• VINAY KUMAR

      Articles written in Sadhana

    • On mechanical and thermal properties of cryo-milled primary recycled ABS

      VINAY KUMAR RUPINDER SINGH I P S AHUJA

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      The virgin thermoplastics have numerous applications in fused deposition modelling (FDM) process. Commercially, different thermoplastics are recycled through extrusion (without any reinforcement as primary (1°) recycled materials) for enhancing their reusability and sustainability. However, hitherto very littlehas been reported on mechanical and thermal properties of cryogenic (cryo) milled 1° recycled ABS (to be used on FDM-based 3D printer). In the present research article the cryo ball milling of 1° recycled ABS thermoplastichas been reported to explore the influence of cryo environment (-196 °C) on mechanical, thermal and surface properties of the ABS-based feed stock filament (prepared through screw extrusion) for further use on commercial FDM set-up (without any hardware/software change). The process parameters of cryo-milling (like frequency of vibration, milling time and grinding media weight) have been selected for investigations using Taguchi-based design of experiment (DOE). The study results show significant improvement in peak strength (PS) of the cryo-milled ABS in comparison with non-cryo-milled ABS without any degradation of thermal properties (mainly heat capacity). As regards the process parameters of cryo-milling, 30-Hz frequency, 15-min milling time and 32-g media weight are the best settings for maximum PS. The maximum value of PS observed was 61.32 MPa. The optical photomicrographs supported with 3D rendered images were captured to support the surface characteristics and porosity level in the wires (to be used as feed stock filament for FDM) prepared with cryo-milled ABS (powder samples).

    • Cut-cell-based Direct Simulation Monte Carlo method on a Cartesian grid for rarefied gas flow around complex geometries

      VINAY KUMAR U V BHANDARKAR R K SINGH ATUL SHARMA

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      The present work proposes a cut-cell-based Direct Simulation Monte Carlo (DSMC) solver, for computing rarefied flows around complex geometries on Cartesian grids, wherein analytical expression for the surface of the immersed boundary (IB) is considered to evaluate cut-cell volume as well as to implement the particle–boundary interactions. Consequently the proposed DSMC solver models an accurate collision rate in the cut cells and ensures an analytically expressed IB-based implementation of the boundary conditions at thesurface of the immersed geometry, as in the IB methods for the continuum flows. Performance of the present Cartesian cut-cell-based DSMC solver is tested on a variety of rarefied gas flows around three complex geometries (cylinder, NACA 0012 airfoil and double-wedge airfoil) for various flow speeds (ranging from Ma = 2 to 10) and degrees of rarefication (varying from Kn = 0:25 to around 0.0032). Results of our computations on Cartesian grids show a very good agreement with the corresponding DSMC results in literature computed on body-fitted grids. Furthermore, the present results show a good agreement with the corresponding experimental data in the literature. Straightforward and analytically expressed IB-based implementation in the proposed DSMC solver can make it a natural choice for its coupling with an immersed boundary method (IBM)- based continuum solver for a novel coupled IBM–DSMC method for continuum–rarefied gas flows.

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