC platform through plug-ins,with good openness.