Vibration-induced tribological damage to fracture surfaces via vibrothermography

Vibrothermography is a nondestructive evaluation technique that uses a temperature-sensitive infrared (IR) camera that observes vibration-induced heat generation at defects, such as cracks, to detect and locate defects within a structure. Vibrothermography has been hindered by issues of repeatability even between consecutive experimental excitations on the same sample. This paper presents experimental evidence of tribological damage – or microscopic changes – that can occur on rubbing crack faces resulting from vibration-induced frictional heat generation. The observed changes include plastic deformation, fretting, adhesive wear, oxidation, and phase transformations, such as melting. These tribological damage mechanisms on the rubbing crack faces are partly responsible for the non-repeatability of vibrothermographic testing. These mechanisms can be minimized by limiting vibrational stresses, thus improving vibrothermographic repeatability.