The increased environmental mandates requiring the automotive industry to reduce CO2 emissions is driving a demand for lighter materials that still maintain required safety and performance standards. Replacing cast iron and traditional steel components with lightweight materials such as high-strength steel, magnesium (Mg) alloys, aluminum (Al) alloys, carbon fiber, and polymer composites can directly reduce the weight of a vehicle’s body and chassis by up to 50 percent according to the U.S. Department of Energy. And, a 10 percent reduction in vehicle weight can result in a 6 to 8 percent fuel economy improvement.
With the new materials and new grades rolling out on a continuous basis, advanced lightweight materials use is a key focus for automakers, yet the selection and adoption processes can come with a costly learning curve at times. Materials such as composites and magnesium carry a higher cost as compared to conventional metals such as steel. This has resulted in aluminum and high-strength steel representing the primary lightweight materials employed within the automotive market. Aluminum is experiencing rapid growth in both exterior and structural applications. However, with the vast majority of vehicle weight represented by steel, the opportunity for steel usage to impact weight, performance, and integrity of a vehicle is significant. Steel has remained the leader in average vehicle content on the road — about 60% by weight today.
Multiple Computer-Aided Engineering Tools
Although steel’s proven reliability means it’s likely to remain the primary ingredient in car bodies for some time to come, automobile manufacturers are now approaching the limits of how lightweight a steel car body can be. To fully understand and build within those limits, sophisticated computer-aided engineering (CAE) tools are a requirement in order to optimize designs, provide quality, and meet stringent mileage goals, emissions standards, and crash test regulations cost-effectively.
However, within a global as well as multi-disciplinary environment, it’s common for a variety of CAE tools to be employed in order to simulate the entire body behavior. Today’s automakers require solutions that can validate component and entire vehicle performance in an integrated holistic testing environment to achieve quick results. Improving the virtual testing and validation methods can help automakers and suppliers enhance quality, save cycle time and reduce development costs.
Early virtual simulation in the development process can also save the costs, time and resources associated with physical testing on expensive prototypes later. Realistic simulation and analysis capabilities can validate and optimize design exploration, and extensive functionalities to address various workflows, multi-physics and open co-simulations.
Balancing Performance and Weight
During development of the Mazda CX-5, the design team had a goal to identity the lightest gauge combination of steel parts for the roof structure that would meet target performance values in stiffness, NVH quality, durability and crashworthiness where each of these four areas had its own CAE analysis tool. To bring such a multi-disciplinary optimization together requires a comprehensive and complex analysis system that first optimizes vehicle body behavior in each of the target areas, and then identifies a final design that brings all these best characteristics together at the lightest possible weight.
The team initially employed a manual process of data organization which was taking a great deal of time. With the continual pressure to reduce product development time, project cost constraints, and new material entries into the market, solutions that can automate these analyses are critical. In this situation, Mazda employed Isight, a process automation and design exploration tool within the Dassault Systèmes’ SIMULIA brand offering.
Isight helped the engineers integrate all the various CAE software into customized, ‘drag and drop’ workflows that would run all their performance tradeoff sequences automatically. During the optimization process, in most cases parts that had a low contribution to performance became thinner while some of the parts with a large contribution to performance needed to become thicker and heavier. Optimization with Isight enabled the Mazda team to balance out these opposing needs while still lightening the overall weight. With this approach, the 3.4 percent weight reduction goal was achieved, as compared to the previous design of the CX-5. This multidisciplinary design optimization protocol is now being used in other Mazda programs.
Light, Yet Safe Steering Knuckles
GF Automotive employs modern simulation and optimization software methods as an essential part of the development of its chassis components based upon Tosca™ Structure, part of the Dassault Systèmes 3DEXPERIENCE® technology portfolio under the SIMULIA brand. Tosca Structure is a flexible, modular software system for non-parametric structural optimization. GF Automotive uses the software on a wide variety of design projects in an effort to save weight from vehicle designs.
The benefits of this optimization process are many. For one, a new design concept can be easily transferred from Tosca Structure to a CAD model with little added interpretation effort. In one instance, following optimization results, a steering knuckle, which initially weighed 4.39 kg (9.7 lbs), was reconfigured to 2.98 kg (6.6 lbs) — a 32 percent savings. Since each chassis requires two components, the total reduction is 2.82 kg (6.2 lbs) per vehicle. When projected across 1.6 million vehicles, weight savings from this component alone would cut an estimated 11,600 tonnes (12,787 tons) of CO2 emissions over the life of the part.
Integrated and Automated Analysis
Automakers will continue to be under pressure to meet quickly impending environmental mandates. With their biggest opportunity for meeting these requirements focused on lightweighting, there will be ongoing implementation of new materials and designs within the vehicle structure. To quickly understand how these new components will perform is critical given safety requirements. At the same time, pressure remains to reduce product development time and costs while improving quality.
With all these demands, it is critical to streamline product development processes. Automakers must seek ways to unify and simplify the various software and tools across their enterprise. As illustrated by the examples above, bringing several solutions under a common platform brings both robust results and speed to the process, helping identify the optimal design to meet all design requirements, and creating more time for innovation.
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