The selection of the heat source model plays a significant role in numerical modelling of the GTAW process for achieving the accurate weld pool geometry. The present work involves the development of a finite element method (FEM) based 3-D heat transfer model to analyse the GTAW of Ti-6Al-4V TWB. Initially, the weld pool width for bead-on-plate GTAW was analysed using the Goldak’s double ellipsoidal heat source (DEHS) and the Avocado-shaped heat source (ASHS) models. The efficiency of each model was compared with the experimental data from the literature for three levels of welding speed and current. It was found that the ASHS model was more efficient for high-speed welding conditions, while the DEHS model provided accurate results for low-speed welding. The most accurate heat source was selected to generate the heat transfer model for GTAW of TWB with varying fillet geometries (convex, concave, and flat). The predicted weld pool geometry for these different fillets was compared with the experimental results. Further, the effect of changing the thickness ratio of the TWBs on the tensile strength of the Ti-6Al-4 V TWB was also computed and examined. The analysis aimed to understand how modifications in the thickness ratio affected the strength of the TWBs.

Scan strategies are cost-effective means of mitigating residual stresses and warpage. Numerous optimized strategies have been validated for reducing residual stress in similar metal deposition. However, we still do not know if the same optimized scanning strategy used for similar metals can help reduce residual stresses in dissimilar metal deposition. In this study, a one-way coupled thermomechanical analysis has been performed using the finite element method (FEM), where SS316 steel is taken as the substrate, and copper is the clad layer. The study is performed for six scanning strategies—raster, zig-zag, alternate, out-in spiral, in–out spiral, and an S scan. The anisotropic heat transfer behavior during copper-SS cladding necessitates selecting strategies that promote homogeneous thermal distribution by ensuring that no more than 50

Consumable Tool-Additive Friction Stir Deposition (CT-AFSD), also known as friction surfacing, employs a consumable rotating tool to deposit material by generating heat through friction and plastic deformation. CT-AFSD has potential applications in surface coatings to improve corrosion and wear resistance, strength and high temperature stability. The present study aims to develop a validated Finite Volume Method (FVM) based Heat Transfer and Material Flow (HTMF) model for dissimilar deposition of AA 6061 on steel (CR01). This quasi-steady state moving heat source model incorporates temperature-dependent thermo-mechanical properties of the materials. The model successfully predicts heat generation, temperature and flow fields, thermal cycle, torque, and viscosity. The predicted thermal cycle and peak temperature showed a good agreement with the experimental data recorded using K-type thermocouple, with a deviation of ±5 K. The computed results revealed that plastic deformation heat contributes more than 50

Mechanical and microstructural anisotropy is a pressing issue in Additive Manufacturing (AM), especially in processes with high deposition rates, such as Laser Wire Directed Energy Deposition (LW-DED). While deposition strategies can control anisotropy, the influence of directional stochasticity on microstructural and mechanical homogeneity remains largely unexplored. Therefore, this study investigates the effect of deposition-induced directional stochasticity on the microstructural and mechanical homogeneity of LW-DED IN718 alloy. IN718 is widely used in aerospace, making it suitable for studying LW-DED stochasticity. Four deposition paths (raster, triangle, wiggle, honeycomb) were designed to systematically introduce increasing levels of directional stochasticity. Cuboidal samples were fabricated and systematically analysed across three principal planes: top, build, and diagonal. The grain morphology, phase distribution, crystallographic texture, and mechanical properties of the samples were evaluated. Increasing deposition-induced directional stochasticity progressively reduced microstructural and mechanical anisotropy by disrupting columnar growth and redistributing crystallographic orientations. Low directional stochasticity (raster) produced strongly aligned columnar grains, leading to anisotropy. In contrast, high directional stochasticity (honeycomb) disrupted epitaxial growth, leading to weaker texture and more uniform microstructural distribution. Strengthening mechanism analysis further revealed that directional stochasticity modifies the relative contributions of grain boundary and dislocation strengthening by altering grain morphology and stored dislocation density.

