This paper was produced for the 2019 NAFEMS World Congress in Quebec Canada

Resource Abstract

Prediction of vehicle frame loads in both normal and extreme operating conditions is essential to accelerate the design process. Nevertheless, the loads imposed to the frame are influenced by the frame design itself as its rigidity and geometry affect the load distribution. Traditionally, frame loads are calculated from hub loads that are obtained from experimental data collected from an instrumented prototype. These loads, however, are representative of a specific frame and weight distribution, and the data is often biased by the required instrumentation that adds significant weight to a vehicle, in particular for recreational vehicles [16]. A promising alternative is to consider the use of Multi-Body Dynamics (MBD) software programs to predict input loads on a vehicle going through specific maneuvers via numerical simulation. Use of MBD simulations in the preliminary stage of a product design can reduce the development time and the cost as early prototypes would be more mature.



Simplified models such as quarter vehicles [9-10] and fully rigid frame and suspension links [2-3-15] have been used in the past but they may not capture the actual behavior of a real vehicle. The complexity of determining frame loads and stress distribution stems from the detailed transfer path between the road and the hard points on the frame. Indeed, numerous items such as tires, bushings, suspension and suspension links as well as the coupling between them impact how road inputs are transferred to the frame.



The aim of our study, conducted at the Centre de Technologies Avancées (CTA), in collaboration with the Université de Sherbrooke, was to validate an MBD model with experimental data collected during simple maneuvers that cover a large range of loading conditions. This model is based on the «full analytic» approach in which a virtual road profile and a commercial tire model software are incorporated into a complete vehicle MBD model [2-3-7-11-14]. Once the model is validated, further analysis such as frame input loads and flexible parts strain are performed.



The study focuses on an instrumented three-wheeled recreational vehicle equipped with an inertial GPS, wheel force transducers, strain gages and potentiometers to measure suspension travel. The data was obtained from a vehicle performing numerous dynamic maneuvers representative of normal driving conditions.