Influence Study Of Weld Toe Geometry On Local Mechanical Behavior Of Weld Toe

Welded structures are widely used in industrial production.Due to the local uneven heating characteristics of the welding process,the real weld toe geometry is generally not mathematically perfect,resulting in obvious stress concentration effects at the weld section and along the longitudinal direction of the weld toe.It is manifested in that fatigue cracks often initiation at the weld toe area under cyclic loading,which leads to fatigue failure of the welded structure.Fatigue crack initiation mainly depends on the local stress concentration of the weld toe,and the weld toe geometry directly affects the local stress and strain state of the weld toe.Therefore,this paper takes welded joints as the research object,and conducts experimental research and numerical simulation analysis considering the influence of weld toe geometry on the local mechanical behavior of the weld toe(here,the stress-strain behavior is mainly considered).The main research work is as follows:(1)Based on the theoretical solution formula of the weld toe stress concentration factor(SCF),the geometric parameters of the weld were measured and statistically analyzed with the help of a super depth-of-field three-dimensional microscopy system,and the weld toe stress concentration factor was used as a parameter to study the geometric parameters of the weld on influence of weld toe stress concentration.(2)Taking fillet welded joints as research objects,considering tensile and three-point bending load types,a dynamic measured test of local cyclic strain at weld toe based on fiber Bragg Grating(FBG)strain sensor was conducted.Time history of local strain at the weld toe during the fatigue evolution process of the specimen were obtained,the strain response of the fatigue failure process was explored,the influence of the weld toe geometry on the local stress and strain state of the weld toe was analyzed.The differences of local stress and strain of the weld toe under the two load types were further compared.(3)Taking fillet welded joints as research objects,consider the limitations of experimental research methods,numerical simulation analysis methods were used to establish a number of two-dimensional models of weld section with different weld geometry parameters for numerical simulation calculations.The effects of weld geometry parameters on local stress-strain behavior of the weld toe were investigated.Based on the Manson-Coffin model,the fatigue life of the weld toe crack was predicted.The research in this paper confirms the effect of weld toe geometry on the local stress-strain state of the weld toe.It has certain guiding significance for the test of the weld geometry of the weld structure,the analysis of the local stress and strain of the weld toe,and the calculation of the fatigue life of the weld toe crack,which can be used in the analysis of engineering test.