Continuous welded rails (CWRs) are usually laid under tension in order to counteract the thermal expansion that occurs in warm days. The initial state of stress is such that the rail neutral temperature (RNT), i.e. the temperature at which the net stress in the rail is zero, is comprised between 90°F and 110°F. Over the years the RNT decreases, raising the risk of buckling during the warm season. The knowledge of the RNT or of the longitudinal stress helps transportation authorities and rail operators to minimize the risk of buckling by issuing slow orders.
The ANTEUSW system aims to be a new nondestructive evaluation (NDE) method able to estimate the neutral temperature or the longitudinal stress of CWRs anytime and anywhere with minimal traffic disruption and a single measurement. The method relies on the propagation of highly nonlinear solitary waves along a device, hereinafter called the transducer, placed in a dry point contact with the rail to be inspected and able to support the propagation of solitary waves interacting dynamically with the rail to be inspected. The research hypothesis investigated in this T-86 project was that the axial stress affects the number, amplitude and speed of the pulses reflected from the transducer- rail interface.
The finite element model developed in the T-86 project and the laboratory experiments conducted to validate the model showed that: (1) the transducer necessary to apply the NDE method is easy to assemble, inexpensive, and able to provide repeatable measurements; (2) some features of the solitary waves are monotonically dependent on the rail longitudinal stress, provided that the structural behavior of CWRs is equivalent to a straight beam 3+ meters long; (3) the method works well if an accurate model of the dynamic response of CWRs to localized lateral forces is available.
Although the results of this project confirmed all the research hypothesis and ANTEUSW aims to be used with minimum traffic disruption, with a few measurements that do not require day-long observations under favorable weather, and without permanent wayside installations, a major factor in achieving industry acceptance is to demonstrate the new technology in real railroads.
The next steps of this research include the study of curved rails and the testing of ANTEUSW in the field in collaboration with railroads owners in order to validate the technology under service traffic.
The Final Report is available.