Rear Underfloor Structure Using a Tailor-Welded Blank
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Solution Overview
Problem
Existing rear underfloor structures in motor vehicles are heavy, costly to manufacture, and require multiple parts, which complicates assembly and increases production time, while not adequately addressing safety concerns during crashes.
Innovation Solution
A single tailor-welded blank is used to create a rear underfloor structure with integrated side members and cross members, made from press-hardening steel with aluminum-based coatings and emissivity increasing layers, optimized through hot stamping to achieve high strength and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple individual parts are used to construct the rear underfloor structure, then the structural complexity and assembly steps increase, but the manufacturing precision and safety performance can be improved through multiple forming operations
Solution Approach 1:
The patent merges multiple individual parts (side members and cross members) into a single integrated rear underfloor structure made from one tailor-welded blank. This combining approach reduces the number of parts and assembly steps while maintaining structural precision through optimized forming operations on the integrated structure.
Solution Approach 2:
The patent segments the blank into different zones with varying material properties (different thicknesses and steel grades) within the single integrated structure. This allows different regions to be optimized for specific functions (crash resistance, weight reduction, structural strength) while maintaining overall structural precision.
2Manufacturing precision
If multiple forming operations and assembly steps are used, then the manufacturing precision can be improved, but the productivity decreases and production time increases
Solution Approach 1:
The patent combines multiple forming operations into a single stamping process that forms the entire rear underfloor structure (side members and cross members) from one blank in one operation. This eliminates multiple assembly steps and significantly improves productivity while maintaining geometric precision through optimized tooling and process parameters.
Solution Approach 2:
The patent performs preliminary actions by pre-assembling the tailor-welded blank before the final stamping operation. The sub-blanks are welded together in advance with optimized seam positions, allowing the subsequent stamping operation to form the final structure in one step without requiring post-forming assembly operations.
3Reliability
If traditional multi-part structures are used, then the safety performance can be optimized through multiple forming operations, but the vehicle weight increases
Solution Approach 1:
The patent applies local quality by creating zones with different material properties (thickness and steel grade) in specific locations of the structure. High-strength, thicker material is used in crash-critical areas (front portions, attachment zones) while lighter, thinner material is used in non-critical areas, optimizing crash resistance while reducing overall weight.
Solution Approach 2:
The patent uses composite construction by combining different steel grades and thicknesses within a single integrated structure. The tailor-welded blank comprises sub-blanks of different materials that are welded together, creating a composite structure with optimized weight-to-strength ratio for crash resistance.
4Productivity
If a single integrated structure is used, then the productivity and weight are improved, but the manufacturing complexity of the blank increases
Solution Approach 1:
The patent segments the complex blank into manageable sub-blanks that can be separately manufactured and then welded together to form the tailor-welded blank. This segmentation approach simplifies the manufacturing of individual components while achieving the benefits of an integrated structure, reducing the overall manufacturing complexity.
Solution Approach 2:
The patent performs preliminary welding of sub-blanks to create the tailor-welded blank before the final stamping operation. This pre-assembly allows complex geometric features to be built up from simpler components, reducing the complexity of the blank manufacturing while enabling single-step formation of the final integrated structure.
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 results in a lightweight, cost-effective, and safer rear underfloor structure with improved crash resistance and manufacturing efficiency, maintaining high mechanical strength and geometric precision.
Implementation Method 1
The thickness of the interdiffusion layer in the Aluminum based metallic coated areas of the rear underfloor structure is comprised between 3 microns and 15 microns
Implementation Method 2
the tailor welded blank used to manufacture the rear underfloor structure comprises at least one sub-blank which comprises an emissivity increasing top layer on at least one side
Data Source
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AI summary
Rear underfloor structure (2) for a motor vehicle (1) comprising a first and a second side member (4) and at least one cross member (5) linking said first and second side members (4), wherein said rear underfloor structure (2) is made by stamping a single tailor welded blank (26) comprising at least two sub-blanks.