Multi-objective optimization of surface textured journal bearing by Taguchi based Grey relational analysis

The growing demands of high-speed rotary systems require journal bearings with enhanced tribological performance. Conventional lubricants consistently fall short, so nanolubricants-upgraded with nanoparticles are a viable alternative due to high thermal conductivity and load-carrying capacity. This article presents an extensive experimental investigation on elliptical journal bearing performance utilizing a journal bearing test rig with a variety of operating oils, speed and load parameters. Two base lubricants and nanolubricants synthesized by dispersing titanium dioxide (TiO 2 ) and copper oxide (CuO) nanoparticles at three concentrations (0.5%, 1.0%, and 2.0% by weight) have been studied. Two important performance parameters, namely, hydrodynamic pressure distribution and oil film temperature have been evaluated under steady-state conditions. The results reveal that nanolubricants significantly enhance the static thermal bearing performance with all operating parameters. Specifically, nanolubricants prepared by blending TiO 2 gave better results in comparison to CuO based nanolubricants with marked increase in hydrodynamic pressure (up to 15.67%) with insignificant rise (up to 3.83%) in oil temperature. Bearing performance has been further improved with increase in nanoparticles concentration. In addition, elliptical bearings also had preferred pressure contours compared with conventional circular bearings, which reveals their possible suitability under high-load bearing applications. The findings reveal the potential of nanolubricants and elliptical bearing geometries for increasing the reliability and performance of modern tribosystems.

Spiral groove journal bearings (SGJBs) are widely used in high-performance rotating machinery due to their excellent hydrodynamic performance and wear resistance. However, the strong nonlinear interactions among key geometric parameters made considerable challenges to performance optimization. This study introduces an integrated approach utilizing Response Surface Methodology (RSM) coupled with Finite Element Method (FEM) to systematically investigate the influences of groove width, length, depth, spiral angle, and groove numbers on bearing load-carrying capacity (LCC) and lubricant leakage. Analysis of variance (ANOVA) results identified significant interactions among parameters, with groove width, length, and depth strongly influence LCC, while groove length, depth, and number primarily govern leakage, with spiral angle having a comparatively minor effect. A multi-objective optimization framework was developed, achieving a 6% increase in LCC and a 37.17% reduction in leakage. The results provide valuable insights into the practical design to improve lubrication efficiency in high-performance engineering applications.

Hydrodynamic journal bearings are widely used to support high-speed rotating equipment due to their excellent strength and load-bearing capacity. Therefore, bearings are essential mechanical elements to improve the quality of rotating equipment. Bearing performance depends on various factors but pressure and frictional torque plays a vital role in load carrying capacity of bearing. In this present work, both experimental and analytical approach of a typical journal bearing has been carried out to determine the optimal performance of the bearing. Taguchi-based optimisation method has been proposed for journal bearing. Taguchi L27 orthogonal array has been planned to study peak pressure and frictional torque with three input parameters speed, load and viscosity index. The result shows that loading criterion influences much on performance of bearing. The experimental data is obtained from a journal bearing test rig and the analytical data are generated by MINITAB 18. From the experiment, it can be confirmed that speed – 2000 rpm, load – 600 N and viscosity index – 150 are the ideal process parameters for lower peak pressure and less frictional torque.

The present work focuses to analyse the importance of turning parameters on the responses: machining time, surface roughness and material removal rate in CNC turning while machining of aluminium alloy Al-6082 T6 using tungsten carbide tool. Cutting speed, feed rate and depth of cut with three levels each have been considered in the current work as the machining parameters. The present study uses the Taguchi's DOE methodology, grey relational approach and principal component analysis (PCA) to optimise the response parameters simultaneously. Experiments have been conducted as per Taguchi's L9 orthogonal array. The experimental results were then analysed using the grey relational analysis (GRA) along with the principal component analysis (PCA). The speed and feed are observed to be statistically significant on the responses whereas the depth of cut is insignificant. Optimal levels for the parameters are determined using the grey Taguchi method and PCA. The confirmation test is carried out and the results are validated.

