Lubricants

28 pages, 6659 KiB

Open AccessArticle

Understanding the Influences of Multiscale Waviness on the Elastohydrodynamic Lubrication Performance, Part I: The Full-Film Condition

by Yuechang Wang, Changlin Li, Jianjun Du and Ardian Morina

Lubricants 2022, 10(12), 368; https://doi.org/10.3390/lubricants10120368 - 18 Dec 2022

Viewed by 1556

Abstract

Understanding the responses of tribosystems to multiscale roughness is fundamental for the identification of the relevant roughness scales. This work used a point-contact elastohydrodynamic lubrication (EHL) problem as a representative tribosystem and artificially generated waviness with different amplitudes, frequencies, and directions to mimic [...] Read more.

Understanding the responses of tribosystems to multiscale roughness is fundamental for the identification of the relevant roughness scales. This work used a point-contact elastohydrodynamic lubrication (EHL) problem as a representative tribosystem and artificially generated waviness with different amplitudes, frequencies, and directions to mimic the multiscale roughness. The amplitudes and frequencies are related to the feature geometry of smooth EHL problems. This work consists of Part I (this paper), focusing on the full-film condition, and Part II, focusing on the partial-film condition. Generated waviness is input to a transient thermal EHL model. The simulation is conducted 1600 times for different waviness parameters, loads, and speeds. Seven performance parameters are extracted: the minimum film thickness, maximum pressure, central film thickness, central pressure, mean film thickness, coefficient of friction (COF), and maximum temperature rise. The ratios of these parameters with and without waviness are plotted on the frequency–amplitude coordinate plane as contour maps. The influences of the amplitude, frequency, wave direction, load, and speed on the seven performance parameters are analyzed and summarized. The simulated data and plotted contour maps are provided to the readers in the Supplementary Material. Full article

(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)

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11 pages, 2244 KiB

Open AccessArticle

Modified Ni Nanoparticles as Additives in Various Greases: Assessment of Comparative Performance Potential

by Jiabei Wang, Hong Zhang, Wenjing Hu and Jiusheng Li

Lubricants 2022, 10(12), 367; https://doi.org/10.3390/lubricants10120367 - 17 Dec 2022

Cited by 4 | Viewed by 1519

Abstract

China’s rapid industrial development requires more energy consumption based on non-renewable energy resources. The energy consumption caused by unnecessary friction accounts for about 4.5% of the GDP in China. Although grease effectively lubricates machines, lubrication failure may occur under severe conditions. Nanomaterials exhibit [...] Read more.

China’s rapid industrial development requires more energy consumption based on non-renewable energy resources. The energy consumption caused by unnecessary friction accounts for about 4.5% of the GDP in China. Although grease effectively lubricates machines, lubrication failure may occur under severe conditions. Nanomaterials exhibit intriguing tribological performances and have received much attention regarding lubrication. In this study, oleylamine-modified Ni nanoparticles (OA-Ni) were synthesized and used as lubricant additive in four kinds of commonly used greases: lithium, calcium, composite calcium, and polyurea grease. The OA-Ni were uniformly dispersed in the greases through electromagnetic stirring, ultrasonic vibration, and three-roll grinding. The physicochemical properties and the structure of OA-Ni-doped grease were investigated, while the feasibility of OA-Ni as various grease additives at different contact modes was evaluated by a four-ball friction tester and a UMT-tribolab tester. Tribological tests results revealed that the friction-reducing and anti-wear properties of point-to-point contact were increased by 56.7% and 70.3% in lithium grease, respectively, while those of the point-to-face contact were increased by 59.5% and 68.9% in polyurea grease, respectively. The present work provides not only theoretical guidance of nano nickel modification but also a practical reference for the application of modified nanomaterials to various greases. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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16 pages, 6293 KiB

Open AccessArticle

Performance of Al₂O₃/TiO₂ Hybrid Nano-Cutting Fluid in MQL Turning Operation via RSM Approach

by Ariffin Arifuddin, Abd Aziz Mohammad Redhwan, Wan Hamzah Azmi and Nurul Nadia Mohd Zawawi

Lubricants 2022, 10(12), 366; https://doi.org/10.3390/lubricants10120366 - 16 Dec 2022

Cited by 3 | Viewed by 1707

Abstract

Cutting fluids can be used to cool workpieces at high cutting speeds and remove chips from cutting zones. The effectiveness of cutting fluids may be improved with the addition of hybrid nanoparticle dispersion. This study evaluates the effectiveness of an Al₂O [...] Read more.

