A gradient-enhanced ductile damage model at finite strains is presented, and its parameters are identified so as to match the behaviour of DP800. Within the micromorphic framework, a multi-surface model coupling isotropic Lemaitre-type damage to von Mises plasticity with nonlinear isotropic hardening is developed. In analogy to the effective stress entering the yield criterion, an effective damage driving force—increasing with increasing plastic strains—entering the damage dissipation potential is proposed. After an outline of the basic model properties, the setup of the (micro)tensile experiment is discussed and the importance of including unloading for a parameter identification with a material model including damage is emphasised. Optimal parameters, based on an objective function including measured forces and the displacement field obtained from digital image correlation, are identified. The response of the proposed model is compared to a tensile experiment of a specimen with a different geometry as a first approach to validate the identified parameters.

中文翻译：

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大应变梯度增强延性损伤模型：有限元公式、实验和参数识别

提出了有限应变下的梯度增强延性损伤模型，并确定其参数以匹配 DP800 的行为。在微形框架内，开发了一种将各向同性 Lemaitre 型损伤与 von Mises 塑性与非线性各向同性硬化耦合的多表面模型。类似于进入屈服准则的有效应力，提出了有效的损伤驱动力——随着塑性应变的增加而增加——进入损伤耗散潜力。在概述了基本模型属性之后，讨论了（微）拉伸实验的设置，并强调了包括卸载对于使用包括损坏的材料模型进行参数识别的重要性。最佳参数，基于目标函数，包括测量的力和从数字图像相关性获得的位移场，被识别。将提出的模型的响应与具有不同几何形状的试样的拉伸实验进行比较，作为验证识别参数的第一种方法。