Influence of Fifth Wheel Position on Cab Durability and Dynamics in Tractor-Semitrailer Vehicle

Articulated vehicles contribute to the major portions of cargo transport through roads. Fifth wheel (FW) is an important component in these vehicles, which acts as the bridge between tractor and trailer and is often used as a parameter to adjust the axle loads. Ride and comfort studies linked to FW position exist. However, its influence on durability is often not considered seriously. In this article, three different FW positions placed at 200 mm, 400 mm, and 600 mm in front of the rear axle are studied virtually on a 4x2 tractor with three-axle semitrailer combination. To assess the risk associated with FW movement, acceleration-based pseudo-relative damage, power spectral density (PSD), and level crossing plots are analyzed for each FW position. Further, fatigue analysis is done on the cab structural components to understand the durability. Outcome shows that the FW position has an influence in determining the cab dynamics and durability of the components to a great extent. When the FW is moved toward the front of vehicle, there is an increase in cab pitch, roll, and yaw motion. Acceleration level and cab suspension forces are adversely affected. With FW increments, change in cab yaw is drastic and hence the lateral force induced damage seen on the rear cab components.