arXiv subjects

Asifur Rahman

Publications and source records attributed to Asifur Rahman.

3 recordsLinked to original sources

arXiv2026

Mechanism-based metamaterials with microstructurally invariant shape-change

Metamaterials with floppy modes called mechanisms are a burgeoning template for shape-morphing systems and structures across scales. Here, we present a design recipe that transforms an arbitrary plane tiling into a 2D kirigami pattern with a single degree-of-freedom mechanism motion, greatly expanding the known library of mechanism-based designs. We reveal that these kirigami patterns, when deformed along their mechanism, have a bulk shape change invariant to the underlying microstructure of the pattern. Experimental observations confirm this unusual kinematic prediction in illustrative classes of designs. We also exploit this invariance to elicit different elastic responses in patterns with identical bulk shape change. Finally, we discuss generalizations to compact and non-planar kirigami, as well as 3D metamaterials, highlighting the broad applicability of our new approach to design.

cond-mat.soft↗

arXiv2025

Node-to-node contact-friction problems using run-time parameter updates on a conventional force-deformation finite element

A novel implementation of the traditional node-to-node Coulomb contact-friction problem is presented that utilizes run-time parameter updates on conventional elasto-plastic elements. The two-noded elements are defined by an independent uniaxial force-deformation (or constitutive) relation in each degree of freedom. The location of the two nodes may or may not be coincident. A parameter is a pointer to a value (nodal geometry, element property, material property, etc.) in the finite element domain that can be controlled by the user. Parameters that control the frictional interface normal and tangential responses are updated based on contact detection, and eliminate the need for adding new source code to the finite element library of a given software. The run-time algorithm for updating both an elastic and elasto-plastic force-deformation element to achieve a penalty-based contact-friction model is presented. Static and dynamic cases were investigated for a two-noded unit process and compared with the results obtained from closed-form solutions. Multiple interface elements were then used for the sliding, tipping, and rocking responses of a rigid block on rigid foundation. Finally, several case studies were investigated, and the findings were compared with the experimental results or solutions from the literature. The proposed friction-contact implementation can be deployed in larger finite element models, and parameter updates facilitate implementation of a wider array of friction models by changing only the constitutive model.

physics.app-ph↗

arXiv2024

Shape-retaining beam-like morphing structures via localized snap through

In this study, we present a concept of morphing structure -- featuring an arch mounted on a compliant base -- that can be reconfigured via snap-through buckling and leverages bistability to retain its morphed shape. We show that one-dimensional arrays of such units yield beam-like structures that, upon localized snapping, can attain multiple, morphologically distinct stable shapes. Units are modeled using discrete elastic rods, a reduced-order formulation for beams and beam structures, and the results are validated via experiments. We leverage our model to understand the influence of the geometrical design parameters on the response and final shape of a unit. We then show that the morphed shapes of arrays of units can be predicted by concatenating results of simulations on single units, and leverage this idea to inverse-design structures that can be snapped into target stable shapes. Ultimately, our work suggests an up-scalable way to create shape-retaining morphing structures with target stable shapes.

physics.app-ph↗