Hot-Stamped Closed-Section Frame Member for Buckling Resistance
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Solution Overview
Problem
Existing frame members, despite advancements in strength and buckling resistance, face challenges in achieving high energy absorption efficiency due to elastic buckling and fracture during axial loads, particularly when thinning for weight reduction.
Innovation Solution
A frame member with a closed cross-section formed by hot-stamping a steel sheet, featuring a reference flat part with controlled width and hardness standard deviation ratio, where the Vickers hardness is 300 Hv or greater and the width is 2.0 times or less the effective width, and the standard deviation ratio is less than 1.0, to prevent elastic buckling and fracture during deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the member thickness is reduced to achieve weight reduction, then the weight decreases, but the energy absorption efficiency deteriorates due to elastic buckling and fracture
Solution Approach 1:
The invention applies local quality by creating a non-uniform hardness distribution within the member thickness. The surface layer portion has a different hardness (350 Hv or more) compared to the thickness middle portion (250-350 Hv), with a controlled standard deviation ratio less than 1.0. This localized hardness variation suppresses elastic buckling at the surface while maintaining energy absorption capacity in the core, resolving the contradiction between weight reduction and energy absorption efficiency
Solution Approach 2:
The invention changes the physical parameter of hardness distribution within the member. By controlling the Vickers hardness values at different depths and their standard deviation ratio, the material properties are optimized to prevent buckling instability in thin members while maintaining sufficient ductility for energy absorption through controlled plastic deformation
2Strength
If the proof stress is increased to improve buckling resistance, then the buckling resistance improves, but the energy absorption efficiency deteriorates due to reduced ductility
Solution Approach 1:
The invention creates different mechanical properties at different locations through controlled hardness distribution. The surface layer with higher hardness (350 Hv or more) provides buckling resistance, while the thickness middle portion with lower hardness (250-350 Hv) maintains ductility for energy absorption. The standard deviation ratio control ensures a gradual transition, preventing stress concentration that would reduce overall energy absorption capacity
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 configuration enhances energy absorption performance by suppressing elastic buckling and fracture, allowing for efficient impact energy absorption even with high-strength thin members, thereby achieving excellent energy absorption efficiency.
Implementation Method 1
the frame member formed by hot-stamping a steel sheet
Implementation Method 2
suppressing elastic buckling
Implementation Method 3
energy absorption performance
Data Source
AI summary
Provided is a frame member formed by hot-stamping a steel sheet. The frame member has a closed cross section portion in which a cross section perpendicular to a longitudinal direction is a closed cross section, and the closed cross section portion has at least one flat part having a radius of curvature larger than a maximum external dimension of the cross section. A Vickers hardness of a thickness middle portion in a reference flat part is 300 Hv or greater, a width of the reference flat part is 2.0 times or less the effective width, and a standard deviation ratio obtained by dividing a standard deviation of hardness frequency distribution in a surface layer portion in the reference flat part by a standard deviation of hardness frequency distribution in the thickness middle portion in the reference flat part is less than 1.0.