Topology Optimization for Weldment Structures Using Bezier Curve-Based Cold-Formed Members

Abstract

In an effort to reduce both greenhouse gas emissions and vehicle cost of ownership, the heavy equipment and vehicle design industries are undergoing a large migration from diesel to electric power systems. The battery technology on which electric vehicles are reliant is so far unable to match the operational ranges of combustion engine vehicles, due both to its increased weight and reduced energy density. Therefore, utilizing structural optimization (SO) to design lightweight chassis and manipulator systems is an important step to take in increasing the adoption of these electric systems. Heavy equipment relies on the weldment design paradigm; systems are fabricated via the welding of a series of structural members like plate and hollow structural sections. Current SO efforts in this field generate topology by determining the optimal layout of these structural members or primitives and their connectivity. The resulting structures contain multiple curved load paths. These efforts, however, disregard curvature as an attribute that can be assigned to a structural member itself; primitives used in these works are often limited to straight sections. This is despite the recent noting by purveyors of the industry that using curved members via forming technology can offer both cost savings and reduction of structural degradations caused by excessive welding. To address these shortcomings of existing literature, this work aims to provide a weldment topology optimization tool with three novel advantages. First, the capability of cold-work (CW) technology to generate continuously variable curvature is unlocked via the construction of a Bezier curve-based structural member. Second, the effects that CW has on member material properties are controlled via the implementation of a CW bending strain constraint. This ensures the feasibility of fabrication of the optimal design via cold-working, and allows weldments using CW members to be validated via linear static analysis. Third, material costs associated with the CW manufacturing process are utilized to construct a constraint, able to achieve significant cost savings per member. Academic case studies demonstrate the effectiveness and capability of each feature, which together enhance manufacturing and cost considerations in SO as a whole.