Cross-correlation for feature extraction applied to ultrasonic test for stress evaluation in concrete

Correlação-cruzada para extração de características aplicada a ensaio ultrassônico para avaliação de tensão em concreto

Abstract

Changes in the stress state of a solid medium cause small variations in wave propagation velocities. Cross-correlation (CC) is a tool used for similarity evaluations between two data series. This paper addresses the use of the CC function for the feature extraction of ultrasonic test data that evaluated the stress state in a concrete specimen subjected to compressive loads. The CC function was applied to waveforms, and an analysis of influential parameters (e.g., CC-Domain, time window, and center-time) assessed the differences between the various stress levels. The results showed the variations in ∆V/V₀ vs. stress diagrams were lower in the elastic regime, whereas the analyzed parameters highly influenced the results. S-waves were more suitable for analyses of stress variation, since they were little influenced by time window and center-time.

Keywords:
non-destructive tests; ultrasound; acoustoelasticity; direct waves; anisotropy