Durability impact on air suspension system of using e- axles in truck trailers

Abstract

As part of the global trend towards carbon emission reduction, the road transport sector is motivated to produce solutions that reduce the use of fossil fuels. One of the posed solutions for this purpose is the so-called ‘e-axle’ for freight truck trailers. As a world-leading production company of air suspension systems for truck trailers, VDL Weweler B.V. wishes to provide suspension systems that can be used in combination with e-axles. An e-axle has as much as double the mass compared to a passive axle currently used in truck trailers. As the axle is part of the unsprung mass of the system, the increase will have a significant impact on the dynamics and forces within the air suspension system. Getting a better understanding of these impacts will help formulate the requirements that using an e-axle will pose to the suspension systems produced by VDL Weweler. Of particular interest is the impact on the durability of the trailing arms as a consequence of doubling the unsprung mass. The goal of this research project is therefore to quantify the stresses and the associated durability impacts as a first step towards finding the necessity of design adaptations.

During experiments conducted as part of this research project, an axle was fitted with a 500 kg ballast to reproduce the increased unsprung mass of an e-axle. From data analysis strain gauge data was concluded that the durability of the trailing arm could be reduced with at least 30.8\%. A significant impact to the dynamics of the system was observed in various dynamic indicators of the vehicle. A significant increase in the suspension deflections, which have a direct relation with the load on the trailing arm was observed. Furthermore, a significant reduction of the natural bounce frequency of the axle and higher transmission of axle vibrations to the chassis were found.

A novel kinematic vehicle model was derived to allow the creation of a digital twin model of the RRT durability test. A model validation was conducted to establish the ability of the vehicle and component models to reproduce the RRT. The numerical model proved to strongly reproduce the axle motions and suspension deflections in terms of Power Spectral Density of the dynamic response. The impact of unsprung mass was modelled with high accuracy in relative terms.

Based on the results of this research project, a significant impact to the durability of the trailing arm is expected. Furthermore, a solid start was made in the development of a model that could predict the durability impact of varying system parameters in an air suspension system of a truck trailer.