Automakers are employing an effective way to slim down electric vehicles, just as they have lightened their traditional combustion-engine lineup. They’re using more high-strength aluminum to provide the needed lightweighting. And they intend to continue to use the distinct capabilities of extruded solutions to make their vehicles more energy efficient, without sacrificing performance or aesthetics.
With increasing automotive safety standards and industry regulations, extruders have expanded their research and development capabilities to offer a complete solution to customers. These discussions begin during the design phases, with the end goal of creating customized solutions to meet both customer and industry demands. The extrusion industry is now not only offering expanded capabilities that go beyond supplying a specific component, but also offering modeling and comprehensive testing to maximize performance and efficiency throughout the entire process.
Specifically, the use of aluminum and extruded aluminum products in a North American vehicle is anticipated to climb up to 30 percent over the next 10 years – to 565 pounds by 2028, representing 16 percent of the vehicle’s weight, according to Ducker Worldwide data.
The reasons why auto designers and engineers favor aluminum extrusions are well known. Employing aluminum extrusions allows them to use different aluminum alloys and profile geometries to not only maximize lightweighting but also manage the specific application in the vital aspect of energy absorption and crash-management requirements. Further, aluminum extrusions have a distinct ability to help automakers cost effectively meet the stringent 2025 fuel economy and emissions targets when compared to other materials. For example, aluminum can shave an estimated 40-plus percent of a vehicle’s body weight compared to steel.
Beyond weight savings, aluminum extrusions also offer solutions that increase vehicle safety as demonstrated by numerous vehicles in production today. With this in mind, automakers look for aluminum alloys that deliver excellent crash performance, high-yield strength and reduced weight. This is a direct result of the energy absorption provided by well-designed aluminum alloys; for automakers, 6xxx series alloys are commonly utilized.
Hydro Extruded Solutions has developed and worked with 6xxx series alloys for structural extrusions requiring high tensile strength, such as bumpers and side sills. In addition, Hydro Extruded Solutions has developed alloys with increased strength and good energy absorption for structural extrusion applications such as crash rails. These alloys are more cost-effective and easier to extrude than 7xxx series alloys, which can show similar performance at a significantly higher cost.
Hydro designs the alloy and processing to achieve the application demands. In this, the chemistry, the casting process, the extrusion processing and the thermal treatments are all important in achieving the performance requirements. All aspects are integral and must be considered in the development process as well as the finalized manufacturing processes. Hydro is in a unique position that allows for full control of the incoming materials, full casting capability and a complete extrusion process to produce a “tailored” product solution to ensure consistent performance.
In general, autos and EVs use aluminum and aluminum extrusions to further improve fuel economy, battery range, safety and overall driving performance. Extrusions can commonly be found in space frames, hang-on parts, doors, hoods, truck lids, bumpers, crash boxes, Body in White and car bodies, among other sundry parts. The ability to produce complex extruded solutions for various applications efficiently and at scale also helps auto makers meet design and regulatory requirements.
The use of extruded aluminum delivers distinct advantages in helping solve thermal challenges for EV applications. Aluminum extrusions’ high thermal conductivity makes it an excellent option for removing heat from a vehicle, it being widely used for structural and thermal support of the electric battery pack, electric motor thermal control, thermal management of LED lighting systems, and power electronics systems cooling.
Alloy strength and extrusion profile geometries also play a critical role when taking crash management into consideration, as illustrated through modeling. It is especially critical to understand how certain alloys and geometries will respond in front-end crashes or in side impact crashes. In EV applications, think of the EV battery as the new gas tank – it is paramount for safety’s sake to prevent intrusion into and to protect an EV’s battery compartment in the event of telephone pole-type side impact crash. Aluminum extruders can solve this problem with a strong, lightweight, and lower-cost solution. This is because extruded aluminum offers a high strength-to-weight ratio, high ductility, and design flexibility needed to provide protection to the battery compartment.
Extrusion producers employ energy-absorption and crash management expertise and experience in developing aluminum extrusions, especially as it applies to developing and selecting the right alloy for specific solutions. For example, Hydro is an industry leader that utilizes modeling to optimize alloy choice and geometry designs for extruded solutions that can enhance lightweighting while meeting the applications performance requirements.
The extensive modeling capabilities allows Hydro to work closely with customers in the design phases to develop customized solutions, helping to enhance the utilization of extrusions from lightweighting and manufacturability standpoints. Ultimately, this delivers a predictive set of criteria to determine the likely performance of a specific alloy and extrusion profile design in a specific application. From there, engineers can validate the model through physical testing (Figure 1) and make adjustments to the computer simulations as needed. The modeling shortens the development process and increases the likelihood of a successful design that meets both performance requirements and lightweighting goals.
Figure 1: The above graphic is an example of a Generalized Incremental Stress-State dependent Damage Model (GISSMO) fracture model and exhibits a good correlation between the experiment and simulation.
Engineers can also apply different mechanical properties and various aluminum alloys to determine the best solution that is producible at scale and can be manufactured well. All modeling and designs must undergo tests to ensure they meet National Highway Traffic Safety Administration requirements. The agency’s highest safety ratings illuminate the fact that aluminum absorbs twice the crash energy of mild steel.
To further understand alloy and profile performance, Hydro also uses a digital image correlation system to obtain accurate measurements of deformation, strains, fracture, etc. With this system, materials will go through quantitative material tests, such as a 3-point bend test, to compare to the predicted behaviors shown through modeling and gives engineers data to further improve the models.
Through modeling and testing, engineers can validate the component design for OEMs and predict the type of failure that might occur in a crash, including how much energy is absorbed as well as how/where the material is going to crack. This method streamlines the process, allowing extrusion producers to tailor the extrusion cross-section through computer modeling with fewer trials. As shown in Figure 2, energy absorption can be increased while decreasing extrusion weight. This optimizes weight savings while maintaining and even improving energy absorption.
Figure 2: These graphics illustrate that multi-cell extruded profiles not only absorb more crash energy but also reduce the weight.
As auto manufacturers are anxious to further enhance their vehicles to make them safer and lighter they are relying increasingly on aluminum and extruded aluminum. In concert, extrusion producers are developing aluminum alloys for future generations and to furnish more sustainable solutions, an enhanced economy and environmental sustainability.
Automakers grasp the advantages of aluminum and aluminum extrusions in autos and EVs for delivering the higher-strength lightweighting that pays dividends in energy efficiency, battery power, and energy absorption. All of these factors are essential to differentiate the vehicles and improve their popularity with today’s vehicle buyers.
Dave Lukasak is director of Metallurgy and Research for Hydro Extruded Solutions business in North America. Alex Chen is a senior research engineer – CAE modeling.