Methodical Design of a Subframe for a Novel Modular Chassis Concept without Knowledge of Final Vehicle Parameters

This article presents the methodical development of a subframe for a novel on-the-road-modular vehicle concept, which was developed for the U-Shift project. The subframe serves as the basis for a modular chassis. This chassis offers the possibility to exchange chassis components by the operator, which means after completion by the manufacturer, and thus to adapt the vehicle to different purposes. According to the applied methodology, the relevant wheel loads are determined and a geometric reference model is created. By defining the relevant load cases, the forces acting on the subframe, and thus the physical boundary conditions, can be determined from the wheel loads. In addition to the wheel loads and the geometric boundary conditions, no other vehicle parameters are required for the development of the subframe. The results of the topology optimization are used to identify areas of the geometric reference model that are not exposed to high loads. Based on the results of the topology optimization, a suitable combination of manufacturing processes and suitable materials can also be determined. After the basic topology has been determined, a welded construction is derived from square tubes and plates. Subsequently, excess stresses at critical points are identified in simulation and analysis processes, and constructive changes are made to reduce them. Through validation by simulation of the relevant load cases, a proof of compliance with the physical boundary conditions can be provided. The actually manufactured subframe is presented, and the potential of the modular construction for the development of a chassis modular kit is explained.