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As a maskless nanofabrication technique, friction-induced selective etching can easily produce nanopatterns on a Si(100) surface. Experimental results indicated that the height of the nanopatterns increased with the KOH etching time, while their width increased with the scratching load. It has also found that a contact pressure of 6.3 GPa is enough to fabricate a mask layer on the Si(100) surface. To understand the mechanism involved, the cross-sectional microstructure of a scratched area was examined, and the mask ability of the tip-disturbed silicon layer was studied. Transmission electron microscope observation and scanning Auger nanoprobe analysis suggested that the scratched area was covered by a thin superficial oxidation layer followed by a thick distorted (amorphous and deformed) layer in the subsurface. After the surface oxidation layer was removed by HF etching, the residual amorphous and deformed silicon layer on the scratched area can still serve as an etching mask in KOH solution. The results may help to develop a low-destructive, low-cost, and flexible nanofabrication technique suitable for machining of micro-mold and prototype fabrication in micro-systems.

Fretting damage failure analysis of a Chinese carbon railway axle RD2 was carried out. The wheel hub was in situ cut to expose the damaged surface of the wheel seat to avoid additional damage. A small‐scale axle test rig was developed, and simulation tests were performed at different rotator speeds of 1800 and 2100 rpm. The wear mechanism of fretting damage areas was a combination of abrasive wear, oxidative wear and delamination. The fracture surfaces exhibited characterization of multisource and step‐profile. The fretting fatigue crack initiated at the subsurface and propagated along an inclined angle at the first stage. The fretting damage at the higher speed was more severe compared with the lower speed, which lead to a relatively shorter fatigue life. The damage morphologies of the axle in the simulation tests were in good agreement with that observed in the failure analysis on real axle.

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