Improved modelling of tread braked wheels using an advanced material model

Paper in proceeding, 2022

The objective of the present study is to investigate and examine the capabilities of a novel material model, calibrated using anisothermal experimental data, when employed in detailed braking simulations corresponding to brake test rig conditions. To achieve this, an axisymmetric finite element model of a standard freight wheel exposed to tread braking is used to assess the performance of the material model. The finite element model accounts, in a simplified fashion, for residual stresses introduced by the rim hardening process at wheel manufacturing and also for variations in material properties based on typical hardness values on a wheel cross section. A range of braking situations are assessed to achieve different loads and temperatures, by mimicking downhill braking at constant speed for a prolonged time period. The results are compared between the new anisothermally calibrated model, two other similar material models previously developed for wheel simulations that are calibrated merely by isothermal data as well as a simpler model used in industry. Additionally, some comparisons are also made with the pertinent European standard on technical approval for forged wheels. The results show that the new calibrated material model predicts realistic material behaviour for a wide range of braking situations. Compared with previous models, conservative predictions are found with higher residual tensile stresses after braking and also larger residual displacements, as well as larger areas with plastic strains. The study also highlights the importance of knowing the spatial distribution of the residual stresses when comparing average residual stresses in the wheel rim. The new features of the material model contribute substantially to more accurate modelling of the processes occurring in the wheel during high temperature tread braking, although at the cost of prolonged duration of the numerical analyses.