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首页> 外文期刊>International Journal for Multiscale Computational Engineering >NONLOCAL GRADIENT-DEPENDENT CONSTITUTIVE MODEL FOR SIMULATING LOCALIZED DAMAGE AND FRACTURE OF VISCOPLASTIC SOLIDS UNDER HIGH-ENERGY IMPACTS
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NONLOCAL GRADIENT-DEPENDENT CONSTITUTIVE MODEL FOR SIMULATING LOCALIZED DAMAGE AND FRACTURE OF VISCOPLASTIC SOLIDS UNDER HIGH-ENERGY IMPACTS

机译：高能冲击下粘塑性固体局部损伤与断裂的非局部梯度本构模型

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Understanding the constraints and limitations of various potential hull structure materials and armor is paramount in design considerations of future civil and military vehicles. Developing and applying theoretical and computational models that guide the development of design criteria and fabrication processes of high-impact/ballistic-resistant materials are essential. Therefore, performing accurate computational modeling and simulation of the ballistic response of vehicles made of high-performance materials under impact/blast loading conditions is invaluable. However, as soon as material failure dominates a deformation process, the material increasingly displays strain softening (localization) and the finite-element computations are affected considerably by the mesh size and alignment and gives non-physical descriptions of the damaged regions and failure of solids. This study is concerned with the development and numerical implementation of a novel coupled thermo-hypo-elasto, thermo-visco-plastic, and thermo-visco-damage constitutive model within the laws of thermodynamics in which implicit and explicit intrinsic material length-scale parameters are incorporated through the nonlocal gradient-dependent viscoplasticity and viscodamage constitutive equations. In this current model, the Laplacian of the effective viscoplastic strain rate and its coefficient, which introduces a missing length-scale parameter, enter the constitutive equations beside the local effective viscoplastic strain. It is shown through simulating plugging fracture in ballistic penetration of high-strength steel circular plates by hardened blunt-nose cylindrical steel projectiles that the Laplacian coefficient parameter plays the role of a localization limiter during the penetration and perforation processes allowing one to obtain meaningful values for the ballistic limit velocity (or perforation resistance) independent of the finite-element mesh density. For the corresponding local model, on the other hand, the ballistic limit continuously decreases as the mesh density increases and does not converge even for the finest mesh.
机译：在未来的民用和军用车辆的设计考虑中，了解各种潜在的船体结构材料和装甲的约束和局限性至关重要。开发和应用理论和计算模型来指导高冲击/防弹材料的设计标准和制造工艺的发展至关重要。因此，在冲击/爆炸载荷条件下，对由高性能材料制成的车辆进行精确的弹道响应进行精确的计算建模和仿真是无价的。但是，一旦材料破坏主导了变形过程，材料就会越来越多地显示出应变软化（局部化），并且有限元计算受到网格大小和对齐方式的很大影响，并给出了损坏区域和固体破坏的非物理描述。 。这项研究与热力学定律之间新颖的热-低弹，热-粘塑性和热-粘-损伤本构模型的发展和数值实现有关，在该模型中，隐性和显性固有材料长度尺度参数通过非局部梯度相关的粘塑性和粘滞损伤本构方程将它们结合起来。在当前模型中，有效粘塑性应变率的拉普拉斯算子及其系数（引入了缺失的长度尺度参数）在局部有效粘塑性应变旁边输入了本构方程。通过模拟高强度钝圆圆柱钢弹丸对高强度钢圆板的弹道渗透中的堵塞断裂，拉普拉斯系数参数在渗透和射孔过程中起局部限制器的作用，从而使人可以获得有意义的数值。弹道极限速度（或射孔阻力）与有限元网格密度无关。另一方面，对于相应的局部模型，防弹极限随着网格密度的增加而连续降低，即使对于最细的网格也不会收敛。

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