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Description
Accurate NVH simulation results require the use of models that precisely represent the physical dynamics and interactions occurring under real-world operating situations. This research focuses on the development of a mechanical equivalent model for trailers that accounts for different loading conditions to improve the accuracy of these simulations. Central to this study is the use of experimental modal analysis techniques to investigate the structural dynamics of both a scaled-down trailer model and its full-size counterpart.
The scaled trailer model, designed with dynamic similarity to its real-world counterpart, is tested on a specialized bench allowing excitation at the axle and recording of forces at the kingpin as well as accelerations of the trailer. The experiments include various loading scenarios, with shifts in the centre of gravity, different payload types, load couplings and weight distributions. In addition, a scaled-down version of a fifth wheel is used to investigate the interface forces that occur with different coupling types such as material combinations and different clearances. In parallel, the full-size trailer is tested on a multi-piston test rig to evaluate its dynamic behaviour. Key characteristics, including natural frequencies, mode shapes, and damping ratios, are derived for a comparative analysis.
The results show a correlation between the scaled and full-size models, with the position of the centre of gravity and the clearance in the fifth wheel coupling emerging to be the most influential factors for the dynamic behaviour. Local stiffening effects due to load connections are observed, although their effects are secondary to the overall positioning of the load. Finite element simulations including these effects align with the experimental results and underline the validity of the scaled model for dynamic evaluations.
This research confirms the feasibility of using a scaled model to predict the dynamics of full-size trailers and provides data to create a mechanical equivalent model for integration into NVH simulations. These findings contribute to improved simulation accuracy and enable better design and performance optimization of semi-trailers and tractor units in the transportation industry.
