A thermodynamics-based coupled damage-plasticity model for high strength cold-reduced steel is developed on the basis of a generic form, allowing the use of any yield criterion and damage evolution rule. The model possesses essential features of ductile failure, including large plastic deformation prior to fracture and the effects of both triaxiality and Lode angle on the failure. In conjunction with theoretical development, experimental work for both furthering the understanding of ductile fracture in high strength cold-reduced steel and validation of the proposed model under different loading conditions is also performed. In particular, advanced non-contact measurement techniques based on Digital Image Correlation (DIC) are used not only for characterising the material failure/data in both pre- and post-peak phases but also for calibration of parameters and validation of the proposed model. While the pre-peak hardening responses with homogeneous deformation can be described by a nonlinear hardening rule, in the post-peak regime, localisation of deformation before complete fracture requires the use of energy in both characterisation of the material failure and calibration of the model. In this sense, the essential work of fracture obtained from the experiments is linked with parameters controlling the fracture of the material and also used for a simple regularisation technique based on the concept of smeared deformation. The model responses are validated against experimental data in terms of both macro responses and evolving failure patterns, demonstrating good potential for applications in failure analysis of structures made of high strength cold-reduced steel.

中文翻译：

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一种模拟冷轧 G450 钢板延性断裂的理论-实验组合方法

在通用形式的基础上开发了一种基于热力学的高强度冷轧钢损伤-塑性耦合模型，允许使用任何屈服准则和损伤演化规则。该模型具有延性破坏的基本特征，包括断裂前的大塑性变形以及三轴性和洛德角对破坏的影响。结合理论发展，还进行了实验工作，以进一步了解高强度冷轧钢的韧性断裂，并在不同加载条件下验证所提出的模型。特别是，基于数字图像相关 (DIC) 的高级非接触式测量技术不仅用于表征峰值前和峰值后阶段的材料失效/数据，还用于参数校准和所提出模型的验证。虽然具有均匀变形的峰前硬化响应可以通过非线性硬化规则来描述，但在峰后区域，完全断裂前的变形局部化需要在材料失效表征和模型校准中使用能量。从这个意义上说，从实验中获得的基本断裂功与控制材料断裂的参数相关联，也用于基于涂抹变形概念的简单正则化技术。