Dr. Vipin Agarwal Profile

Dr. Vipin Agarwal

at Univ of Michigan

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Publications (2)

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Proceedings Article | 22 April 2020 Presentation + Paper

The influence of geometry on origami’s deployment dynamics

Yutong Xia, Narayanan Kidambi, Vipin Agarwal, K. W. Wang

Proceedings Volume 11376, 113760L (2020) https://doi.org/10.1117/12.2556550

KEYWORDS: Numerical simulations, Mechanical engineering, Structural design

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This research investigates the effect of the geometric parameters of origami crease patterns on their deployment dynamics. In this study, we construct a dynamic model of a non-rigid Miura origami sheet based on the bar-and-hinge approach, capturing panel flexibility and inertial effects. These effects are critical in describing the dynamics of origami deployment, which are ignored in the state of the art rigid folding kinematics model. Deployment is facilitated by strain energy stored in the torsional springs at the hinged creases, and a controlled deployment velocity at one end of the Miura sheet. We theoretically and numerically analyze the deployment process of integrated Miura sheets with various geometries. Eigenvalue decomposition at different stages during the quasi-static deployment process shows that the Miura pattern’s crease length ratio and panel section angle affect the fundamental natural frequency and damping ratio. Numerical studies show that changing the crease pattern geometries results in deployment paths that may substantially deviate from a nominal Miura unfolding path under rigid folding assumptions. Examination of the theoretical model reveals how crease pattern geometries affect the apparent stiffness, offering insight into this behavior. The findings of this research enable a deeper understanding of the physics behind origami deployment and pave the way for new applications of origami-based deployable structures.

Proceedings Article | 22 April 2020 Presentation + Paper

In-situ tunable auxeticity in pressurized soft mechanical metamaterials

N. Kidambi, V. Agarwal, T. Tallman, K. W. Wang

Proceedings Volume 11376, 1137624 (2020) https://doi.org/10.1117/12.2557127

KEYWORDS: Multifunctional materials, Metamaterials, Mechanical engineering

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Mechanical metamaterials can be designed to give rise to exotic properties such as negative stiffness, negative Poisson’s ratio (auxeticity), and tailorable buckling by selectively designing the geometry of the host material. However, these behaviors are typically fixed and cannot be changed once the metamaterial has been fabricated. Motivated by the goal of post-manufactured application-specific adaptability, we present a soft mechanical metamaterial with pressurized circular voids for in-situ tunable mechanical properties. Prototypes are created by curing a two-component silicone rubber in a 3D printed mold. The circular voids are sealed at one end and independently connected to a pressure source on the opposite side, allowing any subset of the voids to be pressurized. Uniaxial compression tests are then conducted on a universal testing machine. Through selective pressurization of the voids, we demonstrate tunability of the material’s stiffness profiles and the critical loads that lead to the onset of auxeticity and/or buckling. Numerical investigations allow deeper insight, revealing that selective pressurization affects the qualitative shape of the first buckling mode and illustrating how pressurization can break the auxetic behavior of the nominal, unpressurized specimen. Overall, the outcomes demonstrate that soft elastomers with selectively pressurized voids can express quantitatively and qualitatively tunable responses, offering potential for new types of mechanical metamaterials with predictable, in-situ tunability.

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