PhD Theses (Mechanical Engineering)

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Prediction of Textured Journal Bearing Performance Characteristics implementing Mass Conserving Boundary Conditions using Progressive Mesh Densification Method
(2023) Rasool, Syed Nayab
Surface texturing is proven to be a feasible technique for enhancement of the performance characteristics of the hydrodynamic bearings. A considerable amount of numerical and experimental study is carried out on textured hydrodynamic bearings. The surface texturing onto the bearing surface can be done using different micro-fabrication techniques such as laser surface texturing (LST), chemical etching techniques, novel dressing techniques, Additive manufacturing, abrasive jet machining, photolithography, focused ion beam, micro-electric discharge machining, electrochemical texturing, ultrasonic machining, thermal implantation etc. The surface texture of regular geometries, either dimpled or protruded shapes, can be produced on the bearing surface with the above-mentioned manufacturing techniques
Analysis and Identification of Dynamic Transmission Error Parameters in a Geared Rotor Using Full Spectrum
(2023) Rao, Bhyri Rajeswara
Geared rotor bearing systems are widely used torque carrying components in most of the mechanical and electrical equipment in the automotive, aerospace and ship building industries. A dominant source of vibration in geared rotor systems are the gear mesh dynamic transmission error (TE) parameters. These include the static TE, the mesh stiffness and damping, and the gear runout. One needs to know additionally these dynamic parameters along with the gear macro-geometry (for examples, the number of teeth, pitch circle diameter, pressure angle, and tooth geometries), load and rotating speed, for the vibration-based diagnosis of geared rotor power transmission units.
Numerical and Experimental Thermo-Mechanical analysis of Sheet Forming by Laser Line Heating
(2024) Das, Biplab
In this study, a detailed strategy for sheet forming by laser line heating has been presented. The work presented in this thesis is concerned with the evaluation of the effect of process parameters on thermal history, residual deformation, residual stresses, and strains associated with the process of laser line heating. Residual deformation is induced on the metallic sheet due to the heating effect of a laser beam when irradiated over a suitable heating path. The deformation generally takes place due to the combined effect of yielding and temperature distribution across the thickness of the metallic sheet. Both numerical and experimental analyses on laser line heating were carried out to investigate the thermal history and residual deformation.
(A) numerical investigation on augmented heat flux in non-standard variants of turbulent Rayleigh-Bénard convection
(2023) Chand, Krishan
The present work investigates non-standard variants (roughness-aided and tilted convection) of Rayleigh-Bénard convection (RBC) to augment heat flux for a fixed working fluid (Prandtl number = 0.7) over a wide Rayleigh number range (106 ≤ Ra ≤ 1010). For both 2D and 3D, the study focuses on the coherent structures and heat transfer mechanisms in different configurations of Rayleigh-Bénard convection (RBC), considering thermal plumes, boundary layers, and large-scale rolls (LSR). In the smooth case, the absence of lateral direction results in the entrapped thermal plumes, which are subsequently emitted as thermal jets into the bulk. The Nusselt number (Nu) quantifies the heat carried by thermal plumes across the isothermal walls. A positive correlation between vertical velocity and temperature fluctuations is used to quantify thermal plumes. The impact of surface roughness on heat flux is investigated, highlighting the influence of irregular roughness geometries. The study identifies an onset of enhanced heat flux regime and explores the role of bulk-plume interaction and fluid mixing. With increasing Rayleigh number, transformation from a double-roll state to multiple-roll state is associated with the onset of enhanced heat flux regime for the taller configuration. On the other hand, presence of huge number of roughness elements is responsible for enhanced heat flux in the smaller configuration. Near-wall dynamics and the penetration of peaks into the thermal boundary layer are studied, revealing the significance of secondary vortices and the tendency of plume emission. The investigation extends to three-dimensional RBC with conical roughness configurations, emphasizing the role of coherent structures and intense thermal plumes in enhancing heat flux. The study provides insights into the influence of roughness on flow strength and the orientation of large-scale rolls. The effect of inclination angles in tilted RBC is examined, indicating shifts in heat transport effectiveness and early onset of turbulence with increased roughness height. In the smooth case, inclined convection (IC) enhances heat flux below Ra = 108, while above this value, normal RBC yields the highest heat flux. However, for rough surfaces, the effectiveness of IC to transport heat shifts to lower Ra as the roughness height increases, leading to an early onset of turbulence. The maximum heat flux in the smooth case is achieved at a tilt of 75° for Ra ≤ 108, while in roughness cases, it depends on both Ra and the roughness configurations. The study reports a maximum increase of 25% in Nusselt number for roughness-aided tilted convection. Additionally, as Ra increases, the onset of thermal stratification is delayed in the smooth case, while an increase in roughness height results in a similar delay in rough configurations, indicating an early onset of turbulence even at larger inclination angles.