Cutting fluids can be used to cool workpieces at high cutting speeds and remove chips from cutting zones. The effectiveness of cutting fluids may be improved with the addition of hybrid nanoparticle dispersion. This study evaluates the effectiveness of an Al₂O₃-TiO₂ hybrid as a cutting fluid in turning operations. The Al₂O₃-TiO₂ hybrid nano-cutting fluid was prepared using a one-step method in computer numerical control (CNC) coolant with concentrations of up to 4%. Utilizing air-assisted nano-cutting fluids injected through a minimum quantity lubrication (MQL) setup, the effectiveness of turning cutting performance, cutting temperature (°C), average surface roughness (Ra), and tool wear (%) were evaluated. Then, the response surface method (RSM) was utilized as the design of experiment (DOE) to optimize the turning cutting performance parameters. The combination of 4% hybrid nano-cutting fluid concentration, 0.1 mm/rev feed rate, and 0.55 mm depth of cut yielded the lowest cutting temperature, surface roughness, and tool wear values of 25.3 °C, 0.480 µm, and 0.0104%, respectively. The 4% concentration of Al₂O₃/TiO₂ hybrid nano-cutting fluid inclusion achieved the highest surface roughness reduction that led to better surface finish and the lowest tool-wear reduction led to longer tool life. Therefore, Al₂O₃/TiO₂ hybrid nano-cutting fluids were strongly recommended in turning operations for CNC lathes. Full article

(This article belongs to the Special Issue Minimum Quantity Lubrication: Environmental Alternatives in Processing)

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12 pages, 4082 KiB

Open AccessArticle

Impact of Fatty Triamine on Friction Reduction Performance of MoDTC Lubrication Additive

by Camella Oumahi, Thierry Le Mogne, Antonio Aguilar-Tapia, Catherine Charrin, Christophe Geantet, Pavel Afanasiev, Benoit Thiebaut and Maria Isabel De Barros-Bouchet

Lubricants 2022, 10(12), 365; https://doi.org/10.3390/lubricants10120365 - 16 Dec 2022

Cited by 3 | Viewed by 1618

Abstract

The impact of a fatty triamine (Triameen YT) additive was investigated on the friction performance and stability of molybdenum dithiocarbamate (MoDTC) in the formulations containing polyalphaolefin synthetic base oil (PAO) and zinc dialkyldithiophosphate (ZDDP). Triamine has no significant effect when mixed with MoDTC [...] Read more.

The impact of a fatty triamine (Triameen YT) additive was investigated on the friction performance and stability of molybdenum dithiocarbamate (MoDTC) in the formulations containing polyalphaolefin synthetic base oil (PAO) and zinc dialkyldithiophosphate (ZDDP). Triamine has no significant effect when mixed with MoDTC and ZDDP, but it improves the performance of MoDTC alone. However, in the MoDTC—Triamine—PAO solutions, a chemical reaction easily occurred and a reddish precipitate was formed upon storage. According to IR, XPS, TEM, and XAS characterizations, this precipitate is poorly crystalline layered alkylammonium oxothiomolybdate. Formation of the precipitate impaired the tribological performance by decreasing the number of active species delivered at the sliding contact interface. However, low friction coefficients were recovered by redispersion of the precipitate in PAO. Full article

(This article belongs to the Special Issue Advanced Industrial Lubricants and Future Development Trends of Tribo-Systems for Tribological Performance Evaluation)

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11 pages, 2931 KiB

Open AccessArticle

Chemically Modified Silicone Oil with Enhanced Tribological and Anti-Foaming Properties

by Xiaosheng Luan, Enhui Zhang, Yunlong Chen, Rui Ma, Kuiliang Gong, Weimin Li and Xiaobo Wang

Lubricants 2022, 10(12), 364; https://doi.org/10.3390/lubricants10120364 - 15 Dec 2022

Cited by 3 | Viewed by 2367

Abstract

Two kinds of chemically modified silicone oil, diisooctyl phosphate-terminated silicone oil (UCP204) and dioctyl dithiophosphate-terminated silicone oil (UCT2003), were synthesized. The tribological properties of silicone oil were evaluated using an SRV tribometer, and the worn surface and chemical composition were examined by scanning [...] Read more.

