On June 12, 2019, about 1435 Pacific daylight time, a Cessna 140 airplane, N73053, sustained substantial damage when it was involved in an accident near Independence, Oregon. The flight instructor and student pilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the instructor, the accident landing was the second landing of the flight. As the airplane was slowing down and they were exiting the runway, there was a loud "clunk." The airplane slid sideways, bounced, and then ground looped, resulting in substantial damage to the fuselage. The instructor reported that the right wheel assembly separated at the axle. The student pilot, who was the owner of the airplane, reported that he had purchased the airplane in April 2019 and was flying 1 to 3 times a week while working toward his private pilot certificate. During the previous flights, there had been no issues. Examination of the fractured axle assembly revealed that the axle fractured at the transition radius between the longitudinal barrel (tube) portion and the plate portion. A fatigue crack emanated from multiple origins at the outer surface of the transition radius and extended circumferentially around the outer surface of the transition radius. The fracture features outside of the fatigue region showed features consistent with overstress separation. The maintenance history of the landing gear and axle could not be determined.