The large amount of strain combined with high temperature during Friction Stir Welding and Processing (FSWP) results in dynamic recrystallization and grain growth. The final properties of the processed material depend on the recrystallized grain structure. The ability to predict recrystallized microstructural features would take the FSWP modeling efforts one step closer to estimating the final weld mechanical properties. Here we present a computational framework for microstructural feature prediction based on the Discontinuous Dynamic Recrystallization (DDRX) principle considering plastic deformation, nucleation, and growth. The computed strains, strain rates and temperatures from an existing Heat Transfer and Material Flow (HTMF) model are utilized as input parameters for the DDRX model. The microstructural features such as average grain size, dislocation density, Taylor’s factor, number of new grains formation and grain size distribution are predicted using the DDRX model. The grain size prediction is validated against experimentally measured grain size, demonstrating a remarkable 97% accuracy and the reliability of the DDRX model.

Enhancing properties of composite materials through aligned reinforcements in an extrusion-based additive manufacturing (AM) process, is a critical objective in engineering applications. The extrusion process involves study of complex multiphase flow to determine the directionality of the reinforcement. Advanced numerical techniques are to be deployed to study the interplay of various forces and process parameters in the process. In this study, we use coupled Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) numerical techniques to investigate the flow of a graphite-reinforced PVA polymer matrix through a nozzle, a process not easily achievable through experimental means. The drag force, pressure gradient force, and virtual mass force are found significant based on a comprehensive analysis of simulation and experimental data. Non-linear regression analysis is performed to quantify the impact of these forces on reinforcement alignment. The orientation angle of reinforcements is chosen as the output parameter, with input parameters comprising nozzle outlet diameter, reinforcement aspect ratio, volume flow rate, polymer viscosity, and reinforcement concentration. Additionally, the nozzle clogging during printing is studied using the developed model. Nozzle rotation is proposed as an effective method to mitigate clogging, further enhancing the efficiency of the reinforcement alignment process. This research advances our understanding of composite material printing and offers practical solution for optimizing the alignment of reinforcements in polymer matrices, paving the way for developing high-performance composite materials with tailored properties using extrusion based AM processes.

This study explores the extrusion-based additive manufacturing of silicon carbide (SiC)-reinforced polyvinyl alcohol (PVA) composites, focusing on the influence of reinforcement concentration (1 wt%, 3 wt%, and 5 wt%) and nozzle outlet diameter (0.6 mm, 0.8 mm, and 1 mm) on print quality, reinforcement distribution, and mechanical properties. The die swell effect, a critical factor in extrusion-based printing, was found to intensify with smaller nozzle diameters and higher reinforcement concentrations. Mechanical testing revealed a significant enhancement in tensile strength for samples containing 1 wt% SiC printed using 0.6 mm and 0.8 mm nozzles, whereas higher SiC concentrations negatively impacted strength. However, for the 1 mm nozzle, tensile strength improved progressively with increased SiC content. Scanning Electron Microscopy (SEM) of extruded wires demonstrated that reinforcement orientation varied with nozzle diameter. SiC particles aligned perpendicular to the flow in the 0.6 mm nozzle, while random orientation prevailed in larger nozzles. A coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model incorporating an adhesion force interaction effectively simulated the behavior of SiC particles within the nozzle. The model revealed that interactions between SiC particles and the nozzle wall dominated in the 0.6 mm nozzle, inducing perpendicular orientation. This comprehensive investigation provides insights into the interplay between process parameters, material distribution, and mechanical performance, offering guidance for optimizing extrusion-based printing of reinforced composites for advanced applications. The findings establish a foundation for tailored design of nozzle geometries and reinforcement concentrations in additive manufacturing of polymer composites.

A coupled CFD-DEM framework was developed to investigate red blood cell (RBC) transport and cellular adhesion in constricted microchannels, with a primary objective of reducing computational cost while preserving physiological accuracy. Initially, numerical softening factors were implemented, allowing greater overlap between particles to expedite computations, with an optimal value of 0.03 selected. Adhesion forces between RBCs and the channel wall were incorporated, with a minimum effective distance of 0.4□µm identified as computationally feasible. However, RBC–RBC adhesion led to artificial clustering and was therefore omitted. Coarse-graining methods were applied up to a factor of 2 to further reduce simulation time, with a value of 1.8 chosen based on consistent cell-free layer (CFL) thickness and drag force characteristics. To correct for the increased drag in coarse-grained models, rolling resistance (Type C) with a coefficient of 0.8 was employed, bringing deviations within 10%. The validated model was then extended to simulate the detachment of adherent C2C12 myoblasts under physiological flow. Experimental validation showed increasing cell retention with seeding time, and simulations reproduced this trend with <5% deviation. The resulting Detachment Force Ratio (DFR) at 6 hours indicates near-equivalence between adhesion and hydrodynamic forces, establishing the model’s robustness for cell-substrate interaction studies in microfluidics. ### Competing Interest Statement The authors have declared no competing interest.

