scholarly journals Enhancing Full-Film Lubrication Performance Via Arbitrary Surface Texture Design

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Yong Hoon Lee ◽  
Jonathon K. Schuh ◽  
Randy H. Ewoldt ◽  
James T. Allison
Keyword(s):  
Surface Texture ◽  
Performance Metrics ◽  
Optimization Problems ◽  
Spline Interpolation ◽  
Load Capacity ◽  
Improve Performance ◽  
Disk Radius ◽  
Lubrication Performance ◽  
Texture Design ◽  
Film Lubrication

Minimizing energy loss and improving system load capacity and compactness are important objectives for fluid power systems. Recent studies reveal that microtextured surfaces can reduce friction in full-film lubrication, and that asymmetric textures can reduce friction and increase normal force simultaneously. As an extension of these previous discoveries, we explore how enhanced texture design can maximize these objectives together. We design surface texture using a set of distinct parameterizations, ranging from simple to complex, to improve performance beyond what is possible for previously investigated texture geometries. Here, we consider a rotational tribo-rheometer configuration with a fixed textured bottom disk and a rotating top flat disk with controlled separation gap. To model Newtonian fluid flow, the Reynolds equation is formulated in cylindrical coordinates and solved using a pseudospectral method. Model assumptions include incompressibility, steady flow, constant viscosity, and a small gap height to disk radius ratio. Multi-objective optimization problems are solved using the epsilon-constraint method along with an interior-point (IP) nonlinear programming algorithm. The trade-off between competing objectives is quantified, revealing mechanisms of performance enhancement. Various geometries are explored and optimized, including symmetric and asymmetric circular dimples, and novel arbitrary continuous texture geometries represented using two-dimensional cubic spline interpolation. Shifting from simple dimpled textures to more general texture geometries resulted in significant simultaneous improvement in both performance metrics for full-film lubrication texture design. An important qualitative result is that textures resembling a spiral blade tend to improve performance for rotating contacts.

Shape Parameterization Comparison for Full-Film Lubrication Texture Design

2016 ◽  
Author(s):  
Yong Hoon Lee ◽  
Jonathon Schuh ◽  
Randy H. Ewoldt ◽  
James T. Allison
Keyword(s):  
Performance Metrics ◽  
Normal Force ◽  
Optimization Problems ◽  
Spline Interpolation ◽  
Load Capacity ◽  
Fluid Power ◽  
Textured Surface ◽  
Interior Point Algorithm ◽  
Texture Design ◽  
Film Lubrication

Minimizing energy loss and improving system load capacity and compactness are important objectives for fluid power applications. Recent studies have revealed that a micro-textured surface can reduce friction in full-film lubrication, and an asymmetric textured surface can further improve the performance by reducing friction and increasing normal force simultaneously. As an extension of these previous discoveries, we explore how enhanced texture design can maximize these objectives together. We design the surface texture using a set of distinct parameterizations, ranging from simple to complex (including very general geometries), to improve friction and normal force properties beyond what is possible for limited texture geometries. Here we use a rotational visco-rheometer configuration with a fixed bottom disc, a periodic textured surface, and a rotating top flat disc. The Reynolds equation is formulated in a cylindrical coordinate system and solved using a pseudo-spectral method to model Newtonian fluid flow within the gap between discs. Model assumptions include incompressibility, steady flow, constant viscosity, and a small gap height to texture radius ratio. Multiobjective optimization problems are solved using the epsilon-constraint method with an interior-point algorithm. The trade-off between competing objectives is quantified, revealing important insights. Arbitrary continuous texture geometries are represented using two dimensional cubic spline interpolation. Shifting to more general texture geometries resulted in significant simultaneous improvement in both performance metrics for full-film lubrication texture design. An important qualitative result is that textures resembling a helical blade tend to improve performance for rotating contacts in fluid power systems.

