Studies On Finite Element Analysis Model Of High Cycle Fatigue Damage For Steel Structure

The problem of fatigue damage of metal structures has been found in engineering field for a long time. As a whole of metal structure, about 80% ~ 90% fatigue accidents are related with fatigue and rapture. With the development of welded structure and the increasing frequency of the structure used, fatigue damage problem of civil steel structure becomes more and more serious. And at the present time, for highway bridge and industrial and civil buildings, applicable codes of steel structure (such as GB50017-2003) generally use simple linear accumulation damage standard and a given structure requirement to guarantee that there are no fatigue failures in structures or elements during the usage time. Their applicability is narrow and the results of calculation are not exact. Even are they useless to the fatigue analysis for complex structures and elements. But fatigue damage of civil steel structure mostly belongs to high cycle fatigue damage under recular service (except special cases such as earthquake), which has no obvious plastic deformation when damage and rapture happen, and the hazard is serious while the damage happens suddenly. So it is significant to establish fatigue model for steel structure.Depending on the reinforcement of steel bridge over Yellow River in Wubu and according to the characteristics of steel structure in highway bridge and industrial and civil buildings, this article initially establishes finite element analysis model of high cycle fatigue damage for steel structure by using fatigue damage theory and finite element analysis. This article analyzes high cycle and low cycle fatigue of unnotched steel samples on the basis of theoretical analysis to generalize elastic and plastic fatigue damage and get different rules of evolutionary process under different fatigue damages. Meanwhile, it studies and discusses the calculation of damage evolution and determination of some material constants. Then, this article uses universal finite element program ANSYS to simulate the development of crack of notched samples under the high cycle of constant-amplitude stress and the distributions of elastic and plastic areas and so on. So itcan completely describe the whole variation of stress field, strain field and damage field. To compare it with the experimental results, We can analyze and appraise the applicability and practicability of the model.This article puts forward basic ideas of using finite element program to analyze fatigue problems of complex structures or elements. Using finite element to analyze fatigue problems, at one hand, can reduce the cost of fatigue research, at another hand, make it possible to use theoretical fatigue analysis for the complex structures or elements. It has great development potential.