Numerical simulations of the plastic deformation of insulating joints
Examensarbete för masterexamen
Numerical simulations were carried out to evaluate the performance of insulating joints in railway tracks. Although insulating joints are considered weak spots on the track due to the imposed rail discontinuity, they are nevertheless essential to monitor and control train traffic. All simulations presented were conducted using the commercial FE code Abaqus. Results were extracted, processed and plotted with the help of the programming languages Python and Matlab. No dynamic effects were included in the simulations. This study consists of three major parts: The first part was to compare hyper-elastic Neo-hookean and linear elastic material models for the insulating layer in the joint. The simulations showed that there was no significant difference in stresses or displacements between the two models. Investigating the effects of increasing the stiffness of the insulating material was performed in the second part. The investigation showed that increased stiffness decreases the plastic deformation in the steel. However when increasing the stiffness the interfacial shear stress increases. This will promote failure of the glue that ties insulation and rail together. The effect of having an inclined insulating joint was analyzed. Four different inclination angles θ, were tested ranging from 0◦ (no inclination) to 60◦ . By increasing the angle the plastic deformation in the steel on both sides of the insulating layer increased under pure rolling conditions. Inclination did not seem to cause any significant changes in interfacial shear stresses. Finally a comparison was made of the vertical displacement of the wheel cen- ter between the quasi-static ABAQUS simulations and approximations derived from Newtonian physics. These approximations indicate that the time that it takes for the wheel to travel over the gap is not sufficient to allow for the wheel displacements predicted by the quasi-static simulations when traveling on a speed exceeding roughly 85 km/h.
Fastkroppsmekanik , Solid mechanics