Nickel-based superalloys are widely used in important applications in various industries, including aerospace, defence, chemical processing, and marine. However, the difficulties encountered in machining these alloys pose specific challenges regarding the efficiency and quality of the parts. Thus, adopting economical and environmentally friendly cutting strategies during machining is essential for the environment and performance. For this purpose, silicon dioxide (SiO2) and aluminium oxide (Al2O3) nanoparticles were added to a base-cutting fluid to develop a novel hybrid nanofluid MQL (HNFMQL) cutting fluid, which is then applied during turning experiments. The thermo-physical characteristics, namely pH, thermal conductivity, and coefficient of friction of different fluid mixtures, are studied. The machining experiments are performed on Hastelloy C4 under conventional (dry, MQL, HNFMQL) and heat-assisted (HA) machining (HA dry, HA MQL, HA HNFMQL), and the cooling-lubrication ability is analyzed by measuring machining responses. Compared to HNFMQL and dry conditions, heat-assisted machining with HNFMQL reduced surface roughness by 20 % and 55.56 % and decreased tool wear by 14 % and 41.47 %. The SEM and EDX analysis of worn cutting tools revealed the efficacy of HNFMQL and HA HNFMQL with lower abrasive wear. Whereas, abrasion, adhesion, and chipping are observed under dry machining. The study of the material's microstructural behaviour using Electron Backscatter Diffraction (EBSD) revealed important details about its behaviour under various machining conditions. The EBSD investigation revealed a well-aligned microstructure, proving that heat impacts a limited region in heat-assisted machining.

Understanding columnar-to-equiaxed transition (CET) is a critical aspect of microstructural evolution in additively manufactured (AM) alloys, since proportions of columnar and equiaxed morphologies impact strength-ductility synergy. Traditional methodologies for CET prediction, primarily based on power-law relation between growth-rate and laser travel speed independent constitutional undercooling, have limitations in capturing transition domains at higher growth-rate, characteristic to AM. The existing Kurz-Giovanola-Trivedi (KGT) framework was leveraged as the basis for a modified CET model to predict microstructures more accurately for laser-directed energy deposition and powder-bed fusion for the whole laser-velocity domain. Two major alterations were implemented to modify the KGT model: first, undercooling was redefined by incorporating growth-rate and multi-component dependent thermo-kinetic parameters to radial, kinetic, thermal, and constitutional undercooling and second, marginal growth-rate instability domains were introduced. Compared to conventional KGT plot, the proposed model can provide better prediction for any AMed material, thus paving the way for designing location-specific microstructures.

Mastication is an essential and preliminary step of the digestion process involving fragmentation and mixing of food. Controlled muscle movement of jaws with teeth executes crushing, leading towards fragmentation of food particles. Understanding various parameters involved with the process is essential to solve any biomedical complication in the area of interest. However, exploring and analyzing such process flow through an experimental route is challenging and inefficient. Computational techniques such as discrete element numerical modeling can effectively address such problems. The current work employs the Discrete Element Method (DEM) as a numerical modeling technique to simulate the human mastication process. Tavares and Ab-T10 breakage models coupled with Gaudin Schumann and Incomplete Beta fragment distribution models have been implemented to analyze the fragmental distribution of food particles. The effect of particle shape (spherical, polyhedron, and faceted cylinder), size (aspect ratio), and orientation (vertical and horizontal) on breakage and fragment distribution is analyzed. To account for the elastic-plastic behavior and moisture content in food particles, modifications has been made in breakage models by incorporating numerical softening factor and adhesion force. The study demonstrates how numerical modeling techniques can be utilized to analyze the mastication process involving multiple process parameters.

