水冰作为天然存在的固体物质，广泛分布于地球极地地区与太阳系内许多低温星球的地表，其在冲击等动态载荷作用下的失效行为对海洋资源开发、极地武器布局以及地外生命探测都具有重要意义。冰动力学是一个复杂而又古老的课题，目前相关的理论分析和数值模拟多是基于唯象的本构模型，无法准确反映冰在动态载荷作用下表现出的温度、应变率、多级相变以及杂质作用的复杂耦合效应。在实验的基础上明晰冰晶在上述不同影响参数下的微观变形机制是准确理解冰动态失效行为的必由之路。本文以在动力学实验中观察到的诸如冰在低温条件下散失温度敏感性等反常现象为基础，通过分子动力学模拟的手段得到了冰晶在冲击载荷作用下的应力波传播衰减途径及温度演化规律；报导了一个在压缩波作用下形成的五边形七边形缺陷；测得了水冰动态拉伸强度的反常温度效应，并结合不同温度条件下的缺陷演化、损伤形式以及断口形貌等微观失效机制给出了合理的解释。此外，还评估了溶解氯化钠浓度对水冰动态压缩强度的影响规律和杂质原子的作用机制。本文的主要内容有：

（1）使用动量镜法模拟了柱状冰1h模型在冲击载荷作用下的微观力学响应。模型在冲击过程中形成了固−固相变和固−液相变两种明显的相变形式；当模型在163 K以上温度弛豫时，发现了冰晶格在第一道压缩波作用后形成由大量五边形−七边形缺陷堆积而成的损伤区域；分析了该缺陷在晶胞尺度范围内的演化规律和温度依赖性，其结果显示缺陷的临界生成压力在163 K以下突然增强，由此解释冰在动态压缩实验中表现出的反常温度效应。

（2）测得了冰1h在73 ~ 215 K温度区间内的动态拉伸强度，其结果表明冰的动态拉伸强度存在与动态压缩实验中类似的温度不敏感区间：按照温度从高到底的顺序，可以将冰动态拉伸强度的温度效应分为四个作用机制不同的区域，分别是缺陷敏感区(163 ~ 215 K)、损伤熔化竞争区(117 ~ 163 K)、颗粒增强区(100 ~ 117 K)和韧脆转化区(73~ 100 K)；综合考虑了体系损伤密度、断口形貌、碎裂区颗粒破碎程度以及韧脆转化机制对上述四个温度区间做出了机理性的解释。

（3）比对了TIP4P/2005、TIP4P/ICE和SPC/E三种不同水分子模型对冰动态压缩强度的估计，并依据势函数的熔点性质对弛豫温度进行了修正；使用TIP4P/2005模型模拟了纯水冰和氯化钠掺杂冰(溶解氯化钠数目1 ~ 5个)在弛豫温度200 K和应变率3×10⁸ s⁻¹下的动态压缩强度。结果显示冰的动态压缩强度随着杂质浓度的升高而下降；较之纯水冰，杂质冰的熔化会更早的触发且不由切应力引导，而是由压应力集中在缺陷位置而形成的局部高温区域触发熔化。

Ice, as a naturally occurring solid material, is widely distributed in the polar regions of the Earth and on the surface of cryogenic planets in the solar system. Its failure behavior under dynamic loads such as shock loading is of significant importance for marine resource exploitation, polar weapon layout, and extraterrestrial life detection. Ice dynamics is a complex and ancient subject, and most of the current theoretical analyses and numerical simulations are based on image-only constitutive models, which cannot accurately reflect the complex coupling effects of temperature, strain rate, multi-level phase transition and impurity effects exhibited by ice under dynamic loading. Clarifying the microscopic deformation mechanisms of ice crystals under the above-mentioned influencing parameters on the basis of experiments is a must to accurately understand the dynamic failure behavior of ice. With the backing of anomalous phenomena observed in dynamics experiments such as ice dissipation of temperature sensitivity under cryogenic conditions, this paper obtains the stress wave propagation and structural temperature rising under shock loading by molecular dynamics simulation, reports a pentagonal-heptagonal defect formed under the action of compression waves, measures the anomalous temperature effect on dynamic tensile strength of ice, and gives a reasonable explanation for the microscopic failure mechanism by combining the defect evolution, damage form and fracture morphology under different temperature conditions. In addition, the influence law of dissolved sodium chloride concentration on the dynamic compressive strength of ice and the mechanism of the action of impurity atoms are evaluated. The main contents of this paper are:

(1) The micromechanical response of the column ice 1h model under impact loading was simulated using the momentum mirror method. The model formed two distinct phase transition forms, solid-solid phase transition and solid-liquid phase transition, during the impact process; when the model relaxed at temperatures above 163 K, the ice lattice was found to form a damage region consisting of a large number of pentagonal-heptagonal defect accumulation after the first compressional wave. The evolution pattern and temperature dependence of the defects in the cell-scale range are analyzed, and the results show that the critical generation pressure of the defects is abruptly enhanced below 163 K, thus explaining the anomalous temperature effect exhibited by ice in the dynamic compression experiments.

(2) The dynamic tensile strength of ice for 1h was measured in the temperature range of 73 ~ 215 K. The results indicate that there is a temperature insensitive zone similar to that in dynamic compression experiments: in the order of temperature from high to low, the temperature effect on the dynamic tensile strength of ice can be divided into four regions with different mechanisms of action, namely the defect-sensitive region (163 ~ 215 K), the pulverization-melting competition region (117 ~ 163 K), particle-enhancement region (100 ~ 117 K) and the brittle transformation region (73 ~ 100 K). The above four temperature intervals are mechanistically explained by considering the system defect density, fracture morphology, the degree of particle crushing and the ductile-to-brittle transformation mechanism.

(3) The estimates of dynamic compression strength of ice from three different water molecule models, TIP4P/2005, TIP4P/ICE and SPC/E, were compared and the relaxation temperature was corrected based on the melting point of the potential function. Pure water ice and NaCl-doped ice (number of dissolved NaCl 1 ~ 5) were simulated using the TIP4P/2005 model at a relaxation temperature of 200 K and a strain rate of 3 × 10⁸ s^-1. The results show that the dynamic compressive strength of ice decreases with increasing impurity concentration. The melting of impurity ice is triggered earlier than pure water ice, and the melting is not caused by the maximum shear stress, but by the concentration of compressive stress at the defect location to form a local high-temperature zone.