Y.B. Liu

Friction and wear characteristics of hot-extruded leaded aluminum bearing alloys

The friction and wear characteristics of hot-extruded Al-Pb alloys with lead contents in the range 0–25 wt.% and as-cast Al-Pb alloys with lead content of 20 wt.% were investigated under dry-sliding conditions using a pin-on-disc test machine. It was found that hot extrusion greatly decreased the porosity that was caused by powerful stirring and considerably improved the mechanical properties of stircast Al-Pb alloys, including wear behavior. The coefficient of friction and wear rate decreased with increasing lead content, and especially the antiseizure property of hot-extruded Al-Pb alloys containing 20 wt.% and 25 wt.% lead were improved remarkably. Optical observation revealed that the reason for this was the formation of a black compact film of lubricant that covered almost the entire worn surface of specimens at a highly applied load level. This film is a mixture of different constituents containing Al, Fe, Si, O, and Pb.

Experimental Investigations on Manufacturing Different-Shaped Bio-Inspired Drag-Reducing Morphologies and Hydrodynamic Testing

Fascinating sharkskin effect has drawn so many attentions in the recent several decades, and it been becoming more well-known since the Olympic Games in 2000, and there were many athletes wearing sharkskin swimming suit to obtain the good grades. Biological sharkskin is all covered by the tiny and stiff scales, and there are microgrooves sitting on them, which can protrude out of the viscous sublayer and reduce the wall friction. However, sharkskin effect is the imperative consequence of nature selection in a long time, which enable shark fit the living surroundings perfectly, and for expanding its application in more fields, it should be adjusted or deformed. In this research, experimental investigations on manufacturing different-shaped sharkskin morphologies are performed and the hydrodynamic drag reduction testing is conducted, the results show that deformed sharkskin morphologies can improve drag reduction effect, which has important potential applications in fluid engineering.