Simulation Study On Fatigue Crack Propagation

With the development of fracture mechanics, more and more researchers tend to applythe fracture theory to solve structural fatigue and fracture problems. However, theconditions of materials and environmental equipments in fatigue experiments are far moreideal from the pointview of fracture mechanics, and the low reliability of thoseexperiments leads to poor fatigue pridiction. Therefore, the finite element simulation ofthe fracture parameters and the fatigue crack propagation are meaningful for strucuturalfatigue and fracture problems.In this thesis, simulations of fracture parameters and crack propagation process by useof common finite element analysis softeare were investigated. The comparisons offracture parameters among theoretical and experimental results with simulation resultswere were carried out. The main research contents and results are listed as follow:1. The researches on fracture parameters and crack propagation, along with theapplication of finite element method to facture problems, were generally introduced.2. The stress intensity factor K of both surface crack and three-dimensional crack weresolved respectively by the common finite element analysis software ANSYS (Ver.14.5).The variation of K value under different loads and different crack tip angles were thendiscussed. It is found that2/5of the crack length is considered as the most accurateintegral path by comparison with other different J integral path. The mutual integrationmethod would deduce more accurate K values than displacement interpolation method.3. Through the three-point bending fatigue crack propagation experiment, the doublelogarithmic Paris curve was obtained, and the threshold value of stress intensity factor Kthwas measured. Meanwhile, the heterodyne method and integral method were used tosimulate the K value during the process of crack propagation, also the double logarithmcurve was obtained and its error analysis was carried out. It is can be concluded that theintegral method is more accurate on calculation of the K and the double logarithmregression curve.4. Based on fracture mechanics method and the cohesive zone model, simulation ofcrack propagation were implemented by the common software ANSYS and ABAQUS. The crack propagation path of different crack such as oblique crack, single edge crack andmultiple cracks was demonstrated. The influence of load effect on the path and rate ofcrack propagation were investigated.