Mechanical and hydrophobic properties of chromium carbide films via a multi-objective optimization approach

This paper presents an analysis of the pressure distribution of hydrodynamic journal bearing for different surface texture, velocity variation and load variation. The performance of journal bearing depends on speed, load carrying capacity, viscosity of oil and temperature condition. Therefore, the effects of these parameters on the performance of journal bearing, on the pressure distribution and on the load carrying capacity have been analyzed on the basis of number of revolution per minute of the shaft. The lubricating oil used for the experimental work is SAE 40. Eight pressure distribution profiles were generated by making eight combinations of speed of the shaft and load on journal bearing. It was observed from the profiles that texture bearing can sustain at more pressure as compared to the smooth bearing. Reason behind this result is the presence of holes in texture bearing. These holes behaves like a reservoir and lubricating oil was filled in it, due to which metal to metal contact reduced and friction was minimized. Hence the performance of the bearing was improved.

Interconnects have become a major obstacle in chip scaling. Spoof surface plasmon polariton (SSPP) modes have gained attention for their ability to manipulate light beyond diffraction limits at a given frequency, leading to SSPP interconnects. This article investigates the transmission characteristics of SSPP interconnect pairs placed side by side in the terahertz frequency range with comprehensive performance analysis. The proposed SSPP waveguide pair exhibits a maximum transmission coefficient of around −0.05 dB in the −3 dB band in the terahertz frequency range. Due to field confinement near the metal–dielectric interface, energy remains confined for the designed SSPP interconnect pair system. The proposed SSPP structure shows several bands in the terahertz frequency range, whereas conventional interconnects shows almost zero transmission at such frequencies. Additionally, the effect of geometric parameters on transmission coefficients (S21) and coupling coefficients (S41) has been investigated. Moreover, it has been shown that the bandwidth, as well as the upper cutoff frequency, can be tuned by varying the geometric parameters such as groove height, groove width and groove density. Since global interconnects undergo bending in actual circuits during distant data transmission on chips, geometric mismatches may occur between adjacent pairs of SSPP interconnects. Hence, it has also been examined how bending and mismatches affect transmission and coupling coefficients. Several SSPP schemes have been simulated, among which the best performance is obtained with 2 μm mismatch in groove height. For this optimized design, two corrugated metal interconnects are considered with groove heights of 20 μm and 22 μm, respectively, a groove width of 3 μm, a period of 20 μm, and the number of grooves at 50. For this particular configuration, an ultra-wide passband is found having a bandwidth of almost 400 GHz, with a signal reflection of below −12 dB and little insertion loss of ∼−1.43 dB.

In this paper, parametric analysis of various operating and surface texturing parameters on the performance characteristics of water lubricated journal bearing was carried out using Fluid Structure Interaction approach. Initially, a simulation model was validated with experimental results from the literature. An effect of journal speed and eccentricity ratio along with elastic deformation on performance characteristics viz. lubricant pressure, load carrying capacity, and coefficient of friction with different groove location was studied. Further investigation was carried out to examine the influence of the number of grooves on the performance characteristics. From the analysis, it was observed that 0–180° grooved journal bearing with 5 number of grooves has shown improved performance as compared to journal bearing with 0–90° grooved, 90–180° grooved and plain surface.

Performance of worn non-recessed hole-entry hybrid journal bearings

The multi response optimisation of process parameters like surface roughness (SR) and metal removal rate (MRR) of electrical discharge machining (EDM) of carbon nano tube (CNT) mixed dielectric fluid using grey relational analysis are performed. Experiments are performed with designated EDM conditions obtained using an L9 orthogonal array. Based on the results of the grey relational analysis a set of optimum EDM parameters is obtained. The analysis of variance (ANOVA) approach is used to find the significant parameters influencing the EDM machining process. The results show that the optimum machining conditions determined using grey relational analysis are much better than the original preliminary set of experimental conditions. Atomic force microscope (AFM) is used to analysis the surface characteristics such as surface roughness, micro cracks and topography of CNT-based machining surface. The paper describes the application of a fuzzy logic system to investigate precision and accuracy of EDM process parameters for determining the efficiency of each parameter influencing the machining for with and without using CNT mixed dielectric fluid.

