Negative Stiffness Shell Structure for High-Load Energy Dissipation
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Solution Overview
Problem
Existing metamaterial structures that exhibit negative stiffness are limited by small force thresholds and energy dissipation capabilities, making them unsuitable for applications requiring higher forces or energy dissipation, such as impact protection and blast protection.
Innovation Solution
A shell structure designed to exhibit negative stiffness behavior with higher force thresholds and energy dissipation capabilities, featuring a dome-shaped member supported by a continuous annular sidewall that transitions from a convex to a concave shape under load, allowing for significant energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional honeycombs and beams are used to display negative stiffness, then the structure can achieve negative stiffness behavior, but the force threshold and energy dissipation capability remain small
Solution Approach 1:
The patent employs a dome-shaped shell structure with convex exterior surface that transitions to concave shape under load. This curvature-based design enables negative stiffness behavior while significantly increasing the force threshold compared to conventional linear beams or honeycombs. The spherical/dome geometry allows the structure to sustain higher forces before buckling and dissipate more energy through the snap-through transition.
Solution Approach 2:
The patent utilizes composite material construction for the shell structure, combining materials with different properties to achieve both the desired negative stiffness behavior and enhanced force threshold. The composite structure allows optimization of both strength and energy dissipation characteristics while maintaining the bistable convex-concave transition capability.
2Loss of energy
If existing negative stiffness beams are used, then the structure can damp sound and vibration, but the energy dissipation capability is insufficient for impact and blast protection
Solution Approach 1:
The dome-shaped shell structure with its curved geometry provides significantly higher energy dissipation capability during the snap-through transition from convex to concave shape. The curvature allows the structure to absorb and dissipate large amounts of energy from impact and blast loads, far exceeding the capability of conventional linear beams while maintaining structural integrity.
Solution Approach 2:
The patent exploits the bistable phase transition of the shell structure between convex and concave configurations. This phase transition mechanism enables sudden, large-scale deformation that dissipates substantial energy during impact events. The structure transitions between two stable states, absorbing energy during the transition process and providing superior impact and blast protection.
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 designed shell structure achieves higher force thresholds and energy dissipation compared to conventional honeycombs and beams, enabling its use in applications such as impact protection, blast protection, and energy dissipation systems.
Implementation Method 1
The shell portion is configured for movement in response to a load being applied to an exterior of the shell portion from the first position to a second position in which the shell portion has a concave shape while continuing to absorb energy
Implementation Method 2
The base portion is constructed to resist movement of the shell portion from the first position to the second position by resolving the load applied to the shell portion and transferred to the base portion at the connection of the perimeter edge base portion into a hoop stress resisted by the base portion
Data Source
AI summary
A negative stiffness shell has a convex first position, but can transition or snap to a concave second position under a force applied to the exterior surface of the shell in the convex first position. During the transition, the shell exhibits negative stiffness that permits a large amount of energy to be absorbed. The negative stiffness shell can withstand a high initial force threshold prior to transitioning. In the second, concave position the shell can still resist force. Moreover, it is possible for the shell to revert back to the first, convex position with minimal plastic deformation for subsequent use. The negative stiffness shells can be used collectively and/or in layers to increase the efficiency of the overall negative stiffness shell unit.