Navigant Research Blog

High-Strength Steel or Aluminum for Vehicle Body Parts: That Is the Question

— August 10, 2015

In a presentation to the 2015 CAR Management Briefing Seminars, Eric Petersen, the vice president of research and innovation at AK Steel, outlined his plans to produce the next generation of high-strength steel. He was confident that new innovations from steel suppliers will prevent the loss of more market share to aluminum. As Petersen demonstrates, Ford’s decision to convert its F-150 to all-aluminum has prompted steel suppliers to get creative.

However, there are a lot of things to consider when choosing a material for manufacture of vehicle components. Current vehicle bodies and closures are made primarily of sheet metal, although carbon and glass fiber-reinforced plastic are also used. Original equipment manufacturer (OEM) designers and engineers have to consider both the requirements of the finished vehicle and the ability to manufacture it efficiently.

Modern production lines depend on assembly techniques that can be automated, and fixing parts together must use a process that can be done by robots both for speed and repetition. Depending on the material, this may involve spot welding, seam welding, rivets, bolts, glue, etc. If production facilities are already equipped with a certain capability, changing to a material that needs a different joining process might require a major investment, which may only be practical when the existing equipment is reaching the end of its useful life.

Part manufacture is another consideration. Many body parts have complex shapes. If they are stamped and need a deep draw, then there may be a limit on how thin the material can be. Steel that is developed to have high strength has a higher yield stress than ordinary mild steel, which is a benefit in the finished article to absorb loads, but makes it harder to form during manufacture. Other lightweight materials such as magnesium have poor formability for body panels but can be cast for uses such as the instrument panel beam in the 2015 Ford Mustang. Some materials are treated after shaping to make them harder, but that also adds cost. Different materials also require different post-manufacture treatments to prevent corrosion.

Once a part is manufactured and assembled, it has to meet various performance specifications. A vehicle body structure has to be stiff in torsion and bending, cope with fatigue loading at load points, handle rollover and side impact loads, and absorb crash energy while keeping occupants safe. In addition to meeting these structural goals, overall vehicle fuel efficiency targets mean that keeping the weight low is now critical. And, as always, there is the ever-present need to keep costs as low as possible.

No Silver Bullet

Just as with powertrains, there is no silver bullet material that is ideal for every application. Material suppliers should recognize the big-picture approach of the automotive manufacturers, which involves reducing the number of platforms to increase volume of many parts and to streamline manufacturing processes. OEMs are increasingly using multi-disciplinary optimization for part design, which considers a wide range of factors including manufacturability, assembly, structural performance, weight, functionality, and overall cost.

Future vehicles are more likely to be made from a variety of materials than to stick with one or shift entirely to another. Material suppliers should consider how to make parts with their products that not only perform better than the competition at lower cost, but also integrate easily into existing platforms.


Upcoming U.S. Fuel Economy Standards Achievable

— August 6, 2015

In July, the International Council on Clean Transportation released a new technical briefing paper entitled Hybrid vehicles: Trends in technology development and cost reduction. It is a good read and covers a lot of interesting information about light duty hybrid vehicles. The document points out that the two current hybrid vehicle market leaders, Toyota and Ford, both use a system that has two large electric motors and a planetary gear system in place of the conventional transmission. This is known as a power-split hybrid system. Most other manufacturers with recently introduced hybrid models have chosen to go with variants of a single-motor, twin-clutch hybrid system, commonly referred to as a P2 hybrid.

There are also other approaches in production today. A third option was chosen by General Motors (GM), which has implemented a simpler mild hybrid technology based around a powerful belt-alternator-starter. Honda has its Integrated Motor Assist and Mazda has i-ELOOP in production, which uses ultracapacitors rather than batteries to capture regenerative braking energy.

The message from the paper is that the incremental costs of adding hybrid drive are expected to continue falling as the systems are refined, by as much as 5% per year, thus making the technology more affordable. Some examples of how small changes have produced these improvements in the past are shown (for example, replacing a separate hybrid cooling system by expanding the existing engine cooling system). OEMs and suppliers are also expected to be able to improve efficiency in increments so that the return on investment (ROI) becomes more attractive for buyers.

Also mentioned are some of the topics that Navigant Research has covered in recent studies, such as 48-volt systems and fuel efficient technologies such as lightweighting and turbocharging. There is a lot of incentive to improve fuel economy as new government regulations on the horizon will require tough targets to be met or fines will be assessed.

Not All Gloom and Doom

But it is not all gloom and doom. The National Research Council has also recently published a report on the Cost, Effectiveness and Deployment of Fuel Economy Technologies for Light-Duty Vehicles. One interesting chart shows that many manufacturers already are selling vehicles that meet future standards. The Corporate Average Fuel Economy (CAFE) standard sets targets for fuel economy based on vehicle footprint so that the mile-per-gallon number is higher for smaller vehicles.

Some vehicles available today already exceed the targets for 2021 and 2025, including hybrids from Toyota, Ford, and Hyundai. The conventional 2015 Mitsubishi Mirage with a 1.2-L engine and continuously variable transmission (CVT) is close to meeting the 2023 target. Already close to meeting the 2021 target are non-hybrid vehicles such as the Volkswagen Golf diesel, Honda Civic HF, Toyota Corolla LE Eco, Mazda3, and Dodge Dart.

