An automated procedure for determining crack opening level from differential displacement signal data

Abstract The crack opening point is commonly measured from load-displacement records or load-differential displacement records. In this study, an automated method is developed to determine the crack opening point from differential displacement signal curves. To improve measurement precision, a noise reduction method using a digital low-pass filter was employed. In order to assess the measurement accuracy and precision of the proposed method, computer simulation was extensively performed, generating differential displacement signals of various S/N ratios. The measured results of crack opening points for these simulated signals show good accuracy and precision. The proposed method was applied in practice to constant-amplitude loading, and two kinds of random loading: narrow- and wide-band random loading. As a result, the method is found to be very effective even for random loadings.