Evaluating the Potential
for Secondary Mass Savings
in Vehicle Lightweighting
- Publication date
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Abstract
Secondary mass savings are mass reductions that may be
achieved
in supporting (load-bearing) vehicle parts when the gross vehicle
mass (GVM) is reduced. Mass decompounding is the process by which
it is possible to identify further reductions when secondary mass
savings result in further reduction of GVM. Maximizing secondary mass
savings (SMS) is a key tool for maximizing vehicle fuel economy. In
today’s industry, the most complex parts, which require significant
design detail (and cost), are designed first and frozen while the
rest of the development process progresses. This paper presents a
tool for estimating SMS potential early in the design process and
shows how use of the tool to set SMS targets early, before subsystems
become locked in, maximizes mass savings. The potential for SMS in
current passenger vehicles is estimated with an empirical model using
engineering analysis of vehicle components to determine mass-dependency.
Identified mass-dependent components are grouped into subsystems,
and linear regression is performed on subsystem mass as a function
of GVM. A Monte Carlo simulation is performed to determine the mean
and 5th and 95th percentiles for the SMS potential per kilogram of
primary mass saved. The model projects that the mean theoretical secondary
mass savings potential is 0.95 kg for every 1 kg of primary mass saved,
with the 5th percentile at 0.77 kg/kg when all components are available
for redesign. The model was used to explore an alternative scenario
where realistic manufacturing and design limitations were implemented.
In this case study, four key subsystems (of 13 total) were locked-in
and this reduced the SMS potential to a mean of 0.12 kg/kg with a
5th percentile of 0.1 kg/kg. Clearly, to maximize the impact of mass
reduction, targets need to be established before subsystems become
locked in