Safety Considerations in Optimal Automotive Vehicle Design.

Abstract

While automobiles provide society with an unprecedented amount of mobility, motor vehicle crashes are a leading cause of injury and death worldwide. Designing safer vehicles is a priority of governments and automakers alike; however, other requirements such as increased fuel economy and performance have driven designs in conflicting directions. Because society benefits from reductions in traffic injuries and fuel consumption, governments impose standards and incentives for safer and more fuel efficient vehicles. One form of incentive is a consumer-information test, such as a New Car Assessment Program (NCAP), using standardized crash tests in various impact directions to help customers compare the crashworthiness of different automobiles. Automakers strive to perform well on these tests by optimizing vehicle designs to the specified scenarios. Another type of standard uses injury thresholds to ensure a minimum level of protection, such as the U.S. Federal Motor Vehicle Safety Standards and the U.S. Army ground vehicle blast protection criteria. This dissertation uses these standards to examine the impact of safety optimization formulations and tradeoffs on vehicle design and competing objectives. Physics-based modeling is used to simulate crash or blast events, and computational designs of experiments are conducted with the resulting data fit to response surfaces. Single- and multi-objective optimization formulations are developed to demonstrate relationships between occupant protection and vehicle weight for civilian vehicle crashes and military vehicle blast events. Using these formulations, the civilian case study is extended to understand the impact of the frontal NCAP test speed on injuries in frontal on-road crashes, as well as the effect safety considerations have on manufacturer profit-maximizing decisions and consumer behavior in a competitive market. The military case study is also expanded to demonstrate how high vehicle weight and fuel consumption increase the need for convoys, posing additional injury risks to personnel and thereby making fuel economy a safety objective in a casualty-minimization formulation. The results of these studies demonstrate the need for designers and engineers to consider safety in new, more holistic ways, and this dissertation establishes a new type of design thinking that can contribute to decreased vehicle-related injuries while also accounting for other objectives.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91402/1/shoffens_1.pd