Advanced Materials in Automotive Engineering

Jason Rowe

• Publisher: Woodhead Publishing
• Year: 2012
• ISBN:
  9780857095466
• Topic: Tecnología e ingeniería
• Subtopic: Transporte e ingeniería automovilísticos

The automotive industry is under constant pressure to design vehicles capable of meeting increasingly demanding challenges such as improved fuel economy, enhanced safety and effective emission control. Drawing on the knowledge of leading experts, Advanced materials in automotive engineering explores the development, potential and impact of using such materials.Beginning with a comprehensive introduction to advanced materials for vehicle lightweighting and automotive applications, Advanced materials in automotive engineering goes on to consider nanostructured steel for automotive body structures, aluminium sheet and high pressure die-cast aluminium alloys for automotive applications, magnesium alloys for lightweight powertrains and automotive bodies, and polymer and composite moulding technologies. The final chapters then consider a range of design and manufacturing issues that need to be addressed when working with advanced materials, including the design of advanced automotive body structures and closures, technologies for reducing noise, vibration and harshness, joining systems, and the recycling of automotive materials.With its distinguished editor and international team of contributors, Advanced materials in automotive engineering is an invaluable guide for all those involved in the engineering, design or analysis of motor vehicle bodies and components, as well as all students of automotive design and engineering.

• Explores the development, potential and impact of using advanced materials for improved fuel economy, enhanced safety and effective mission control in the automotive industry
• Provides a comprehensive introduction to advanced materials for vehicle lightweighting and automotive applications
• Covers a range of design ideas and manufacturing issues that arise when working with advanced materials, including technologies for reducing noise, vibration and harshness, and the recycling of automotive materials

1

Introduction: advanced materials and vehicle lightweighting

J. Rowe,     Automotive Consultant Engineer, UK

The UK automotive industry is a large and critical sector within the UK economy. It accounts for 820,000 jobs, exports finished goods worth £8.9 bn annually and adds value of £10 billion to the UK economy each year [1]. However, the UK automotive industry is currently facing great challenges as road transport released 132 million tonnes CO₂ in 2008, accounting for 19% of the total UK annual CO₂ emission. Furthermore, its global competitiveness is threatened by the emerging new economic powers, such as China and India. In addition, the UK government is committed to reduce CO₂ significantly by 2050 and the EU requires 95% recovery and reuse of ELVs (end of life vehicles) by 2015. A solution to these challenges comes from the development and manufacture of LCVs (low carbon vehicles), and this is clearly presented in the vision of the UK automotive industry set by the NAIGT [1].

Vehicle lightweighting is an effective approach to improve fuel economy and reduce CO₂ emissions. CO₂ emission per km driven is linearly related to vehicle curb weight [2]. Studies have shown that every 10% reduction in vehicle weight can result in 3.5% improvement in fuel efficiency (on the New European Drive Cycle (NEDC)) [3]. In terms of greenhouse effect, this means that every 100 kg weight reduction results in CO₂ reduction of about 3.5 gCO₂/km driven for the entire vehicle life [3]. In addition to such primary benefits, vehicle lightweighting reduces the power required for acceleration and braking, which provides the opportunity to employ smaller engines, and smaller transmissions and braking systems. These savings have been termed secondary weight reduction in the literature and would allow a CO₂ reduction of up to 8.5 gCO₂/km [3]. Furthermore, if appropriate technologies are used, vehicle weight reduction can be achieved independent of size, functionality and class of vehicle. It is important to point out that similar benefits of mass reduction can be demonstrated for hybrid vehicles (HVs) and electric vehicles (EVs).

Approaches to vehicle mass reduction include deployment of advanced materials and mass-optimised vehicle design. One of the major systems of the vehicle is the body (body-in-white, or BIW) that represents about one-quarter of the overall vehicle mass and is the core structure and frame of the vehicle. The body is so fundamental to the vehicle that sometimes it is the only portion of the vehicle that is researched, designed and analysed in mass reduction technology studies [2]. Over many years there has been a fundamental material shift from wood, cast iron and steel to high strength steel (HSS), advanced high strength steel (AHSS), aluminium, magnesium and polymer matrix composites (PMCs). Between 1995 and 2007, the use of aluminium increased by 23%, PMCs by 25% and magnesium by 127% [2]. Further vehicle mass reduction can be achieved by mass-optimised design technology. Mass-optimisation from a whole vehicle perspective opens up the possibility for much larger vehicle mass reduction. For example, secondary mass reduction is possible since reducing the mass of one vehicle part can lead to further reductions elsewhere due to reduced requirements of the powertrain, suspension and body structure to support and propel the various systems. New and more holistic approaches that include integrated vehicle system design, secondary mass effects, multi-materials concepts and new manufacturing processes are expected to contribute to vehicle mass optimisation for much greater potential mass reduction [4]. As reviewed by Lutsey [2], there have been 26 major R&D programmes worldwide on vehicle mass reduction. Compared to a steel structure, the HSS intensive body structure by the Auto Steel Partnership achieved 20–30% mass reduction [5], the Al intensive body structures of the Jaguar XJ, Audi A8 and A2 achieved 30–40% mass reduction (e.g. [6]) and a multi-material body structure featuring more Al (37%), Mg (30%) and PMCs (21%) by the Lotus High Development Programme achieved 42% mass reduction [4]. It is clear that although a single material approach can achieve substantial mass reduction the greatest potential comes from an integrated multi-material approach that exploits the mass and functional properties of Al, Mg, PMCs and AHSS. Despite the greater use of the higher cost advanced materials, mass-optimised vehicle designs could have a minimal or moderate cost impact on new vehicles [2] if a holistical whole vehicle design approach is used. For instance, the Lotus High Development Programme demonstrated a 30% whole vehicle mass reduction could be achieved with only a 5% increase in cost, whilst the VW-led Super Light Car achieved a 35% body mass reduction for a cost of less than 78 for every kilogram of mass reduction. The combination of a multimaterial concept and a mass-optimised whole vehicle design approach can achieve significant mass reduction with a minimal or moderate cost impact on vehicle structure and it is most likely that the future materials for LCVs are an optimised combination of Al, Mg, PMCs and AHSS.

