Among the many focus areas in the global automotive industry, reducing component and in turn overall vehicle weight which leads to improved fuel efficiency has become de rigueur. In India too lightweighting is being accorded prime importance, both at OEMs and at the vendor level, albeit currently at the bigger companies.
While the developed economies are yet to fully come out of the global economic downturn and trying ways and means to utilise existing capacities, emerging countries like India are stepping to the next level – of designing automobiles that are lighter and efficient in terms of fuel economy and emissions.
Industry body Automotive Components Manufacturers Association (ACMA) along with the Society of Indian Automobile Manufacturers (SIAM) has taken an initiative to enable faster implementation of lightweighting technologies to the Indian market. To do this, ACMA has followed a structured approach. Based on the lead given by Professor Charles Fine of the Massachusetts Institute of Technology at the last AGM held in September 2009 that India can emerge as a global player in lightweight technologies, ACMA along with SIAM organised a delegation to Fraunhofer Institutes in Germany in September last year. Following that visit, Fraunhofer has extended a helping hand to develop the R&D initiative for ACMA member companies. The Fraunhofer Group is among the largest technology institutions in Germany with around 60 centres of excellence. These institutes have a high level of expertise in a large array of manufacturing processes and automotive technologies.
Lightweight engineering
Giving the initiative a formal touch, an MoU was signed on March 23 between Fraunhofer, SIAM, National Automotive Testing and R&D
Infrastructure Project (NATRiP) and ACMA in New Delhi during a one-day conference on ‘Automotive Lightweighting’. The objective of the event was to provide a platform to the Indian automotive industry in India, for new R&D activities in various fields of engineering at a competitive cost. Dr (Prof) Hans-Joerg Bullinger, president, Fraunhofer, along with his team, was present for the signing ceremony.
The conference, which was attended by a large cross-section of industry comprising senior executives from OEMs, NATRiP and ACMA member companies, saw a number of speakers deliberate on the need to develop generic lightweighting technologies to a pre-competitive level, which could be employed by vehicle and component manufacturers to reduce weight of the components and the vehicles they manufacture in India. ACMA president Jayant Davar said the objective of this event was to enable a platform for the Indian auto industry in the area of light weighting, which will not only provide competitive edge but also address the issues of climate change and fuel-efficient vehicles in India. “I am sure this partnership will bring new opportunities and openings for the entire automotive industry and pave the way for future R&D in India.”
A number of topics were covered during the day-long conference. They included industrial thin film processes for cost-effective lightweight construction, media-based hydroforming, tempered forming, electromagnetic forming, material testing, engineering parameters and the basics of numerical simulation.
Speaking to Autocar Professional, Vishnu Mathur, ACMA’s executive director, said Fraunhofer will collaborate in the development of new technologies to reduce vehicle weight. According to him, there are three ways in which the consortium will help do this. Firstly it will look at options to reduce weight using the same material but with weight using the same material but with individual step towards CO2 emission, optimisation and improve vehicle agility. Taking a cue from nature, he noted that the skeleton of a horse is less than 10 percent of its total weight while a human being’s skeleton is less than 20 percent of the total weight. In comparison, an automotive body is about 20 percent of the total weight. In order to reduce weight of automobiles, the immediate attempt will be in reducing steel content, which will have to get substantiated with alternate materials which in turn have to be fused with steel in some part of the other in manufacturing. This, says Heim, will be a critical issue.
Austempered ductile iron improves metallurgical properties while reducing the weight against use of traditional cast iron products. Fibre-reinforced polymer products offer significant lightweight potential by specific strength/stiffness improvement compared to metal parts. However, product design and testing has to account for anisotropic material behaviour. Moreover, material characterisation has to be performed that has environmental impact.
For instance, an automobile wheel usually has mass in the range of seven to 13kg for the rimdiameter ranging from 14 to 20 inches. Typically wheels use medium strength steels and flow forming process and in the case of alloy wheels – aluminium casting or forging. Fibre-reinforced plastics offer tremendous potential for mass reduction and produce differentiation.