As Navigant Research’s Automotive Fuel Efficiency Technologies report discusses, there is no single quick solution for meeting emissions targets. The goals will be met by a combination of lower weight, better aerodynamics, and more efficient powertrains. The challenge for the automotive industry is to accomplish this at the lowest cost.


Autonomous Trucks Make Progress

— August 3, 2015

Autonomous vehicle technology continues to advance steadily, with new testing facilities opening to great fanfare at the University of Michigan being a recent highlight. Around the world, plans are being put into action to test self-driving cars in many different localities, and work continues within all the major automotive manufacturers and large suppliers. The first freeway cruising and traffic jam applications are going into production in a few 2016 models, and many more are promised by 2017.

The focus from large OEMs is still on incremental improvements to existing advanced driver assistance systems, with more capable software and sensor fusion. The marketing appeal to car buyers is based on convenience and comfort with the added benefit of greater safety. Prevailing wisdom says that the personal vehicle market will continue as it has done for the past century, but there is the potential for significant change if the technology delivers and legislation is updated to allow it. This topic is discussed in the latest version of the Navigant Research Autonomous Vehicles report.

Under the Radar

What is flying a little under the radar is the work going on to launch autonomous commercial vehicles. Daimler caused a stir in May when it gave a demonstration of its Freightliner Inspiration Truck at the Hoover Dam.  In July, the company announced that it expected to be able to begin testing on public roads in Germany before the end of 2015.

Another option that is an incremental step toward autonomous driving is offered by U.S. company Peloton, which offers a platooning feature that can be added to existing vehicles. Peloton’s technology connects two trucks wirelessly and allows the following truck to close the gap safely, with speed and braking controlled by the lead vehicle while the driver remains responsible for steering. The company claims that fuel savings on a long drive are approximately 4.5% for the front vehicle and 10% for the follower.

Deciding Whether to Invest

Fuel savings are the first step toward justifying new technology for fleet managers who must decide whether to invest. The ultimate potential of autonomous vehicles is to reduce or eliminate the cost of the driver, which produces the inevitable result of lost jobs, a topic beginning to stimulate some debate in the media.

New technology almost always brings societal change, but the rate of change has increased in the computer age, and a serious commitment to retraining programs needs to be made by governments as they make changes to legislation to support the emergence of autonomous driving capability and other forms of robotics. It isn’t all bad news though. The new truck pilot jobs will need new skills on top of the conventional driving ones and should command higher pay.


Turbocharger Suppliers Have a New Market to Pursue

— June 25, 2015

The recent Navigant Research report, Automotive Fuel Efficiency Technologies, concluded that one of the main approaches to delivering better fuel economy for cars is to downsize existing engines but coax more power out of them. The principle of increasing air pressure at an internal combustion engine intake to produce extra power is well-established and is known generically as forced induction. The two main mechanical types of forced induction are usually defined as:

• Turbocharging, where the compressor is driven by exhaust gases
• Supercharging, where the compressor is driven directly off the engine crankshaft

Turbochargers are well known for being a relatively simple way to get more power from a small engine, but also have the disadvantage of lag because the maximum boost is not available until the engine speed is high. Superchargers can be set up to provide boost at low engine speeds, but they also use power when they are not needed, and so they can adversely affect fuel economy under normal driving conditions.

A third variant, electric turbochargers, now looks set to hit the market. An electric turbocharger offers an engine boost on demand without the lag of an exhaust-driven component or the physical drag that a supercharger places on the engine. The technology operates from electrical energy that is recovered by regenerative braking and takes advantage of the fact that electric motors develop their maximum torque immediately from a stationary position.

The concept has been under development for some years, and the biggest challenge so far is to get enough usable power from a 12V electric motor. However, with the imminent rollout of 48V electrical subsystems for advanced stop-start systems (as discussed in detail in the Navigant Research report, 48-Volt Systems for Automotive Applications), it will become practical to implement an electric turbocharger for the first time. Audi is the only manufacturer to announce a planned launch so far, but most other manufacturers are thought to be working on similar concepts.

Other Suppliers

French Tier One supplier Valeo is one of the first to offer a production-ready electric turbocharger. The company acquired the switched reluctance motor technology from U.K.-based Controlled Power Technologies in 2011. The motor is liquid-cooled and the 48V system needs additional power electronics and a bigger battery than normal, so there are additional costs to consider. Benefits include improved performance as well as better fuel economy, so manufacturers are expected to be able to charge a premium.

Conventional turbocharger suppliers are also developing electric products. BorgWarner offers electric turbocharging in its eBOOSTER system, which has been tested on both gasoline and diesel engines. Honeywell is another well-established supplier of conventional turbochargers, and it is thought to be developing an electric version for introduction in a couple of years’ time. As is often the case, emerging technology stimulates innovation from brand new companies as well as established suppliers; one example is U.K.-based Aeristech.

Fuel efficiency is a key focus for automotive manufacturers that want to avoid financial penalties for missing emissions targets in the coming years in many countries around the world. Incremental improvements of 1%–2% may not be enough, so investing in technology that has the potential to deliver significant fuel economy increases without sacrificing performance or drivability may be money well spent. Electric turbocharging looks likely to be the first application that will launch 48V systems into series production. And this shift brings many other benefits of electrification that will challenge hybrid technology at a much lower price point.


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