Vehicle Body Top Structure with Variable Thickness Front Rail
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Solution Overview
Problem
Existing vehicle body upper structures face challenges in achieving sufficient weld penetration and strength at T-shaped intersections where thick front rails are welded to roof side rails, leading to inadequate weld strength and reduced rigidity and safety during rollover events.
Innovation Solution
A vehicle body upper structure design incorporating a front rail with alternating thick and thin plate portions, where the thin plate portions are welded to the side rails with sufficient penetration, and the thick plate portions extend to overlap the side rails, enhancing the intersection's rigidity and strength through a combination of overlapping members and strategic placement of stays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the front rail is made thick to increase the strength of the intersection, then the rigidity and strength of the T-shaped intersection are improved, but the weld penetration becomes insufficient and the weld strength between the front rail and roof side rail decreases
Solution Approach 1:
The front rail is segmented into multiple thickness zones along its length, with a thicker portion at the intersection with the roof side rail and a thinner portion at the center. This segmentation allows the thick portion to provide high strength at the critical intersection while the thin portion enables sufficient weld penetration, resolving the contradiction between intersection strength and weld quality.
Solution Approach 2:
The front rail is designed with non-uniform thickness, having a local thick portion at the intersection area and a local thin portion at the center. This local quality variation optimizes the structural performance by providing high strength where needed (at the intersection) while maintaining good weldability in other areas, thus resolving the contradiction between intersection strength and weld penetration.
2Stability of the object's composition
If the front rail is made thick to enhance rigidity of the intersection, then the NV performance and cabin protection are improved, but the weld penetration is insufficient leading to low weld strength
Solution Approach 1:
The front rail is divided into segments of different thicknesses, with a thick segment at the intersection for rigidity and a thin segment at the center for manufacturability. This segmentation enables the thick portion to provide the required rigidity for NV performance and cabin protection while the thin portion ensures sufficient weld penetration during manufacturing.
Solution Approach 2:
The front rail features local quality variation with a thick portion at the intersection and a thin portion at the center. This design provides high rigidity at the critical intersection area while maintaining good weldability at the thin portion, resolving the contradiction between structural rigidity and manufacturing precision.
Data Source
AI summary
A vehicle body top structure for enhancing the rigidity and strength of the intersections of side rails and a front rail. The vehicle body top structure is provided with left and right side rails provided so as to extend in the front-and-rear direction at the top part of a vehicle body side part, and a front rail extending left and right, one end part of which is joined to the left side rail, and the other end of which is joined to the right side rail. Thin-plate parts having a smaller plate thickness than thick-plate parts and thick-plate parts are disclosed at the one end and the other end of the front rail. The thin-plate parts are each connected to the left and right side rails.