Experimental Investigation of Transient Liquid Phase Bonding of IN 718 Superalloy and Enhancement of Bond Quality
(2023) Tarai, Uttam Kumar
The present research work started with an objective to understand the fundamental kinetics of transient liquid phase (TLP) bonding of nickel-base superalloys; Inconel 718 (IN 718) and deliver methodologies for the improvement of bond properties. The role of process parameters in joining IN 718 with the TLP bonding process is explored with an aim to improve the mechanical properties of the bond. From the experimental investigation, it was ascertained that the bonding temperature, time, and interlayer type and size are the most important process parameter of the TLP bonding process. The higher bonding temperature, time, and optimal interlayer thickness improve the mechanical properties of the TLP bonded IN 718 joint. Higher bonding temperature reduces the isothermal solidification (IS) time. Inadequate bonding time leads to the formation of centreline eutectics in the TLP joint due to athermal solidification of the residual liquid remaining in the bond area. The IS time of the TLP bonding process depends upon factors like temperature, the diffusivity of the melting point depressants (MPD), and the width of the interlayer material. To obtain good bond properties, complete isothermal solidification is necessary. In order to determine IS time, the kinetics of TLP bonding should be known to the industries. To study the kinetics of the TLP bonding and to reduce the experimental time and cost, the interrupted differential scanning spectroscopy (DSC) method was used in the current investigation. The DSC method successfully described the kinetics of the TLP bonding. From the enthalpy of solidification of the DSC curve, the IS time of a material was obtained. And the results of the investigations are in good agreement with the experimental results of the other author.
Development of GPU-based Strategies for Finite Element Simulation of Elastoplastic Problems
(2024) Kiran, Utpal
Elastoplasticity is a phenomenon in which materials deform elastically up to a certain load limit and plastically afterwards. The elastic deformation is recoverable, but plastic deformation is permanent. The elastoplastic behaviour is commonly observed in materials of practical interest like metals, concrete, soils, rocks, biological tissues, etc., that yield when subjected to loads high enough. The design and optimization of such materials depend strongly on the elastoplastic analysis for the prediction of displacement and stress. However, elastoplastic analysis is computationally expensive and often requires the use of parallel computers in real-world applications like metal forming and crashworthiness. This thesis presents a parallel computing framework for finite element analysis of elastoplastic problems using massively parallel Graphics Processing Unit (GPU) processor. Considering assembly-based approach, GPU-based parallel algorithms are proposed for all expensive steps in elastoplastic analysis, namely the computation of elemental matrices and their assembly, the computation of stress using the well-known radial-return method and the computation of internal force vectors and their assembly. Since GPUs have limited memory, assembly is done directly into a sparse storage format that can be seamlessly integrated with a GPU-based linear solver. In order to further accelerate the linear solver step in elastoplastic analysis, matrix-free iterative solvers have been proposed. Matrix-free solvers never assemble large sparse global tangent matrix and perform computations with small dense elemental matrices, reducing the storage requirement and avoiding the use of expensive sparse storage formats. For problems using unstructured mesh, a novel matrix-free strategy is developed that uses only symmetric part of elemental tangent matrices to compute sparse matrix-vector product (SpMV) by following element-by-element technique. For problems using voxel-based structured mesh, single kernel and improved split kernel strategies are proposed to efficiently handle branching issues due to the presence of both elastic and plastic states. For GPU implementation, node-based, degree-of-freedom-based and element-by-element matrix-free strategies have been used with suitable modifications. The performance of the proposed strategies are demonstrated by solving a number of benchmark examples from elastoplasticity. Compared with single-core CPU implementation, speedups of several orders of magnitude are achieved. When compared with existing GPU-based strategies from literature, the proposed strategies show significant speedups and occupy lesser memory space.
