Vehicle Cross Member with Fragile Portion for Side Collision Load Distribution
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Solution Overview
Problem
Existing vehicle-body structures fail to effectively distribute and transfer side collision loads in the vehicle width direction, leading to potential injury from the intrusion of the B pillar into the passenger compartment during a side collision.
Innovation Solution
A vehicle-body structure featuring a cross member with a reinforcement member and a fragile portion at the side sill-side end, where the fragile portion crushes under collision load to absorb energy and guide the load in the vehicle width direction, preventing buckling deformation and ensuring load distribution through the reinforcement member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the floor panels are lowered to the same height as the undercover to reduce air resistance, then fuel economy is improved, but the cross-section of the cross member on the vehicle-width-direction outer side increases, causing unexpected deformation under side collision load
Solution Approach 1:
The cross member is segmented into multiple portions along its length, with each portion having different thickness specifications. The first portion (near side sill) has greater thickness to resist deformation, while the second portion (central) has reduced thickness to lower weight and air resistance, effectively dividing the structural requirements into zones.
Solution Approach 2:
Different portions of the cross member are given different local qualities in terms of thickness and strength. The first portion near the side sill maintains greater thickness for high strength where collision loads are concentrated, while the second portion has reduced thickness to minimize air resistance and weight, matching structural properties to local functional requirements.
2Reliability
If a cross member is used to receive side collision load and prevent B pillar intrusion, then occupant safety is improved, but the side collision load concentrates on the floor tunnel with huge cross-section, causing ineffective load distribution
Solution Approach 1:
The floor structure is segmented into multiple load-bearing elements including the cross member, floor upper frame, and side sill portions. This segmentation distributes the collision load across multiple paths rather than concentrating it on the floor tunnel, improving both safety and load distribution effectiveness.
Solution Approach 2:
The cross member acts as an intermediary element that receives the side collision load from the side sill and transfers it to the floor upper frame and other structural components. This intermediary function prevents direct concentration of load on the floor tunnel while maintaining effective load distribution throughout the vehicle body.
3Ease of manufacture
If the cross member has uniform thickness throughout, then manufacturing is simplified, but the cross member deforms unexpectedly under side collision load when floor panels are lowered
Solution Approach 1:
The cross member transitions from uniform thickness to variable thickness, with the first portion near the side sill having greater thickness for deformation resistance and the second portion having reduced thickness for weight reduction. This local quality variation maintains manufacturing feasibility while improving structural performance under collision loads.
Solution Approach 2:
The thickness parameter of the cross member is changed along its length to optimize performance. The first portion maintains greater thickness for strength, while the second portion reduces thickness to minimize air resistance and weight, demonstrating parameter optimization to balance manufacturing ease with structural requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively distributes and transfers side collision loads, reducing the risk of B pillar intrusion and minimizing impact on occupants by controlling deformation and maintaining structural integrity.
Implementation Method 1
the fragile portion crushes first under a side collision load causing inward falling deformation of the side sill and thereby absorbs energy of the side collision
Data Source
AI summary
A vehicle-body structure that effectively distributes and transfers a side collision load in the vehicle width direction. A cross member includes a cross member top face facing a floor panel, and a cross member front face and a cross member rear face extending from respective ends in a front-rear direction of the cross member top face to the floor panel. A reinforcement member is at a side sill-side end of the cross member top face of the cross member, and a fragile portion extending in the vehicle front-rear direction is provided at a position at a side sill-side end of the cross member and overlapping the reinforcement member. The fragile portion is selected from a cutout, a bead, and a hole. The reinforcement member is a seat mounting bracket, and the fragile portion is on a vehicle-width-direction outer side of a seat mounting surface of the seat mounting bracket.