The Numerical Simulation Of Quasi-Isentropic Compression Via Graded Impedence Flyer

This thesis describes the numerical simulation for quasi-isentropic compression which is produced by graded-impedance flyers impacting target, which was done by a one-dimensional difference program. Take Tungsten for example, the calculation results show how the factors influence the effects of quasi-isentropic compression, such as the number of layers, the index of impedance distributing, impacting velocity and the thickness of target. The results is that a flyer should be less than ten layers, it is the best when the index of impedance distributing approximating equals to 2, the impacting velocity and the thickness of target should be matched with each other. At last we summarized the principles of optimizing the geometry construction of a flyer and designed a flyer.We calculated the entropy increasing of quasi-isentropic compression. The entropy increasing under quasi- isentropic compression only 20% of that under shock compression at last when the impact velocity is 4km/s, and 95 of which is produced by the initial shock compression. So it indicates that the initial shock determined the increase of entropy and the effects of quasi-isentropic compression is good.We also calculated the yield strength of Tungsten under quasi-isentropic loading. The calculation result is larger than the reference data under shock compression, it shows the dynamic yield strength is dependent on the loading rate.The result of interface velocity is agree well with the experimental results in the initial jump velocity, the max velocity and the wave risetime.. Therefore, the method of numerical simulation for quasi-isentropic compression are reliable.