光位置検出素子を用いた混合モードき裂変位計の試作と混合モード弾塑性破壊靭性試験

概要

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A method of testing elastic-plastic fracture toughness under mixed-mode loading was proposed using a single-edge-cracked specimen subjected to bending moment and shearing force. The J-integral of a crack in the specimen is expressed in the form of J=J_1+J_<II>, where J_I and J_<II> are the components of mode I and mode II deformation, respectively. J_I and J_<II> can be estimated from the M-θ diagram (M : bending moment, θ : crack opening angle) and F-U diagram (F: shearing force, U : crack shearing displacement). In order to obtain the M-θ diagram and F-U diagram, a new deformation gauge for a mixed-mode crack was developed by using optical-position-sensing devices. The elastic-plastic fracture toughness tests under mixed-mode loading were carried out on aluminum alloy 6061-T651. The crack initiation from a mixed-mode crack occurs in the tensile type and shear type depending on the loading mode. As the mode I component becomes more predominant, the tensile type crack is initiated in a brittle manner. On the other hand, under a mode-II-predominant loading, the shear-type crack initiation occurs in a ductile manner. The condition of crack initiation from the mixed-mode I-II crack is shown by two curves for the tensile type and shear type on the J_I-J_<II> plane.
社団法人日本機械学会の論文
1991-08-25