Lightweighting: a key engineering mantra

As the automotive sector undergoes a transformative shift towards electric and hybrid vehicles, reducing vehicle weight has become paramount for optimising energy consumption and extending battery range. Moreover, OEMs are also pushing the envelope to stretch every ounce of the costly fuel when it comes to enhancing the efficiency of conventional ICE vehicles.

Optimising vehicle weight is one mantra for sustainability, and lightweighting has emerged as a crucial trend in the automotive industry due to its profound impact on various aspects of vehicle performance, efficiency, and sustainability.

On May 23 and 24, Autocar Professional hosted its annual virtual seminar — Vehicle Lightweighting Conference — that centred its discussions on the prevailing global trends in automotive lightweighting, and explored how sustainability-driven regulatory actions are influencing lightweighting strategies of automakers, as well as the industry’s collaborative approach in addressing the myriad challenges.

The virtual event brought together industry experts of the likes of CV Raman, EC Member and Former CTO, Maruti Suzuki India; Anand Kulkarni, Head of EV Programmes, Tata Passenger Electric Mobility; Glyn Jones, MD, Gestamp India, and Ritesh Agrawal, SVP and Head – Sourcing, Auto Sector, Mahindra & Mahindra, among others. The industry leaders discussed upon the various aspects of lightweighting, including its key drivers, cost implications, design limitations, and supply chain challenges, among others.

On its first day, the event was kicked off by Maruti Suzuki India’s CV Raman, who showcased a detailed presentation, outlining the key lightweighting drivers, of which, tightening emission standards such as the Corporate Average Fuel Efficiency (CAFE), as well as stringent safety norms – of the likes of Bharat New Car Assessment Programme (BNCAP) – were highlighted as the two key regulatory drivers of lightweighting.

According to Raman, there have been a slew of regulatory changes both on the safety, and emissions front, in the last seven years, which has led to an adverse effect on the customers’ affordability of passenger vehicles due to their rising prices, thereby depressing the demand at the lower end. “While the CAFE-II norms kicked off in India in CY22, the next round is slated for CY27, which will make emission targets even more stringent – to 95g/km of CO2. Simultaneously, the safety regulations are also becoming more stringent, with the notification of the BNCAP that was launched in October 2023. All of this is increasing the vehicle cost, weight, development time, and its complexity,” he remarked.

Lightweighting enabling sustainability

Raman mentioned that sustainability needs to be looked at not just from an efficiency improvement perspective, but from an overall greenhouse gas (GHG) reduction standpoint, and therefore, there need to be interventions at both product, and process levels, to reduce the overall GHG.

“It is here at the product level that lightweighting, by virtue of material technology – with the use of environment-friendly, and lightweight materials such as advanced high-strength steel – can significantly contribute to more sustainable vehicles,” he pointed out. Raman cited the example of the Maruti Suzuki Swift hatchback which has seen a significant weight reduction of nearly 100kg over its four generations, starting 2005. “Since the launch of the Swift in 2005, we have changed the powertrain and platform twice, and with the new Suzuki ‘Heartect’ platform underpinnings, the new fourth-generation Swift is the lightest yet,” he mentioned, while adding that the use of advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) is enabling carmakers to usher in an era of lightweight, yet robust vehicles that are high on efficiency. The new Swift, launched in India on May 9, sees an increased implementation of UHSS from 6% to 17%, while AHSS has grown from 2% to 4% in the latest iteration. “We have enhanced the usage of these materials in structural parts that have significantly higher minimum tensile strength requirements."

The keynote was followed by a panel session discussing the key drivers and challenges of vehicle lightweighting, and according to Anand Kulkarni, Chief Products Officer, Head of HV Programs and Customer Service, Tata Passenger Electric Mobility, “OEMs have been eyeing switching to lighter and stronger materials as they vie for more efficient vehicles, but have to compromise due to cost and supply chain challenges. This has become a tough balancing act which extends beyond steel to aluminium, and composites, among other materials. The most plausible solution must be taken by factoring in all the interlinked parameters," Kulkarni added.

