Study On The Viscosity Of Iron Under Shock Compression

The earth is our home for survival, so the internal structure of the earth and the dynamic process of the earth’s evolution is related to the survival and development of our human beings. The earth is mainly composed by three prats:crust, mantle and core. Due to the heat generated by the cooling of the earth core will through the outer core to reach the mantle boundary, which will cause the interaction between the core mantle and mantle convection, and the mantle plume formation. So the study of the outer core material transport properties under the conditions of high temperature and high pressure, especially the viscosity, is an important basic research topic to understanding the evolution of the earth dynamic process.So far, people tired all kinds of methods to solve the problem of iron’s viscosity under high pressure, but the results obtained by different methods have not to be coordinated. The falling ball method in static high pressure experiments and molecular dynamics simulation measurement of iron’s viscosity coefficient magnitude is 10-3 Pa-s; seismology by seismic wave attenuation measurments obtained in earth core matter of viscosity coefficient magnitude is 107～1011 Pa·s; geophysicists according to the rotation of the earth is associated with the electromagnetic torque calculation mainland nuclear viscosity coefficient magnitude is 1012～1017Pa·s. In addition, there is not a regular knowledge for the change of material viscosity under high pressure with pressure. In view of these problems,this paper uses the method of flying plate impact small disturbance test and numerical simulation technology to measure the shear viscosity of iron in the 57-114Gpa pressure range,and we got the results as following:1、The evolution of the disturbed shock front in iron under the pressure of 58GPa、81GPa、 103GPa and 114GPa are measured using the flyer-impact perturbation method.2、Imitating the real experimental settings, the flyer-impact perturbation experiment is simulated by the finite difference method considering the constitutive relation, and the evolution of the perturbation amplitude on the shock front in iron are obtained. Beside, we obtained the quantitative relationship between the equivalent viscosity coefficient and the phase zero point of the disturbance attenuation curve. Finally,we got the equivalent viscosity coefficient of iron under 58GPa、81GPa、103GPa and 114GPa pressure is 3000 Pa·s、3500 Pa·s、3500 Pa·s and 2000 Pa·s respectivly.3、By analysis the equivalent viscosity coefficient of iron under 58GPa-114GPa, we found that the equivalent viscosity coefficient of iron will increase with the pressure increase, the it will decrease with the pressure increase at about 103GPa.In short, this paper mainly studies the equivalent viscosity coefficient of iron by the method of flyer impact disturbance, and obtained the basic change law of the equivalent viscosity coefficient of iron in the 58GPa-114GP pressure range.