| The influence of welding residual stress on the fatigue strength and life of welded structure has always been the focus of research on the reliability of welded structures.However,the relevant research mainly relies on empirical formulas and curves based on experiment and statistics.In order to simplify the problem,according to T.R.Gurney "Fatigue of Welded Structures",it is possible to more accurately describe the effect of welding residual stress on the fatigue strength of welded structures by describing the load feature of the welded structures with the actual stress range,but the assuming of ideal elastic-plastic,the loading direction and loading stress range are unclear,whose applicability and scope of application are necessary for further study.In this paper,the static load mechanical properties and strain fatigue properties of 590 MPa high strength steel 10 Cr Ni3Mo V with yield strength ratio of 0.922 have been studied,also the welding process of matched butt joint and the cyclic loading process after welding are studied by finite element method.And the distribution characteristics of welding residual stress for butt joint of high strength steel and the influence of different stress ratio,different cyclic loading direction and different loading range to the attenuation of welding residual stress,and the effect of welding residual stress on the actual cyclic stress range of plant butt joint was also studied.The study found that :1.The distribution of welding residual stress for butt joint of high strength steel with 10 Cr Ni3Mo V is same with butt joint of low carbon steel.The peak value of longitudinal residual stress reaches yield strength of the material.2.The redistribution of internal stress of butt joint is caused by external load under various conditions,after unloading,the peak value of welding residual stress attenuated with various degree.The longitudinal residual stress attenuation of the longitudinal load ratio of 0 is much larger than that the stress ratio of-1.3.Under the condition of transverse cyclic load(the external load is perpendicular to the direction of the maximum principal stress after welding),the upper and lower limits of the actual cyclic stress range of the maximum principal stress near the weld are higher than the theoretical values recommended by the literature.When the cyclic stress amplitude is less than the yield strength and the stress ratio is 0,the upper limit of the maximum principal stress near the weld is 745 MPa,which is higher than the yield strength(702 MPa)43 MPa,and the cyclic stress amplitude is smaller,The lower limit of the actual cyclic stress range is much higher than the theoretical value recommended in the literature;when the applied cyclic stress amplitude is 780 MPa(greater than the yield strength)and the stress ratio is 0,the upper limit of the actual cyclic stress range of maximum principal stress is 783 MPa,When the cyclic stress is-1,the upper limit of the maximum cyclic stress range is about 745 MPa,and the cyclic stress amplitude is about 1/4 of the applied cyclic stress amplitude,and the lower limit of the cyclic stress range is-27.2 MPa.Much higher than the theoretical value recommended by the literature.Therefore,the cyclic stress range recommended by the literature is not applicable to the case where the high-strength steel butt joints are subjected to transverse cyclic loading.4.Under the condition of longitudinal loading cyclic loading(the superposition of the external load and the maximum principal stress after welding),the upper and lower limits of the actual cyclic stress range near the maximum principal stress near the weld are higher than the theoretical values recommended by the literature.When the stress ratio of cyclic load is 0 and-1,the upper limits of the actual cycles tress range of maximum principal stress near the weld corresponding simulated were 822MPa(close to the tensile strength of the material)and 756 MPa,which were higher than the yield strength of the material 120 MPa and 54 MPa,and the cyclic stress amplitude is close to that of the external load.The lower limit was much higher than that recommended by the literature value.Therefore,when the cyclic stress range recommended by the literature is not applicable to the case where the high-strength steel butt joints which are subjected to longitudinal cyclic loading situation,It is necessary to re-calibrate the upper limit of actual cyclic stress range. |
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