Strategic Development of Lightweight Platforms Made of Steel
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Successful lightweight steel design in large-scale automotive production requires the strategic use of optimization methods already in the early development phase. The Swedish automotive company NEVS relies on Altair's C123 method for simulation-driven and cross-vehicle lightweight design.
Steel Dominates Mass Production
While there is an ever-increasing trend to apply new materials and material mixes to car body designs in order to optimize vehicle weight, the automotive industry still mainly uses steel - especially when it comes to mass production. On the one hand, this is due to the material's excellent workability, and on the other hand, this is because of the numerous new developments in the area of high strength steels, which enable a thinner wall thickness and hence less weight while offering a constant stiffness. This is why the automotive industry expects steel to be the dominant material in the automotive sector also in the next 20 years. In order to reach the ambitious weight and safety goals car makers have set, it is time to find out how to efficiently use these high strength steels.
To successfully create lightweight concepts with steel and to use them in mass production, appropriate development methods are required. These methods have to be applied very early in the development process - focusing on the set weight goals for the body in white during the entire development process.
Concept Design Process C123
Following this approach, various vehicle configurations sharing the same platform can be integrated into the numerical design process without the need for a detailed view of each variant.
In summary, this means that the process begins with creating design spaces for the different vehicle variants and that the vehicle models are already connected in the areas where identical components such as a front module or an underbody structure will be used. In a second step, the occurring load paths are used to create a beam-based structure which already includes all needed cross section properties. In the final step, all connection details are defined and further studies derived.
The C123 Process at NEVS
the development of an ideal structural concept as a combination of vehicle platform, battery carrier, automotive body, and other load-carrying structures
the guidance and monitoring of load paths during the concept phase in order to successfully develop the vehicle architecture as well as a support concept to treat individual vehicle configurations (panoramic roof, motor configuration, vehicle dimensions etc.)
good monitoring and control options to develop an optimum balance between different attributes such as weight, costs, performance etc. and the structural feasibility studies
a maximum modularity between the single segments and vehicle types.
Since the development engineers at NEVS had to consider a wide spectrum of vehicle variants, they first chose and investigated a basis variant. This step was carried out jointly by NEVS and Altair. They decided on an SUV for the global market as a starting point on which to base the platform.
At first, they applied the C123 process to develop the basic concept. Since all vehicles of the company are operated fully electrically, the battery carrier was especially important for NEVS. To ensure that all vehicle variations and platforms can be considered simultaneously they performed so-called multi-model optimizations allowing the engineers to consider several questions at the same time.
In one of their studies, they wanted to assess which consequences a certain variant of the battery carrier would have for the performance of other vehicle structures. Due to the effect on the different vehicle structures, this process was very dynamic. Especially during the crash simulation, it became apparent that the battery carrier could also be used as an additional load path, with the result that the load distribution between the different load paths could be better resolved. Subsequently, the connections were investigated to find the ideal connection for the battery carrier and to reach the best possible performance.
Basis for Development Decisions
Using the C123 development approach it was possible to actively support the concept development at NEVS with simulation and optimization. By systematically employing optimization technology the engineers could highlight design alternatives, determine design sensitive factors, solve trade-offs, and run what-if scenarios to identify the optimal design balance between partly competing attributes such as performance, weight, and costs. In addition, NEVS obtained significantly more information providing a basis for important design decisions, especially in the early concept phase. Implementing the C123 process the development team was able to rely with confidence on the created concept and the well-balanced design.
Particularly, the design teams benefitted from the new approach since now they are able to quickly assess how design changes will affect other components of the vehicle. This resulted in an unprecedented degree of concept maturity and convinced the NEVS developers to employ the C123 process in future projects as a standard procedure.
In contrast to using simulation to validate single components, which is still the main area of application in many companies, the C123 process offers a real simulation-driven and cross-vehicle design approach. Using such a method is the only way to identify and follow-up the most promising development directions for a lightweight design concept very early in the development process of a vehicle. This is particularly the case when developing a platform that should use as many synergies as possible across vehicle variants. As a result, this process leads to lightweight concepts which are also optimized regarding costs and performance. |