Deformation of Metals - Electrically Assisted Forming - page 20

1.6 Conclusions
Metal forming is one of the most ancient manufacturing methods. Only in the
last century have the atomic deformation mechanisms such as crystallographic
arrangement of metallic atoms, preferential slip systems, dislocation motion, and
crystal twinning been well modeled and understood. We now have both experi-
mental and theoretical descriptions of plastic deformation, and its limitations as a
process in the areas of forming power and achievable strain before fracture.
We can therefore begin to explore enhancements to the forming process to over-
come these limitations. Traditional enhancements include heating the metal to a sig-
nificant fraction of its absolute melting temperature to improve formability, thermally
annealing material to “reset” its properties and allow further forming, and alloying to
allow improved formability while maintaining desired properties in the end product.
In this work, we examine the Electrically Assisted Forming (EAF) process,
whereby electric current is passed through a part during forming. The added electri-
cal energy works to lower the flow stress, to improve the achievable elongation, and
to relieve residual stress in situ, and at much higher rates-of-change of material prop-
erties than can be achieved with thermal energy. In this topic, we seek to empirically
describe what can be achieved with this process and to investigate the atomic mecha-
nisms underlying the benefits. The remainder of Section 1 (Chaps. 1 - 3 ) describes the
EAF approach, and how electricity affects metal deformation. Section 2 (Chaps. 4 - 7 )
explores various ways to model the observed effects both empirically and through the
use of first physical principles. Different architectures, both model-based and model-
free, are examined for control of the process with current as a new control variable.
Finally, Section 3 (Chaps. 8 - 11 ) gives further considerations of process design for
EAF and the interaction effects related to tribology and microstructure evolution.
References
1. United States Department of Labor (2011) Motor vehicle and parts manufacturing. Bureau of
labor statistics. http://www.bls.gov/oco/cg/cgs012.htm . Accessed 02 Oct 2011
2. Keith D (2010) HSS, AHSS and aluminum jockey for position in the race to cut auto curb
weight. American Metal Market Monthly. February 1
3. Pfestorf M (2009) Multimaterial lightweight design for the body in white of the new BMW
7 series. BMW Group. Innovative Developments for Lightweight Vehicle Structures.
Wolfsburg. May 26-27
4. Krinke S (2009) Life cycle assessment and recycling of innovative multimaterial applica-
tions. In: Conference Proceedings of Innovative Developments for Lightweight Vehicle
Structures. Volkswagen AG, Wolfsburg. May 26-27
5. Ford H (1924) My life and work. In: collaboration with S. Crowther. Kessinger Publishing
Co., Montana, 2003
6. U.S. Environmental Protection Agency (U.S. EPA) (2009a) Light-duty automotive technol-
ogy and fuel economy trends: 1975 through 2008. EPA420-R-08-015
7. Glennan TB (2007) Strategies for managing vehicle mass throughout the development pro-
cess and vehicle lifecycle. Society of Automotive Engineers. 2007-01-1721