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phys_org 00405.txt

#Discovery is key to metal wear in sliding parts (w/Video) Researchers have discovered a previously unknown mechanism for wear in metals: a swirling, fluid-like microscopic behavior in a solid piece of metal sliding over another. The findings could be used to improve the durability of metal parts in numerous applications.""Wear is a major cause of failure in engineering applications, "said Srinivasan Chandrasekar, a Purdue University professor of industrial engineering and materials engineering.""However, our findings have implications beyond wear itself, extending to manufacturing and materials processing.""The findings are the result of a collaboration of researchers from Purdue, the Indian Institute of Science in Bangalore, India, and M4 Sciences, a company in West Lafayette, Indiana.""Using high-resolution imaging of sliding contacts in metals, we have demonstrated a new way by which wear particles and surface defects can form, "said Purdue postdoctoral research associate Anirban Mahato, who is working with Chandrasekar; Narayan Sundaram, an assistant professor at the Indian Institute of Science; and Yang Guo, a research scientist at M4 Sciences. Findings are detailed in a research paper to appear Wednesday (July 23) in Proceedings of the Royal Society A a publication of the Royal Society in the United kingdom. The researchers, using a microscope, high-speed camera and other tools, had revealed previously the formation of bumps, folds and vortex-like features on sliding metal surfaces. The new findings build on the previous paper, published in 2012 in Physical Review Letters, to show how the behavior leads to cracks and wear particles. The findings were counter-intuitive because the experiment was conducted at room temperature, and the sliding conditions did not generate enough heat to soften the metal. Yet, the swirling flow is more like behavior seen in fluids than in solids, Chandrasekar said. The team observed what happens when a wedge-shaped piece of steel slides over a flat piece of aluminum or copper. The metals are used commonly to model the mechanical behavior of metals.""We speculated in the earlier paper that the swirly fluid-like surface flow discovered on sliding metal surfaces is likely to impact wear in sliding metal systems, "he said.""Now we are confirming this speculation by direct observations

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