Development of impact characteristics response model for combined tube expansion axial splitting module

Combined tube-expansion and axial splitting mechanism yields excellent force-displacement characteristic and high stroke efficiency. In this paper, a mathematical model to estimate and optimise impact response of such mechanism was developed, to correlate the impact response to the module dimensional parameters, i.e. diameter-to-thickness ratio, D1/t and expansion ratio, D2/D1 and other design parameters such as material strength, expansion angle, and friction coefficient. Accurate finite element (FE) analysis, validated with experimental results were performed to generate results sufficient to form a response surface model (RSM). The current mathematical model successfully captured the effect of expansion ratio, thickness ratio, and initial diameter of the tube, with R2 of 0.99 for specific energy absorbed and 0.81 for mean crushing force throughout 80 data points. A case study was also presented which shows the result comparison between numerical and the proposed model, yielding error below 1% difference for mean and peak crushing force, total energy absorbed, specific energy absorbed (SEA), stroke and crushing force efficiencies. The model has also been implemented in an optimisation for railway vehicle case study using the proposed mathematical model. The current research found that the combined module could reach SEA and stroke efficiency values of 29.74 kJ/kg and 0.99, respectively, significantly better than most of the metallic-based impact energy absorbing mechanisms.