AN AUTOMATED PROCEDURE FOR DETERMINING CRACK OPENING LEVEL FROM DIFFERENTIAL DISPLACEMENT SIGNAL DATA

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 SIN 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.