Hybrid ultrasonic transducer for the characterization of rail head defects

A concept of an ultrasonic defect detection system is introduced. Based on the principles of dynamic beam steering and ultrasonic shadowing, the transducer system consists of two sub-arrays: an assembly of a linear phased array for directing and steering an ultrasonic beam in a test specimen, and a static array for sensing the boundaries of the near and far shadows of a defect from the reflected beam. Using a dynamic pitch-catch configuration, the transducer is capable of determining the location, size and orientation of a planar defect without any mechanical scanning or relocating the transducer. A theoretical shadow analysis carried out in this study allows for developing a scheme for characterizing a defect. To demonstrate the feasibility of the technique, a rail specimen with real defect has been assessed. This scheme proves to be a viable approach for characterizing transverse defects with good accuracy.