Design and Development of Different Applications of PATB (Porous Aerostatic Thrust Bearing): A Review

In several applications demanding precise and ultra-precision movements, porous aerostatic thrust bearings had been employed as a crucial precision engineering component and enabling technology. By acting as a lubricant between the moving part and the stationary part in aerostatic bearings, pressurized air almost completely eliminates friction. Since air acts as the lubricant, oil-based lubricants leave no debris behind. The air prolongs the life of the substances by preventing them from slipping and wearing. The aerostatic type uses graphite as a porous film to disrupt the air uniformly over the surface, or a tiny hole is drilled through the centre of the bearing to let the air circulate and produce a thin layer between the components. With an increased reliance on computational and mathematical methodologies for design and bearing performance optimization, this review paper aims to present the state-of-the-art in aerostatic bearings advancement and research. It also conducts a critical analysis of their future research directions and development trends in the next ten years and beyond. Air bearings are utilized in the production of tools like lathes, CMM, and grinders because they are highly precise in their operation and decrease mistakes and production time. Air bearings are available in a variety of forms and sizes. The assessment of future trends and obstacles in aerostatic bearings investigation, as well as their prospective applications in the precision engineering sectors, concludes the study

Selection of Suitable Lubricant for Sliding Contact Bearing and the Effect of Different Lubricants on Bearing Performance: A Review and Recommendations

The word bearing implies to an element of the machine which allows one moving or vibrating part to support other rubbing surfaces by which the load can transmit. Depending upon in nature and application of load, an extensive variety of different bearing is available. They can generally be categorized into two kinds of bearing such as rolling element bearing and a sliding bearing. Lubrication is required in the middle of rubbing surfaces, which enacts as a medium between the moving surfaces to diminish friction and to take away heat for survival during the transmission of the load. In this paper, a literature review has been made on the influence of different lubricants on the performance of various bearing. The selection of an appropriate lubricant is a very critical decision to take for the efficient performance of a bearing because each lubricant has its own merits and demerits on various kinds of bearing. In the later portion of this paper, a selection process of right lubricant in sliding contact bearing is analyzed mathematically. This critical decision is being made by using PROMETHEE method (broadly Preference Ranking Organization Method for Enrichment Evaluations) hybridized by Entropy Weight Measurement method and Fuzzy scale. As per the ranking of Entropy-PROMETHEE method, the best suited lubricant for sliding contact bearing is SAE20W40

An Investigation to Find the Effects on Air Foil Bearing by the Variation of Foil’s Structural Parameters

603-608The newest advancement in the realm of bearing technology, Air Foil Bearings (AFB) is a marvel that allows for operation at both incredibly low and high temperatures without fail. Their minimalistic design eliminates the requirement for lubrication and sealing systems, making them not only more efficient but also more eco-friendly. When it comes to speed, these bearings give no quarter - they can handle even the most extreme of conditions with ease. Air foil bearings rely on the structural design of top and bump foils to support and distribute pressure in the air film. To increase bearing capacity, these foils must be thick enough to withstand greater force. It is crucial to explore how varying foil thickness and bump height-pitch ratios may affect the performance of an air foil bearing. The researchers at the ANSYS Fluent lab set out to understand the dynamics of air foil bearings. By adjusting the thickness of the top and bump foils, they were able to observe how stress, stiffness, and air film clearance changed in relation to each other. Their results showed that even minor changes in foil thickness, bump height, and bump pitch had a significant impact on bearing performance. With their discoveries, these engineers have unlocked a new understanding of this complex technology - one that will help guide its continued development into the future. The thickness of the foil may not confer much strength, but it certainly does wonders for reducing stress and maintaining load-bearing capabilities. Its suppleness, however, cannot be denied – a boon for air foil bearings

Loading effect on friction behavior of ordered/disordered graphite in ambient and inert condition

19-25Load dependent friction behavior of structurally ordered and disordered graphite is measured in ambient and nitrogen gas atmosphere. Friction coefficient is significantly less in graphite in order as compared to disorder in ambient atmosphere. This behavior is attributed to structural defects in graphite lattice. However, under nitrogen gas, friction coefficient graphite is significantly high irrespective of structural order or disorder of graphite. This typical behavior is mainly attributed by chemical reactivity of graphite surface which is high in nitrogen gas and not much influenced by structural ordering/disordering. In both types of graphite, steep increase in friction coefficient is observed at high load. This is explained by reasonable increase in contact area and followed by the Johnson−Kendall−Roberts (JKR) model

