Lower Vehicle-Body Structure With Asymmetric Rigidity for Collision Buckling
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Solution Overview
Problem
Existing vehicle-body structures face challenges in achieving both bending strength and impact absorption while maintaining formability and cabin space, particularly in side sills where buckling is insufficient under bending loads due to improper flange positioning.
Innovation Solution
A frame member with a closed-cross section is designed, comprising a compression face portion and side face portions with varying rigidity, where the compression-side area has higher rigidity than the tension-side area, allowing for secure buckling and suppressed bending deformation during collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the flange portions of the side sill inner and side sill outer are positioned on the outward side of the sectional center to secure sufficient cabin space, then the cabin space is improved, but the formability of the side face portion is deteriorated and proper buckling cannot be generated
Solution Approach 1:
The side face portion is divided into a compression-side area with higher rigidity and a tension-side area with lower rigidity. This local differentiation of mechanical properties allows the outward-positioned flange portions to maintain sufficient cabin space while the compression-side area provides the necessary structural support for proper buckling formation during side collisions.
Solution Approach 2:
The side sill structure employs asymmetric rigidity distribution where the compression-side area has higher rigidity than the tension-side area. This asymmetric design enables the structure to achieve both adequate cabin space with outward flange positioning and proper buckling characteristics under compressive loading conditions.
2Loss of energy
If the side sill outer has a hat-shaped sectional structure with bending portions to enable impact absorption, then the impact absorption capability is improved, but the bending strength of the side sill as a whole may be compromised
Solution Approach 1:
The rigidity parameter is changed along the length of the side face portion, with the compression-side area having higher rigidity and the tension-side area having lower rigidity. This parameter variation allows the bending portions to effectively absorb impact energy while the higher rigidity compression-side area maintains the overall bending strength of the side sill structure.
Data Source
AI summary
A lower vehicle-body structure of a vehicle is provided with a frame member having a closed-cross section. The frame member comprises a first portion and a second portion. The first portion comprises a compression face portion and a pair of side face portions. The side face portion comprises a bending portion, a compression-side area which is positioned on a side of the compression face portion relative to the bending portion and where a compressive stress is generated when the bending load is applied, and a tension-side area which is positioned on a side away from the compression face portion relative to the bending portion and where a tensile stress is generated when the bending load is applied. The compression-side area is configured to have higher rigidity than the tension-side area.