衝撃破壊靭性試験におけるコースティックス法の三次元有限要素解析

概要

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The caustics method as applied to the measurement of the impact fracture toughness K_<Id> is studied by using a three-dimensional finite-element method (3D-FEM). A semi-infinite crack in an elastic plate with a finite thickness is considered, and a time-dependent (ramp) uniform pressure is assumed to be applied to the crack surfaces. The dynamic J-integral, J, is calculated for various points on the crack front and is converted to the dynamic stress intensity factor K_I(t). The crack is assumed to begin to propagate when the value of K_I(t) at the mid-thickness of the plate reaches a critical value K_<crit>. The caustics in reflection are generated by using the reflection law of light. The "measured" K_I(t) is obtained from the diameter of the caustics, and the "measured" K_<Id> is determined from the peak of the time history of the "measured" K_I(t). It is found that the delay time to detect the crack initiation is larger than that predicted by 2D-FEM, and the "measured" K_<Id> depends on the shape of a propagating crack front.
社団法人日本機械学会の論文
1992-10-25