Plasma spray forming shows overwhelming advantages in rapid fabricating parts and moulds. The coating microstructure is strongly dependent on the splat morphology and inter-splat contact nature. Therefore,it is necess...Plasma spray forming shows overwhelming advantages in rapid fabricating parts and moulds. The coating microstructure is strongly dependent on the splat morphology and inter-splat contact nature. Therefore,it is necessary to investigate the splat formation mechanism in order to analyze the coating properties. A dynamical process of a single fully molten droplet impacting onto a smooth surface was investigated. At the same time,the interaction between the two molten droplets in the horizontal and vertical directions was also simulated. Finally,the simulations of impact of a molten droplet on an inclined plane and a sharp edge were presented. It is concluded that the relative distance of the two droplets strongly influences the dynamics of the two droplets interaction. The various surface conditions have direct effects on the dynamics of splat formation. When a droplet impacts onto an inclined surface and a sharp edge,the splat morphology changes obviously and the phenomenon of break up is observed.展开更多
The mechanical properties of thermally sprayed metallic coatings are limited by the bonding between splats.In this study,tungsten coatings were deposited at different deposition temperatures by controlling the substra...The mechanical properties of thermally sprayed metallic coatings are limited by the bonding between splats.In this study,tungsten coatings were deposited at different deposition temperatures by controlling the substrate temperature through shrouded plasma spraying.The dependence of the splat bonding and mechanical properties of W coatings on deposition temperature was investigated.The results showed that the apparent porosity of the coatings decreased from 3.2%to 0.3%with the increase of the deposition temperature.The Young's modulus of W coating was significantly increased from 128 to 307 GPa as the deposition temperature increased from room temperature to 800°C.The microhardness of the coatings was less influenced by the deposition temperature.It was found that splat bonding across lamellae was formed when the deposition temperature was higher than 600°C compared to the obvious lamellae interface in the coatings deposited at temperatures lower than 600°C.The results evidently revealed that the mechanical properties of plasma-sprayed W coatings could be controlled through the splat bonding by altering deposition temperature.展开更多
Plasma sprayed coatings are built up by the accumulation of splats formed by the impacting,spreading and solidifying of molten droplets on the substrate.A three-dimensional computational model including heat transfer ...Plasma sprayed coatings are built up by the accumulation of splats formed by the impacting,spreading and solidifying of molten droplets on the substrate.A three-dimensional computational model including heat transfer and solidification is established to simulate the formation process of a single splat using the computational fluid dynamics(CFD)software,FLUENT.The fluid flow and energy equations are discretized and solved according to typical finite volume method on an unstructured grid.A volume of fluid(VOF)tracking algorithm is used to track the droplet flow with free surface.In order to understand the splat formation mechanism,the process of splat formation caused by impacting and spreading of a molten nickel droplet on a polished mild steel surface is simulated.On this basis,the simulations of impact of a molten droplet on substrate with different conditions including the surface morphology,thermal conductivity,initial temperature of the substrate and the thermal contact resistance are presented.The results clearly show the effect of those parameters on the shape of the final splat and splash behaviors.展开更多
Elliptical splats are used to represent and render the isosurface of volume data. The method consists of two steps. The first step is to extract points on the isosurface by looking up the case table. In the second ste...Elliptical splats are used to represent and render the isosurface of volume data. The method consists of two steps. The first step is to extract points on the isosurface by looking up the case table. In the second step, properties of splats are computed based on local geometry. Rendering is achieved using surface splatting algorithm. The obtained results show that the extraction time of isosurfaces can be reduced by a factor of three. So our approach is more appropriate for interactive visualization of large medical data than the classical marching cubes (MC) technique.展开更多
基金Project (50675072) supported by the National Natural Science Foundation of Chinaprojects (E0610018, 20062178) supported by the Natural Science Foundation of Fujian Province and Liaoning Province, China, respectively
文摘Plasma spray forming shows overwhelming advantages in rapid fabricating parts and moulds. The coating microstructure is strongly dependent on the splat morphology and inter-splat contact nature. Therefore,it is necessary to investigate the splat formation mechanism in order to analyze the coating properties. A dynamical process of a single fully molten droplet impacting onto a smooth surface was investigated. At the same time,the interaction between the two molten droplets in the horizontal and vertical directions was also simulated. Finally,the simulations of impact of a molten droplet on an inclined plane and a sharp edge were presented. It is concluded that the relative distance of the two droplets strongly influences the dynamics of the two droplets interaction. The various surface conditions have direct effects on the dynamics of splat formation. When a droplet impacts onto an inclined surface and a sharp edge,the splat morphology changes obviously and the phenomenon of break up is observed.
基金National Natural Science Foundations of China(50725101)
文摘The mechanical properties of thermally sprayed metallic coatings are limited by the bonding between splats.In this study,tungsten coatings were deposited at different deposition temperatures by controlling the substrate temperature through shrouded plasma spraying.The dependence of the splat bonding and mechanical properties of W coatings on deposition temperature was investigated.The results showed that the apparent porosity of the coatings decreased from 3.2%to 0.3%with the increase of the deposition temperature.The Young's modulus of W coating was significantly increased from 128 to 307 GPa as the deposition temperature increased from room temperature to 800°C.The microhardness of the coatings was less influenced by the deposition temperature.It was found that splat bonding across lamellae was formed when the deposition temperature was higher than 600°C compared to the obvious lamellae interface in the coatings deposited at temperatures lower than 600°C.The results evidently revealed that the mechanical properties of plasma-sprayed W coatings could be controlled through the splat bonding by altering deposition temperature.
文摘Plasma sprayed coatings are built up by the accumulation of splats formed by the impacting,spreading and solidifying of molten droplets on the substrate.A three-dimensional computational model including heat transfer and solidification is established to simulate the formation process of a single splat using the computational fluid dynamics(CFD)software,FLUENT.The fluid flow and energy equations are discretized and solved according to typical finite volume method on an unstructured grid.A volume of fluid(VOF)tracking algorithm is used to track the droplet flow with free surface.In order to understand the splat formation mechanism,the process of splat formation caused by impacting and spreading of a molten nickel droplet on a polished mild steel surface is simulated.On this basis,the simulations of impact of a molten droplet on substrate with different conditions including the surface morphology,thermal conductivity,initial temperature of the substrate and the thermal contact resistance are presented.The results clearly show the effect of those parameters on the shape of the final splat and splash behaviors.
基金the Program of Advance Research between France and Chinese(No.PRA SI 03-03)the Region Rhone-Alpes of France within the Project"MIRA Research 2003"the Project of Image Guided Surgery of Shanghai,China(No.045115001)
文摘Elliptical splats are used to represent and render the isosurface of volume data. The method consists of two steps. The first step is to extract points on the isosurface by looking up the case table. In the second step, properties of splats are computed based on local geometry. Rendering is achieved using surface splatting algorithm. The obtained results show that the extraction time of isosurfaces can be reduced by a factor of three. So our approach is more appropriate for interactive visualization of large medical data than the classical marching cubes (MC) technique.
