Computational Facture Analysis And Experiment Research Of The New All Fracture Modes-specimen

Currently, the theories of two-dimensional fracture mechanics have been developedperfectly. However, few researches are taken on three-dimensional problems. Practicalthree-dimensional fracture problem is usually reduced to a two-dimensional problem to solve,which may lead to inaccurate results because of ignoring some essential characteristics ofthree-dimensional crack. Therefore, a new three-dimensional fracture sample is studied bytaking numerical simulation and experimental measurements. This research has theoreticaland practical significance to a certain extent.Firstly, classic samples are analyzed and the sample of this paper and its load principleare derived from them. The finite element model of the sample is constructed in the ABAQUSsoftware. And the singularity at crack tip is simulated to confirm the accuracy of analysisresults by using degenerate elements.Secondly, a few classic numerical calculation methods of fracture mechanics areanalyzed and compared, basing on which the J-integral method is used to analyze the newthree-dimensional sample at the state of plane strain. Comparing the results of finite elementanalysis to the results of two-dimensional empirical formula, it is indicated that finite elementmodel of the new three-dimensional sample is correct and the J-integral method is efficient.At the same time, the model is loaded in the formⅠ,Ⅱ,Ⅲ,Ⅰ+Ⅱ and Ⅰ+Ⅲ, by which thestress distribution at the crack tip and the dimensionless stress intensity factors are obtained,and the three-dimensional effects near crack front are proved.Thirdly, Richard fracture criterion is used to take the analysis of the newthree-dimensional sample in the crack form Ⅰ,Ⅱ and Ⅰ+Ⅱ so as to forecast the crackinitiation angles at each form.Finally, experimental measurements are taken to prefabricate fatigue crack of the newthree-dimensional sample. The fatigue crack samples which are meeting requirements areloaded in the crack form Ⅰ,Ⅱ,Ⅰ+Ⅱ,Ⅰ+Ⅲ and Ⅲ. Crack initiation angles at each crackform are measured. And the stress intensity factors are obtained by a data processing.Comparing the results of finite element analysis to the results of experiment, it is indicatedthat geometric model of the new three-dimensional is correct and Richard fracture criterion is efficient.