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1. Systematic Variation of Friction of Rods

   https://doi.org/10.1115/1.4055544  

   Ibrahim Khalil, Md; Tong, Dezhong; Wang, Guanjin; Khalid Jawed, Mohammad; Khoda, Bashir (November 2022, Journal of Applied Mechanics)

   Abstract The mechanical response of a knot tied in elastic rods strongly depends on the frictional force due to rod–rod contact. The behavior of a knot can be qualitatively different based on the frictional coefficient of the elastic rod. Systematic variation of friction during rod–rod contact is a crucial component of any experimental design to uncover the underlying ingredients behind the mechanics of knots. In this paper, we demonstrate a novel process of controlling the friction of a continuous rod by adhering non-spherical inorganic micro-particles. Polymeric binder is used to deliver the particles as asperities over the rod substrate and by controlling their size and distribution the coefficient of friction of the rod is determined. In parallel, numerical simulations with the discrete elastic rods algorithm are used to reproduce the experimental observations. Tabletop experiments are performed where overhand knots with a variety of unknotting numbers are pulled tight. The force–extension curve of these experiments shows that the proposed process can successfully tune the friction between rods. 

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2. Effect of Withdrawal Velocity on Particle Entrainment From Density Mismatched Mixture

   https://doi.org/10.1115/MSEC2022-85745  

   Shovon, S. M.; Khalil, Ibrahim; Alam, Adeeb; Khoda, Bashir (June 2022, Proceedings of the ASME 2022 17th International Manufacturing Science and Engineering Conference)

   Abstract In this work, the physical phenomenon of the polydisperse micro-particle entrainment process from density mismatch mixture is investigated with the variation of substrate withdrawal speed. A liquid carrier system (LCS) is prepared by a polymer-based binder and an evaporating solvent. Nickel-based inorganic and spherical particles with a. moderate vol%. of 35% are added to the LCS solution. The cylindrical AISI 1006 mild steel wire substrate is dipped at different withdrawal speed ranging from 0.01 mms-1 to 20 mms-1. The binder vol%. is varied between 6.5% and 10.5%. Once the cylindrical substrate is extracted from the mixture, the surface coverage and the particle size are measured following the image analysis technique. The average particle size, coating thickness and the surface packing coverage by the particles are increasing with the higher withdrawal speed of the substrate. We observed relatively low size of particles (< 10 micrometers) as well as low surface coverage (∼33%) when the withdrawal speed remains at 0.01 mm/s. However, with high withdrawal speed (20 mm/s), we found all sizes of particles present on the substrate with a surface coverage of over 90%. The finding of this research will help to understand the high-volume solid transfer technique and develop a novel manufacturing process. 

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3. Size-Based Filtration of Poly-Disperse Micro-Particle by Dipping

   https://doi.org/10.1115/MSEC2022-85680  

   Khalil, Md Ibrahim; Khoda, Bashir (June 2022, Proceedings of the ASME 2022 17th International Manufacturing Science and Engineering Conference)

   Abstract In manufacturing industries, spherical micro-particles are commonly used as (e.g., brazing powder, metal filler, and 3D printing powder) which are produced with droplet-based particle fabrication techniques. Such processes create spherical morphology but introduce polydispersity and follow a continuous exponential pattern commonly expressed with Rosin-Rammler expression. Sorting those micro-particles in a narrower size range is an important but difficult, costly, and challenging process. Here we demonstrate the successful separation of the particles from a poly-disperse mixture with a particle volume fraction of 10% by dipping process. Nickel-based micro-particles (avg. dia. 5.69 μm) are added in a binder-based liquid carrier system. To encounter the gravitational force, external kinetic energy in the form of agitation is applied to ensure the uniform dispersion of the particles. The cylindrical substrate is prepared and dipped in the ‘pseudo suspension’ to separate the particles by adhering to it. The substrate is dried, and images are taken to characterize the separated particles using image J software. A clear size distribution can be observed which is also plotted. Additionally, a relationship between the process parameter and sorted particles has been established. The proposed method is quick, controllable, and easy to implement, which can be a useful tool for sorting wide-range poly-disperse particles. 

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4. Micro-particle entrainment from density mismatched liquid carrier system

   https://doi.org/10.1038/s41598-022-14162-5  

   Shovon, S. M. Naser; Alam, Adeeb; Gramlich, William; Khoda, Bashir (June 2022, Scientific Reports)

   Abstract Micro-scale inorganic particles (d > 1 µm) have reduced surface area and higher density, making them negatively buoyant in most dip-coating mixtures. Their controlled delivery in hard-to-reach places through entrainment is possible but challenging due to the density mismatch between them and the liquid matrix called liquid carrier system (LCS). In this work, the particle transfer mechanism from the complex density mismatching mixture was investigated. The LCS solution was prepared and optimized using a polymer binder and an evaporating solvent. The inorganic particles were dispersed in the LCS by stirring at the just suspending speed to maintain the pseudo suspension characteristics for the heterogeneous mixture. The effect of solid loading and the binder volume fraction on solid transfer has been reported at room temperature. Two coating regimes are observed (i) heterogeneous coating where particle clusters are formed at a low capillary number and (ii) effective viscous regime, where full coverage can be observed on the substrate. ‘Zero’ particle entrainment was not observed even at a low capillary number of the mixture, which can be attributed to the presence of the binder and hydrodynamic flow of the particles due to the stirring of the mixture. The critical film thickness for particle entrainment is$${h}^{*}=0.16a$$ $h^{\ast }=0.16a$for 6.5% binder and$${h}^{*}=0.26a$$ $h^{\ast }=0.26a$for 10.5% binder, which are smaller than previously reported in literature. Furthermore, the transferred particle matrices closely follow the analytical expression (modified LLD) of density matching suspension which demonstrate that the density mismatch effect can be neutralized with the stirring energy. The findings of this research will help to understand this high-volume solid transfer technique and develop novel manufacturing processes. 

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5. PREDICTIVE MODELING OF INORGANIC 3C-SiC FRICTION MATERIALS USING MOLECULAR DYNAMICS SIMULATION

   https://doi.org/10.1615/IntJMultCompEng.2022043612  

   Zhang, Yizhan; LeNeave, Cortney; Yi, Yun-Bo (January 2023, International Journal for Multiscale Computational Engineering)

   Metallic friction materials currently used in industry may adversely impact the environment. Substitutions for metals in friction materials, on the other hand, can introduce operational safety issues and other unforeseeable problems such as thermal-mechanical instabilities. In this work, a molecular dynamics model has been developed for investigating the effects of material composition, density, and surface asperities on the tribological properties of inorganic 3C-SiC under various contact conditions at the atomic level. Predictions on the following results have been made: (1) elastic modulus, (2) tensile strength, (3) thermal conductivity, and (4) friction coefficient. The research findings can help improve the design of metal-free friction materials against thermal-mechanical failures. Parametric studies were performed by varying a number of conditions including (1) ambient temperature, (2) sliding speed, (3) crystal orientation, (4) asperity size, (5) degree of asperity intersection, (6) types of loading, and (7) surface contact. Plastic deformation and material transfer were successfully modeled between two sliding pairs. Some of the computational results were validated against existing experimental data found in the literature. The evaluation of wear rate was also incorporated. The model can easily be extended to deal with other nonmetallic friction composites. 

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