Vibrothermography (also known as Sonic IR) is a method for finding cracks using vibration-induced crack heating. The most widely accepted theory of crack heating is that some sort of frictional process dominates the heating, but that theory does not explain how cracks can heat in mode I (tension/compression) loading as opposed to mode II (shear) loading. We present a model of crack heating based on angled asperity contacts that is able to explain the magnitudes of observed heating based on first principles and minimal fitting parameters. The angled asperities, loaded by crack closure, transform the normal opening/closing motion into shearing motion that can cause frictional heating. The model explains the observed sensitivity of vibrothermography to normal and shear vibration, crack closure effects, and the amplitude dependence of heating.Vibrothermography nondestructive evaluation, also known as Sonic IR and thermosonics, finds cracks by vibration-induced crack heating. The physics of the crack heating has long been a subject of debate. The most widely accepted theory is that some sort of frictional process dominates the heating, but friction does not easily explain how cracks can heat in mode I (tension/compression) loading as opposed to mode II/III (shear) loading.Any model of crack heating needs to explain how cracks can heat in both tension and shear. It needs to be able to predict, consistent with experiment, that the magnitude of crack heating is between linear and quadratic. It needs to predict the experimental observation that heating primarily occurs near the closure point, where the crack goes 
from open to closed, and that cracks do not generally heat at the tips where closure stresses are largest.&nbsp;&nbsp;

Crack Heating Model for Vibrothermography Based on Angled Friction

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.