The paper describes a fully automated process to generate a shell-based finite element model of a large hybrid truck chassis to perform mass optimization considering multiple load cases and multiple constraints. A truck chassis consists of different parts that could be optimized using shape and size optimization. The cross members are represented by beams, and other components of the truck (batteries, engine, fuel tanks, etc.) are represented by appropriate point masses and are attached to the rail using multiple point constraints to create a mathematical model. Medium-fidelity finite element models are developed for front and rear suspensions and they are attached to the chassis using multiple point constraints, hence creating the finite element model of the complete truck. In the optimization problem, a set of five load conditions, each of which corresponds to a road event, is considered, and constraints are imposed on maximum allowable von Mises stress and the first vertical bending frequency. The structure is optimized by implementing the particle swarm optimization algorithm using parallel processing. A mass reduction of about 13.25% with respect to the baseline model is achieved.

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In this research, Columbia Helicopters, Inc. (CHI) and Virginia Polytechnic Institute and State University collaborated to conduct the numerical model Verification and Validation (V&V) of a Global Finite Element Model (GFEM) of a tandem rotor helicopter developed by CHI. The V&V process is followed based on the ASME V&V guide for computational solid mechanics. The target mathematical model is verified with a convergence study by improving the mesh density and quality. For the model validation, the authors compare the dynamic and static finite element analyses (FEA) with the experimental results. During 1980s, NASA along with some industry participants pursued a Design Analysis Methods for Vibration (DAMVIBS) project to develop and validate accurate FEM based framework for dynamic analysis of helicopters. This work utilizes NASA's DAMVIBS project results to validate the dynamic responses for vertical, lateral, and pitch loading cases. In addition, for static validation, the authors have used CHI's static pull experimental data. This data includes measured strain values at various locations on the fuselage structure. Both dynamic and static FEA results match within 10 % of the DAMVIBS and static pull experimental results, respectively. Thus, this study successfully validates the reliability of the numerical model.