This conference paper was submitted for presentation at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Although the rate of use of air suspension is increasing in terms of ride comfort, commercial trucks are still selling vehicles equipped with rigid axles and leaf spring suspension mainly due to high loading and rough road driving. Due to these structural characteristics, geometry errors inevitably occur according to vehicle driving loads, and it takes a lot of time to solve the braking pull problem due to geometry errors in the vehicle development stage. Therefore, this study studied a methodology that could predict geometry errors during vertical and braking loads of suspension steering system more reliably in the early stages of design and applied the methodology to develop vehicles to improve braking pull. FEM 3D leaf spring simulation has the advantage of being able to check deformation and stress for various loads, but it has the disadvantage of taking a lot of modeling and simulation time to respond to repetitive design changes. On the other hand, FEM 2D leaf spring analysis can quickly and reliably predict leaf spring behavior under vertical load and braking load required in the early design stage review, and it can be used together with design review for stiffness, strength, and durability performance, so it has an advantage when used in conjunction with performance review with the steering system in the early design stage. Therefore, this study compared and verified with 3D FEM analysis and system test measurement to determine a reliable 2D FEM modeling level and predicted the leaf spring behavior according to load conditions. FEM leaf modeling was performed from the 2D shape of each individual plate in the free camber state to the U-bolt tightening condition, so that the free camber state shape of the leaf spring assembly could be predicted, so that the behavior of the leaf spring assembly under vertical and braking loads could be predicted well even at the design stage before the leaf spring manufacturing. Based on this 2D model simulation, the geometry errors for various knuckle arm hp positions, draglink and pitman arm combinations were quickly and reliably reviewed. In addition, a kinematic model was generated using the basic library of open modelica to perform a kinematic review of the steering device, which was utilized to design a steering suspension system that minimizes braking drift in the early stage of vehicle design.