Numerical analysis of periodic laminar and fibrous media undergoing a jamming transition

Vasios, Nikolaos; Narang, Yashraj; Aktaş, Buse; Howe, Robert D.; Bertoldi, Katia

doi:10.1016/j.euromechsol.2019.02.002

Cited by 16 publications

(10 citation statements)

References 24 publications

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“…These structures have been particularly useful in applications with long and slender elements that need variable bending stiffness in more than one direction, such as endoscopes and surgical manipulators. [ 9,15,20 ] With fiber jamming structures, a change in bending stiffness of 5:1 has been achieved. [ 8 ]…”

Section: Resultsmentioning

confidence: 99%

“…C) Representative force–deflection curve for the frictional mode in which the applied force only causes sliding between the constituents. [ 20,34 ] D) Representative force–deflection curve for the frictional deformation mode in which there is not only sliding, but also bending and/or twisting. [ 9,10,14,19 ] E–G) Contact geometries for jamming structures with grains, fibers, and layers are, respectively, points, lines, and surfaces.…”

Section: Resultsmentioning

confidence: 99%

“…For jamming structures with circular fibers under bending, the theoretical modeling of the bending stiffness is not as trivial, since different packing arrangements are possible. [ 20 ] Considering hexagonal packing (shown in Figure 3F), which achieves the highest packing density possible for circles and assumes the gaps between the fibers are negligible, we can estimate the moment of inertia of the resulting hexagon and therefore the change in stiffness upon jamming. If there are N number of fibers each with diameter d , the side dimension of the resulting hexagon will be

a = d \sqrt{\frac{N}{3}}

.…”

Section: Resultsmentioning

confidence: 99%

“…These have provided great insights on application, geometry, and scale‐specific behavior of jamming structures. [ 10,20–26 ] There have been a few studies comparing the performance of structures with different constituent geometries (e.g., layers and grains) as well, but these studies have been limited to specific applications. [ 6,27–29 ] Thus far, there has not been a global and systematic approach to the design space of jamming for target applications.…”

Section: Introductionmentioning

confidence: 99%

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A Modeling Framework for Jamming Structures

Aktaş

Narang

Vasios

et al. 2021

Adv Funct Materials

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Jamming is a structural phenomenon that provides tunable mechanical behavior. A jamming structure typically consists of a collection of elements with low effective stiffness and damping. When a pressure gradient, such as vacuum, is applied, kinematic and frictional coupling increase, resulting in dramatically altered mechanical properties. Engineers have used jamming to build devices from tunable‐stiffness grippers to tunable‐damping landing gear. This study presents a rigorous framework that systematically guides the design of jamming structures for target applications. The force‐deflection behavior of major types of jamming structures (i.e., grain, fiber, and layer) in fundamental loading conditions (e.g., tension, shear, and bending) is compared. High‐performing pairs (e.g., grains in compression, layers in shear, and bending) are identified. Parameters that go into designing, fabricating, and actuating a jamming structure (e.g., scale, material, geometry, and actuator) are described, along with their effects on functional metrics. Two key methods to expand on the design space of jamming structures are introduced: using structural design to achieve effective tunable‐impedance behavior in specific loading directions, and creating hybrid jamming structures to utilize the advantages of different types of jamming. Collectively, this study elaborates and extends the jamming design space, providing a conceptual modeling framework for jamming‐based structures.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

a = d \sqrt{\frac{N}{3}}

.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Modeling Framework for Jamming Structures

Aktaş

Narang

Vasios

et al. 2021

Adv Funct Materials

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“…Material jamming uses pressure to control the interaction between disconnected pieces of inextensible material (either granular, [ 15–19 ] planar, [ 20 ] or fibrous [ 21 ] ) enabling a transition between soft and rigid states. For example, in atmospheric conditions, particles such as sand or coffee easily slide over each other in a fluid‐like state, but when pressed together, the grains pack tightly and resist shear like a solid.…”

Section: Introductionmentioning

confidence: 99%

Jamming Skins that Control System Rigidity from the Surface

Shah

Yang

Yuen

et al. 2020

Adv Funct Materials

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Numerous animals adapt their stiffness during natural motions to increase efficiency or environmental adaptability. For example, octopuses stiffen their tentacles to increase efficiency during reaching, and several species adjust their leg stiffness to maintain stability when running across varied terrain. Inspired by nature, variable‐stiffness machines can switch between rigid and soft states. However, existing variable‐stiffness systems are usually purpose‐built for a particular application and lack universal adaptability. Here, reconfigurable stiffness‐changing skins that can stretch and fold to create 3D structures or attach to the surface of objects to influence their rigidity are presented. These “jamming skins” employ vacuum‐powered jamming of interleaved, discrete planar elements, enabling 2D stretchability of the skin in its soft state. Stretching allows jamming skins to be reversibly shaped into load‐bearing, functional tools on‐demand. Additionally, they can be attached to host structures with complex curvatures, such as robot arms and portions of the human body, to provide support or create a mold. We also show how multiple skins can work together to modify the workspace of a continuum robot by creating instantaneous joints. Jamming skins thus serve as a reconfigurable approach to creating tools and adapting structural rigidity on‐demand.

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Layer Jamming of Magnetorheological Elastomers for Variable Stiffness in Soft Robots

Atakuru,

Züngör,

Samur

2024

Exp Mech

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Background One of the biggest challenges in soft robotics is the variability and controllability of stiffness. Jamming-based approaches have been of interest to change stiffness dramatically by increasing friction between grains, layers, or fibers. Besides, magnetorheological elastomers (MREs) that exhibit magnetic field-dependent viscoelasticity have significant potential as a stiffness variation material. This study investigates the unique mechanics of magnetic jamming of MRE sheets exploring stiffness change both due to jamming and variable viscosity. Methods Sample MREs and flexible neodymium-iron-boron (NdFeB) magnets are manufactured. Uniaxial tensile tests supported with digital image correlation are performed to characterize the materials. Multi-layer jamming structures comprised of MREs and NdFeB magnets are developed and validated through 3-point bending experiments and finite element simulations. Results Results show that the stiffness of the multi-layer structure is higher under magnetic field. Furthermore, the stiffness change is increased when MREs are used instead of PDMS as layers. Conclusion This study proves the concept of magnetic jamming of MRE layers. The results are crucial for the possible soft robotic implementation of the proposed hybrid stiffening approach combining jamming with viscoelasticity modification.

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Numerical analysis of periodic laminar and fibrous media undergoing a jamming transition

Cited by 16 publications

References 24 publications

A Modeling Framework for Jamming Structures

A Modeling Framework for Jamming Structures

Jamming Skins that Control System Rigidity from the Surface

Layer Jamming of Magnetorheological Elastomers for Variable Stiffness in Soft Robots

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