Two kinds of chemically modified silicone oil, diisooctyl phosphate-terminated silicone oil (UCP204) and dioctyl dithiophosphate-terminated silicone oil (UCT2003), were synthesized. The tribological properties of silicone oil were evaluated using an SRV tribometer, and the worn surface and chemical composition were examined by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The friction coefficients of UCP204 and UCT2003 were reduced by approximately 62.7% and 56.7% compared with untreated silicone oil. The results indicated that the incorporation of phosphorus and/or sulfur could significantly enhance the tribological performance of modified silicone oil. Benefiting from their unique chemical structure, chemically modified silicone fluids also exhibit good dispersion stability and excellent anti-foaming properties, which are mainly attributed to the low surface tension properties imparted by the silicone backbone and the better dispersion stability provided by the dialkyl dithiophosphate group in chemically modified silicone fluids. It is also found that lubricants containing modified silicone oil remain clear after three months of storage and still maintain good anti-foaming properties. Full article

(This article belongs to the Special Issue Advances in Novel Lubricant Additives)

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17 pages, 3531 KiB

Open AccessArticle

Study on Friction Characteristics of Slipper Pair of Large Displacement High-Pressure Piston Pump

by Zekui Li, Shunhai Xu, Guofang Gong, Yankun Bi, Liping Xu, Liang Zhang and Zhen Ren

Lubricants 2022, 10(12), 363; https://doi.org/10.3390/lubricants10120363 - 15 Dec 2022

Cited by 4 | Viewed by 1365

Abstract

The reference value of the oil film thickness and friction coefficient of the slipper pair is critical to the development of the piston pump, especially for 750 mL/r displacement piston pumps. To explore the computing method and range of the reference value mentioned [...] Read more.

The reference value of the oil film thickness and friction coefficient of the slipper pair is critical to the development of the piston pump, especially for 750 mL/r displacement piston pumps. To explore the computing method and range of the reference value mentioned applicable to 750 mL/r displacement piston pumps, this study aims to propose the modified calculation model of the oil film thickness based on the real clearance flowrate and obtain the value range of the friction coefficient of the slipper pair. Through the friction test of the slipper pair, the mean deviation ratio of the oil film thickness between the modified value, theoretical value, and the measured value was calculated and compared, respectively. The variation law of the friction under the influence of different speeds and working pressures was analyzed. Finally, the range of the equivalent friction coefficient with the upper and lower limit surfaces was obtained. The results show that the mean deviation ratio between the modified oil film thickness value and the measured value is mainly within 6%, while that of the theoretical method is mainly from 6% to 8%, and the mean of the difference between the two deviation ratios is about 3%, verifying the feasibility of the modified model used for the calculation of the reference value. Meanwhile, the value of the equivalent friction coefficient fluctuates in the range of 0.006–0.018, which is affected more significantly by the working pressure than the speed, suggesting that the working pressure can be given priority as the design basis of the friction coefficient for 750 mL/r displacement piston pumps. Full article

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16 pages, 4142 KiB

Open AccessReview

Evaluation of the Role of Lubricant Additives in Emission Control

by Huifang Shao, Joseph W. Roos and Joseph E. Remias

Lubricants 2022, 10(12), 362; https://doi.org/10.3390/lubricants10120362 - 14 Dec 2022

Cited by 4 | Viewed by 2085

Abstract

In the last several decades, emission regulations have become a significant driving force for vehicle technologies, from powertrain design to emission control. These technologies will experience continuous improvement and may require a paradigm shift to address more stringent emission regulations. As essential components [...] Read more.

In the last several decades, emission regulations have become a significant driving force for vehicle technologies, from powertrain design to emission control. These technologies will experience continuous improvement and may require a paradigm shift to address more stringent emission regulations. As essential components of powertrain systems, fuel and lubricant additives have uniquely enabled powertrain performance and durability. This review focuses on the complex interactions between the fluids and the emissions control system. Investigations into the impact of fuel aromatic content on both primary and secondary emissions are discussed. This work provides the methodologies and context to evaluate the studies into the interactions between fluids and the emission system components. Research on lubricants interactions with particulate filters shows that the lubricant, when formulated appropriately, does not substantively degrade particulate filter performance. In fact, it was found that the lubricant additives can have positive impact on carbonaceous accumulation in the filter and improve particulate emissions. This work provides an overview and context for assessing the role of lubricant additives in the performance of the complete emission system. Understanding the full impact of the fluids, lubricant and fuel, and the powertrain hardware provides the foundation to design additives to deliver optimized performance for the vehicle with advanced emission control systems. Full article

