Light Pulses Emitted at Microfractures Formed by Friction between Two Solid Materials

Abstract

Short-duration light pulses have been observed to be emitted at the moment of microfracture (pit size of 10-20 µm) when two solids are rubbed against each other. When a fused silica sample is scratched by a diamond grain, the observed light pulses have a rise time of less than 10 ns and pulse width of 10-20 ns. A continuous spectrum at 500-800 nm is observed, suggesting 3000° C material part. At 300-400 nm, intense line spectra are observed, which suggests the existence of gaseous *O2 molecules desorbed from SiO2. When the solid fractures, the fractured part heats up to a very high temperature almost instantaneously, and cools down within 10-20 ns.

Fracture‐induced Physical Phenomena and Memory Effects in Rocks: A Review

“…Elevated temperatures of 3000 °C caused by microfracturing are confirmed by the spectral analysis of light pulses occurring when a transparent sample of fused silica, SiO 2 , is scratched with diamond [40]. Desorption of gaseous O 2 from crack surfaces in SiO 2 and Al 2 O 3 was deduced from the spectra [40].…”

Two-dimensional spatial distribution of electric-discharge plasma around a frictional interface between dielectric surfaces

“…To measure the temperature of a frictional surface, thermal radiation generated by the friction has always been observed in the visible light and infrared regions. 6,7 On the other hand, when a dielectric material is fractured, 8-10 deformed, 11,12 peeled, 13 or scratched ͑under various pressures of Ar, He, and O 2 , 14 and n-butane 15 ͒, i.e., some mechanical force is exerted on the material, emission of radiation and/or luminescence induced by production and relaxation of defects occurs. The mechanism of this triboluminescence 16,17 is not still known well.…”