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冲击物理温度是武器弹药性能测试、极端环境材料状态的重要参量,温度的精准获取在国防建设和工业制造领域有重要意义。冲击过程由于持续时间短、较难接触式测量以及温度范围广等特性,常规测温方法较难满足要求。利用多光谱辐射测温法,获取材料辐射强度值,以普朗克辐射定律为基础建立温度反演模型,从而获取目标的冲击物理温度值。实际中,由于不同目标发射率存在一定随机性,在模型反演温度时误差较大。冲击压缩下材料的结构可能发生相变,发射率随之变化,因此直接将发射率模型假定用于冲击物理温度求解,很难准确的获取温度值。基于约束优化理论,将多光谱测温实验中温度求解问题转为约束优化问题。针对每个通道获取到的温度值应该相同,将物体发射率限制在特定范围,利用约束优化算法计算获取目标温度和发射率,克服了未知发射率对于冲击物理温度求解的障碍。同时,将平衡优化器算法(EO)与序列二次规划法(SQP)相结合应用于温度模型的求解中,避免了单一算法求解稳定性差和速度慢的缺点,提高了温度反演的效率和准确性。对四种常见的发射率模型在3 000 K时的发射率数据进行了仿真验证,结果表明温度反演误差均小于1%,反演时间小于3 s。最后利用本算... 相似文献
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A fiber-array probe technique for measuring the viscosity of a substance under shock compression 下载免费PDF全文
A fiber-array probe is designed to measure the damping behavior of a small perturbed shock wave in an opaque substance, by which the effective viscosity of substance under the condition of high temperature and high pressure can be constrained according to the flyer-impact technique. It shows that the measurement precision of the shock arrival time by using this technique is within 2 ns. To easily compare with the results given by electrical pin technique, the newly developed method is used to investigate the effective viscosity of aluminum (Al). The shear viscosity coefficient of A1 is determined to be 1700 Pa.s at 71 GPa with a strain rate of 3.6× 10^6 s-1, which is in good agreement with the results of other methods. The advantage of the new technique over the electrical pin one is that it is applicable for studying the non-conductive substances. 相似文献
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Structural,electronic,optical,elastic properties and Born effective charges of monoclinic HfO_2 from first-principles calculations 下载免费PDF全文
First-principles calculations of structural, electronic, optical, elastic, mechanical properties, and Born effective charges of monoclinic HfO2 are performed with the plane-wave pseudopotential technique based on the density-functional theory. The calculated structural properties are consistent with the previous theoretical and experimental results. The electronic structure reveals that monoclinic HfO2 has an indirect band gap. The analyses of density of states and Mulliken charges show mainly covalent nature in Hf-O bonds. Optical properties, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, loss function, and optical conductivity each as a function of photon energy are calculated and show an optical anisotropy. Moreover, the independent elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, compressibility, Lam6 constant, sound velocity, Debye temperature, and Born effective charges of monoclinic HfO2 are obtained, which may help to understand monoclinic HfO2 for future work. 相似文献