Thermo-mechanical analyses of discrete defect repair process for rails

Övrigt konferensbidrag, 2018

Discrete defects in a rail head may form due to aggressive wheel–rail contact in terms of thermal and/or mechanical loads, or due to indentations from foreign objects trapped in the contact. If large, such defects need to be repaired or the rail section removed. These are costly operations that cause operational disturbances. Discrete defect repair (DDR) procedures that include repair welding provide a cost-efficient alternative to rail replacements. Investigations of such repair methods have been conducted in the frame of the European project In2Rail and reported in Deliverable report D3.1, see Kallander (2017). The present work has been focused on investigating a novel DDR procedure through numerical simulations. The new technique employs significantly lower preheat temperature (80 °C in contrast to widely used 350 °C) and equipment that can be carried to the working place. However, the low preheating temperature introduces high temperature differences between the molten filler material and the surrounding rail steel. This may lead to the formation of defects and has to be assessed.

The quality of the weld is highly influenced by the thermal field induced by the repair welding process. This topic was investigated in detail by thermal analyses in Maglio (2017). The study showed the possibility of numerical simulations and investigated in detail requirements and sensitivities of numerical models. In particular, it quantified the sensitivity related to both simulation parameters and to experimental measurements. The thermal analysis has been extended to a thermomechanical analysis that is able to investigate the residual state of stress after repair welding. Such analyses can be used to compare repair welding methods and also investigate the sensitivity to different operational parameters.