Numerical analysis and optimization of rectangular texture for gas foil thrust bearing

2020 ◽  
Vol 235 (8) ◽  
pp. 1599-1613
Author(s):  
Zhenpeng He ◽  
Chun Zhang ◽  
Jianqiang Li ◽  
Yuanyuan Zhao ◽  
Aijun Sun
Keyword(s):  
Surface Texture ◽  
Texture Parameters ◽  
Lubrication Performance ◽  
Foil Thrust Bearing ◽  
The Stability ◽  
Texture Size ◽  
Rectangular Groove ◽  
Radial Arrangement ◽  
Texture Design ◽  
Oil Film Pressure

Accurate surface texture design is of great significance to improve the performances of gas bearings. In this article, the finite difference method and Newton’s method were combined to obtain the oil film pressure distribution, and the effect of rectangular groove on the lubrication performance was analyzed by changing representative texture parameters. The results show that the performances were more affected by the rectangular texture size compared with the distribution and the bottom shape of texture. The increasing of the surface texture number can only enhance the stability of the bearing. The bearing can provide 30% more bearing capacity by choosing larger size, radial arrangement and plane bottom. These results and analysis can provide technical reference for the bearing texture design.

scholarly journals A Survey of Recent Extended Variants of the Traveling Salesman and Vehicle Routing Problems for Unmanned Aerial Vehicles

Drones ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 66 ◽  
Author(s):  
Ines Khoufi ◽  
Anis Laouiti ◽  
Cedric Adjih
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Vehicle Routing ◽  
Performance Metrics ◽  
Recent Literature ◽  
Optimization Problems ◽  
Load Capacity ◽  
Traveling Salesman ◽  
Path Optimization ◽  
Routing Problem ◽  
Aerial Vehicles

The use of Unmanned Aerial Vehicles (UAVs) is rapidly growing in popularity. Initially introduced for military purposes, over the past few years, UAVs and related technologies have successfully transitioned to a whole new range of civilian applications such as delivery, logistics, surveillance, entertainment, and so forth. They have opened new possibilities such as allowing operation in otherwise difficult or hazardous areas, for instance. For all applications, one foremost concern is the selection of the paths and trajectories of UAVs, and at the same time, UAVs control comes with many challenges, as they have limited energy, limited load capacity and are vulnerable to difficult weather conditions. Generally, efficiently operating a drone can be mathematically formalized as a path optimization problem under some constraints. This shares some commonalities with similar problems that have been extensively studied in the context of urban vehicles and it is only natural that the recent literature has extended the latter to fit aerial vehicle constraints. The knowledge of such problems, their formulation, the resolution methods proposed—through the variants induced specifically by UAVs features—are of interest for practitioners for any UAV application. Hence, in this study, we propose a review of existing literature devoted to such UAV path optimization problems, focusing specifically on the sub-class of problems that consider the mobility on a macroscopic scale. These are related to the two existing general classic ones—the Traveling Salesman Problem and the Vehicle Routing Problem. We analyze the recent literature that adapted the problems to the UAV context, provide an extensive classification and taxonomy of their problems and their formulation and also give a synthetic overview of the resolution techniques, performance metrics and obtained numerical results.

scholarly journals Impact of chosen force fields and applied load on thin film lubrication

Friction ◽  
2021 ◽  
Author(s):  
Thi D. Ta ◽  
Hien D. Ta ◽  
Kiet A. Tieu ◽  
Bach H. Tran
Keyword(s):  
Thin Film ◽  
Shear Stress ◽  
Surface Structure ◽  
Rheological Properties ◽  
Surface Potential ◽  
Applied Load ◽  
Velocity Slip ◽  
Thin Film Lubrication ◽  
Lubrication Performance ◽  
Film Lubrication

AbstractThe rapid development of molecular dynamics (MD) simulations, as well as classical and reactive atomic potentials, has enabled tribologists to gain new insights into lubrication performance at the fundamental level. However, the impact of adopted potentials on the rheological properties and tribological performance of hydrocarbons has not been researched adequately. This extensive study analyzed the effects of surface structure, applied load, and force field (FF) on the thin film lubrication of hexadecane. The lubricant film became more solid-like as the applied load increased. In particular, with increasing applied load, there was an increase in the velocity slip, shear viscosity, and friction. The degree of ordering structure also changed with the applied load but rather insignificantly. It was also significantly dependent on the surface structure. The chosen FFs significantly influenced the lubrication performance, rheological properties, and molecular structure. The adaptive intermolecular reactive empirical bond order (AIREBO) potential resulted in more significant liquid-like behaviors, and the smallest velocity slip, degree of ordering structure, and shear stress were compared using the optimized potential for liquid simulations of united atoms (OPLS-UAs), condensed-phase optimized molecular potential for atomic simulation studies (COMPASS), and ReaxFF. Generally, classical potentials, such as OPLS-UA and COMPASS, exhibit more solid-like behavior than reactive potentials do. Furthermore, owing to the solid-like behavior, the lubricant temperatures obtained from OPLS-UA and COMPASS were much lower than those obtained from AIREBO and ReaxFF. The increase in shear stress, as well as the decrease in velocity slip with an increase in the surface potential parameter ζ, remained conserved for all chosen FFs, thus indicating that the proposed surface potential parameter ζ for the COMPASS FF can be verified for a wide range of atomic models.

