B-pillar with Soft Zones for Lateral Collision Energy Absorption
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Solution Overview
Problem
Existing B-pillar designs in vehicles do not effectively absorb energy during a lateral collision without compromising the integrity of the weld region, which can lead to reduced passenger protection.
Innovation Solution
The B-pillar is designed with a hat-shaped member and soft zones in the side flanges that are partially hardened, allowing for deformation and energy absorption while maintaining the strength of the weld region, achieved through press hardening and spot welding with a cover plate and outer panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the B-pillar is designed with high strength throughout to prevent fracture, then the structural integrity is improved, but the energy absorption capacity through plastic deformation is reduced
Solution Approach 1:
The B-pillar is designed with non-uniform material properties: the side flanges contain soft zones with lower strength (500-1100 MPa) that enable plastic deformation for energy absorption, while other regions maintain high strength (over 1400 MPa) to prevent fracture. This local differentiation allows the pillar to simultaneously absorb energy and maintain structural integrity.
Solution Approach 2:
The B-pillar is divided into distinct zones with different material properties: soft zones in the side flanges for energy absorption and harder zones for structural support. This segmentation allows different regions to perform different functions - the soft zones deform plastically to absorb energy while the harder zones maintain overall structural integrity.
2Manufacturing precision
If the edges are trimmed after forming and hardening, then the final dimensional precision is improved, but crack formation in the weld region occurs due to reduced ductility
Solution Approach 1:
Edge trimming is performed before the press hardening process rather than after. This preliminary action allows the material to maintain higher ductility during trimming, preventing crack formation in the weld region. The trimming is done on the softer, more formable material before hardening reduces its ductility.
Solution Approach 2:
The conventional sequence of operations is inverted: instead of trimming after hardening, the trimming is performed before hardening. This reversal of the process sequence solves the contradiction by performing the trimming operation when the material is still ductile enough to avoid cracking.
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 enhances passenger protection by enabling the B-pillar to absorb maximum energy through plastic deformation without fracturing, thereby improving safety in lateral collisions.
Implementation Method 1
certain parts of its side flanges 25, 26 are not fully hardened and have a breaking strength below 1100 MPa. Portions of this kind which have not been fully hardened can be referred to as soft zones A
Implementation Method 2
The main section 20 is manufactured by press hardening, i.e. it is hot-formed and hardened from a flat blank of boron steel in one step in cooled forming tools
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a B-pillar for a vehicle including a main section (20) with a hat-shaped section (21) comprising a central flange (22), two web portions (23, 24) and two side flanges (25, 26). At least the hat-shaped section (21) is press-hardened and has a breaking strength in excess of 1400 MPa and the side flanges (25, 26) of the hat-shaped section (21) have a breaking strength below 1100 MPa along at least part of the length of the side flanges (25, 26). The B-pillar (13) includes a cover plate (40) welded to the side flanges (25, 26) of the hat-shaped section (21) so as to form a closed profile, the cover plate (40) having a breaking strength below 1100 MPa at least in the region in which it bears against the side flanges (25, 26). The side flanges (25, 26) of the hat-shaped section have a breaking strength below 1100 MPa in the region in which the side flanges bear against the cover plate (40).