Bioinspired Fluid Dynamic Designs and Implementation of Soft Computing Techniques in Savonius Wind Turbine Rotors
(2024) Rathod, Umang Harshadbhai
To address the problem of imminent energy crisis, pollution from fossil fuels, and global warming, it is necessary to incorporate the renewable technologies. In that context, the drag-based Savonius wind turbine has tremendous potential to extract wind energy and can be operated as a standalone system at remote areas where the conventional electricity cannot be provided. With such merits in mind, literature review is presented in this thesis besides the research directions and research gaps. It is found that the ongoing research directions are the bioinspired Savonius rotor designs, surrogate modelling, and optimization using soft computing techniques. Concise literature review on the reported bioinspired and nature-inspired blade design of the Savonius rotor is presented. Furthermore, applicability of using soft computing techniques for wind turbines, and especially for the Savonius rotor, is discussed. The potential research gaps are identified and are addressed in this thesis.
Investigation of Anodic Dissolution Process to Overcome the Challenges during Micro-Manufacturing
(2023) Kumar, Abhinav
The present thesis focuses on solving the two major challenges of micro-manufacturing via the electrochemical-based method. The significant advantage of this method is high dimensional accuracy and better surface integrity. The thesis is divided into two sections. The first section includes the development of electrochemical micromachining (EMM) setup and the fabrication of microtools. The second section consists of developing an electropolishing (EP) setup and improving the surface integrity of electrical discharge machined components.
Near Field Examination of Sonic/supersonic Nozzle flows
(2023) Jraisheh, Ali
This thesis presents a numerical study on compressible flow within and downstream sonic/supersonic nozzles. It is a close look on the effects of thermodynamics and geometry configuration on the gas flow inside and downstream the ducts. An in-house CFD solver is developed to accommodate the complex flow structure that accompanies the under expanded jet and impose the proper boundary conditions, in order to simulate the flow field. More focus is drawn to the phenomenon of Mach disk that occurs in case of highly under expanded flow, its location and height are thoroughly studied and analysed.