scholarly journals Surface Texture Design and Its Tribological Application

2019 ◽  
Vol 55 (17) ◽  
pp. 85 ◽  
Author(s):  
ZHANG Hui ◽  
LIU Yang ◽  
WANG Wei ◽  
QIN Liguo ◽  
DONG Guangneng
Keyword(s):  
Surface Texture ◽  
Tribological Application ◽  
Texture Design

Do Common User Interface Design Patterns Improve Navigation?

2002 ◽  
Vol 46 (14) ◽  
pp. 1315-1319 ◽  
Author(s):  
Carlos A. Maldonado ◽  
Marc L. Jlesnick
Keyword(s):  
Web Sites ◽  
Interface Design ◽  
Design Patterns ◽  
Performance Metrics ◽  
Statistical Significance ◽  
A Priori ◽  
Improve Performance ◽  
Subjective Preference ◽  
On Line ◽  
Quantitative Performance

The Internet has become a growing channel for consumer purchases. Half of all U.S. consumers made at least one purchase on-line in 2001. However, many consumers report frustration with the lack of support for navigation within many Internet retailers' web sites. Several design patterns have been suggested to overcome these limitations, such as expanded hierarchies and breadcrumbs. This study investigated the effects of these design patterns on users' quantitative performance and subjective preference for ecommerce web sites. Expanded hierarchies, a design pattern that is commonly used by many retail web sites, degraded all of the performance metrics assessed in the study. Users required more time, made more errors, used more clicks, and had lower satisfaction scores for sites designed with expanded hierarchies. The results for breadcrumbs suggest that they may improve performance. The inclusion of breadcrumbs reduced the number of clicks required by users to complete the tasks, but other performance metrics did not reach statistical significance. The results indicate that design patterns that are believed to improve performance a priori may not yield the results expected.

A Mixed-TEHL Analysis of Cam-Roller Contacts Considering Roller Slip: On the Influence of Roller-Pin Contact Friction

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Shivam S. Alakhramsing ◽  
Matthijn B. de Rooij ◽  
Aydar Akchurin ◽  
Dirk J. Schipper ◽  
Mark van Drogen
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Contact Friction ◽  
Sudden Increase ◽  
Low Friction ◽  
Pure Rolling ◽  
Lubrication Performance ◽  
Cam Follower ◽  
Film Lubrication

In this work, a mixed lubrication model, applicable to cam-roller contacts, is presented. The model takes into account non-Newtonian, thermal effects, and variable roller angular velocity. Mixed lubrication is analyzed using the load sharing concept, using measured surface roughness. Using the model, a quasi-static analysis for a heavily loaded cam-roller follower contact is carried out. The results show that when the lubrication conditions in the roller-pin contact are satisfactory, i.e., low friction levels, then the nearly “pure rolling” condition at the cam-roller contact is maintained and lubrication performance is also satisfactory. Moreover, non-Newtonian and thermal effects are then negligible. Furthermore, the influence of roller-pin friction coefficient on the overall tribological behavior of the cam-roller contact is investigated. In this part, a parametric study is carried out in which the friction coefficient in the roller-pin contact is varied from values corresponding to full film lubrication to values corresponding to boundary lubrication. Main findings are that at increasing friction levels in the roller-pin contact, there is a sudden increase in the slide-to-roll ratio (SRR) in the cam-roller contact. The value of the roller-pin friction coefficient at which this sudden increase in SRR is noticed depends on the contact force, the non-Newtonian characteristics, and viscosity–pressure dependence. For roller-pin friction coefficient values higher than this critical value, inclusion of non-Newtonian and thermal effects becomes highly important. Furthermore, after this critical level of roller-pin friction, the lubrication regime rapidly shifts from full film to mixed lubrication. Based on the findings in this work, the importance of ensuring adequate lubrication in the roller-pin contact is highlighted as this appears to be the critical contact in the cam-follower unit.

