Investigation On Preparation And Dynamic Behaviors Of Tungsten Alloy

Theoretical analysis, experiment investigation and numerical simulation on preparation and application of tungsten alloys were implemented. The way to enhance the preparation properties of tungsten powders was analyzed. The velocity and temperature distribution of induction plasma torch in preparation of superfine tungsten powders, temperature field and densification during spark plasma sintering processing were obtained, and the relationship among temperature field, microscopic properties and mechanical properties were determined by numerical simulation method. Experiments and numerical simulation were carried out to obtain dynamic tensile, compression and shearing properties of tungsten alloys and different targets at vary temperatures and strain rates. And the mechanical properties of long rod tungsten alloys and targets during high speed penetration process were simulated by adding numerical model to LS-DYNA numerical software. The results have certain reference value for preparation and property research of tungsten heavy alloys. The detailed contents are as following:(1) Numerical simulation of temperature distribution of induction plasma torch in superfine tungsten powders preparation was carried out. To obtain the velocity and temperature field in radio frequency induction plasma torch, the control equations coupling electric field, temperature field and flow field were set up based on the theory of heat transfer, electromagnetic and incompressible Navier-Stocks equations. An extended field model was proposed for inductively coupled plasma to optimize the simple infinite field boundary condition. The velocity and temperature distribution of inductively coupled plasma in flow process were simulated based on the finite element method, and the vortex was obtained in the flow field. The parameters during powder preparation processing were researched on the different power inputs of induction coupled plasma torch.(2) The temperature field during spark plasma sintering processing and its effect on bulk tungsten materials were investigated. The control equations of electrothermal coupling electric field and temperature field were set up based on the theory of heat transfer and electromagnetic under typical spark plasma sintering (SPS) conditions. The electrothermal phenomena of tungsten powder during sintering process were simulated using the software COMSOL MULTIPHYSICS based on the finite element method. The current density, power density and temperature distribution were obtained. And a new sintering mechanism model was carried out to explain the phenomena during the spark plasma sintering processing.(3) The dynamic tensile, compression and plugging test were performed to explore the dynamic tensile, compression and shearing properties of tungsten alloys, steels and alumina at different temperatures and strain rates by the self-developed Hopkinson tensile system and improved Hopkinson pressure bar system. These properties were analyzed by vary material models, the parameters of different materials were determined by using the curve fitted method. By means of investigated the fractography of materials, the failure mechanisms of these materials were obtained. The results provide theoretical and numerical basis for researching the penetration property of long rod tungsten heavy alloy.(4) The penetration of steel/alumina composite plate by long rod projectile of tungsten heavy alloy at high speed velocity was investigated by adding the numerical model to LS-DYNA explicit dynamic software. To obtain the results of physical asymmetric semi-infinite concrete penetrated by long rod projectile of tungsten alloy at1000-3000m/s, the Johnson-Holmquist concrete model was used to analyze the damage and energy expenditure of projectile and target. The model could simulate the crater formation, spall of concrete target and the fracture occurring inside it during the process of impact effectively. The deformation and ballistic excursion of long rod projectile were obtained in the process of penetration, and a theory method for estimating critical velocity due to different failure types of projectile was given.