Purpose

The purpose of this paper is to calculate the Hugoniot relations of polyurea; also to investigate the atomic-scale energy change, the related chain conformation evolution and the hydrogen bond dissociation of polyurea under high-speed shock.

Design/methodology/approach

The atomic-scale simulations are achieved by molecular dynamics (MD). Both non-equilibrium MD and multi-scale shock technique are used to simulate the high-speed shock. The energy dissipation is theoretically derived by the thermodynamic and the Hugoniot relations. The distributions of bond length, angle and dihedral angle are used to characterize the chain conformation evolution. The hydrogen bonds are determined by a geometrical criterion.

Findings

The Hugoniot relations calculated are in good agreement with the experimental data. It is found that under the same impact pressure, polyurea with lower hard segment content has higher energy dissipation during the shock-release process. The primary energy dissipation way is the heat dissipation caused by the increase of kinetic energy. Unlike tensile simulation, the molecular potential increment is mainly divided into the increments of the bond energy, angle energy and dihedral angle energy under shock loading and is mostly stored in the soft segments. The hydrogen bond potential increment only accounts for about 1% of the internal energy increment under high-speed shock.

Originality/value

The simulation results are meaningful for understanding and evaluating the energy dissipation mechanism of polyurea under shock loading, and could provide a reference for material design.

中文翻译：

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高速冲击下聚脲 Hugonot 关系与能量耗散的原子尺度模拟

目的

本文的目的是计算聚脲的 Hugoniot 关系；还研究了高速冲击下聚脲的原子级能量变化、相关链构象演变和氢键解离。

设计/方法/方法

原子级模拟是通过分子动力学 (MD) 实现的。非平衡MD和多尺度冲击技术都用于模拟高速冲击。能量耗散在理论上由热力学和 Hugoniot 关系导出。键长、角度和二面角的分布用于表征链构象演化。氢键由几何标准确定。

发现

计算的 Hugoniot 关系与实验数据非常吻合。发现在相同的冲击压力下，硬链段含量较低的聚脲在冲击释放过程中具有较高的能量耗散。主要的耗能方式是由动能增加引起的散热。与拉伸模拟不同，分子势增量主要分为键能、角能和二面角能在冲击载荷下的增量，且大多存储在软链段中。高速冲击下氢键势增量仅占内能增量的1%左右。

原创性/价值

仿真结果对于理解和评价聚脲在冲击载荷下的能量耗散机理具有重要意义，可为材料设计提供参考。