Stress analysis and Design Optimization of Piston Slipper assembly in an Axial Piston Pump

318-323The amount of research carried out on piston assemblies of axial piston pump is a good indication of the problems which have been encountered. Fortunately this is one branch of engineering where research is usually well ahead of production failures. A representative domain for the high development of the axial piston pumps manufacturing is the aeronautics. In this industrial branch, light hydraulic transmissions that operate in very safe conditions are required. The mass reduction must be done according to an optimal design of the machines geometry, taking into account the static and dynamic stress and deflection states of the mechanical components. In this paper, a steady state stress analysis and also an optimization of the piston slipper assembly has been carried out by using ANSYS software. Optimization is done using Sub-problem approximation method where the main objective is to minimize the volume of the piston and slipper. Dimensions of the assembly are taken from SPV 22 axial piston pump, made by ZTS Company. This optimization technique minimizes the volume of the piston and also slipper. The paper concludes with the Comparison of the piston and slipper dimensions before and after optimization

Exploring the synergistic potential of response surface methodology based multi-objective optimization in the performance–emission-stability trade-off envelope of an existing diesel engine

The present study reveals synergistic possibilities of split-injection techniques under different exhaust gas recirculation (EGR) profiles to meet the emission-performance-stability trade-off from existing diesel engines under the Bharat Stage constraints. The coefficient of variance for indicated mean effective pressure (COVIMEP) and Exergy efficiency was selected as engine stability and performance indicators. At the same time, emission responses are marked by nitrogen oxide and hydrocarbon-particulate matter (NHC-PM) profile. The study undertook a comprehensive design-of-experiment (DoE) effort to identify operational limitations and subsequently determine the parametric design space. Trade-off zones have been optimized by meta-model-based objective function formation and desirability maximization approach. It seeks to find a robust optimization by reducing the level of uncertainty and standard errors of estimation during model generation based on the DoE selection and response surface methodology (RSM) approach. The study attempts to create a niche in the archetypical DoE-RSM-based engine response calibration endeavors by invoking several robustness fitness metrics. From the pilot experimental results, EGR has shown its potential as a reducing agent of NHC emission. Whereas in the case of split injecting strategies, the NHC-PM-exergy trade-off can be observed. The response parameters subsequent to the best Pareto solution corresponding to the highest desirability obtained from the optimization study were registered 5.2 g/kW-hr of NOx, 0.9 g/kW-hr of Soot, 23% of Exergy efficiency with the COVIMEP of 4.9. Optimum predicted sets obtained from optimization strategies have been compared with the respective pilot experimentation and concluded that the multifactor at a time (MFAT) strategy through RSM showed a significantly better result than the one factor at a time (OFAT) strategy

Discrimination of Ligands with Different Flexibilities Resulting from the Plasticity of the Binding Site in Tubulin

Tubulin, an α,β heterodimer, has four distinct ligand binding sites (for paclitaxel, peloruside/laulimalide, vinca, and colchicine). The site where colchicine binds is a promising drug target for arresting cell division and has been observed to accommodate compounds that are structurally diverse but possess comparable affinity. This investigation, using two such structurally different ligands as probes (one being colchicine itself and another, TN16), aims to provide insight into the origin of this diverse acceptability to provide a better perspective for the design of novel therapeutic molecules. Thermodynamic measurements reveal interesting interplay between entropy and enthalpy. Although both these parameters are favourable for TN16 binding (Δ<i>H</i> < 0, Δ<i>S</i> > 0), but the magnitude of entropy has the determining role for colchicine binding as its enthalpic component is destabilizing (Δ<i>H</i> > 0, Δ<i>S</i> > 0). Molecular dynamics simulation provides atomistic insight into the mechanism, pointing to the inherent flexibility of the binding pocket that can drastically change its shape depending on the ligand that it accepts. Simulation shows that in the complexed states both the ligands have freedom to move within the binding pocket; colchicine can switch its interactions like a “flying trapeze”, whereas TN16 rocks like a “swing cradle”, both benefiting entropically, although in two different ways. Additionally, the experimental results with respect to the role of solvation entropy correlate well with the computed difference in the hydration: water molecules associated with the ligands are released upon complexation. The complementary role of van der Waals packing versus flexibility controls the entropy–enthalpy modulations. This analysis provides lessons for the design of new ligands that should balance between the “better fit” and “flexibility”’, instead of focusing only on the receptor–ligand interactions