By Jonathan Gourlay
Savings lead to reduced components, smaller powertrain, improved quality, and capability to cut product development costs by 35-40%.
It’s no secret in the automotive industry that reducing weight and mass in vehicles saves big money in both materials for the manufacturer and gas for the consumer. But such reductions can compromise structural integrity and so have come in modest improvements and led to complex redesign. Add to that increasingly stringent environmental and safety regulations that will be taking effect through 2016 and unclear prospects with regard to fuel costs, and it’s easy to see why an industry group wants to change the game.
With an eye toward coupling efficiency with crashworthiness, the Auto/Steel Partnership—six steel companies (Ak Steel, US Steel, Mittal, Defasco, Nucor, and Severstal) that joined with GM, Ford, and Chrysler—wanted to develop a lightweight passenger compartment using advanced high-strength steel. In 2004, the partnership approached Engineering Technology Associates, Inc. (ETA) to solve the problem.
ETA had a track record of successful CAE analyses for various automotive OEMs over the course of 26 years, so ETA VP of Engineering and Consulting Akbar Farahani, Ph.D. and his team had the street cred to take on the challenge of reducing automobile mass while improving crashworthiness, stiffness, and quality at the same time.
Using the ULSAB-AVC (Ultra-light Steel Auto Body Advanced Vehicle Concepts) model donated by the Auto/Steel Partnership (A/SP) for Phase 1 of the project, ETA started on the Future Generation Passenger Compartment (FGPC) project. It provided Farahani and ETA’s advanced engineering group with the opportunity to develop the idea that many design concepts could be evaluated under multiple load conditions simultaneously. Further, no design would be initiated until a concept met all of the design and manufacturing targets set at the beginning of the project. The idea was dubbed the Accelerated Concept to Product (ACP) process.
“The methodology is a multidisciplinary and holistic design solution,” says Farahani. “The nucleus of the idea came [during] a project for GM about seven years ago, but software was not mature enough then to accomplish ACP.”
In the conventional development process, a product is designed, analyzed, tested, and then redesigned. With the ACP process, CAE, design, and manufacturing are all synchronized.
To reach the goal of reducing the vehicle’s mass by 25 percent, the ETA team brought all the tools at its disposal to bear. That includes multiple CAE tools—modeling tools, application specific tools, solver technology, and optimization solutions—as well as one of the most important tools used in the ACP process, ETA’s own advanced modeling suite eta/VPG. VPG provides the pre/post, safety, structure, fatigue, drop test, ALE-FSI, and material handling analyses. Another ETA-authored solution, eta/DYNAFORM, is used for formability analysis, die face engineering, die structure analysis, and manufacturing process simulations. The team also uses Nastran, LS-DYNA from Livermore Software Technology Corp., HEEDS from Red Cedar Technology, and SFE CONCEPT from SFE GmbH.
Once an optimized concept is identified, further design, analysis, and optimization takes place using loading, manufacturing, material, and cost constraints. Finally, CAD data is generated for an ideal production-ready design.
With funding from Auto/Steel Partnership members as well as the U.S. Department of Energy, two A/SP engineers and five from ETA started work. The vehicle package was adapted for both conventional diesel and hydrogen fuel cell powertrains and in 2007, the team realized a mass reduction of 30 percent when compared with a typical passenger compartment of the same vehicle class. The team beat the goal by five percent while maintaining the required structural parameters for stiffness and durability, and improved the vehicle’s crashworthiness. The final optimized design was proven by a series of studies demonstrating the design’s ability to accommodate variations in vehicle curb weight and impact barrier height.
Phase 2 Enabled by HPC, Other Gains
Because of that success story, the development continued. This time, Farahani had further advances in sophisticated advanced CAD/CAE (modeling and analytical) software, newer advance high-strength steel, and gains in high-performance computing (HPC) at his disposal.
“Our challenge was to, first, make the process faster, quicker, and better,” says Farahani, “and to further reduce the mass while keeping safety and performance intact.” Engineers were aided in this second phase of the FGPC project by a 64-CPU HPC cluster using hardware from HP and SGI to crunch numbers.
A U.S. OEM was selected to donate a 2008 model year luxury vehicle and a target of reducing its mass by 20 percent became the next goal.
“Every six months or so, we made an improvement,” says Farahani. Along the way, he added, automation was added to the process as a result of newly developed tools. “Recently, we felt it was the right time to announce the process and how it could impact product development.”
The FGPC Phase 2 achieved a mass reduction of 15 percent to 20 percent via the ACP process. “It’s a significant reduction in product mass and cost,” says Farahani.
Fuel Efficiency Gained
While lighter weight clearly results in better fuel efficiency, actual gains will vary depend on tires, transmission, and the powertrain. But according to figures attributed to a study by MIT’s Laboratory for Energy and the Environment, a mass reduction of 10 percent results in fuel-consumption savings between 4.5 to 8 percent.1 Another study found that when the same mass reduction occurs in a conventional vehicle with no change in powertrain, fuel savings range between 1.9 and 3.2 percent, but when the powertrain is resized, the savings improve to between 6 and 8 percent.2 Yet that can be improved upon when one considers the ability to incorporate smaller, more fuel-efficient engines.
According to ETA, the program also proved that advanced joining technology (laser-weld or adhesive bonding) could further reduce the mass of a passenger compartment.
Using ACP to drive the project proved that at the same time CAE and CAD designs change, maximum mass reduction is possible while design robustness and efficiency can be significantly improved. It also showed that system or sub-system components can be reduced to improve manufacturing efficiency. Taken together, the reductions in parts and mass translate to reductions in product development costs between 35 and 40 percent. Finally, though the FGPC project focused on a steel product, the ACP process is applicable to numerous structural materials.
Hardware Makes it Happen
“If I were to have presented this five years ago, people would have laughed at me…,” says Farahani, explaining there were four “wings” to the process. “Software is getting smarter and better, new tools are becoming available, there are advanced materials, and then hardware. Hardware is absolutely the base ingredient of this process.”
In December, ETA was chosen as the winner of the 2nd Annual SAE (Society of Automotive Engineers) Detroit Section/MITEF Vehicle Innovation Competition for the ACP process. Farahani says that ETA is currently working on refining a product, trying to make it “more automated, cleaner, and faster.”
In the meantime, the ACP process is being offered as an engineering service, and just might become the tool needed to optimize the high-efficiency car of the future.
1. Cheah, L. et al. (2007). Factor of Two: Halving the Fuel Consumption of New US Automobiles by 2035. MIT LFEE 2007-04.
2. Forschungsgesellschaft Kraftfahrwesen mbH Aachen (fka). Determination of Weight Elasticity of Fuel Economy for Conventional ICE Vehicles, Hybrid Vehicles, and Fuel Cell Vehicles.