The Use Of Continuum Damage Theory Study Of Structural Damage Analysis And Life Prediction

The damage analysis and fatigue life prediction of metal structures is an important research domain in the engineering field. The fatigue failure process consists of two stages: fatigue crack initiation and crack propagation. The life of the second stage can be calculated by Paris formula, but Paris formula is no use to predict the life of the first stage.The main purpose of this paper is to develop a fatigue and damage analysis model based on continuum damage mechanics. This model is applied to study damage evolution. Using the model the life of crack initiation can be predicted as well as the life of the crack propagation.The following three factors are well combined with each other in this paper: theory knowledge, investigation and experiment.Through investigation the real needs and the basic data have been mastered. In this paper, the research work and accomplishment in this domain in the past several decades has been reviewed in brief which includes research and innovation in theory and the main kinds of approaches in experiment. The basic knowledge frame and theory system of continuum damage mechanics has been introduced mainly. Combining with the experiment, the mechanism of fatigue failure has been analyzed in details and the whole process of fatigue failure has been illustrated. The loading analysis and stress calculation on the metal structures has been carried out, and the locations of fatigue cracks have been pointed out.A new damage variable has been defined while a damage accumulation model and a fatigue life model have been developed. The whole process of fatigue damage accumulation in the metal structure has been well illuminated by the expressions of these two models.The main classic fatigue cumulative damage theories and the representative definitions of damage variable have been introduced briefly. Considering the characteristic of the metal structure and using continuum damage mechanics, a new damage variable has been defined related to the effective loading area. Further more, a fatigue damage accumulation model and a fatigue life calculation model have been acquired and the relationship curves have been described in coordinates. The damage state and fatigue life can be confirmed instantaneously.The experimental results have shown that a damage variable based on the effective loading area decrease can be used to measure cumulative damage and provide a good estimate of the fatigue damage process, as well as to predict the fatigue life. Thus, the original assumption and purpose are realized.The disadvantage of this model has been illuminated and the development prospect of cumulative damage analysis and fatigue life prediction of metal structures has been suggested.