The effect of post-deposition heat treatment on microstructure and fatigue crack growth has been analyzed for electron beam melted Ti-6Al-4V plates. Samples have been heat-treated at temperatures of 950 degrees C and 1050 degrees C, and subsequently cooled at different cooling rates in the furnace and the water. The as-built sample possesses columnar prior beta grains filled with exceptionally fine alpha+beta beta Widmanstatten patterns and epitaxially grows in the vertical direction. Heat treatment with a slow cooling rate increases the alpha lath thickness, whereas fast cooling results in multiple needle-shaped alpha/alpha ' ' phases inside the prior beta grains. The yield strength and ultimate tensile strength in as-built conditions are greater than the extruded mill annealed sample. The as-built samples show better crack growth resistance during the fatigue crack growth rate test than the heat-treated and mill-annealed samples. The lower plastic deformation of the as-built sample than the mill-annealed sample is attributed to the existence of fine alpha laths that restrict the motion of dislocation.

The spouted fluidized bed process is a multiphase heat and mass transfer flow. The process requires effective solid-gas and solid-solid interaction. Various numerical models have been developed to understand and optimize these interactions. However, most of these models have used spherical particle definition, whereas the actual particles are non-spherical. Here we present coupled Computational Fluid Dynamics(CFD) and Discrete Element Method(DEM) based model to analyze the fluidized bed process for non-spherical particles (Faceted cylinder). The model results are validated with experimental results for spherical particles. The model is further used to understand mixing during the process as a function of non-spherical particle geometry. Aspect ratio and corner count were the geometrical input parameters for faceted cylinder-shaped particles. Transient plots for bubble diameter and bed height for spouted fluidized beds were created for all cases. The bubble diameter and bed height values were much lower for faceted cylinder particles than for spherical particles. For non-spherical particles, the increased number of corners was a crucial factor that brought the outcomes closer to those of spherical-shaped particles. The aspect ratio values increased, and the bubble diameter shrank as a result of more resistance to particle movement. The results would be of great use to correctly simulate non- spherical particles based fluidized bed process and optimize various process parameters.

Low-density polyethene (LDPE) is extensively used in single-end-use food packaging and contributes significantly to global waste plastic. This study addresses this challenge by introducing a sustainable approach to reclaim and valorise waste LDPE from milk packaging by converting them into 3D printing filaments. The process involves extruding shredded LDPE pouches into continuous filaments using a modified thermal extruder. The research comprehensively investigates the effects of two key extrusion parameters, nozzle temperature and screw speed, on the resulting filament's physical and mechanical properties. Characterisation efforts include dimensional analysis, morphological evaluation, chemical integrity assessment, thermal stability analysis, and tensile testing. The results show that filaments remain consistently close to 1.75 mm diameter, which is required by most commercial FDM 3D printers. The filaments are chemically intact, thermally stable, and have high toughness across the range of extrusion parameters. The results and a preliminary demonstration of 3D printing indicate that the LDPE waste can be effectively transformed into consistent filaments that have the potential for 3D printing. A carbon footprint assessment underscores the environmental benefits of this approach, showing substantial reductions in estimated CO2 emissions compared to conventional filament production methods. While challenges related to the quality of printed parts remain, the research opens avenues for optimizing 3D printing parameters and exploring multiple recycling cycles. This work represents a step towards sustainable plastic waste management and offers insights into transforming single-use plastic items into valuable resources.

4D printing refers to the additive manufacturing of a component by incorporating smart materials. The smart materials add the “4th dimension” to 3D-printing by altering the shape/functionality/configuration of the part in response to external stimulus such as heat, stress, pH, electric field, etc. In the current study, shape memory alloy (SMA) plugs were implanted into mild-steel via gas metal arc welding (GMAW) assisted wire-arc additive manufacturing (WAAM). The NiTi SMA powder was employed as secondary addition within the printed layers, while the FeMnSi based alloy evolved in-situ during the 4D-printing process. Significant elemental heterogeneity was found in the Fe-Mn-Si based SMA plugs containing NiFe rich solidified droplets, owing to the composition of the wire used for deposition. The NiFe rich phases depicted the substitution of Ti by Fe in the NiTi pre-cursors. The large SMA plugs incorporated into the printed mild steel depicted the formation of a macro composite structure. The presented results are expected to considerably reduce the cost of SMA application through the printing of novel monolithic SMA-steel composites using wires and SMA powders as raw materials.

