混合モード荷重下における延性破壊機構の研究

概要

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Three point bend specimen is used for ductile fracture tests with different mixed mode ratio. K_<II>/K_I. The crack growth direction in mid-plane of the specimen changes largely with the change of K_<II>/K_I value. Detailed observation of fracture surface is conducted, and it is shown that the average void diameter becomes smaller as K_<II>/K_I becomes lager. Numerical simulation is also carried out using Gurson's yield function. By in troducing stress-controlled void nucleation model, as well as plastic-strain-controlled nucleation model, it is shown that crack growth directions at mid-plane and free surface are estimated well and results agree with experimental observations qualitatively. Distributions of stress triaxiality and plastic strain are also evaluated and their effects on dimple fracture process are discussed.
2008-09-25