反応速度論に基づくクレーズ発展式の構築および均質化分子鎖塑性モデルを用いた結晶性ポリマに対するクレーズ進展シミュレーション

概要

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The fracture of ductile polymers occurs on a boundary between the molecular chain-oriented region and the non-oriented region after the neck propagation. This behavior is caused by the concentration of craze that is a microscopic damage typically observed in polymers. In this paper, the craze evolution behavior is decomposed into the nucleation and the growth of craze. A craze evolution equation is newly developed on the basis of chemical kinetics introducing strain rate and stain dependencies into an activation energy. Furthermore, in order to reflect the damage effect to the constitutive equation of molecular chain plasticity model, damaged and pseudo-undamaged configurations are defined. Then, using a multiscale material model homogenizing mixed structure of the glassy phase expressed by the molecular chain plasticity model and the crystalline phase represented by the usual crystal plasticity model in an unit cell, a FE simulation coupling with the craze evolution equation is carried out for a crystalline polymer subjected to the uniaxial load. It is attempted to computationally reproduce characteristic behaviors of craze evolution, i.e., the propagation of craze concentration region with the neck propagation in macroscopic specimen, the cessation of increase of craze in the molecular chain-oriented region and the craze nucleation before the macroscopic yielding.