Schemes of local fitting for damage detection of bars using longitudinal operating deflection shapes measured by 3D laser scanning

Abstract

Longitudinal operating deflection shapes (ODSs) of a bar can be measured by three-dimensional laser scanning. The difference between slopes of ODSs (SODSs) under damaged and intact statuses of the bar can be used to indicate and locate the damage. This study inspects ODSs in a multiscale manner, whereby multiscale ODSs (MODSs) and multiscale SODSs (MSODSs) are produced. Noise interference can be eliminated by increasing scale parameters to their satisfying values. In addition, two schemes of local fitting are applied to measured MODSs to generate locally fitted MSODSs under virtual intact statuses of the bars. By relying on differences between measured and locally fitted MSODSs, two individual damage indices (DIs) are established, namely the type-I DI and the type-II DI, in which damage-induced peaks can indicate and locate the damage. The capability of the two schemes of local fitting is theoretically verified and experimentally validated by detecting two-sided notches in bars.