Experimental Study Of The Initiation Of Fatigue Crack For Tall Guyed Mast's Earplate Welded Joint

The tall guyed mast is different from normal building structure,it's in the long length direction and the width direction is short,that is to say the length of the guyed mast is very long but very thin.The guyed mast in the larger wind loads due to the instability of the destruction of all damage accidents accounted for a small proportion,guyed mast is mostly in circulating wind load in service period.So fatigue crack occurred,resulting in a collapsed mast structure accident.Structural members subjected to cyclic loading under the action of certain parts of the structure fatigue damage,the tensile strength of the material than the material at this time is to a large maximum stress,maximum stress and even below the yield limit of the material.This causes a phenomenon,the material plastic deformation does not occur,thereby deteriorating the breaking time shorter,it belongs to brittle failure.The fatigue life of the structural member is composed of fatigue crack initiation life and fatigue crack growth life.However,relatively rapid crack propagation,and therefore fatigue crack initiation life research structure for the actual project has a guiding role.We design the guyed mast's earplate welded joint specimen and then start the experimental study of fatigue.In the paper,ten test models of welding pull ear node are divided into two groups according to five test models in one group.One group is carried out invariant stress amplitude reversed loading by MTS landmark,the amplitude cyclic loading applied during the test.Finally,the results of two groups of test specimens can be mathematically processed to obtain two tall guyed mast's earplate welded joint fatigue crack initiation stress amplitude-the number of cycles(S-N)curve.By converting the Coffin-Manson formula,we get the two tall guyed mast's earplate welded joint fatigue crack initiation strain amplitude-the number of cycles((35)?-N)curve.In this paper,results of that with the stress amplitude increases,the fatigue life of tall guyed mast's earplate welded joint is a downward trend.Welding residual stress has an adverse effect on the fatigue life of the structure.Eliminate residual impact by ultrasonic method can eliminate part of the residual tensile stress,and pull in compressive stress,thereby increasing the fatigue life of the structure.Stress ratio hasan influence of the fatigue life of structural parts.If the stress ratio is larger,the fatigue life of the structure is shorter.At higher stress amplitude where the fatigue life of the structure is reduced quickly;while in the lower places stress amplitude,the fatigue life of the structure change slowly.