The Residual Fatigue Life Evaluation Of Steel Crane Beam

In recent years, through many surveys to the industrial workshop, The phenomenon that the heavy steel crane beam has appeared fatigue cracks of under repeated loads in different degrees is found. It is endanger of production. Currently, it is lack of better fatigue fatigue life evalution method to steel crane beam. Sudying and proposing a better residual fatigue life evalution method to steel crane beam has a very important application value.The main form and cause of fatigue failure of steel crane beam are analyzed first, and focused the welded steel crane beam. After analysis, the paper thinks that the fatigue crack of uniform cross-section steel crane beam is mainly caused by the eccentric, and the fatigue crack of variable cross-section steel crane beam is mainly caused by the large stress concentration at variable cross-section.Currently, the residual fatigue life evaluation of steel crane beam is based on the traditional fatigue analysis method. The Deficiency of this approach is that the components of structure is presumed without any defects, This does not match the actual situation. Fracture mechanics theory admits the initial defects, so the linear elastic fracture mechanics is introduced to asses the residual fatigue life of steel crane beam. The main fatigue life of welded structure is crack propagation life. The Paris equation is used to evaluate the fatigue life of steel crane beam. Due to the uncertainty of parameters in assessment formula, parameters are deemed as certain probability distribution, then the result of assessment is closer to actual situation. Verified by examples, probabilistic fracture mechanics can evaluate residual fatigue life of steel crane beam reasonably.the probability characteristics of is updated by destroyed components of the same batch, then the residual fatigue life of other components in the same batch is evaluated by updated information.