On-Site Flexible Rotor Balancing and Crack Characterization in Rotor-Bearing System Through Virtual Excitation by Active Magnetic Bearings
(2022) Ranjan, Gyan
The conventional influence coefficient method is being widely utilized for on-site balancing of the rotor system. For the balancing of the flexible rotor, the system is required to be operated above critical speeds, which is difficult in the presence of residual unbalances. Also, repetitive stopping and the opening and closing of the casing of the rotor system for the manual addition of trial unbalances (conventional method), the system may get contaminated with foreign particles. To solve the above difficulties, a new balancing method has been proposed using the Virtual Trial Excitation Influence Coefficient Method (VTEICM) for a flexible rotor system integrated with Active Magnetic Bearing (AMB). The AMB is utilized for both controlling vibrations while accelerating through various critical speeds during measurements and generating virtual trial unbalance (VTU) as magnetic excitation. The VTU allows the identification of unbalances with a lesser number of rotor runs and manual effort than the conventional method. Initially, for numerical illustration of the VTEICM, the mathematical model of the rotor-AMB system is developed using the finite element method. The effectiveness of the VTEICM is shown through the balancing of the rotor-AMB system with the estimated unbalances. However, the occurrence of failure in the system while surpassing critical speed even in the presence of a control structure is required to be reduced. The periodic balancing of the flexible rotor system with the change in the level of unbalances is required to be carried out while operating the system at low speeds. A new technique is developed with Virtual Excitation at Low-Speed for High-Speed Balancing (VELSHSB) that utilizes the influence coefficients obtained at high speed and unbalances identified at the low speed to effectively estimate the balance masses required for the high-speed flexible rotor balancing. The influence coefficients at high speeds are required to be obtained just once, whereas the balance masses can be estimated periodically by identifying the unbalances at low speeds. The methodology is extended to balance the dual rotor system that is widely utilized in aero-engines because of its compact structure and efficient operation. Due to the compact structure of the system, it is difficult to balance the rotor system with the manual addition of the trial unbalances. Hence, a novel balancing strategy, i.e., Multiple Virtual Excitation for Dual rotor Balancing (MVEDRB), has been utilized to balance the dual rotor system with AMB control and excitation. Also, the rotor system with multiple faults such as cracked rotor system are required to be analyzed with the utilization of AMBs. Therefore, an identification algorithm is designed to obtain the fault parameters in the cracked rotor system integrated with AMB based on the Multiple Harmonic Influence Coefficient Method (MHICM). The present approach allows us to monitor the behavior of a fatigue crack in the system and to successfully estimate the additive crack stiffness, residual unbalances, and the internal damping factor in the system. There is a lot of practical difficulty in high-speed balancing with accelerating the rotor system above its critical speed in the presence of AMB. The control structure of the AMB requires a large magnitude of bias current to accommodate the excessive control current near the critical speed that increases the heating of coils and power consumption. So, the implementation of VTEICM for high-speed balancing of experimental rotor test rig supported on the conventional bearings and integrated with the AMB is also carried out. The control structure with PID controller is developed on dSPACE-SIMULINK platform based on the differential driving mode control. To limit the utilization of bias current, the switching of bias current is performed that allows the rotor-AMB system to switch between high and low values of the bias current on the requirement. The practical difficulties in synchronizing the excitation frequency of VTU and operating speed are addressed with voltage/speed factor and phase-lag correction in the motor speed control unit.
Convergence Acceleration of Fluid-Flow Computation with Special Emphasis on Multigrid Technique
(2022) Kalita, Subhra Sankar
This thesis is concerned with the study and analysis of various convergence-acceleration strategies that can help CFD practitioners to obtain their simulation results quickly. Convergence-acceleration can be achieved either by choosing a fast algorithm or by parallelizing the solution strategy. The multigrid method lies in the former category and is considered as one of the most powerful convergence-acceleration strategies. CUDA, which is a relatively new method for parallelizing CFD codes falls under the second category and as a part of the convergence-acceleration efforts embodied in this thesis, CUDA is used to parallelize LBM-based computations
Design And Development Of A Novel Ball-On-Cup Tribometer For The Characterization Of An Ingenious Total Hip Prosthetic Liner Made Of Uhmwpe And Its Composite
(2023) Jana, Ashirbad
Total hip replacement (THR), regarded as the orthopaedic operation of the 20th century, uses ultra-high molecular weight polyethylene (UHMWPE) as the acetabular liner since 1960s. However, the life of a metal-on-plastic THR is often limited to 15-20 years, primarily due to excessive wear debris generation during its operation, leading to osteolysis and aseptic loosening of the prosthetic joint leaving behind a painful revision surgery. Presently worldwide research is dedicated in improving the life of a metal-on-plastic THR by the improvement of tribological characteristics of an UHMWPE acetabular liner.
