Frame Member Hardness Gradient for Crash Deformation and Load Resistance
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Solution Overview
Problem
Frame members made of high-strength materials like high-tensile steel sheets face limitations in achieving both improved deformation capability and load resistance during collisions, as existing technologies with partially changed hardness struggle to balance these requirements effectively.
Innovation Solution
A frame member design featuring a softening layer on the corner and side wall sections, with specific hardness gradients and thickness ratios, to enhance deformation capability while maintaining high load resistance, achieved through careful control of the bending radius and distribution of the softening layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-tensile steel sheet is used as the material of the frame member, then load resistance is improved, but deformation capability deteriorates
Solution Approach 1:
The patent applies local quality by creating a softening layer with different hardness properties at specific locations (corner sections and side wall sections) while maintaining high hardness in other areas. The softening layer has a hardness gradient where the surface hardness is 0.5-0.9 times the central section hardness, and the layer thickness is 2-20% of the sheet thickness. This localized property variation allows the frame member to exhibit both high load resistance (from the high-hardness central section) and good deformation capability (from the softer surface layer) in different regions simultaneously.
2Ease of manufacture
If a softening layer is provided to improve deformation capability, then deformation capability is improved, but load resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hardness gradient and thickness parameters of the softening layer. The surface hardness is maintained at 0.5-0.9 times the central section hardness (not too soft), and the layer thickness is limited to 2-20% of the sheet thickness (not too thick). Additionally, the bending radius R is controlled to satisfy R/t ≤ 2.5. These parameter optimizations ensure that the softening layer provides sufficient deformation capability while the high-hardness central section and controlled geometry maintain adequate load resistance.
3Ease of manufacture
If the softening layer thickness is increased to improve deformation capability, then deformation capability is improved, but load resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the softening layer thickness to be within 2-20% of the sheet thickness. This controlled thickness range ensures that the softening layer is thick enough to provide deformation capability at the surface while remaining thin enough to maintain load resistance through the high-hardness central section. The specific thickness ratio parameter allows balancing the competing requirements of deformation and load-bearing functions.
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 proposed frame member design significantly improves both deformation capability and load resistance during collisions, ensuring effective energy absorption and reduced stress concentration, thereby preventing breakage and maintaining high load resistance across various stages of impact.
Implementation Method 1
the frame member needs to behave in a desired deformation mode to efficiently absorb the impact
Implementation Method 2
ensuring effective energy absorption and reduced stress concentration
Implementation Method 3
Hardness of a sheet-thickness-direction central section in a portion where the softening layer is provided is greater than or equal to 400 Hv, and the softening layer is an area having hardness smaller by at least 10 Hv than the hardness of the sheet-thickness-direction central section
Data Source
AI summary
In a frame member, the hardness of a sheet-thickness-direction central section in a portion where a softening layer is provided is greater than or equal to 400 Hv, the softening layer has hardness smaller by at least 10 Hv than the hardness of the sheet-thickness-direction central section in the portion where the softening layer is provided, the thickness of the softening layer is greater than or equal to 2% of the sheet thickness but smaller than 20% of the sheet thickness, the hardness of the softening layer at the surface is greater than or equal to 0.5 times the hardness of the sheet-thickness-direction central section but smaller than 0.9 times the hardness of the sheet-thickness-direction central section, the softening layer has a first hardness changing area and a second hardness changing area, an absolute value ΔHv1 of a change in hardness of the first hardness changing area in the sheet thickness direction is greater than an absolute value ΔHv2 of a change in hardness of the second hardness changing area in the sheet thickness direction, and R/t≤2.5 is satisfied, where R represents the bending radius of the corner section, and t represents the sheet thickness of the corner section.