Friction and Acoustic Emission (AE)

• The friction phenomenon produces elastic stress waves generated by the release of energy stored within a material, called acoustic emission (AE), that propagate through the material and can be detected by adequate sensors when they arrive at the material surface, provoking small displacements

• The mechanical signal can be turned into an electrical signal of low amplitude and high frequency by a piezoelectric AE sensor

• Electronically processed signals can be later analysed with mathematical and computational techniques

• AE signals can be classified into two types:

• continuous (signals are associated with plastic deformation in ductile materials)

• burst (signals are observed during crack growth, impact or breakage)