Thermodynamic Analysis of Active and Passive Drag Reduction Techniques for Elevated Enthalpy Hypersonic Reacting Flows
(2023) Patil, Ajay Vijay
Initial investigations are based on counter flow injection and spike based drag reduction techniques to compare them on a common platform. Test case of supersonic flow over hemisphere, provided with counterflow injection, portrayed monotonic variation for percentage drag reduction and percentage exergy destruction for increase in injection pressure ratio. However, injection effectiveness, suitable assessment parameter for counterflow injection, shows inversion characteristics with a peak at specific injection pressure ratio. Mounting of a spike also shows similar trend for percentage drag reduction and percentage exergy destruction. Present investigations recommend percentage exergy destruction as a unified performance assessment parameter for passive and active drag reduction techniques. Afterwards, investigations are carried to examine the effect of higher freestream stagnation enthalpy on flow field alteration for counter−jet drag reduction technique for a hemispherical object. Drag coefficient is found to reduce with freestream total enthalpy in the presence of real gas effects. Higher pressure ratio of the jet has resulted in lower surface pressure and Stanton number on the object. Then, efforts are further continued to reveal the thermodynamic behaviour of opposing jet technique which includes variation of entropy generation rate, exergy destruction and drag force analysis considering real gas effects. Results revealed that linear reduction in drag forces and sharp rise in entropy generation rate and exergy destruction is obtained with jet momentum ratio irrespective of freestream and jet parameters. At last, real gas effects on surface pressure and flow field are analysed for the combinatorial technique (opposing jet and cavity) for hypersonic flow over the blunt body. A new thermodynamic parameter named entropy generation rate is proposed which can be used as a tool to analyze the performance of any drag reduction technique. Results showed that perfect gas assumption over−estimates the surface pressure and wave drag. Introduction of cavity reduces the surface pressure, drag and entropy generation rate but significant reduction in these parameters is noted when the opposing jet is turned on. For given jet pressure ratio, opposing jet technique predicts lower drag and entropy generation rate as compared to combinatorial technique.
Robust Control Schemes for a Pediatric GAit Exoskeleton System in Passive-assist and Active-assist Mode
(2023) Narayan, Jyotindra
Over the years, a significant rise in neurological disorders has been observed for different age groups, such as stroke, spinal cord injury (SCI), and cerebral palsy (CP). Many pediatric subjects face dyskinesia and muscle atrophy in their lower limbs. In the last few years, the proliferation of exoskeleton technology has enabled the therapy process to be less cumbersome and more sustainable. However, there are minimal exoskeleton devices available for pediatric gait rehabilitation. Moreover, the control design to achieve the desired gait training in different therapy modes is still open to research and a benchmark problem statement due to significant parametric perturbations and external disturbances (PPED) in pediatric exoskeleton systems. Therefore, this thesis proposes a few robust control schemes for a newly designed pediatric exoskeleton in passive- and active-assist rehabilitation mode.
Analysis of Three Phase Carbon/(CNT+Epoxy) Composites with Flaws
(2024) Rao, Chukka Atchuta
Three phase FRP composites like carbon/(CNT+epoxy) are developed where the matrix dominated properties of FRP composites are enhanced to improve the performance. FRP composites though possess a very high specific strength and stiffness sometimes show poor performance when their interlaminar strengths are challenged. Especially when defects like ply break and embedded delaminations occur due to events like low velocity impact, delaminations usually grows at the interface of the broken and intact plies leading to the final fracture. These defects are sub-surface in nature many a time go unnoticed and results in catastrophic failure. It is therefore extremely important to strengthen the laminates against such failure. Resistance against such failures are decided predominantly by matrix dominated properties like interlaminar strengths. Therefore, three phase composites such as carbon/(CNT+epoxy) with modified matrix properties is expected to provide improved resistance against such failure. The present thesis thus aimed at investigating the performance of three phase carbon/(CNT+epoxy) laminates having internal flaws like ply break and impact induced embedded delamination subjected to loading with the specific objective of understanding qualitatively and quantitatively how adding CNTs to the epoxy enhances the resistance delamination growing from such defects. To study this, full 3D finite element analyses (FEA) have been carried