Optimising weight in EVs

Kulkarni also touched upon the critical aspect of optimising weight of the current-carrying wiring harness in an EV. He explained that high-voltage systems allow for the reduction in the size of the conducting wires as they then need to transmit lesser current to generate the same output power at the motor.

“Every doubling of voltage can therefore reduce the amount of copper (conductor) required by up to 45 %, thereby contributing to weight reduction. That is why EVs are increasingly moving to high-voltage systems of the likes of 350V, and 800V systems among other architectures. Moreover, avenues of flat wiring harnesses are also currently being evaluated, alongside other areas, bases their integration and cost constraints,” Kulkarni said.

According to Ritesh Agrawal, SVP and Head — Sourcing, Auto Sector, Mahindra & Mahindra, “Despite the lack of an engine, EVs come with an added baggage of the battery pack which tends to increase the weight by up to 350kg. It is imperative to counter it by lightweighting techniques to enhance the range per charge.”

An SUV specialist, Mahindra & Mahindra (M&M) has achieved weight reduction to the tune of 200 kg to meet the current CAFE requirements by implementing a mix of materials such as aluminium, and high-tensile steel.

However, Agrawal raised the challenges associated with lightweighting, and said, “While over 175 grades of steel are now available in India, advanced materials such as UHSS are not produced in the country due to economies of scale. Since the supply chain is largely dependent on countries outside of India, there is a huge risk to it. Uncertain volumes often result in either excess or shortage of materials, leading to inventory costs, and obsolescence risks.”

To address these challenges, M&M employs technologies like hot stamping of sheet metal panels which offers higher structural strength at lower costs, as well as implementing honeycomb structures for weight and cost reduction. “Additionally, advancement in engine technology such as integrating the engine oil cooler, allows for cost reduction throughparts integration,” Agrawal pointed out. Emphasising on certain aspects of design can also contribute to lightweighting, and with the concept of digital twins, there is an opportunity for companies to reduce cost while implementing lightweighting materials into a design,” said, Srikumar Srinivasan, Delivery Head – Automotive, Tata Elxsi.

“While we are a bit far off as far as proportions are concerned, several aspects of lightweighting are creeping into the sector, which is a welcome development,” he said.

In an exclusive one-on-one interaction session, Sushil Mane, Senior Director, Technology and Customer Support, and Simulation and Design Support, Altair, said, “The digital tools and strategies available today provide engineers with extensive opportunities to reduce structural weight throughout the design process.”

“The integration of optimisation techniques in the early stages of the design process offers engineers a significant advantage in creating lightweight structures,” he added.

Advanced materials and lightweighting technologies

The second day of the virtual conference focused on the various materials, design, and process technologies available to induce lightweighting in vehicle platforms, and the product. Speaking in a panel discussion, Dr K Subramanian, SVP, Product Development, Ashok Leyland, said, “Lightweighting is not just about the structure, but also about rethinking whether some of the legacy parts are necessary. Therefore, it is about innovatively eliminating what we do not need.”

“Lightweighting takes on a new level of significance as we move to new propulsion systems such as EVs and hydrogen, which require vehicles to be more efficient,” he added. From a material standpoint, Dr Subramanian revealed that commercial vehicle major Ashok Leyland is exploring several options, including advanced steel, and aluminium, in select areas of the vehicle. The company is also looking at composites, as well as introducing plastics into crash-absorbing systems because certain classes of materials offer better crash-force absorption characteristics.

Although carmakers use steel to make the body shell and various components, the shift to aluminium is also happening.

“We are trying to see in which parts composite materials make sense. I think born-electric vehicles is where we need to bring composites as it is proving difficult for one-to-one replacement of existing parts,” he pointed out.

Structural lightweighting in vehicles

As a global leader in lightweighting structures, Gestamp has observed a significant and rapid adoption of weight reduction technologies in India. According to Glyn Jones, MD, Gestamp India, “The use of hot-stamping materials has increased by about 40 % compared to 2016. However, the current market situations in the country pose challenges, particularly due to the insufficient localisation content, impacting both Gestamp and its clients.” “Having said that, the adoption of advanced steel and stamping technologies in India has seen a paradigm shift. At Gestamp, we have leveraged advanced tools and technologies, including Computer-Aided Analysis (CAA) data and G-lab models to enhance our capabilities,” Jones said. He further highlighted a new aspect of the lightweighting process — giga-casting — which while offers vehicle weight optimisation by stamping the entire chassis as a single member, remain problematic in terms of the environmental impact because of the currentneed to import the raw materials to the country.

