Paper Title
Measurement of Continuous Welded Rail Residual Stress with the Digital Discrete Image Processing Photoelasticity Method

A digital discrete image processing photoelastic coating system has been developed to determine the magnitude of the residual stress in a prestressed long welded rail subjected to a uniform uniaxial compression load and expansion stress analysis. By performing digital image processing fringe analysis, the optical data contained in the reflection photoelastic isochromatics are converted into values of residual stress. Evaluation is conducted by measuring the in-plane stress field generated by the introduction of a small hole. The stress field is determined with the calculation of the photostress distribution by means of the digital discrete image processing method. The magnitude of the residual stress field is finally evaluated through a discrete tricolor (R.G.B.) grey level calculation and compared with the prestress value applied to the long welded rail. Keywords - Reflection Photoelasticity, Digital Discrete Image Processing, Residual Stress