Cold forming of polycarbonate films results in the formation of shear bands in the necking zone. The numerical results obtained from standard viscoplastic material models exhibit mesh size dependency, requiring mathematical regularization. For this purpose, we present in this work a large deformation gradient theory for a viscoplastic isotropic material model published before. We extend our model to a micromorphic model by introducing a new micromorphic variable as an additional degree of freedom along with its first gradient. This variable represents a microequivalent plastic strain. The relation between the macroequivalent plastic strain and the micromorphic variable is accomplished by a micromorphic coupling modulus. This coupling forces proximity between the macro- and microvariables, leading to the targeted regularization effect. The micromorphic model is implemented as a three-dimensional initial boundary value problem in an in-house finite element tool. The analysis is performed for both uniaxial and biaxial specimens. The provided numerical examples show the ability of our model to regularize shear bands within the specimens and address the issue of localization.

聚碳酸酯薄膜的冷成型导致在颈缩区域形成剪切带。从标准粘塑性材料模型获得的数值结果表现出网格尺寸依赖性，需要数学正则化。为此，我们在这项工作中提出了之前发表的粘塑性各向同性材料模型的大变形梯度理论。我们通过引入一个新的微形态变量作为附加自由度及其第一个梯度，将我们的模型扩展到微形态模型。该变量代表微当量塑性应变。宏观等效塑性应变与微形态变量之间的关系通过微形态耦合模量来实现。这种耦合迫使宏观变量和微观变量之间的接近，从而产生有针对性的正则化效果。微形态模型在内部有限元工具中实现为三维初始边值问题。对单轴和双轴样本进行分析。提供的数值示例表明我们的模型能够规范样本内的剪切带并解决定位问题。