MxV Rail and the University of Missouri completed the second phase of laboratory investigations of non-contact ultrasonic nondestructive evaluation (NDE) methods for detecting fatigue cracks in railroad joint bar heads. Phase I work explored and demonstrated the effectiveness of using different ultrasonic shear waves (S-waves) and surface waves (SW) approaches to detect reflectors and natural fatigue cracks in joint bars at different locations.1 Phase II work focused on optimizing S-Waves and SW specifically for detecting simulated fatigue cracks of varied sizes in areas of joint bar heads that are inaccessible to visual inspections during revenue service. Challenges associated with using ultrasonic testing (UT) NDE technology for joint bar inspection include surface conditions, complex geometry, and limited or variable access to the surface of the joint bars head, making it difficult to effectively launch and receive ultrasonic waves. Figure 1 shows a joint bar in services and the areas in the…