Fracture mechanics approach to crack depth determined through ultrasonic method

In general, the evaluation of crack depth in concrete members through the ultrasonic method is carried out by using the propagation time of the ultrasonic pulse diffracted at a crack tip. However, it is well known that the fracture process zone (FPZ) with a large number of micro-cracks exists around and ahead of the main crack tip. Therefore, it is important to clarify the influence of cracks on the propagation of ultrasonic pulses in order to confirm the validity of the ultrasonic method for crack depth determination. In this study, the crack depth determined through the ultrasonic method was compared with those measured by dyeing and estimated by finite element analysis (FEM Analysis) with a tension softening diagram.