Research On Life Prediction Method Of Mechanical Structure Under Fatigue Load

Fatigue failure of mechanical structures is one of the main reasons for failure of mechanical structures in actual use environment.Since people realized the damage caused by fatigue loads to mechanical structures,people have begun to study how to predict the actual working life of mechanical structures under fatigue loads,put forward many fatigue analysis theories,and have successfully predicted the fatigue of mechanical structures under actual working conditions life.However,due to the complexity of the fatigue problem,there is currently no universally accepted method for predicting fatigue life.In-depth research on fatigue damage of mechanical structures is also needed.At the same time,with the continuous development of Computer assistance technique,more and more engineers use computers to predict fatigue life of mechanical structures,research on how to use the results of finite element method and multi-body dynamics simulation to predict fatigue life of mechanical structures,has important guidance for the development,design,and subsequent repair and maintenance of mechanical structures.In this paper,the research on multi-axis fatigue and the life prediction process based on mechanical structure is carried out.A new multi-axis low-cycle fatigue life model is proposed and the Abaqus fatigue life analysis module is developed.The main work is as follows:(1)By studying the factors that affect the fatigue life of materials under non-proportional multiaxial loading,considering the effect of non-proportional loading paths on the fatigue life of materials and the sensitivity of materials to fatigue failure under non-proportional path loading,A new multiaxial non-proportional additional influence factor is proposed.Based on the critical surface method,combined with the non-proportional additional influence factors,the shear strain amplitude and normal strain amplitude on the maximum shear strain plane are used as control parameters,a new multiaxial fatigue life prediction model is proposed.The fatigue life data of various materials were verified and compared with other fatigue life prediction models,and the predictive ability of the new model was confirmed.(2)The analysis method of fatigue life prediction based on the results of finite element analysis combined with load spectrum was studied.By extracting the node stress and strain on the finite element element,combined with the load spectrum,different fatigue analysis methods are used to analyze the fatigue of the mechanical structure.The fatigue analysis methods include the nominal stress method and the multiaxial fatigue analysis method.The nominal stress method uses the rain flow counting method to count the stress loads on the element nodes,and calculates the damage and fatigue life of the structure through the S-N curve and Miner linear accumulation.The multi-axial fatigue analysis method uses the Wang-Brown multi-axis cycle counting method to count the stress and strain on the element nodes,and combines the corresponding multi-axial fatigue damage model and Miner linear accumulation to predict the life of the structure.(3)Based on Abaqus secondary development technology,program the above fatigue analysis methods and develop Abaqus custom GUI application to directly perform fatigue life analysis in Abaqus.With the help of Abaqus post-processing module,the fatigue life of the structure can be visualized.The fatigue life of two mechanical structures under specific working conditions is used to predict the fatigue life data of the structure.