out for carbon/(CNT+epoxy) laminates having two types of flaws viz. ply break and embedded delamination. Delamination at the interface has been modelled using a very thin resin rich layer and the interlaminar stresses around the ply break and embedded delaminations are obtained from the 3D FEA. Using the stresses and displacements from FEA, Virtual Crack Closure Integral (VCCI) has been used to determine strain energy release rate (SERR) components as measures of propensity of delamination. FE results show that delamination from such defects is a mixed mode phenomenon and in the case of embedded delamination the mode mix ratio also varies along the delamination front making the estimation of delamination growth difficult. Delamination at the interface arising from such flaws are observed to be influenced by many factors such as size, shape, relative fiber orientation, loading condition. Critical SERR as a measure of resistance to such delamination has been evaluated in the present work using stress based criteria and virtual crack closure integral from LEFM. From the results, it is clear that in the case of three phase carbon/(CNT+epoxy), addition of CNTs to epoxy leads to significant improvement in resistance to delamination at the interface from ply bear as well as from embedded delamination in all the cases studied. In addition, it was also observed that tendency of two neighbouring delamination to grow as a large delamination is also reduced by adding CNTs to the epoxy. However, results from the FE simulations also show that there is a limit till which CNTs could be added to the epoxy for best performance and beyond this the performance further reduces and it is important to know the limit to the adding CNTs will enhance the resistance to such delamination.
Development of Pseudopotential-Based LBM Solver to Explore the Microdynamics of Liquid-Vapor Phase Change Processes
(2022) Mukherjee, Aritra
The pseudopotential-based LB multiphase model has enormous potential in the simulation of phase-change heat transfer problems. It facilitates the natural development and migration of interfaces during the multiphase simulation as well as saves a lot of computational time. Along with these, this model enjoys several advantages like simple implementation procedure, excellent parallelizability, and easy applicability in complex domains. Due to these superiorities, it is becoming increasingly popular among researchers working on numerical simulation of multiphase flow. A pseudopotential model based thermal multiphase flow solver is developed as this thesis work, which is employed in several phase change heat transfer problems related to boiling and condensation. The first problem successfully explores the capability of the pseudopotential-based thermal lattice Boltzmann model in emulating the underlying thermohydrodynamics of subcooled flow boiling in a narrow fluidic horizontal channel in detail. The next study uses the multiple-relaxation time based LB model to explore the role of surface morphology and cold spot temperature in determining the visual state of the condensate droplet, i.e. Cassie and Wenzel mode of droplet nucleation and associated rates of energy and mass interactions in temperature controlled condensation process. The same numerical framework is employed to study condensate droplet formation and movement on several vertical and inclined microstructured surfaces, and corresponding mass condensation and heat transfer rates are analyzed thoroughly. Being motivated by the prime weakness of the pseudopotential based thermal LB model about its incapability of simulating boiling problems with a large density ratio, the last work of this thesis focuses on augmentation of the basic pseudopotential based thermal multiphase algorithm by enhancing the isotropy of the discrete equation and thermodynamic consistency of the overall formulation, to expedite simulation of pool boiling at higher-density ratios. Various pool boiling scenarios, and all three regimes of pool boiling have aptly been captured with both plain and structured heaters, allowing the development of the boiling curve. The predicted value of critical heat flux for the plain heater agrees with Zuber correlation within 10%, illustrating both quantitative and qualitative capability of the proposed algorithm.
Effective Utilization of Data for Enhancing the Performance of Manufacturing
(2024) Chatterjee, Kaustabh
The effective utilization of data is becoming increasingly important for enhancing the performance of manufacturing processes. In the era of Industry 4.0, advancements in technology have enabled the collection of vast amounts of data from various manufacturing processes, making it possible to analyze the data and derive insights that can help enhance the performance. One of the main advantages of using data-driven manufacturing is the ability to identify quality issues early in the production process. It reduces the likelihood of defective products, thereby enhancing customer satisfaction, reducing wastage and improving the profitability.