(This article belongs to the Special Issue Advances in Fuel-Lubricant Interactions)

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15 pages, 2601 KiB

Open AccessArticle

Effects of Viscosupplementation on Tribological Behaviour of Articular Cartilage

by Matúš Ranuša, Martin Ondra, David Rebenda, Martin Vrbka, Jiří Gallo and Ivan Křupka

Lubricants 2022, 10(12), 361; https://doi.org/10.3390/lubricants10120361 - 14 Dec 2022

Cited by 1 | Viewed by 1616

Abstract

Osteoarthritis (OA) is one of the frequent conditions in the orthopaedic practice. The number of OA patients is increasing and the efficacy of the current treatment methods is relatively low in terms of slowing or even preventing of the disease progression. The current [...] Read more.

Osteoarthritis (OA) is one of the frequent conditions in the orthopaedic practice. The number of OA patients is increasing and the efficacy of the current treatment methods is relatively low in terms of slowing or even preventing of the disease progression. The current research suggests that the lubrication function of the cartilage depends on its articulating surfaces. These surfaces are characterized by extracellular matrices with a three-dimensional porous structure that ensures a proper lubrication regime to protect the surface against the wear. Viscosupplementation is one of the possible treatments to slow the OA progression. This therapeutic intervention is frequently used in the clinical practice for the knee osteoarthritis. Viscosupplementation can, to a certain extent, supplement the lubrication ability of the cartilage by doping the hyaluronic acid (HA) and thus delay the degradation. However, selection of a proper viscosupplement remains a challenge, both in terms of the correct evaluation of the HA properties and their interaction with different stages of the OA. The viscoupplements differ in their HA molecular weight that may influence the CoF development from both the short term and the long-term perspective. The aim of this study is to analyze the coefficient of friction (CoF) between the real surfaces of a bovine cartilage after applying viscosupplements. The experiments were conducted on a pin-on-plate tribometer with a real bovine cartilage to simulate the lubrication regimes of a human joint. The model joint was doped with 4 different commercially available viscosupplements with different molecular weights and cross-linking of the HA. The OA damage was simulated by using a model synovial fluid with a concentration that corresponds to an OA patient. A compression of the cartilage surface was observed during the experiment and the interstitial fluid drained away from the porous cartilage structure. This, in combination with a migrating contact area (MCA), led the synovial fluid (SF) to mix with the viscosupplement. Decrease in the CoF was observed after the application of the viscosupplements with an increasing molecular weight. This was observed under a functional boosted cartilage lubrication regime, what suggests that the viscosupplementation yields the benefits especially for the conditions where the cartilage is not substantially damaged by the OA. Full article

(This article belongs to the Special Issue Synovial Lubricated Joints—Devices and Mechanical Behavior)

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11 pages, 4701 KiB

Open AccessArticle

High-Precision Flow Field Simulation of Aerostatic Bearings Based on the Interior Penalty Discontinuous Galerkin Method

by Weijie Hou, Qiushi Ding, Yongbo Hao, Jingshuo Cao, Shixi Hao, Kai Feng and Ming Zhao

Lubricants 2022, 10(12), 360; https://doi.org/10.3390/lubricants10120360 - 13 Dec 2022

Cited by 1 | Viewed by 1182

Abstract

All the static performance, dynamic characteristics, and stability are strongly associated with the flow field inside the aerostatic bearings. Therefore, a high-precision numerical method is beneficial for the detailed description of the bearing flow field. To this end, a modified interior penalty discontinuous [...] Read more.

