Skylab Paulas Bhore

An experimental setup is developed to examine the tribological performance of the meso-scale plane and textured air journal bearings. These bearings are fabricated using a novel texturing technique: metal 3D printing (additive manufacturing). First, plane and different-sized textured bearings (small: Tx1, medium: Tx2, and large: Tx3) are tested. The textured bearing, which offers minimal friction and wear, is proposed. Further, for the proposed textured bearing, the influence of texture distribution (full texturing and different partial texturing, viz. 0°–90°, 90°–180°, 180°–270°, 270°–360°, 0°–180°, and 180°–360°) is examined. These studies are performed at variable loading conditions (1N to 5N) operating in the speed range of 500– 25,000 rpm. Among various textured bearings, Tx1 performed best at variable rotational speed and applied loading. The partial texturing in 0°–180° is beneficial in the hydrodynamic regime at higher loading (4N–5N). Abrasive wear is dominant in the plane bearing, and adhesive wear in textured bearings.

Material extrusion-type additive manufacturing (AM) is widely adopted due to its simplicity and accessibility. The use of metal–polymer composite filaments, followed by debinding and sintering, is emerging as a promising approach for metal AM. This three-stage process is acknowledged as metal fused filament fabrication (MFFF). While most existing research has focused on stainless steel-based systems, this study investigates the relatively underexplored area of copper-polymer composite filament processing. In this work, a copper-polymer composite filament was used to print (shape) the green parts. The influence of shaping parameters—print temperature, bed temperature, print speed, and fan speed—on dimensional accuracy and density was systematically studied. A central composite design was adopted for experimentation, followed by the analysis of variance and regression modeling. Results showed that all shaping parameters significantly affected part properties, with certain interaction effects being particularly dominant. Multiobjective optimization by ratio analysis method was applied to identify optimal conditions, representing a novel contribution for copper MFFF. Based on the best parameters, successful green part was achieved. Subsequently, debinding and sintering operations were performed, resulting in a dense copper-rich part. The final part exhibited anisotropic shrinkage and geometric deviations, highlighting the importance of understanding material-specific behaviors. This study offers key insights into optimizing copper MFFF for reliable and high-quality part production.

Metal fused filament fabrication (MFFF) is an emerging additive manufacturing process to fabricate metal components by extruding metal–polymer composite filaments to form green parts, followed by debinding and sintering. Part quality is affected throughout the shaping, debinding, and sintering stages of MFFF, with porosity, surface roughness, and dimensional inaccuracy remaining the primary challenges. This study focuses on optimizing green part fabrication, a relatively less explored stage than sintering. The effects of print temperature (PT), print speed (PS), and fan speed (FS) on the dimensional accuracy, density, and surface quality of 316L stainless steel green parts were studied using a one-factor-at-a-time approach and range analysis. Dimensional accuracies in the x and y directions were significantly affected by PT, FS, and PS in descending order. However, in the z direction, FS, PT, and PS significantly affected the accuracy in descending order. Density was significantly influenced by PT, followed by FS and PS. FS, PS, and PT influenced surface roughness on the top face, while on the side face, PT, FS, and PS influenced in descending order. Higher PT and PS reduced dimensional accuracy and overall part quality while increasing density and surface roughness due to excessive material fluidity and unstable extrusion. FS improved accuracy by enhancing layer cooling. However, it resulted in lower density due to inadequate inter-layer fusion.

In this paper, the bump foil journal bearing (FJB) is developed with five different foil materials: Inconel X750 (IN-X750), Stainless steel 316 (SS316), Beryllium copper (BC), Spring steel EN42J (SP EN42J) and Phosphor bronze (PB). A complete fabrication process is described in detail, along with the design of fixtures, to develop the bump FJB. This fabrication process includes various machining operations such as milling, rolling, cutting, threading, forming etc. The forming load versus deflection curve is obtained for all the foil materials with the metal forming operation. After fabricating it, the load-deflection test is performed to evaluate the structural characteristics (stiffness, energy dissipation and damping coefficient) of these developed bump FJB. Further, the tribological characteristics of bump FJB such as wear rate and surface roughness are evaluated by the experimental study. Moreover, the interface temperature of bump FJB is also captured by using the thermal imager. This study shows that the metal forming operation is the most challenging step among all the fabrication steps of bump FJB Among all the foil materials, the minimum wear rate and maximum surface roughness of bump FJB are observed for the IN-X750. The maximum spring-back effect in bump FJB is found for the Spring steel EN42J. These results demonstrate that the maximum energy dissipation and stiffness of bump FJB are observed for the Phosphor bronze and Inconel-X750 respectively. In addition, the damping coeffcient of bump FJB is evaluated.

This study explores the tribological performance of bump foil journal bearing (FJB) equipped with micro-pocket. The influence of micro-pocket on the load capacity (LC) and friction factor (FF) of FJBs is evaluated for various foil materials, including Inconel X750 (IN), Spring steel EN42J (SP), SS 316, Beryllium copper (BC), and Phosphor bronze (PB). The compressible Reynolds equation is solved numerically to assess the tribological behavior of bump FJB under various operating conditions. Initially, the impact of micro pocket on the tribological characteristics such as load capacity and friction factor of bump FJB is examined by comparing their performance with plain FJB. Subsequently, the effect variable parameters such as pocket depth (PD), bearing number (Λ), and eccentricity ratio (ε), on the tribological behavior is analysed by using response surface methodology (RSM). The multi-objective grey relational analysis (GRA) technique is employed to determine the optimal values of these variable parameters for each foils material. The findings reveal that micro-pocket enhance the dimensionless LC of bump FJB beyond a bearing number of 2.061. Moreover, micro-pocket reduce the friction factor of bump FJBs. Within the presence of micro pocket, SS 316 exhibits the most significant foil material for the better tribological characteristics of bump FJB, while phosphor bronze is the least signifcant. For SS 316, the optimal values of pocket depth (PD), bearing number (Λ), and eccentricity ratio (ε) are 3 μm, 2.061, and 0.5 respectively. Under these optimal conditions, the load capacity (LC) and friction factor (FF) of bump FJBs are 0.7740 and 13.645, respectively. Micro-pocket reduces the friction factor (FF) by 2 to 15%. The impact of pocket depth on the LC and FF of bump FJB is significant for the phosphor bronze. Additionally, increasing the pocket depth enhances the dimensionless LC of bump FJBs while decreasing the friction factor.

The area of application of Fused filament fabrication (FFF) printing is regularly expanding, and the need for simulation of the geometry and mechanical properties to reduce the experimentation time and cost is a prime objective. In FFF printing, the input CAD model is converted into an STL file and then sliced with some software in a combination of layers, and accordingly, a tool path is generated, guiding the 3D printer to print. Thus, the printed part is not the same as the solid CAD model, but it is a layered solid part with various tool path settings or slicing parameters. This difference between the solid part and the layered replica part can cause errors in the calculations of mechanical properties. All the information related to layers, infill percentage, infill pattern, walls, etc, are stored in the form of various G or M codes in a G code file. The part orientation can also be visualized with the G code file. This G code file is the soft raw material for the FFF printer to execute the printing process. The correct reading and interpretation of the G code file are very essential to understand the 3D printing process from the core. The G code file can be used for multiple applications if the data is correctly extracted from it. This can be used to model the sliced or layered solid parts or to understand the extruder motions. In this work, a MATLAB code is generated to extract the data from the G code file and get the extrusion pattern with various infill patterns and percentages. The code was tested with multiple G code flavors, available in Cura and Slic3r software, and found suitable for all. The extracted data can be used further to model the sliced or layered solid model.