NECKING AND NECK PROPAGATION IN ORIENTED ANISOTROPY AMORPHOUSGLASSY POLYMERS 1)
预延伸非晶聚合物材料各向异性变形局部化

Polymeric mechanics is a rising frontier science based on polymeric physics and continuum mechanics. The research on macro and micro mechanical behavior of polymers will provide the theoretic foundation and analyzing way for increasing ductility of the polymers and for improving their formability. At present, a subject on the field is to study deformation localization development and flow character of the polymers. In this paper, a 3D expression of the back stress tensor describing oriented anisotropy propagation of amorphous glassy polymers is proposed. The necking and neck propagation of plane strain tensile test of oriented amorphous glassy polymers with initial texture is numerically simulated by introducing the 3D expression and an Eight chain molecular network model into a finite element driving stress method. The influences of the initial drawing ratio (IDR) and the initial drawing direction (IDD) on deformation resistance, neck propagation rule, shear band direction and the chain stretch ratio at the center of specimen are discussed in detail. The simulation results are compared with some experimental ones, and show good agreement between both. The further simulations obtained the following conclusions: The deformation resistance decreases as the IDD value increases, and the diffusing speed for the deformation localization development of the strain soft polymers is very fast, however, the necking speed is insufficient. In addition, both the strain soft polymers and strain harden polymers show strong necking abilities and slow diffusing speed when the IDD value becomes larger. An interesting phenomenon is that shear band angle increases as the IDD value does, but is always smaller than the initial drawing direction.