This research investigates the impact of shoulder-workpiece separation on the friction stir channeling of copper, comparing two distinct tool designs. One design includes a clearance between the tool shoulder and workpiece; while, the other utilizes a grooved tool shoulder to eliminate this clearance. The findings reveal that direct contact between the tool shoulder and workpiece in the no-clearance design significantly affects the channel’s dimensions, microstructure, and mechanical properties. Notably, a distinct interface separating microstructural zones acts as a crack initiation site under tensile stress, leading to premature fractures of the channel roof. The results suggest that channels fabricated with shoulder-workpiece clearance improve tensile strength, offering a promising approach for manufacturing advanced heat sinks.

Using the multi-principal element based high entropy alloy (HEA) concept, single-step ultra refinement and solidstate alloying of Cu with NiTi, Y, Fe, Cr, and Co were achieved simultaneously for the first time via friction stir processing (FSP). A bimodal microstructure with an average grain size smaller than 1.5 mu m was attained. The microstructure consisted of inter-dispersed regions of high and low density of geometrically-necessary dislocations. The fraction of high-angle grain boundaries was observed to increase from -33% in the unstirred region to -80% in the processed alloy. Intercalated bands having sharp variations in grain size were formed in conjunction with the bimodal microstructure. The entropic stabilization due to addition of diverse elements assisted multifaceted heterogeneity and grain refinement along. This study paves the way for the development of HEAs via FSP.

The fabrication of compact heat exchangers with precisely designed micro- and mini-channels is crucial for enhancing the efficiency of thermal management systems. Friction stir channeling (FSC) emerges as a cost-effective advanced manufacturing process to create complex integral channels, offering channel shape and size flexibility. This review article highlights the pivotal role of processing parameters in channel formation and maintaining their integrity, necessitating a comprehensive understanding of material flow dynamics. A rigorous assessment has been conducted on the channel under mechanical stresses, including tension, bending, and fatigue. The paper emphasizes the potential of FSC to revolutionize heat sink applications by exploring the fundamental concepts, governing parameters, ongoing enhancements in tool design, microstructural and mechanical properties, and heat transfer performance.

The present study aims at identifying the critical Reynolds number for transition from laminar to turbulent in irregular shaped mini-channels. Numerical study including conjugate heat transfer and axial conduction is carried out using commercially available software ANSYS Fluent®. The channel of length 105 mm, width 4.5 mm, and height 2 mm is fabricated in an aluminium substrate of length 114 mm (L), width 15 mm (W), and height 6.3 mm (H). Water is used as working fluid. Average hydraulic diameter (Dh) of mini-channel is 2.86 mm, and cross-section area varies non-uniformly from 10 mm2 to 18 mm2 along the length. Problem is set up with mass flow rate and outflow boundary condition at inlet and outlet, respectively. Bottom wall is given with uniform heat flux (q) of 200 watts thus incorporating conduction in solid wall of channel. Temperature difference between the inlet and outlet is compared with experimental measurement and found to be in good agreement. It is observed that the heat transfer coefficient as well as pressure drop both increases with increase in mass flow rate; however, increase in pressure drop is found larger compared to increase in heat transfer coefficient. Further, we also found the axial conduction in the solid wall. It is interesting to note that the transition from laminar to turbulent is observed at lower Reynolds number. Present work provides platform to study thermal and fluid flow behaviour of the irregular shaped mini-channels.

High-strength alloys can be efficiently welded utilizing laser beam welding because of their attributes, such as minimized fusion, heat-affected zone extensions, and minor deformation. Computational study of the laser material interaction process assists in analysing numerous process variables and their effect, which is challenging experimentally. This work developed a 3D numerical model for pulsed laser welding of high-carbon alloy steel. A hybrid 3D conical heat source model with a double ellipsoid and a 3D conical heat source model was employed to study laser–material interaction in the finite element modelling of the process. Post-processing of the simulation results for both the heat sources was compared to investigate the suitability of the volumetric heat source depicting experimental data. The analysis was carried out by comparing the models and calculating the dimensions of weld geometry for various process parameters. A suitable heat source for the weld geometry was identified using the isotherms. Commercial software (Comsol Multiphysics 5.6) is used to solve the conduction and heat flux equations using Finite Element Methods. By altering the welding speed at three different peak powers, the weld pool depth and width were calculated. The results were plotted and matched with the experimental data for the two different heat sources. Finally, the heat sources were compared to obtain the laser peak power for full-depth penetration of the weld joint. The simulations were further validated by comparing the experimental results of weld geometry at different laser peak power.