Construction of Design Guidelines for Optimal Automotive Frame Shape Based on Statistical Approach and Mechanical Analysis

A body frame composed of thin sheet metal is a crucial structure that determines the safety performance of a vehicle.Designing a correct weight and high-performance automotive body is an emerging engineering problem.To improve the performance of the automotive frame,we attempt to reconstruct its design criteria based on statistical and mechanical approaches.At first,a fundamental study on the frame strength is conducted and a cross-sectional shape optimization problem is developed for designing the cross-sectional shape of an automobile frame having a very high mass efficiency for strength.Shape optimization is carried out using the nonlinear finite element method and a meta-modeling-based genetic algorithm.Data analysis of the obtained set of optimal results is performed to identify the dominant design variables by employing the smoothing spline analysis of variance,the principal component analysis,and the self-organizing map technique.The relationship between the cross-sectional shape and the objective function is also analyzed by hierarchical clustering.A design guideline is obtained from these statistical approach results.A comparison between the statistically obtained design guideline and the conventional one based on the designers’experience is performed based on mechanical interpretation of the optimal cross-sectional frame.Finally,a mechanically reasonable new general-purpose design guideline is proposed for the cross-sectional shape of the automotive frame.

Design and Optimization of Steel Car Body Structures via Local Laser-Strengthening

Continuously rising demands of legislators require a significant reduction of CO2-emission and thus fuel consumption across all vehicle classes. In this context, lightweight construction materials and designs become a single most important factor. The main engineering challenge is to precisely adapt the material and component properties to the specific load situation. However, metallic car body structures using “Tailored blanks” or “Patchwork structures” meet these requirements only insufficiently, especially for complex load situations (like crash). An innovative approach has been developed to use laser beams to locally strengthen steel crash structures used in vehicle bodies. The method tailors the workpiece hardness and thus strength at selected locations to adjust the material properties for the expected load distribution. As a result, free designable 3D-strengthening-patterns surrounded by softer base metal zones can be realized by high power laser beams at high processing speed. The paper gives an overview of the realizable process window for different laser treatment modes using current high brilliant laser types. Furthermore, an efficient calculation model for determining the laser track properties (depth/width and flow curve) is shown. Based on that information, simultaneous FE modelling can be efficiently performed. Chassis components are both statically and cyclically loaded. Especially for these components, a modulation of the fatigue behavior by laser-treated structures has been investigated. Simulation and experimental results of optimized crash and deep drawing components with up to 55% improved level of performance are also illustrated.

Performance improvement of car body structure in 100% frontal impact

During the 100%front impact,all the parts of front car will participate in the course;the crash stiffness of bodywork will also reach the peak.During the crash,rational structure of bodywork can resist the distortion,absorb more energy and get better mode of distortion and low deceleration rate,so as to meet the performance of crash safety.The paper mainly makes optimization analysis based on the problems of front side rails,subframe,firewall,and optimization cases are confirmed which can decrease the intrusion and deceleration rate of the whole car.The structure of bodywork after optimization can meet the performance of crash safety.