Crack propagation identification in concrete sleepers/bearers in railway switches and crossings using acoustic eemission

Prestressed concrete sleepers so-called ‘bearers’ in railway switches and crossings (or turnout systems) are safety-critical elements that distribute the dynamic wheel loads from the rails to the track support system. At the turnout area, wheels often generate detrimental dynamic loading conditions to the bearers. These loads often cause cracks and damage on the bearer components. Often, cracks on the bearers develop and propagate under cyclic impact loadings. These cracks can cause broken bearers and sometimes damage the fastenings and baseplate too. Such components failure can cause widening gauge and possible train derailments. This paper is the world first to present an application of non-destructive acoustic emission technology for crack propagation in railway concrete turnout sleepers and bearers. It presents full-scale experimental investigations in order to demonstrate the application of acoustic energy to identify crack propagations in the prestressed concrete component. Experimental laboratory testing involves three-point bending tests of four concrete sleepers. Three-point bending tests correspond to a real failure mode, when the loads are not transferred uniformly to the ballast support. It is observed that AE sensing provides an accurate means for detecting the location and magnitude of cracks. Cyclic load test is also highlighted in the paper to demonstrate the capability for crack propagation identification of acoustic emission technology.