Reconstruction of residual stresses in railroad rails from measurements made on vertical and oblique slices

Abstract

The paper addresses the problem of experimental determination of the residual stress state in railroad rails. A new and original method of rail residual stress examination is proposed. The novelty of the method, which is called “oblique slicing technique”, is based on its mechanical, experimental and numerical foundation. Although the new procedure can be seen as a variation on the well known and established in the field Battelle 3D technique (sometimes called Battelle slicing technique), it actually redefines the previous concepts and approaches, bringing a seemingly unparalleled means for determining the 3D stress state in railroad rail by examination of two (or more 1) 2D states measured on thin slices cut out from the rail length at different inclination angles. The paper presents a unique mechanical algorithm of restoring the full 3D stress state in the rail as if it had not been cut, and its numerical implementation is complemented with previously developed proprietary techniques of physically based approximation and/or data smoothing. The whole approach is based on moiré interferometry measurements. Apart from theoretical considerations, the paper shows some results of an extensive range of tests carried out on simulated experimental data. The purpose of the tests is to evaluate the technique on a benchmark problem and answer some technical questions. Finally, possible extensions and/or modifications as well as future research plans are discussed.