Experimental Study Of Fatigue Life For Guyed Mast’s Earplate Welded Joint

Guyed mast is a kind of high-rise structure which mainly subjects to wind load and consists of a slender bar body and several layer cables of3or4orientation stretching obliquely along height. Recently it has been widely used in radio communication, broadcast television, ocean and air navigation, environment protection, energy explore and other important fields of national economy.During the period of its serve, guyed mast has long been under pressure from cyclic dynamic loading (wind forces, moving forces, earthquake effects). A lot of research and engineering examples show that cyclic stress easily lead to the formation of fatigue cracks in the welding area of welding nodes, which constantly grows until causing the brittle fracture of nodes. Lastly, these will lead to the safety depression of guyed mast and even the collapse of the whole guyed mast. Therefore, it is necessary to analyse fatigue damage of welding nodes of guyed mast and study the initiation and extension of fatigue crack for predicting the structural fatigue life in oder to ensure the safety of guyed mast.In this paper, the fatigue damage theory is described in detail, the characteristics of structural fatigue under cyclic loading are studied, the characteristics of fatigue problems and the effect on fatigue performance from welding residual stress are summarized. In fact, during the period of its serve, the cyclic stress of welding pull ear node is lower and the cyclic number is higher. When destroyed, section stress is below material tensile strength and maybe even under Yield Point, plastic deformation is also very small. Therefore, the fatigue damage of welding pull ear node belongs to brittle failure of no obvious deformation with greater danger.For the comprehensive research of fatigue damage mechanism of welding pull ear node. In the paper, sixteen test models of welding pull ear node are divided into two groups according to eight test models in one group. One group is carried out eliminate remnant process under the same level. Two groups is separately carried out invariant stress amplitude Reversed Loading by INSTRON1341until crack initiation and the loading cyclic times of test models under different stress amplitude until crack initiation is tested. According the test results, the datum are processed and classified to obtain the distribution curve accord with fatigue life, which is "the stress amplitude—number of cycles"(Sa-Nf) curve under steel structure high-cycle fatigue damage. Lastly, the results are curve fitting through the Matlab software, then a more reasonable "the stress amplitude—fatigue life" curve is obtained.