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Secondary Mass Changes

Secondary Mass Changes in Vehicle Design

Estimation and Application in Vehicle Design

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Vehicle design engineers intuitively know that an unplanned mass increase in a component during vehicle design has a ripple effect throughout the vehicle; subsystems need to be resized to function with this additional mass. This further increases vehicle mass even more than the initial mass increase. The phrase ‘mass begets mass’ describes this phenomenon. A more encouraging view of this behavior is considering a reduction in the mass of a component enabled by a new technology, which then results in a greater mass savings due to the resizing of other subsystems because of the initial mass reduction. These secondary mass changes can be significant, and it is important to consider them during the mass budgeting process. This is because important vehicle metrics, such as fuel consumption and greenhouse gas assessments, depend upon vehicle mass.

Secondary mass reduction may be modeled using subsystem mass influence coefficients—the incremental change in subsystem mass for a unit change in gross vehicle mass. This paper focuses on means to estimate influence coefficients and has several objectives:

1. Review prior work on secondary mass change estimation

2. Suggest uniform terminology for secondary mass change (Appendix 1)

3. Review secondary mass change modeling equations

4. Provide and compare estimates for mass influence coefficients using two methods: Analytical and Regression.

5. Provide a recommended application of secondary mass change analysis to vehicle design



Dr. Donald E. Malen University of Michigan – College of Engineering Integrative Systems + Design

René Göbbels Institut für Kraftfahrzeuge – RWTH Aachen University Body Department

Roland Wohlecker Forschungsgesellschaft Kraftfahrwesen mbH Aachen Body Department