Experimental and Computational Studies on Exit-Hole-Free Friction Stir Spot Welding Processes
(2024) Bhardwaj, Nitish
This thesis contributes to understanding friction stir spot welding (FSSW) by investigating friction, heat generation and exit-hole elimination. Lubricants were applied during FSSW of aluminum alloy sheets resulting in a 44–55% reduction in torque and 12–24% reduction in plunge force requirements. More than 50% reduction in energy requirement while maintaining good joint strength is observed. This suggested the more important role of plastic deformation in heat generation as compared to friction. The study introduces an inverse approach to model friction during FSSW, utilizing finite element (FE) simulations in DEFORM 3D and validating with experiments. Further, this thesis investigates ways of producing exit-hole-free welds during FSSW. In one method the exit-hole is filled with waste aluminum chips and friction stir processing is performed over it. The process delivered 16% and 84% higher load-bearing capacities during T-peel tests compared to conventional FSSW with and without pin, respectively. A novel method of using consumable pin during FSSW is introduced to produce exit-hole-free joints. The feasibility and performance of FSSW using three consumable pin materials viz., AA6061-T6, mild steel and oil hardened non-shrinking die steel, are explored. Additionally, the research evaluates the impact of rotational speed and plunge rate on joint quality. It is found that the joint strength increases with increase in rotational speed up to 900 RPM and further increase in rotational speed decreases joint strength. A 1.7 times increase in joint strength at 900 RPM compared to 360 RPM is achieved. On the other hand, optimum plunge rate for highest joint strength is found to be 15 mm/min. A 4% increase in lap shear strength at 15 mm/min plunge rate compared to 6 mm/min, with an 8.5% decrease in energy requirements is obtained. A good match between experiments and FE simulations is obtained. Adhesive-bonded consumable pin along with application of lubrication is suggested for industrial application, which results in faster production speed and lower energy requirement while delivering good joint quality. This study provides a comprehensive understanding of FSSW, spanning friction, heat generation, exit-hole-free FSSW joints, parametric study and the integration of lubricants and adhesive-bonded consumable pins.
Application of Cold Metal Transfer Technology for Cladding of ER70S-6 Alloy on AA 6061-T6 Aluminum Alloy
(2024) Das, Bappa
The Cold Metal Transfer (CMT) process is a specialized welding technique used for cladding and coating, which involves applying a layer of metal onto a base material. In fact, CMT cladding is an efficient additive manufacturing technology that finds application in the automotive, defence, and power plant sectors. As Additive Manufacturing evolves, new welding methods have emerged, including CMT, an advanced version of Metal Inert Gas (MIG) welding known for reduced spatter and low heat input. CMT-based cladding processes have gained attention for improved aesthetics and lower heat input. Utilizing a wire as feedstock and a robotic arm for deposition enables precise material placement in complex shapes, with heat input determined by process parameters like voltage, current, wire feed speed, and stand-off distance.
Performance Evaluation of Lubricated Polymer Gears
(2023) Bharti, Sarita
Injection molded polymer gears are being widely utilized as they offer several advantages, such as lightweight, good damping capacity, easy production, low manufacturing cost, and good mechanical properties for low and moderate-load applications. Many works have been earlier attempted to improve mechanical properties by incorporating fiber reinforcement. In this work, an attempt has been made to investigate the potential of using oil lubrication for performance improvement. In addition, the present study also aims to check the feasibility selective laser sintering (SLS) process and elastomeric material (thordon SXL) for gearing application. The sliding contact performance of these materials was also investigated using pin on disc configuration. The surface durability of the test gear was investigated using a house-developed gear rig at various loading conditions and a constant rotational speed under dry and lubricated conditions by observing the thermal response of gear teeth, lubricant temperature, periodically monitoring gear teeth surface, and failure morphology.

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