arXiv subjects

Bir Bahadur Chaudhary

Publications and source records attributed to Bir Bahadur Chaudhary.

3 recordsLinked to original sources

arXiv2026

Multi-Material Topology Optimization for Targeted Structural Dynamic Vibration Attenuation

Resonance-induced excessive vibrations can degrade performance, reduce reliability, and shorten the service life of engineering structures. To reduce the risk of resonance, structural natural frequencies are generally engineered to be shifted away from excitation frequencies. To achieve these frequency shifts, topology optimization provides a systematic approach to tailor structural stiffness and mass as an effective inverse design approach. Multi-material topology optimization exploits the high-dimensional design space of spatially varying material constituents by simultaneously optimizing material selection and spatial distribution over the design domain, offering great flexibility in controlling natural frequencies. This study proposes a multi-material topology optimization that attenuates excessive structural dynamic vibrations in free-vibration scenarios via a novel multivariate weight-based interpolation method. Additionally, to address non-smoothness due to mode switching amid optimization, we employ a bound formulation with an auxiliary scalar design variable to replace the max-min eigenvalue objective with constraints on individual eigenvalues. Furthermore, we study and compare three optimization formulations for multi-material design to attenuate vibrations, including maximizing fundamental eigenfrequency, maximizing the gap between adjacent eigenfrequencies, and excluding frequencies from targeted frequency bands, which are smoothly approximated by a proposed rational polynomial formulation. Numerical examples are presented to demonstrate the effectiveness and applicability of our proposed method.

cs.CE↗

arXiv2026

Multi-Material Topology Optimization of Phononic Crystals for Targeted Elastic Wave Bandgap

Phononic crystals are periodic elastic structures that exhibit frequency bandgaps within which elastic waves cannot propagate. The formation and width of these bandgaps depend on the spatial distribution of material properties within periodic phononic unit cells. In this work, we propose novel topology optimization formulations to achieve multi-material design of phononic crystals for bandgap optimization at targeted frequencies, where we discover the influence of spatially varying properties of base materials on the band structures that block and permit elastic wave propagation. Specifically, we model wave propagation by Floquet-Bloch theory and solve the resulting eigenvalue problem by the finite element method along the boundary of the irreducible Brillouin zone. We first propose a multivariate weight-based method via a novel interpolation scheme that maps the design variables of an arbitrary number of candidate materials into effective density and stiffness for elastic wave-propagation calculations, where bandgaps arise from the contrast in the stiffness and inertia among material constituents. We then develop two formulations for bandgap optimization. The first formulation maximizes the gap between two adjacent frequency bands using a bound-based approach, where we introduce two auxiliary scalar variables as additional design variables and incorporate them directly into the design objective, yielding a linear, differentiable design objective, with the eigenfrequencies entering the formulation through associated constraints. The second formulation places a bandgap over a user-defined target frequency range through a dynamic band-pairing strategy, where we adaptively identify the relevant pair of adjacent bands amid optimization iterations. Towards the end, we validate the bandgap performance of our designs against the transmission loss spectra computed from COMSOL Multiphysics.

cs.CE↗

arXiv2022

Design of Chemical Propellant Thruster to Deorbit Nano satellite: StudSat II

An increase in satellite application has skyrocketed the number of satellites, especially in the low earth orbit (LEO). The major concern today is that these satellites become debris after the end of life, negatively affecting the space environment. As per the International Guidelines of the European Space Agency, it is mandatory to deorbit the satellite within 25 years of its end of life. This paper is aimed to design the solid chemical propellant thruster to deorbit the StudSat II from its original orbit to the lower orbit. StudSat II carries the heritage of StudSat I, successfully launched on 12th July 2010 AD, and is the first Pico Satellite in India by the undergraduate students of seven engineering colleges. This paper explains how a solid monopropellant thruster could be used to deorbit the satellite after the end of life with the least difficulty compared to other active and passive methods of deorbiting. The deorbiting mechanism consists of a solid propellant, Convergent Divergent nozzle, ignition system, and electronic actuators. The components of the thruster were designed in the CATIA V5, and the combustion studies and flow analysis were done in ANSYS. The concept of Hohmann transfer was used to deorbit the satellite, and STK was used to simulate it.

astro-ph.EP↗