AI 中文总结
本研究采用多尺度方法，结合分子动力学与流体动力学计算，建立含晶界特性的多晶金属层裂模型，经Al飞片撞击实验验证，层裂强度与厚度偏差均控制在较小范围内，可准确预测金属高应变率层裂行为。
AI 中文摘要
本论文采用一种多尺度方法，将基于分子动力学（MD）的信息与流体动力学宏观计算相连接，以研究金属的冲击响应与层裂现象。首先，对Cu、Al、Ni单晶中的冲击传播进行模拟，压力最高达100 GPa，应变率大于10^6 s^-1；模拟得到的冲击雨果尼奥（U_s-U_p）关系与实验结果吻合度极高，误差小于6%，其中Foiles EAM势对Ni的偏差最小。其次，建立了将MD原子空洞动力学与流体动力学宏观计算相连接的多尺度框架；利用粒子群优化（PSO）算法，提取了Cu、Nb、Mo、Al的形核与生长（NAG）参数，得到的自由表面速度（FSV）剖面与Al的实验结果匹配度在8%以内。第三，对10个Al倾斜（STGB）和扭转（STwGB）双晶在10^10至10^11 s^-1的应变率下的变形研究表明，层裂阈值取决于晶界取向差；晶界附近的相变会在高U_p下降低层裂强度，而晶界塑性会延长回弹过程并延迟层裂（例如14.2° STwGB），同时发现FSV方法会低估真实的峰值抗拉强度。第四，该框架通过11个STGB和12个STwGB构型扩展至多晶体系；空洞始终在弱化的晶界处形核，利用PSO为全部23个双晶拟合得到了独特的NAG参数，并引入了流体单元内平均空洞生长（AVGFE）模型，以将这些不同的晶界特性映射到一维流体动力学代码中；该组合模型通过Al飞片撞击的实验进行验证，撞击速度分别为518 m/s、1588 m/s和2275 m/s，模拟得到的时间相关FSV曲线与实验结果一致，层裂强度偏差分别严格控制在2.15%、2.9%和6.0%以内，层裂厚度偏差在2.4%至4.0%之间。
英文摘要
This thesis utilizes a multiscale method by connecting molecular dynamics (MD) based information to hydrodynamic macroscopic calculations for investigating the shock response and spallation of metals. First, shock propagation in Cu, Al, and Ni single crystals is simulated up to $100$ GPa at strain rates $>10^6$ s$^{-1}$. Shock-Hugoniot ($U_s$-$U_p$) relations agree strongly with experiments (error $<6\%$); the Foiles EAM potential shows the least deviation for Ni. Second, a multiscale framework linking MD atomic void kinetics to hydrodynamic macro-calculations is established. Using particle swarm optimization (PSO), Nucleation and Growth (NAG) parameters are extracted for Cu, Nb, Mo, and Al, yielding free surface velocity (FSV) profiles matching experiments within $8\%$ for Al. Third, deformation across ten Al tilt (STGB) and twist (STwGB) bicrystals at rates of $10^{10}$-$10^{11}$ s$^{-1}$ proves that threshold spallation depends on boundary misorientation. Phase transitions near GBs lower spall strength at high $U_p$, whereas GB plasticity prolongs pull-back and delays spallation (e.g., $14.2^\circ$ STwGB). FSV methods are found to underestimate true peak tensile strength. Fourth, the framework is extended to polycrystals via 11 STGB and 12 STwGB configurations. Voids consistently nucleate at weakened GBs. Unique NAG parameters are fitted using PSO for all 23 bicrystals. An Average Void Growth in a Fluid Element (AVGFE) model is introduced to map these distinct boundary properties into 1D hydrodynamic codes. The combined model is validated against empirical Al flyer impacts at $518$, $1588$, and $2275$ m/s. The simulated temporal FSV curves mirror experiments, with spall strength deviations tightly bounded within $2.15\%$, $2.9\%$, and $6.0\%$, respectively, and spall thickness deviations within $2.4$-$4.0\%$.
CommentsPhD Thesis, Andhra Univ., India (Jan 2024). Shodhganga: hdl.handle.net/10603/550672. Enhanced archive ed. Core content unchanged: 37 figs, 13 tabs, 110 refs. Published parts: (i) Comput. Mater. Sci. 211 (2022) 111543; (ii) J. Dyn. Behav. Mater. 9 (2023) 24-35; (iii) Mater. Today Proc. 87 (2023) 164-169, 204-209; (iv) post-award ext.: Phys. Scr. 101 (2026) 325907. Full copyrt info on page ix
