直接测量材料高压动态剪切强度的磁驱压剪实验技术研究

The strength of materials is defined as the ability to sustain deviatoric (shear) stress and not to yield plastically at high pressure and strain rate,which is closely related with hydrostatic pressure, temperature and loading strain rate of materials, and which is a critical aspect of material behaviors for many applications including technologies of shock defense, weapons physics and planetary science. With the equation of state, strengh is used to characterize the properties of compression and deformation of materials . In this study, a new technique of magnetically applied pressure shear loading for directly measuring the shear strength of materials at high pressures is to develop and demonstrate using pulsed high current and quasi-static magnet field, which is presented in recent several years in the world .The dynamic loading of 20GPa in longitudinal direction and about 1GPa in transverse direction and strain rate of about 10^4 1/s are planned to be realized in this study, which includes the design and establishment of 1-2ms,10 Tesla quasi-static magnet field generator, the applicaton of quasi-static magnet field to the pulsed high current maichine, the techniques of optimal design and diagnosis of strength measurement of aluminum samples under ramp wave loading and the experimental data processing method, and the measurements of the strength of aluminum below the loading pressure of 20GPa and so on. Compared with other techniques of strength measurement of materials published in references, the advantage of this study is that pure shear stress combined with shockless compression is loaded on the samples at high pressure and strain rates, and that the shear strength can be determined directly from the experimentaly recorded data.

强度是材料抵抗偏应力（剪应力）作用而不发生塑性屈服的能力，与材料静水压力、温度和加载应变率密切相关，是与状态方程一起表征材料压缩和变形特性的重要物理性质，在冲击防护技术、武器物理、地球（行星）科学等方面应用广泛。本研究拟发展一种基于脉冲大电流和准静态磁场联合作用装置实现纵向加压和横向剪切动态联合加载的新实验技术，是国际上近年内提出的用于直接测量材料在高压下的动态剪切强度，本技术拟实现纵向20GPa、横向1GPa以内、应变率10^4 1/s的动态加载。包括1-2ms、10T准静态磁场发生装置的设计和建立，准静态磁场与脉冲大电流联合作用的磁压剪加载技术研究，磁压剪联合加载下金属铝样品强度测量优化设计、诊断技术以及数据处理方法研究，20GPa压力下金属铝的强度测量等。与现有的材料剪切强度实验技术比较，本研究最大的亮点在于纯剪应力与非冲击压缩的联合加载，可根据实验诊断数据直接确定材料样品的强度值。

强度是表征材料物性的一个重要物理参量，用于描述物体抵抗剪切变形的能力，是影响材料高压高应变率加载下的动力学行为的主要因素之一，因此开展相关研究具有重要学术意义和工程应用价值。本项目提出、发展并建立了一种用于直接测量动载荷下材料强度的新方法即磁驱动压剪联合加载实验技术，简称磁压剪实验技术。理论和数值计算方面，分析了压-剪联合作用下材料的应力偏量与屈服强度关系，计算了斜波加载下压-剪联合作用下应力偏量与屈服强度的时空演化特性，给出了材料强度数值的计算方法，验证了该技术的可行性。实验方面，研制了一套上升时间约1.4ms、幅值10T的准静态磁场发生装置；基于该10T准静态磁场发生器和现有的强脉冲电流磁驱动装置CQ-4，发展并建立了一种用于测量磁压剪实验的多点横向速度激光干涉仪PDV，建立了一套用于磁压剪技术材料强度测量的实验数据处理方法，在此基础上开展了磁驱动斜波压-剪联合加载实验技术研究，建立了磁驱动压剪实验技术。利用建立起来的磁驱动压剪实验技术，开展了20GPa压力范围内斜波加载下冷轧纯铝和抛光纯铝的高压强度测量，获得了可靠的实验数据。利用该技术探索了典型非金属材料聚乙烯的动态强度测量，获得了8-12GPa斜波加载下聚乙烯的强度数据。理论、计算和实验结果表明，本项目建立的磁驱动压-剪联合加载技术是一种可靠的、具有较高实验精度材料动态强度测量方法，为材料的高压强度直接测量提供了一种新途径。