According to Rahul Nikhanj, Head, Projects and Production Technology, Asahi India Glass (AIS), “When it comes to vehicle lightweighting, glass is usually not the first thing that comes to mind. However, it occupies more than 30 % of the vehicular space. While vehicles have traditionally been adding about 50kg weight owing to the glasses, with modern features such as sunroofs, the glass weight in the vehicle has increased to up to 70kg. We can offer up to 11-14 % weight reduction through lightweighting techniques in glass. While the thickness of the side window glasses has reduced from 3.2mm to 2.8mm, we are now seeing the trend move towards the industry adopting even 2.5mm to 2.6mm of the side tempered glasses.” Nikhanj explained that despite the reduction in the thickness, there is about 11 % enhancement in weight reduction, without compromising on the strength of the glass.

As per IV Rao, Former Engineering Head, Maruti Suzuki India, and Distinguished Fellow, Transport and Urban Governance, TERI, “It is important to optimise all parameters to get the best out of a vehicle’s configuration. Innovative engineering like integration of parts, and usage of lightweight materials helps in reducing vehicle weight.”

Design critical for lightweighting

Talking specifically about the Indian market, Rao said that India is a price-sensitive market, and automakers must configure vehicles in a way that meets the price equation. Some of the commonly-adopted engineering methodologies at Suzuki included combining various parts into a single system, as well as removing fasteners in favour of joining techniques like spot welding.John Johnston, Chief Engineer, Body Structures, Tata Technologies, said that the importance of lightweighting has increased in the last 20-25 years, and has particularly reached a new level with the advent of electric vehicles. “While the philosophy of reimagining the entire vehicle with the advent of EVs gives a huge opportunity for lightweighting, the challenge is to do lightweighting in low-cost vehicles,” he said, while adding that the industry’s approach has fundamentally changed, wherein more lightweighting-related topics are being taken up at the conceptualisation stage of the project itself. “It is all in the initial planning. We find that vehicle packaging and dimensions can be whetted at the conception stage, so getting the targets right in the beginning helps save cost and time,” said Johnston.

Steel works lightweighting wonders

In an exclusive fireside conversation being the last session of the event, Kinshuk Roy, EVP — Application Engineering and New Business Development, JSW Steel, said that steel is a wonder material from a lightweighting perspective. Sharing his thoughts, Roy said that with the advancements in advanced-high-strength, and ultra-high-strength steel, vehicle manufacturers can achieve significant weight savings without compromising structural integrity — a crucial factor for enhancing driving dynamics, and improving the vehicle efficiency. Lightweight vehicle structures are essential not only for improving the fuel economy for ICE automobiles but also increasing the driving range of EVs by offsetting the weight of power systems like batteries, he explained. According to Roy, “Beyond the use phase, factors such as material production emissions and end-of-life recyclability play a pivotal role in determining the overall environmental footprint. Initiatives like the government's vehicle scrapping policy signal a step towards enhancing recyclability and sustainability within the ecosystem.”

Processes like hot stamping and hydroforming complement the use of high-strength steel, enabling the fabrication of complex components with improved efficiency.

While the automotive industry grapples with the rapid pace of technological advancements, Roy underscores the need for collaboration and innovation. He emphasised that processes like hot stamping and hydroforming complement the use of high-strength steel, enabling the fabrication of complex components with improved efficiency. “Moreover, multi-material design approaches involving magnesium and aluminium offer further optimisation opportunities, albeit with unique challenges.” The two-day seminar brought about thought exchange among industry experts on the nuances of lightweighting, including weight optimisation design philosophies, material trends, and process technologies such as giga-castings, which are emerging as modern-day solutions to slash vehicle weight and offer safer, and more sustainable products.

This feature was first published in Autocar Professional's June 1, 2024 issue.