Experiment And Simulation Analysis For Bilateral Crack Propagation In Steel Fracture

Damage and crack propagation of engineering materials is closely related.Thereasons for crack propagation are complicated, but propagation is mainly due tothe change of stress,strain and microstructure damage of very small area incrack tip. The complex engineering structure is generally composed of simpleelements, such as the connecting pieces, beam, and rod etc. In some advancedmaterials and structures, there often exist singularities caused by thediscontinuity of the material or geometry mutation, such as the interface end andbreach where the failure start. Because the stress near singularity is very largeand this may lead to the expansion of crack,the carrying capacity of material orstructure is greatly reduced. So, research on crack behavior and its propagationhas a positive effect on the improvement of the whole life cycle of products on acertain extent.The experiment of bilateral crack propagation of steel fracture is studied inthis thesis. At the same time, the finite element method is used to simulate thespecimen crack expansion. Comparing the test results with the finite elementmethod results, the rule and path of crack propagation under tension orcompress loading can be predict.Firstly, the theory of fracture mechanics and fracture criterion are introduced,from the view of linear elastic fracture mechanics and elastic-plastic fracturemechanics.And then,the basic models of fracture mechanics are analysed,themixed mode fracture.Based above,three kinds of bilateral crack model of steelare given,a reasonable sample size and chucking appliance for the experimentare designed. The performance parameters of materials are obtained by usingSHIMADZU experiment machine.According the bilateral crack experimentdatum,the force-time curves of crack propagation are draw out and themaximum stress when crack initiation appears is got. At the end of thisthesis,XFEM extended finite element module of Abaqus software is used tosimulate the crack fracture, and the maximum traction of crack propagation isobtained with different two crack distance. The numerical simulation results arecompared with experimental results at the same time.Based on the experiment results, the sample size and fixture can reflect species crack propagation very well. Comparing experiment results of bilateralcrack, its propagation path is different from the increased distance of bilateralcrack, but the maximum traction is nearly the same. The maximum traction ofsimulation results are in good agreement with that of experimental resultss.