Rear Side Frame Bending-Promotion Portions for Collision Load Absorption
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Solution Overview
Problem
The rear side frame of automotive vehicles, particularly those made from high-tensile steel plates or other materials lacking excellent formability, face challenges in absorbing collision loads effectively due to thin plate thickness and improper buckling, leading to potential frame breakage and welding issues, especially in torsion-beam axle types without a subframe for support.
Innovation Solution
A rear vehicle-body structure featuring a rear floor panel with right-and-left rear side frames that include front, middle, and rear bending-promotion portions designed to bend inward in a trough-folding shape during collisions, with specific longitudinal distances between these portions to enhance load absorption, and reinforced with S-shaped beads to improve rigidity and prevent deformation at non-bending points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-tensile steel plate is used to reduce weight and thickness of the rear side frame, then weight and thickness are reduced, but bucking performance deteriorates and breaking or welding peeling occurs
Solution Approach 1:
The rear side frame is segmented into multiple sections with different plate thicknesses. The front portion uses thinner plate (0.7-1.2mm) for weight reduction, while the rear portion uses thicker plate (1.5-2.0mm) for strength. This segmentation allows the frame to achieve both weight reduction and adequate bucking performance by distributing material strategically where needed.
2Device complexity
If the rear side frame is configured in a cantilever manner without sub frame support, then the structure is simplified, but buckling deformation cannot be stabilized
Solution Approach 1:
The rear side frame incorporates a local quality feature through the rear support portion that extends downward from the rear end. This support portion provides localized structural reinforcement and stability at the critical rear end region, enabling the cantilever configuration to maintain adequate buckling deformation stability without requiring a full subframe structure.
3Device complexity
If fewer bending-promotion portions are provided, then the structure is simpler, but load absorption capability is insufficient
Solution Approach 1:
The rear side frame is segmented into multiple sections with different plate thicknesses. The front portion uses thinner plate (0.7-1.2mm) for weight reduction, while the rear portion uses thicker plate (1.5-2.0mm) for strength. This segmentation allows the frame to achieve both weight reduction and adequate bucking performance by distributing material strategically where needed.
Solution Approach 2:
Bending-promotion portions are pre-formed at specific locations along the rear side frame to predictably control deformation patterns during collision. These pre-positioned features ensure that the frame bends at intended locations to absorb collision loads effectively, rather than deforming unpredictably.
4Ease of manufacture
If the longitudinal distance between bending-promotion portions is not optimized, then manufacturing is simpler, but load absorption and deformation control are insufficient
Solution Approach 1:
The longitudinal distances between bending-promotion portions are specifically optimized: the front section distance is set to 300-600mm and the rear section distance to 150-300mm. These parameter changes ensure predictable deformation patterns and adequate load absorption while maintaining manufacturability through standard fabrication processes.
Data Source
AI summary
A pair of rear side frames respectively comprise front bending-promotion portions, middle bending-promotion portions and rear bending-promotion portions which cause the rear side frames to bend inward, in a vehicle width direction, in a trough-folding shape in a rear collision of a vehicle, and a longitudinal distance L2 between the front bending-promotion portions and the middle bending-promotion portions is set to be longer than a longitudinal direction L1 between the middle bending-promotion portions and the rear bending-promotion portions. Thereby, there is provided a rear vehicle-body structure of an automotive vehicle which can properly absorb a collision load at a vehicle-body rear portion, even if a rear side frame is made from material which may not cause smooth bucking of the rear side frame.