High-speed rotating machinery has extremely high requirements for the performance and reliability of aerostatic bearings, and the design of pressure-equalizing groove structure is a key factor determining the performance of aerostatic bearings under high-speed conditions. At present, research on the influence of pressure-equalizing groove structure on the performance of high-speed aerostatic bearings is still relatively limited. In this study, aerostatic thrust gas bearings with three pressure-equalizing groove structures (rectangular, fan-shaped and drop-shaped) were designed, and their performance characteristics were comprehensively analyzed by numerical simulation method. A CFD model of the bearing was established based on the Navier-Stokes equations and the model accuracy was verified. The performance of bearings with each structure under different working conditions of air film thickness, supply pressure and rotational speed was explored. The study found that the shape of pressure-equalizing groove has a significant impact on the load-carrying capacity, pressure distribution, stiffness and stability of the bearing. Under high-speed conditions, vortices in the groove critically affect the pressure distribution in the high-pressure zone of the bearing, which in turn determines the load-carrying capacity. Fan-shaped and drop-shaped grooves can effectively suppress vortices due to their divergent structures, and their load-carrying capacity and stiffness during high-speed operation are superior to those of rectangular grooves, while rectangular and fan-shaped grooves have smaller pressure fluctuations and exhibit better stability. There is a clear correlation mechanism between the divergent characteristics of different pressure-equalizing grooves and vortex suppression. Fan-shaped and drop-shaped grooves can promote the expansion of the high-pressure area of the air film and enhance the hydrodynamic effect, while the complete vortex in the rectangular groove limits the development of the high-pressure area. The research results provide theoretical support for the design and optimization of aerostatic bearings, and contribute to the research and development of high-performance bearings adapted to high-speed rotating machinery.

Behavior of seawater sea sand concrete-filled plastic-lined steel tube stub columns under axial compression

PurposeThe application of reinforcing old bridges by adding external prestressed steel bundles is becoming more and more widespread. However, the long-term safety performance test of the strengthening method is rarely carried out. In this paper, the bearing capacity of a 420 m prestressed concrete (PC) continuous girder bridge after five years of strengthening is analyzed.Design/methodology/approachThe bridge model of the bridge structure and strengthening scheme is established by the finite element software of the bridge. The theoretical load-bearing capacity of the bridge under the latest standard load grade is obtained by finite element analysis. The actual bearing capacity of the bridge is obtained by field test. Through the comparative analysis of theory and practice, the health state of the bridge after five years of reinforced operation is judged. The damage to the overall stiffness and external prestressing of the bridge is also analyzed.FindingsThe results of deflection and strain show that the stiffness and strength of the secondary side span and the middle span decrease slightly, and the maximum reduction of bearing capacity is 4.5%. The static stiffness of the whole bridge decreases as a result of cracks, and the maximum decrease is 21%. In the past five years, the relaxation loss of the external prestressing of the bridge is 3.31–3.97%, which is the main reason for the decrease in bearing capacity.Originality/valueThrough the joint analysis of the bridge stiffness and the loss of external prestressing, the strengthening condition of the bridge after five years of operation is effectively analyzed. The strengthening effect of the external prestressed steel beam strengthening method is analyzed, which can provide a reference for similar bridge strengthening.

Numerous previous numerical studies have investigated the effect of surface texturing upon the static characteristics of journal bearings, including their load-carrying capacity and friction torque. In general, the dynamic characteristics of journal bearings are also important, since they are essential factors in predicting the vibration behavior of actual rotors supported by journal bearings. However, the effects of surface texture upon these dynamic characteristics have not been investigated through either numerical or experimental analysis. Thus, in the present study, such analyses were conducted to investigate the dynamic characteristics of textured journal bearings, such as their dynamic coefficients of oil film and the stability-threshold shaft speed supported by the bearings. Numerical analysis was done using a model that included inertial effects and energy loss; this model agreed well with experimental results concerning static characteristics from our previous study. Dynamic testing based on a sinusoidal-excitation method was also performed using textured journal bearings with uniform square dimples to verify the numerical results, which agreed qualitatively with those of experiment, confirming the validity of the numerical analysis. These results suggest that under the same operating conditions, the main effect of texturing upon the dynamic coefficients is to yield the cross-coupled stiffness coefficients with lower absolute values than the conventional ones with a smooth surface. The linear stability-threshold shaft speed of the rotor supported by the textured journal bearings became higher than that of a smooth bearing, mainly due to the reduction of cross-coupled stiffness coefficients. This tendency became more pronounced for high Reynolds number operating conditions and textured bearings with a large number of dimples.

An analysis and development of a dry-face mechanical shaft seal concept : G. Wilkes and P. F. Donlevy, Lubrication Eng., 26 (8) (1970) 273–280; 7 figs., 6 refs.