高分子材料における疲労き裂先端のクレーズの変形と応力の解析

概要

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Deformation of the craze during fatigue cycling was measured continuously at the fatigue crack tip in polymethylmethacrylate by an optical interference method. Based on the line-zone craze model proposed previously, the measured craze contour was analyzed. With the craze stress, being discretized along the craze length, simultaneous non-linear equations were solved numerically. The craze stress concentrates gradually near the crack tip with applied load, which may cause fibril breakage there, and hence crack propagation. At an almost unloaded condition, about half of the craze length was subjected to compression, but the craze-crack boundary was still clearly distinguished. Any value of the elastic modulus of the craze fibril gives similar craze stress, but only the appropriate value, 100 MPa, resulted in the invariant original craze thickness with the load. The geometry of craze contours may also be used to evaluate the stress state around the crack tip without referring to the applied load. More than 30 % of the applied stress intensity was estimated.
一般社団法人日本機械学会の論文
1988-04-25