Tribological performance of a surface textured meso scale air bearing

2019 ◽  
Vol 72 (5) ◽  
pp. 599-609
Author(s):  
Nilesh D. Hingawe ◽  
Skylab P. Bhore
Keyword(s):  
Friction Coefficient ◽  
Journal Bearing ◽  
Load Capacity ◽  
Tribological Performance ◽  
Design Parameters ◽  
Content Type ◽  
Thin Film Model ◽  
Maximum Improvement ◽  
Meso Scale ◽  
Texture Design

Purpose The purpose of this study is to improve the tribological performance of meso scale air journal bearing by adopting texture on the bearing surface. Design/methodology/approach The present study is based on numerical analysis. The detailed numerical investigation is carried out using a fluid flow based thin-film model in COMSOL 5.2 software. Findings The influence of texture design parameters: geometry (shape, orientation and slender ratio), and position on the tribological performance of meso scale air journal bearing is investigated. It is found that texture shape has a strong influence on the tribological characteristics such as load capacity and friction coefficient of the bearing. Slender texture improves the load capacity, but it has a negligible effect on the reduction of friction coefficient. In contrast, texture orientation is found to be insignificant for both increasing load capacity and decreasing friction coefficient. Furthermore, the maximum improvement in load capacity is obtained for partially textured bearing, but the minimum friction coefficient is achieved for full texturing. Originality/value The present study investigates the influence of texture design parameters viz geometry (shape, orientation and slender ratio), and position on the tribological performance of meso scale air journal bearing.

A Review of Surface Texture of Tribological Interfaces

2010 ◽  
Vol 37-38 ◽  
pp. 41-45 ◽  
Author(s):  
Zhi Wei Wang ◽  
Mei Wei Chen ◽  
Jian Wei Wu ◽  
Hai Hui Zheng ◽  
Xiao Feng Zheng
Keyword(s):  
Modeling And Simulation ◽  
Surface Texture ◽  
Review Paper ◽  
Tribological Performance ◽  
Current Status ◽  
Comprehensive View ◽  
Lubrication Performance ◽  
Mechanical Components ◽  
Friction And Lubrication

Surface texture of tribological interfaces has the potential to improve friction and lubrication performance of various mechanical components. This review paper emphasizes on the current status of the research of surface texture, including the features, the effects on tribological performance, the forming techniques, and the modeling and simulation of surface texture. It is intended to help readers to gain a more comprehensive view on surface texture of tribological interfaces.

Multiobjective Differential Evolution Based on Fuzzy Performance Feedback

2014 ◽  
Vol 5 (4) ◽  
pp. 45-64 ◽  
Author(s):  
Chatkaew Jariyatantiwait ◽  
Gary G. Yen
Keyword(s):  
Evolutionary Algorithms ◽  
Differential Evolution ◽  
Performance Feedback ◽  
Performance Metrics ◽  
Fuzzy Inference ◽  
Optimization Problems ◽  
Evolution Process ◽  
Exploration And Exploitation ◽  
Multiobjective Optimization Problems ◽  
Mutation Strategy

Differential evolution is often regarded as one of the most efficient evolutionary algorithms to tackle multiobjective optimization problems. The key to success of any multiobjective evolutionary algorithms (MOEAs) is maintaining a delicate balance between exploration and exploitation throughout the evolution process. In this paper, the authors propose a Fuzzy-based Multiobjective Differential Evolution (FMDE) that uses performance metrics, specifically hypervolume, spacing, and maximum spread, to measure the state of the evolution process. The authors apply the fuzzy inference rules to these metrics in order to dynamically adjust the associated control parameters of a chosen mutation strategy used in this algorithm. One parameter controls the degree of greedy or exploitation, while another regulates the degree of diversity or exploration of the reproduction phase. Therefore, the authors can appropriately adjust the degree of exploration and exploitation through performance feedback. The performance of FMDE is evaluated on well-known ZDT and DTLZ test suites. The results validate that the proposed algorithm is competitive with respect to chosen state-of-the-art MOEAs.

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