Evaluating the Potential for Secondary Mass Savings in Vehicle Lightweighting

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.

Lap shear strength and fatigue life of friction stir spot welded AZ31 magnesium and 5754 aluminum alloys

“…As the global resource and environmental problems tend to be increasingly severe in recent years, considerable attention has been paid to the weight reduction of aerospace structures, automotive bodies, and high speed passenger cars in order to improve the fuel economy and reduce the damaging effect of anthropogenic greenhouse gas emissions [1][2][3][4][5][6][7][8]. To achieve such goals and meet legislative regulations, the manufacturers in the automotive and aerospace sectors have to reduce the vehicle weight via applying advanced lightweight materials [4,5,[9][10][11][12][13][14][15].…”

Derivation of Criteria for Identifying Lightweight Potential – A Literature Review

“…Thirdly, some of the methods found within the papers take other additional criteria into account, such as functional importance (Albers et al, 2013;Caldwell et al, 2013), customer requirements (Posner et al, 2014) and material composition (Lewis et al, 2014). Three papers appeared in both reviews (Albers et al, 2018;Caldwell et al, 2013;Alonso et al, 2012). The investigation within this paper revealed several issues concerning the criteria used for deriving lightweight potential.…”

Holistic Approach for Secondary Weight Improvements

“…The paper of Alonso et al [1] and the contribution of Bjelkengren [6] propose a method extending the traditional empirical estimation of secondary weight savings to an analytical estimation which quantifies the uncertainty in the estimation and the importance of expert classification of data at component level for managing the mass-independent effects as well as characterizes the inherent upper-bound bias of this method. The method focuses on the early design phases during the development process in the automotive sector.…”

“…Several approaches for the identification and handling of the possible additional weight improvements come from the automotive and aeronautical sector where systematical procedures for these so-called secondary weight improvements are established [1][2][3][4]. Different approaches [5,6] assume that for a detailed analysis of the secondary weight optimizations a better understanding of system and subsystem mass interdependencies and a quantification of subsystem-specific mass decompounding effects are crucial.…”