The bump-type gas foil bearing (GFB) is widely used in various high-speed oil-free turbomachinery due to its extra features such as high-speed capability without any external oil lubricant. Under the high-speed condition, the performance characteristics of GFB are majorly dependent on its design parameter. Thus, this paper briefly analyzes and optimizes the design parameters of bump-type GFB to improve its performance characteristic. The numerical simulation of bump-type GFB is performed in ANSYS software. The effect of various design parameters such as foil thickness, bump half-length, bump pitch, and bump angle on the output responses are analyzed using a response surface methodology based CCD design matrix. Here, the output responses are structural stiffness and the equivalent stress in foil bearing. To optimize it, the multi-objective GRA technique is used. These results show that the foil thickness is the most influencing and the bump angle is the least influencing design parameter. The optimal value of foil thickness, bump angle, bump half-length and bump pitch are 0.14 mm, 63.75 deg., 1.55 mm and 4.6 mm respectively. At these optimal design parameters, the deviation between the predicted regression model and the numerical results are within 3.5%. Moreover, with these optimal design parameters, the structural stiffness of foil bearings increases by 68.4% and stress distribution reduces by 44.22% compared to the general configuration of foil bearings.

Meso scale air journal bearing has widespread application in miniaturized systems and there is a strong need to improve its tribological performance. Although surface texturing can improve its performance, very few studies have addressed this issue. Therefore, this paper investigates the influence of texture geometrical parameters on the tribological performance of meso scale air journal bearing. A numerical study is carried out in a thin-film model of the COMSOL 5.2 package. The effect of texture geometrical parameters viz. position, depth, orientation, and slender ratio on tribological characteristics such as load-carrying capacity and friction coefficient is first analyzed by response surface methodology based Box-Behnken design. Further, a multi-objective optimization study is carried out using grey relational analysis. For the optimum design, textured air bearing has obtained 12.15% more load carrying capacity, and 19.65% lesser friction coefficient than the plane air bearing. For this improvement, texture depth and orientation are found to be the most and the least significant parameters, respectively. Also, at variable bearing parameters such as eccentricity ratio and rotational speed the optimum textured bearing performed better than the regularly textured bearings.

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.

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.