Longitudinal Crash Member With Internal Guide Against Buckling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Energy absorbing devices in motor vehicles face limitations in deformation guidance and energy absorption due to high slenderness ratios, leading to potential buckling and reduced energy dissipation, especially when the slenderness ratio exceeds 25, resulting in catastrophic damage and inefficient energy absorption.
Innovation Solution
An energy absorbing device design featuring a hollow longitudinal member with a longitudinal guide, where the guide's length to member length ratio is between 1/5 and 3/5, incorporating structural weaknesses and a guide wall thickness of 1-4 mm, ensures controlled deformation and maximized energy absorption by promoting fold formation along the axis during impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the slenderness ratio of the energy absorbing device is increased to fit limited space, then the device can link mechanical parts at greater distances, but the device becomes prone to generalized buckling under compressive load
Solution Approach 1:
The energy absorbing device is divided into multiple segments or sections along its length, with each segment capable of independent deformation. This segmentation prevents generalized buckling by localizing deformation to specific segments while maintaining overall structural integrity, allowing the device to achieve high slenderness ratio without catastrophic failure
Solution Approach 2:
Internal guides or support structures are introduced as intermediary elements within the hollow longitudinal member. These intermediaries provide lateral support to prevent buckling of the slender structure while allowing controlled axial deformation, enabling the device to maintain reliability at high slenderness ratios
2Reliability
If local alterations are introduced to prevent generalized buckling, then localized buckling is forced to dissipate energy, but the load capacity is reduced to a maximum level
Solution Approach 1:
The device incorporates local variations in wall thickness, material properties, or cross-sectional geometry at specific locations along the longitudinal member. These local quality changes create predetermined zones that buckle at lower loads to dissipate energy, while other sections maintain higher load capacity, achieving a balance between preventing generalized buckling and maintaining overall force resistance
3Stability of the object's composition
If a longitudinal guide is arranged inside the energy absorbing device to guide deformation, then axial deformation is controlled and displacement away from original axis is prevented, but the device complexity increases
Solution Approach 1:
The longitudinal guide is nested within the hollow longitudinal member, with the guide positioned coaxially or eccentrically inside the main structural element. This nesting approach provides deformation guidance while utilizing the existing hollow space, minimizing additional complexity and material requirements
4Loss of energy
If the guide length to member length ratio is optimized between 1/5 and 3/5, then energy absorption is maximized by promoting fold formation, but the design precision requirements increase
Solution Approach 1:
The optimal guide length ratio parameter (1/5 to 3/5 of member length) is established through analysis and experimentation. By defining this specific parameter range, the device achieves maximum energy absorption through controlled fold formation, while the relatively broad range (spanning 20-60% of member length) provides manufacturing tolerance that reduces precision requirements
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 optimized design enhances energy absorption by up to 14% compared to devices without a longitudinal guide, preventing generalized buckling and ensuring efficient energy dissipation through controlled folding, thereby reducing damage to the vehicle and its occupants.
Implementation Method 1
a longitudinal guide (6) extending along a second longitudinal axis (20) arranged within the longitudinal member (4) and suitable for guiding the deformation of the longitudinal member (4) in case of an impact
Implementation Method 2
these energy absorbing devices are arranged to be deformed according to a specific kinematic, when the force applied on the device is greater than a predetermined value, such that the deformed material dissipates a part of the impact energy
Implementation Method 3
deforming the energy absorbing devices along their main axis such that the material of the energy absorbing devices forms folds while absorbing energy
Implementation Method 4
When the slenderness ratio λ is above 25, the energy absorbing device is prone to generalized failure of the part by buckling under compressive load
Data Source
AI summary
An energy absorbing device is designed to increase the amount of absorbed energy and control the deformation of the device in case of an impact. The energy absorbing device consists in a hollow longitudinal member extending along a first longitudinal axis and a longitudinal guide extending along a second longitudinal axis, arranged within the longitudinal member and suitable for guiding the deformation of the longitudinal member in case of an impact. The length ratio between the longitudinal guide and the member is comprised between the values of 1/5 and 3/5.