Energy dissipation using negative stiffness shells
AssigneeThe Curators of the University of Missouri
InventorsMohamed El-Gawady, Yasser Darwish
Life of this patent
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Abstract
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.
Claims15
An energy dissipation device for use in absorbing energy associated with an impact to provide protection for a structure, the energy dissipation device comprising a shell portion having a convex shape in a first configuration that defines an interior cavity, the shell portion having a perimeter edge extending in a closed loop around the periphery of the shell portion, and a base portion including a mounting edge connecting the perimeter edge of the shell portion to the base portion, the mounting edge extending in a closed loop around the shell portion and the perimeter edge of the shell portion is attached to the mounting edge along at least a majority of the closed loop of the mounting edge, the shell portion being configured for movement in response to a load being applied to an exterior of the shell portion from the first configuration to a second configuration in which the shell portion has a concave shape while continuing to absorb energy, and being configured to return to the first configuration from the second configuration upon removal of the load, the base portion being constructed to resist movement of the shell portion from the first configuration to the second configuration 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, wherein the shell portion and base portion are constructed to exhibit negative stiffness behavior over at least a majority of a transition of the shell portion from the first configuration to the second configuration.
A hybrid profile energy dissipating device comprising a shell portion having a convex shape in a first configuration that defines an interior cavity and a base portion, the shell portion including a first member and a second member, the first member having a different profile in cross section than the second member, the second member being connected to the base portion and the first member being connected to the second member to cooperatively form a dome-shaped member, the first member of the shell portion being configured for movement in response to a load at a first threshold being applied to an exterior of the shell portion from the first configuration to a second configuration in which the first member of the shell portion has a concave shape while continuing to absorb energy, and the second member of the shell portion being configured for movement in response to a load at a second threshold higher than the first threshold being applied to an exterior of the shell portion from the first configuration to a second configuration in which the second member of the shell portion also has a concave shape while continuing to absorb energy, whereby the energy dissipation device exhibits at least two peaks of force thresholds with large energy dissipation capability.
A hybrid profile energy dissipating device comprising a shell portion having a convex shape in a first configuration that defines an interior cavity, the shell portion including a first member and a second member, the first member having a different profile in cross section than the second member, the profile of the first member of the shell portion having a smaller radius of curvature than the radius of curvature of the profile of the second member of the shell portion, the first member of the shell portion being configured for movement in response to a load at a first threshold being applied to an exterior of the shell portion from the first configuration to a second configuration in which the first member of the shell portion has a concave shape while continuing to absorb energy, and the second member of the shell portion being configured for movement in response to a load at a second threshold higher than the first threshold being applied to an exterior of the shell portion from the first configuration to a second configuration in which the second member of the shell portion also has a concave shape while continuing to absorb energy, whereby the energy dissipation device exhibits at least two peaks of force thresholds with large energy dissipation capability.
Dependencies are inferred from the claim text.