Thermo-mechanical coupling analysis of expansion tubes: Theoretical prediction and experimental investigation

Thick-walled expansion tubes have been widely used in high-speed trains as passive energy-absorbing devices. Previous studies mainly focused on thin-walled expansion tubes with thickness less than 5 mm, and the theoretical model is in good agreement with experiments. However, a deviation of about 4.3% for the thickwalled tubes with a thickness of 15 mm is found between the predictive reaction force and experimental results. In this study, the thermal effect was investigated for the deviation. Firstly, a modified theoretical model was proposed by a plastic hinge moving method. Secondly, the temperature distribution was calculated, and a new reaction force was obtained by the temperature-dependent material properties. A thermal reduction coefficient was used to represent the ratio of the reaction force considering the temperature effect or not. Finite element simulations and experimental measurements were performed to verify the current model. The results show that the thermal reduction coefficient is mainly affected by the geometrical structure, material properties, and ambient temperature. The deformation modes of expansion tubes can be divided into point contact mode and surface contact mode, as the increase of the expansion angle. The deformation of the point contact mode is similar, so is the reaction force and the thermal reduction coefficient. The thermal reduction coefficient can vary from 0.98 to 0.97 for the thickness of 7-33 mm. This study provides a better understanding of the temperature effect on expansion tubes and an evaluation method with higher accuracy for the design.