arXiv subjects

G. K. Ananthasuresh

Publications and source records attributed to G. K. Ananthasuresh.

5 recordsLinked to original sources

arXiv2026

A passive universal grasping mechanism based on an everting shell

A passive monolithic compliant grasping mechanism that works based on the eversion of an elastically deformable bistable shell is conceptualized. It comprises grasping arms made of beam segments that work in conjunction with the everting shell. The grasper is capable of picking up a stiff object of any shape up to a maximum size and weight. The bistable shell everts upon contact with the object to enable the grasping arms envelop the object forming an enclosure. The mechanism then stays in that configuration until it is actuated again to turn the shell back to its original configuration and thereby opening the enclosure to release the object. The stiffness of the arms decides the payload of the mechanism. The size of the arms decides the largest object that can be grasped and held. The arms have distributed compliance so that they can conform to the shape of the object without applying undue force on it.

cs.RO↗

arXiv2025

A hinge effect that anomalously decreases the stiffness of slender fiber-reinforced composite structures

We present experimental evidence for an anomalous decrease in stiffness in a fiber-reinforced polymer composite because of the embedded fiber. A shell with carbon fiber showed about 20% less stiffness and 100% more strength under compressive loading. We ruled out the role of debonding of fiber due to imperfect impregnation by using a fiber-pullout test, which revealed that the fiber-matrix interface is strong in the direction of the fiber. Therefore, we hypothesize that a fiber allows the matrix material to rotate around it as in a hinge. We corroborate this phenomenon, which we call the hinge effect, with analytical modelling and experimental data for small and large deformations of a fiber embedded in slender composite beams. We also demonstrate the design of foldable and deployable sheets with hill and valley folds enabled by the embedded fibers. Moreover, the hinge effect warrants further research into physics of how fibers in slender composite structures give rise to the anomalous flexibility. This effect can be gainfully used in designing novel origami structures and compliant mechanisms should be flexible and strong.

cond-mat.soft↗

arXiv2023

Selectively embedding multiple spatially steered fibers in polymer composite parts made using vat photopolymerization

Fiber-Reinforced Polymer Composite (FRPC) parts are mostly made as laminates, shells, or surfaces wound with 2D fiber patterns even after the emergence of additive manufacturing. Making FRPC parts with embedded continuous fibers in 3D is not reported previously even though topology optimization shows that such designs are optimal. Earlier attempts in 3D fiber reinforcement have demonstrated additively manufactured parts with channels into which fibers are inserted. In this paper, we present 3D printing techniques along with a printer developed for printing parts with continuous fibers that are spatially embedded inside the matrix using a variant of vat photopolymerization. Multiple continuous fibers are gradually steered as the part is built layer upon layer instead of placing them inside channels made in the part. We show examples of spatial fiber patterns and geometries built using the 3D printing techniques developed in this work. We also test the parts for strength and illustrate the importance of spatially embedding fibers in specific patterns.

cond-mat.soft↗

arXiv2022

Switching Dynamics of Shallow Arches

This paper presents an analytical method to predict the delayed switching dynamics of nonlinear shallow arches while switching from one state to another state for different loading cases. We study an elastic arch subject to static loading and time-dependent loading separately. In particular, we consider a time-dependent loading that evolves linearly with time at a constant rate. In both cases, we observed that the switching does not occur abruptly when the load exceeds the static switching load, rather the time scale of the dynamics drastically slows down; hence there is a delay in switching. For time-independent loading, this delay increases as the applied load approach the static switching load. Whereas for a time-dependent loading, the delay is proportional to the rate of the applied load. Other than the loading parameters, the delay switching time also depends on the local curvature of the force-displacement function at the static switching point and the damping coefficient of the arch material. The delay switching occurs due to the flatness of the energy curve at static switching load. Therefore, we linearize the arch near the static switching point and get a reduced nonlinear ordinary differential equation to study the switching dynamics of the arch. This reduced equation allows us to derive analytical expressions for the delay switching time of the. We further compare the derived analytical results with the numerical solutions and observed a good agreement between them. Finally, the derived analytical formulae can be used to design arches for self-offloading dynamic footwear for diabetics.

math.DS↗

arXiv2021

Towards Optimal Heterogeneity in Lattice Structures

We present a multi-phase design parameterization to obtain optimized heterogeneous lattice structures. The 3D domain is discretized into a cubical grid wherein each cube has eight distinct unit cell types or phases. When all phases are present, the domain resembles a densely connected ground structure. The cross-section area of beam segments in lattice units, modelled using Timoshenko beam theory, are the design variables. All beam segments in a particular lattice phase have the same area of cross-section to keep the number of design variables low. The optimization problem is formulated for stiff structures and is solved using the optimality criteria algorithm. We present a case study to show the superiority of topology-optimized heterogeneous structures over uniform lattices of a single phase. In order to interpret the phase composition, we perform four basic load tests on single phases, namely, tension or compression, shear, bending, and torsion. The phases are ranked based on the stiffness corresponding to individual loading conditions. The results show that in the optimized structure, the local internal load configuration drives the selection of phases. We also note that micropolar elasticity captures the bulk behaviour of heterogeneous lattice structures, and helps not only to interpret the optimality of phases but also to improve the computational efficiency of the proposed optimization technique.

cond-mat.mtrl-sci↗