ULTRASONIC TOMOGRAPHY FOR RAIL FLAW IMAGING

摘要

In the railroad industry there is a need to have quantitative information on internal rail flaws, including flaw size and orientation. Having such information can ultimately lead to an increase the safety of train operations by preventing derailments using a knowledge-based decision of remedial action to be undertaken on the rail flaw. Current ultrasonic inspection methods leave such determinations to a rather subjective interpretation by the inspector which is influenced by experience and other factors. However, this quantitative information can be obtained by 3-D imaging of the rail flaws. This paper will present a method for 3-D imaging of internal rail flaws based on Ultrasonic Tomography. Combining tomographic elements from radar and sonar imaging, high resolution images of flaws can be obtained with a stationary array of ultrasonic transducers. Operated in a "full matrix capture" scheme that minimizes the number of ultrasonic transmitters, the practical implementation is simplified and the inspection time is reduced with such an array. In this method, a full 3D image of the rail volume identifies the location, size and orientation of the defect. This will help to eliminate human error involved with the typical manual, single transducer inspection methods currently used. The results of advanced numerical simulations, carried out on rail profiles with an internal defect will be presented. The simulations show the effectiveness of the technique to image a 5% Head Area Transverse Defect in the rail head. Current efforts are aimed at developing an experimental prototype based on this technology, whose design is in process.