Vehicle Apron Upper Member Fracture Design
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Solution Overview
Problem
Existing apron upper member structures in vehicles buckle easily under collision loads, leading to inadequate deceleration of occupants, causing them to approach the vehicle body excessively, especially during high-speed collisions.
Innovation Solution
The apron upper member is designed with a rear half of sheet metal and a front half of casting product, featuring a strength lowering portion ahead of the connection, which undergoes breaking fracture under large collision loads, increasing initial deceleration and temporarily reducing deceleration to prevent occupant approach, while the rear half absorbs subsequent loads through bending deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the apron upper member is designed to buckle smoothly under collision load, then the structure can absorb impact force, but decelerating acceleration becomes too small and occupants significantly approach the vehicle body
Solution Approach 1:
The apron upper member is divided into a front half portion (casting product) and a rear half portion (sheet metal structure). The front half portion undergoes breaking fracture to provide initial deceleration, while the rear half portion absorbs subsequent loads through bending deformation. This segmentation allows different parts to perform different functions at different stages of collision.
Solution Approach 2:
The front half portion is designed with a strength lowering portion that has different strength characteristics from the rest of the structure. This local weakening allows controlled breaking fracture at a specific location, providing the necessary initial deceleration while maintaining overall structural integrity through the rear half portion.
2Speed
If the apron upper member uses a brittle casting product, then initial deceleration increases to restrain occupants, but the structure may crash through under large collision loads
Solution Approach 1:
The structure is segmented into a front half portion made of brittle casting product and a rear half portion made of ductile sheet metal. The front half provides initial deceleration through controlled fracture, while the rear half provides reliability and prevents barrier invasion through elastic-plastic deformation.
Solution Approach 2:
The material parameters are changed along the length of the apron upper member, transitioning from brittle (casting) to ductile (sheet metal). This parameter change allows the structure to exhibit different failure modes: fracture in the front for deceleration and plastic deformation in the rear for load absorption and barrier resistance.
3Loss of time
If the strength lowering portion is positioned ahead of the connecting portion, then time for deceleration increases to suppress occupant approach, but the structure becomes more complex
Solution Approach 1:
The strength lowering portion is locally positioned ahead of the connecting portion to the rear half portion. This localized design creates a specific weak point that controls the timing and location of fracture, providing sufficient deceleration time without requiring complex overall structural modifications.
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 effectively suppresses the significant approach of occupants to the vehicle body by enhancing initial deceleration and allowing the rear half to absorb collision loads without crushing, thereby preventing barrier invasion.
Implementation Method 1
the strength lowering portion undergoes breaking fracture due to a subsequent input of a large collision load
Implementation Method 2
the rear half portion has a sheet metal structure capable of large elongation deformation, the rear half portion remains without being crushed when the front half portion undergoes breaking fracture, receives a collision load after the front half portion undergoes breaking fracture, and can absorb the collision load due to bending deformation
Implementation Method 3
a crash box which undergoes compressive plastic deformation in a vehicle front-rear direction at the time of front collision of the vehicle
Data Source
AI summary
An apron upper member of a vehicle extends from a front pillar to a front side of the vehicle, and includes: a rear half portion having a sheet metal structure and having a vehicle rear end connected to the front pillar; and a front half portion formed of a casting product, the front half portion being connected to the rear half portion, extending to the front side of the vehicle, and having a vehicle front end connected to a crash box. The front half portion has a strength lowering portion immediately ahead of a connecting portion connected to the rear half portion. This suppresses significant approach of an occupant to a vehicle body at the time of collision.