Damage detection under varying environmental and operational conditions using Wavelet Transform Modulus Maxima decay lines similarity

• Damage detection under varying environmental and/or operational conditions.
• Normalized Cross Correlation (NCC) measures the similarity between WTMM decay lines.
• Pointwise Summation, DSSD, of Similar WTMM decay lines as a measure of distance.
• NCC and DSSD are used to reject varying environmental and operational conditions.
• Demonstration of the proposed methodology on simulated and experimental data.

Over the last three decades, there have been increasing demands to develop and deploy Structural Health Monitoring (SHM) systems for engineering structures in service. Since these structures are subjected to varying environmental and operational conditions, reliable SHM methodologies must be capable of not misattributing to damage changes due to environmental conditions. This paper presents a novel damage detection methodology based on the similarity between maxima decay lines of the continuous wavelet transform scalogram of the structural responses obtained under different operational and environmental conditions. The normalized cross correlation (NCC) is used as a measure of this similarity. In addition, the pointwise summation of similar Wavelet Transform Modulus Maxima (WTMM) decay lines is used to identify changes due to the presence of damage from different force realizations and/or varying environmental conditions. The effectiveness of the proposed methodology is demonstrated using a simulated 3DOF system and an experimental cantilever beam.