Crack diagnosis and monitoring method using linear-phased PZT sensor array

Crack is one of the most typical damage types in engineering structures, spreading quickly and potentially leading to ultimate structural failure. Although traditional nondestructive testing methods would be effective in inspecting cracks in an offline manner, real-time implementation of these methods is difficult. Currently, most efforts on Lamb wave-based damage detection and monitoring techniques are focused on identification of the occurrence, location, and degree of cracks. Aimed at characterizing the orientation and length of crack-like damage, a linear- and sparse-phased sensor array–based crack detection and monitoring approach was developed. The phase of the reflected Lamb waves was extracted by linear-phased sensor array to first detect the direction of the cracks. Different from the existing PZT-phased array techniques, the distance between the neighbor sensors of the proposed method was much farther to cover large-scale area. Thus, the new array was sparse. The lengths of the cracks were evaluated and illustrated graphically by the projection of the reflection field on the array of the Lamb waves. Experiments on aluminum plate were carried out to validate the proposed approach. The results demonstrated that several artificial crack damages were detected, evaluated, and represented in images accurately.