Slotted Hollow Bumper Cross Member for Impact Joint Integrity
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Solution Overview
Problem
Existing bumper arrangements are prone to joint connection failure between the cross member and crash boxes during a central impact, such as colliding with a pole or post, due to deformation of the cross member, leading to potential detachment.
Innovation Solution
A hollow profile cross member with slots oriented in the longitudinal direction is used, allowing for limited relative movement and reducing shear stresses, thereby relieving connection loads and preventing detachment from crash boxes, while maintaining crash performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cross member is rigid and strongly connected to crash boxes, then the connection strength is improved, but the joint may tear during central impact due to inability to accommodate deformation
Solution Approach 1:
The cross member is segmented by introducing slots (through-slots or blind slots) in the connection areas, dividing the continuous structure into sections that can move relative to each other. This segmentation allows the cross member to deform in a controlled manner during impact, preventing joint tearing while maintaining overall structural integrity.
Solution Approach 2:
The slots change the mechanical parameters of the cross member by reducing shear rigidity in specific zones. This parameter change enables the cross member to accommodate deformation through relative movement between slots, reducing stress concentration at the crash box connections during central impact.
2Reliability
If slots are introduced in the cross member connection areas, then the joint reliability during impact is improved, but the crash performance may be impaired due to reduced structural rigidity
Solution Approach 1:
Slots are introduced only in specific connection areas of the cross member where stress concentration occurs during impact, rather than throughout the entire structure. This local modification maintains the overall crash performance and structural rigidity while improving joint reliability at critical locations.
Solution Approach 2:
The slots are designed with specific dimensions (length, width, depth) that provide sufficient relative movement capability to prevent joint tearing, but are not excessive to the point of compromising overall structural integrity. The partial removal of material creates the necessary deformation freedom without overly weakening the cross member.
3Loss of energy
If the cross member deforms during impact, then the energy absorption is improved, but the joint between cross member and crash boxes may tear
Solution Approach 1:
The slots are pre-designed in the cross member connection areas to anticipate and accommodate deformation during impact. This preliminary structural arrangement allows the cross member to deform in a controlled manner through relative movement between slots, preventing joint tearing while enabling effective energy absorption.
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 enhances crash performance by preventing cross member detachment from crash boxes during impacts, maintaining dimensional stability and reducing manufacturing costs through strategic slot placement and design.
Implementation Method 1
the slot prevents the transfer of shear stresses between the front and rear walls of the cross member in selected sections of the cross member
Implementation Method 2
the crash box connection is preferably achieved by means of a material-to-material coupling, in particular by welding
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3c
AI summary
The invention relates to a bumper assembly (1) comprising a cross member (2) which is coupled to a motor vehicle via crash boxes (3), wherein the cross member (3) has connection areas (5) in which the crash boxes (3) are coupled to the cross member (2), wherein the cross member (2) is designed in cross-section as a closed hollow profile. In the connection area (5), a slot (8) oriented in the longitudinal direction (X) of the motor vehicle is formed in an upper wall (9), lower wall (13) or a central web (5) of a crash box (3) of the cross member (2).