塑性域におけるき裂つき部材の破壊条件

概要

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Ductile fracture criteria would be a very useful engineering tool in predicting failure of metals in practical deformation processes. In the present study, a ductile fracture criterion for a cracked plate of n-th power strain hardening material has been investigated theoretically and experimentally under plastic uniaxial tension. The relation between the critical strain far from a crack at fracture and a crack length was derived theoretically based on the energy conservation law and by analytical estimation of the strain energy for a cracked plate. The experiment on 0.80% C steel was conducted to compare with theory. Also, the strain and stress distributions near a crack tip were discussed. The following conclusions were obtained: (1) The total strain energy I for a cracked plate is expressed as the sum of I_∞ without a crack and I_∞ due to a crack, where I_c is represented by the product of I_∞, square of a crack length C^2 and constant α, that is, I_c=α・C^2・I_∞. (2) The relation between the critical strain ε_∞ and a crack length is given by ε_∞・C^<1/1+n>=const. (3) The experimental results are in good agreement with theory. (4) The strain distribution e near a crack tip is predicted as follows,[numerical formula] (ε_∞: strain far from a crack, γ: radial coordinate)
社団法人日本材料学会の論文
1977-12-15