Closed-loop recycling of advanced automotive materials, however, has been missing from nearly all the LCV programmes worldwide, which have concentrated on the reduction of CO₂ emission during the use phase of vehicles produced from primary advanced materials. The production energy of all primary automotive materials is always much greater than that of their secondary (recycled) counterparts [7]. For instance, production of 1 kg primary Al from the primary route costs 45 kWh electricity and releases 12 kg Co₂, whilst 1 kg recycled Al only costs only 5% of that energy and 5% CO₂ emission [8]. Detailed life cycle analysis (LCA) has shown that a primary Al intensive car can only achieve energy saving after more than 20,000 km driven compared with its steel counterpart, while a secondary Al intensive car will save energy from the very beginning of vehicle life [9]. If all the automotive materials can be effectively recycled in a closed-loop through advanced materials development and novel manufacturing technologies, the energy savings and cost reduction for the vehicle structure will be considerably more significant.

The vision of automotive manufacturers is that future LCVs are achieved by a combination of multi-material concepts with mass-optimised design approaches through the deployment of advanced low carbon input materials, efficient low carbon manufacturing processes and closed-loop recycling of ELVs. Advanced materials will include Al, Mg and PMCs, which are all supplied from a recycled source. A holistic and systematic mass-optimised design approach will be used throughout the vehicle (including chassis, trim, etc.) not only for mass reduction and optimised performance during vehicle life but also for facilitating reuse, remanufacture and closed-loop recycling at the end of vehicle life. Novel manufacturing processes will be used to reduce materials waste and energy consumption, shorten manufacturing steps and facilitate parts integration and ELV recycling. Fully closed-loop ELV recycling will be facilitated by new materials development, novel design approaches, advanced manufacturing processes and efficient disassembly technologies, all of which will be effectively guided by a full life cycle analysis.

The themes described above have been taken from the TARF-LCV 2011 (Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicles Structures) programme submission (reproduced with the kind permission of Professor Zhongyun Fan, Chair of Metallurgy at Brunel University), and are developed within the following chapters of this book using contributions from leading experts from both academia and industry.

1.1 References

[1] NAIGT. An Independent Report on the Future of the Automotive Industry in the UK, 2009.

[2] Lutsey, N.UCD-ITS-RR-10-10. Davis: University of California, 2010. [May].

[3] Goede, M. SLC Project, 2003. [December and May 2008, VW].

[4] Lotus Engineering Inc. An Assessment of Mass Reduction Opportunities for a 2017-2020 Model Year Vehicle Programme, 2010. [March].

[5] Auto Steel Partnership (ASP). Future Generation of Passenger Compartment, 2007. [December].

[6] Birch, S. Jaguar Remakes XJ, 2010. http://www.sae.org/mags/sve/7547 [March].

[7] Das, S.K. Materials, Design and Manufacturing for Lightweight Vehicles. New York: CRC Press, 2010; 309–331.

[8] Green, J.A.S. Aluminium Recycling and Processing. Materials Park, Ohio, USA: ASM International, 2007; 67.

[9] Inaba, T. Automotive Engineering – Lightweight, Functional and Novel Materials. Taylor and Francis, 2008; 19–27.

2

Advanced materials for automotive applications: an overview

P.K. Mallick, University of Michigan – Dearborn, USA

Abstract:

With increasing demand on fuel economy improvement and emission control, there is great deal of interest in using advanced materials to produce lightweight vehicles. The advanced materials include advanced high strength steels, non-ferrous alloys, such as aluminum, magnesium and titanium alloys, and a variety of composites, including carbon fiber composites, metal matrix composites and nanocomposites. This chapter provides an overview of these materials and their current applications and potential applications in future automobiles.

Key words

advanced materials

advanced steels

aluminum alloys

magnesium alloys

titanium alloys

stainless steels

cast iron

composites

glazing materials

2.1 Introduction

Vehicle weight reduction through material substitution is one of the key elements in the overall strategy for fuel economy improvement and emission control. While the principal material in current vehicles is plain carbon steels, there is now a great deal of interest in replacing them with advanced high strength steels, light non-ferrous alloys, such as aluminum, magnesium and titanium alloys, and a variety of composites, including carbon fiber composites, metal matrix composites and nanocomposites. This chapter is a broad overview of these materials and their applications in the automobiles.

2.1.1 Materials scenario

Plain carbon steel and cast iron were the workhorse materials in the automotive industry prior to 1970s. As shown in Table 2.1, even today steel is used in much larger quantities than any other material; however, high strength steels and advanced high strength steels, on account of their significantly higher strength, are now replacing plain carbon steels in several body structure and chassis applications. As a result, the amount of high strength and advanced high strength steels has increased in recent years, while the amount of plain carbon steels has decreased (Table 2.2). There is also an increasing use of aluminum alloys and polymer matrix composites. For example, the use of aluminum alloys in North American automobiles has increased from 2% of the curb weight in 1970 to nearly 8.8% in 2010 and is projected to reach 10% or higher in 2020. Much of this growth in the use of aluminum alloys has occurred at the expense of cast iron in engine and transmission components and copper-based alloys in radiators; but aluminum alloys, becaus...