Floor Pan Corner Reinforcement Welding for Side Impact
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Solution Overview
Problem
The existing vehicle structures are prone to floor pan separation during side impact collisions due to inadequate spot weld strength, particularly with the use of lower gauge sheet metal, which fails to resist separation forces from rocker assemblies and kick-up cross members.
Innovation Solution
A vehicle body structure incorporating a corner reinforcement (doubler) welded to the floor pan, rear rail, and kick-up cross member with three thickness resistance welds, utilizing mild steel for the floor pan and high-strength low-alloy steel for the reinforcement and kick-up cross member to enhance joint stiffness and fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lower gauge sheet metal is used in the floor pan, then vehicle weight is reduced and fuel economy is improved, but spot weld strength becomes inadequate to prevent floor pan separation in side impact collisions
Solution Approach 1:
The patent applies local quality by adding corner reinforcements (doublers) specifically at the floor pan corners where separation is most likely to occur during side impact. These reinforcements are made of higher gauge steel than the floor pan itself, creating localized strength enhancement at critical areas without requiring the entire floor pan to be thicker. This resolves the contradiction by maintaining lightweight construction overall while providing targeted strength where needed.
Solution Approach 2:
The patent employs composite materials by combining lower gauge sheet metal for the floor pan with higher gauge steel for the corner reinforcements and kick-up cross members. This composite approach allows the structure to achieve both weight reduction (through the lighter floor pan) and adequate strength (through the stronger reinforcement components), directly resolving the technical contradiction between weight and spot weld strength.
2Ease of manufacture
If spot welds are used to attach the floor pan to rocker assemblies and cross members, then manufacturing is simplified, but the welds fail under complex loading during collision events
Solution Approach 1:
The patent applies preliminary action by pre-installing the corner reinforcements (doublers) onto the floor pan before final assembly. These reinforcements are strategically positioned and attached in advance to create a strengthened attachment interface. This preliminary strengthening ensures that when the vehicle undergoes side impact, the pre-positioned reinforcements are already in place to distribute and resist the complex loading forces, preventing weld failure while maintaining the simplicity of spot welding processes.
3Weight of moving object
If the floor pan is made thinner to reduce weight, then fuel economy improves, but the floor pan becomes more susceptible to separation forces during side impact
Solution Approach 1:
The patent applies the anti-weight principle by introducing corner reinforcements that counterbalance the structural weakness created by using thinner floor pan material. These reinforcements act as counterweights to the reduced structural capacity, providing the additional force resistance needed to prevent separation during side impact while allowing the main floor pan to remain thin and lightweight for fuel economy benefits.
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
The solution effectively prevents floor pan separation by creating stronger weld nuggets and additional metal reinforcement, maintaining the thinness of the floor pan while providing enhanced resistance to side impact forces, as demonstrated in simulated oblique pole side impact tests.
Implementation Method 1
The resistance weld forms a weld nugget that is stronger than a weld nugget formed by welding the floor pan to the kick-up cross member
Data Source
AI summary
A side impact protective structure is provided for a vehicle floor pan. Right and left rear rails are attached, respectively, to right and left lateral sides of the floor pan. A kick-up cross member extends transversely between the right and left rocker assemblies. A right reinforcement is welded to the floor pan, the right rear rail, and the kick-up cross member. A left reinforcement is welded to the left rear rail, to the floor pan and the kick-up cross member. An assembly method includes the steps of selecting a thin mild steel floor pan between a thicker HSLA steel structural member and a thicker corner reinforcement and welding the components together with three thickness welds.