| Viscosity of condensed mater at high pressures and temperatures has been one of the remarkable parameters in geophysical dynamics and explosive mechanics. However, up to now there is no well-accepted measurement method to determine this physical quantity. Sakharov et al firstly considered the correlation between the flow viscosity and evolution of sinusoidally disturbed shock front, and they designed a so-called Sakharov experiment, by explosive loading and VISAR technique, to measure the amplitude damping and oscillation of sinusoidally disturbed shock front in several metals. Unfortunately, this experimental method did not be widely applied because the data analysis scheme used to deduce the viscosity coefficient from the experimental data was not well-accepted. In this thesis the oscillatory damping method is well developed both in theoretical treatment and in experimental technique.A numerical method is put forward to simulate the evolution of disturbed shock front in flow with viscosity, which is based on the numerical difference solution of two-dimensional Euler equations of fluid mechanics and equation of state (EOS) of concerned substances, including EOS of Hugoniot and EOS of Gruneisen. The non-planar dhock front is captured by a scheme of maximum pressure gradient, which locates the positions of the disturbed shock front. In this work, the real viscosity of flow is supposed to take effects in region behind shock front, and the artificial viscosity is introduced to suppress the numerical oscillation at shock front. By this treatment the effects of real viscosity are separately studied. The newly developed method can give the numerical solutions of the disturbed amplitude of shock front, and it is applied to investigate the Miller's non-uniform flow, the flyer-impact flow, and Sakharov's flow. The flyer-impact small-disturbance method is well-developed to measure the viscosity of metal under shock compression. The sinusoidally disturbed shock wave is generated by a flyer accelerated by two-stage light-gas gun direct impacting a wedged sample of grooved surface, and the evolution of the disturbed amplitude of shock front with the moving distance is directly measured by an array-distributed electric pin technique. Both amplitude decay and its reverse oscillation are observed in one shot of experiment by a well-designed sample. Using flyer-impact experiments the dependence of the disturbed amplitude of shock front on the propagating disturbance is measured in aluminum at shock pressure 78GPa and 101GPa. The main conclusions are as follows:1. The numerical solutions of the disturbance amplitude of shock front are obtained in the non-uniform flow of Miller and Ahrens, and the numerical results are in agreement with the ones of perturbation analytical solution under the conditions of small disturbance and weak viscosity, which proves the numerical solutions in this work are reliable. Because the perturbation requirements are not needed in numerical solution, it reflects the general quantitative relationship between the disturbed amplitude and the propagated distance of shock front under condition of finite disturbance and larger viscosity, and can be applied to analyse more complex flows.2. For the flow generated by flyer-impact experiment, the quantitative relationship between the viscosity coefficient of flow and the damping features of the disturbed amplitude of shock front is firstly found by analyzing the evolution of flow. The effects of the initial distribution of flow, the ratio of amplitude to wavelength of perturbation on shock front, viscosity of flow, and perturbation wavelength on the characteristics of amplitude damping and oscillating are numerically discussed, which provides the theoretical foundation for optimization of sample's design in flyer-impact experiment. By comparing the experiment data with the numerical solutions, the effective shear viscosity coefficients of aluminum under shock pressure of 78GPa and 101GPa are respectively re-determined to be 2800 Pa.s and 3500 Pa.s, which is obviously higher than the results by Miller'analytic solution.3. For Sakharov's flow, the effects of initial condition, the ratio of amplitude to wavelength of disturbance, viscosity of flow, and perturbation wavelength on the evolution history of the disturbed amplitude on shock front are revealed, which is a solid foundation of fluid mechanics to explain the Sakharov's experiment data. According to the quantitative relationship between the phase shift of zero-amplitude point on the disturbance amplitude damping curve and the effective shear viscosity coefficients of aluminum, the experimental data for the disturbance wavelength of 10mm is found to be unreasonable. So, the effective shear viscosity coefficient of aluminum at shock pressure 31GPa is re-calculated to be 1100Pa.s by analyzing the experiment data with the disturbance wavelength of 20mm.4. Combining the results of flyer-impact experiment and that of Sakharov experiment, the effective shear viscosity coefficients of aluminum at several tens of GPa are of the order of-103Pa.s., and it linearly rises from 1100 to 3500Pa.s when the shock pressure increases from 31 to 101GPa. Such a change trend shows the metal aluminum does not melt in this pressure range.In summary, we develop an new experimental method with reliable theoretical foundation for measuring the shear viscosity coefficient of metal at high pressures and temperatures, which consists of a newly developed the numerical simulation method for the disturbance amplitude of shock front and and an improved flyer-impact small-disturbance experimental method.
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