| Flier-plate with graded wave impedance, which can be regarded as a new type of functionally graded material (FGM) since its wave impedance changes gradually along the thickness direction and thus can be used to generate quasi-isentropic compression energy waves in targets or drive projectiles to hypervelocities, has come to show great potential for the application in dynamic high-pressure technique.In the present dissertation, five commercial metallic materials ?tungsten alloy (93W), oxygen free copper (OFC), titanium alloy (TC-t), pure aluminum (Al) and magnesium alloy (MB2) were chosen as the composite system of the flier-plate with graded wave impedance, and their acoustic and mechanical parameters were measured. The thickness of each material was controlled so that flier-plates with a parabolic or cubic wave impedance distribution were designed.By using diffusion welding method (under certain welding parameters such as temperature, pressure, time and atmosphere, etc) and employing rational structural control technique, a kind of 93W-OFC-TC4-A1-MB2 system flier-plate with good parallelism, planeness and high densification was prepared, which met the needs of initial design and the basic requirement of flier-plates. It was found that the interfacial bonding of 93W-OFC was both the joining action of OFC/W grains and that of OFC/Ni-Fe binders, whereas the joining of OFC to TC4 could be seen as the mutual intense diffusion effect between OFC/TC4 and as a result Cu-Ti intermetallic compounds were formed at the joint. The joining of TC4-A1 and A1-MB2 were also attributed to the result of diffusion between elements Ti-Al and Al-Mg respectively. On the other hand, residual thermal stress and stress-induced distortion were produced at the joint simultaneously due to the difference in thermal expansion coefficient of different welding" materials. The planeness and integrality of the flier-plate were ensured effectively by exerting restrictive pressure, controlling heating and cooling rate, lowering welding temperature or reducing welding time as much as possible, etc.Theoretical model of creating quasi-isentropic compression via 93W-OFC-TC4-A1-MB2 system flier-plate with graded wave impedance wasestablished, and numerical simulation of the impact process was then carried out. The results showed that quasi-isentropic compression energy waves were produced after the impact, whose initial velocity jump, peak velocity and front's rise-time were all different from the general shock loading wave profiles. Furthermore, the higher the impact velocity, the smaller the extended wave's front while the higher the peak velocity. At the same time, the thickness of target should also be in accord with the impact velocity.Experiments of quasi-isentropic loading to 93 W alloys by 93W-OFC-TC4-A1-MBz system flier-plate with graded wave impedance were performed on light gas guns. The corrected VISAR-measured wave profiles were profiles with an initial velocity jump followed by a stepwise-rising front to the peak velocity amplitude, indicating that quasi-isentropic compression energy waves had been successfully generated. When flier-plates with different graded structures impacted targets with different thickness at different velocities, the variation of the impact-induced wave profiles accorded with the numerical simulation results. The physical process of quasi-isentropic compression might be considered as the successive overlap of a series of small shock loading waves generated by the transition layers in the flier-plate. As a result, the P-V curve of the target was a quasi-isentropic compression curve, which consisted of small Hugoniot curves (similar to isentropic curves) from different original states, and was located between the Hungoniot curve and isentropic curve but closer to the latter.Finally, on a two-stage light-gas gun, titanium alloy projectiles (with mass of 0.35~2.80g) were driven intact to hypervelocities as over 15km/s by 93W-OFC-TC4-A1-MB2 system flier-plate with graded wave impedance, although the fl...
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