Dr Andreas Sterzing of Fraunhofer in his presentation on key technologies for lightweight design in terms of joints, listed several lightweight materials including aluminium, magnesium, titanium, plastics, composites and metal foams. High-strength steels and manganese boron steels are high-strength materials and can be used for components made through forming and press hardening.
The main objective should be to reduce needless mass and it can be done through material distribution equivalent to load distribution. Besides, structured sheets will also come in handy. However, joining a multi-material mix is the key.
On lightweight design in car manufacturing – chances of resource and energy efficiency in production and operation, Markus Werner of Fraunhofer said lightweight design strategies encompass a symbiotic relationship of machine, equipment, tool and part design, process design and tribology. This will help realise components with complex geometry with high quality and minimum weight.
In a car the mass is distributed up to 40 percent by its body, 24 percent by its chassis, 16 percent by powertrain, 15 percent by equipment and the rest is by electrical equipment. The strategy for lightweight design is classified in to three categories with respect to condition, structure and material. Reduction of excessive safety requirementsand examination concerning constructive over-dimensioning can be looked at to reduce weight. Besides, material adjustment concerning part loading, structure optimisation, use of high-strength materials and deploying innovative semi-finished products like compounds, foams and structured sheets will help contain weight.
Making lighter engines
Low energy engines can be developed by reducing the weight of camshaft, crankshaft, connecting rod, gears and drive shaft. Engine components manufactured based on hydroforming technology will help achieve desired results. Use of magnesium for body parts will help reduce weight. It can also reduce the process time as deep draw process is possible in making sheet metal components. Honeycomb structured sheets can reduce sheet thickness by up to 25 percent, eventually reducing weight.
The current Volkswagen Passat has seen weight reduction of about 25kg against its earlier version due to use of direct press hardening of the B-pillar and roof rail and indirect press hardening of bottom plate including the channel area. In addition, it also helped the OEM to reduce the cycle time, increase tool life and reduce material cost. Form hardening of tubes and profiles will further increase the weight reduction potential by up to 30kg.
Speaking on industrial thin film processes, Dr Bernd Szyszka of Fraunhofer IST indicated that making vehicles lighter does not remain only in materials and construction but based on a holistic approach taking the whole process chain into account – from styling, material, concept, construction, electronics, simulation, prototypes, digital fabrication, resources, tools and production.
The surface and coating technologies improve existing materials and products. Moreover, they are indispensable for the realisation of innovative products based on particular properties of thin films. Tailored coatings allow the adjustment of surface characteristics like mechanical properties in terms of wear and friction, chemical properties in terms of corrosion, permeation and catalysis, electrical properties such as conductivity, optical properties like reflection, absorption and colour besides, ensuring temperature stability, insulation and biocompatibility. The applications of surface technologies in a modern car is huge and can reach to several parts including body, wheel rims, interiors, windscreen wipers and headlight.
The continuous improvement of cutting and forming tools is a must for efficient production processes and tribological coatings are the key. Diamond-like carbon (DLC) films on engine and power train components increase life time and reduce fuel consumption due to low friction. The ultimate goal is an engine that runs without any lubricants. DLC-based force and temperature sensors can be used in harsh environments, such as on cutting inserts and moulds for deep drawing.
The glazing of a car is getting a multi-functional device including improved sun protection, anti-reflection and self-cleaning. Durable outside coatings protect against condensation of water and formation of ice. Further features are the integration of coatings with switchable transmission, transparent displays or thin film solar cells.
The use of polycarbonate instead of mineral glass reduces weight and increases safety. Transparent scratch- resistant and UV protective top layers have to be integrated. Composite films with embedded microcapsules are the basis of self-healing car body surfaces. Though many coatings are available, their successful application in automotive engineering requires simple and low-cost deposition processes as well as suitable coating characterisation methods. Raman Chaudhari of Fraunhofer gave a presentation on composite materials and processes.