Electromagnetic radiation emitted during friction process

A series of studies of electromagnetic radiation (EMR) emitted during fracture of materials, enabled us to obtain a relationship between the width of a fracture and the wavelength of the emitted EMR. Applying this relation to friction we could check one of its suggested mechanisms, namely the Bowden-Tabor model, which states that during a friction process, asperities on the two contacting surfaces are “welded” together (at a microscopic level) and fractured. A uniaxial tension machine was used, whereby two half cylinders of chalk (CaCO3) bound together, were moved one against the other, generating friction. Calculations based on EMR observations showed that the average width of the fractured asperities was ∼26.3 μm, while mechanical profilograph measurements of the average width of the total number of “long” asperilies before and after the experiment, yielded values of 15.6 and 18.4 μm, respectively, implying that ∼25% of “long” asperities were fractured during a single friction process.