Advanced Ultrasonic Techniques for Railroad Inspections: Determining the Structural Integrity of Rail Steel

Laser generated ultrasound and air-coupled ultrasonicdetectors are used to develop an inspection techniquefor the railroad industry. The Laser Air HybridUltrasonic Technique (LAHUT) has the advantage ofperforming inspections without establishing contactwith or the need to come close to the inspectedstructures. This feature makes it possible to performdynamic inspections of tracks from a moving train andstationary wayside inspection of wheels on a passingtrain. The study considers the most critical flawtypes in railroad tracks and wheels. Some are verydifficult to detect with currently availabletechnology, others are not possible without ahandheld device. The second part of the book uses acontact ultrasonic method to monitor microstructuraleffects during fatigue cycling of railroad steel. Twoexperiments configurations are presented. One is verysensitive to microcracks. Once detected, theremainder fatigue life may be predicted. The secondtechnique is sensitive to dislocations on an atomiclevel. As dislocation loop length and density beginsto multiple, certain changes are detected in thevelocity and attenuation of the acoustic signal.