All the static performance, dynamic characteristics, and stability are strongly associated with the flow field inside the aerostatic bearings. Therefore, a high-precision numerical method is beneficial for the detailed description of the bearing flow field. To this end, a modified interior penalty discontinuous Galerkin method was introduced here. Actually, a lift operator was included to eliminate the so-called homogeneity tensor connecting the viscous term and variable gradient, which could improve the numerical feasibility. The accuracy of the above numerical method has been comprehensively validated through viscous cases, including Couette flow and shear-driven cavity flow. Then, the flow fields of three aerostatic bearings were simulated with different orifice geometries. As a result, the Mach number distributions and static pressure could be estimated together with the integration of the pressure acting upon the thrust surface. The acceleration within the orifice and air film could be detected, and the influence of the orifice geometry has been systematically discussed. Full article

(This article belongs to the Special Issue Tribological Characteristics of Bearing System)

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25 pages, 112854 KiB

Open AccessArticle

A Comparative Machinability Study of SS 304 in Turning under Dry, New Micro-Jet, and Flood Cooling Lubrication Conditions

by Barun Haldar, Hillol Joardar, Borhen Louhichi, Naser Abdulrahman Alsaleh and Adel Alfozan

Lubricants 2022, 10(12), 359; https://doi.org/10.3390/lubricants10120359 - 12 Dec 2022

Cited by 4 | Viewed by 2122

Abstract

The main objective of this experimental investigation is to examine favourable machining conditions by utilising fewer resources of machining industries for the techno-economical and ecological benefits. The machining operations are performed in turning SS 304 using coated carbide tool inserts under dry, water-soluble [...] Read more.

The main objective of this experimental investigation is to examine favourable machining conditions by utilising fewer resources of machining industries for the techno-economical and ecological benefits. The machining operations are performed in turning SS 304 using coated carbide tool inserts under dry, water-soluble cutting fluid solution in the form of flood cooling and small-quantity lubrication (SQL) conditions by employing a newly formed micro-jet for a comparative classical chips study and analysis. The machining experiments are conducted in turning by a 25 kW precision CNC lathe with a special arrangement of micro-jets into the machining zone. Machining speeds and feed rates are varied under dry, micro-jet, and flood cooling conditions and their effects are studied on the type of chips and their morphology, chip reduction coefficient (ξ), and chip shear plane distance (d). The effect of machining environments on tool health conditions (such as BUEs, tool-edge chipping, and edge breaking) is examined for the inferences. In the range of low-speed machining (less than 600 m/min), metal cutting seems easier in flood cooling conditions, but it imposes more unfavourable effects (such as edge chipping and edge breaking) on the ceramic cutting tool’s health. On the other hand, the dry machining condition shows a favourable performance for a ceramic cutting tool. The optimum machining condition is found in the micro-jet SQL by the analysis of experimental data and observation results for the tool and work combination. The analysis of the results is carried out by the response surface methodology (RSM) and artificial neural network (ANN). The ANN model is found to be more accurate than RSM. The aspects of effective green machining are emphasised. Full article

(This article belongs to the Special Issue Methods of Application of Cutting Fluids in Machining)

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28 pages, 2359 KiB

Open AccessReview

A Review on Modelling of Viscoelastic Contact Problems

by Dongze Wang, Gregory de Boer, Anne Neville and Ali Ghanbarzadeh

Lubricants 2022, 10(12), 358; https://doi.org/10.3390/lubricants10120358 - 12 Dec 2022

Cited by 9 | Viewed by 4277

Abstract

Approaches to solving viscoelastic problems have received extensive attention in recent decades as viscoelastic materials have been widely applied in various fields. An overview of relevant modelling approaches is provided in the paper. The review starts with a brief introduction of some basic [...] Read more.

Approaches to solving viscoelastic problems have received extensive attention in recent decades as viscoelastic materials have been widely applied in various fields. An overview of relevant modelling approaches is provided in the paper. The review starts with a brief introduction of some basic terminologies and theories that are commonly used to describe the contact behaviour of viscoelastic materials. By building up the complexity of contact problems, including dry contact, lubricated contact, thermoviscoelastic contact and non-linear viscoelastic contact, tentative analytical solutions are first introduced as essential milestones. Afterwards, a series of numerical models for the various types of contact problems with and without surface roughness are presented and discussed. Examples, in which computational tools were employed to assist the analysis of viscoelastic components in different fields, are given as case studies to demonstrate that a comprehensive numerical framework is currently being developed to address complex viscoelastic contact problems that are prevalent in real life. Full article

(This article belongs to the Special Issue Multiscale and Modern Solutions in the Simulation of Lubricated Contacts)

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14 pages, 4304 KiB

Open AccessArticle

Deformation Behavior of Crystalline Cr–Ni Multilayer Coatings by Using Molecular Dynamics Simulation

by Kuk-Jin Seo and Dae-Eun Kim

Lubricants 2022, 10(12), 357; https://doi.org/10.3390/lubricants10120357 - 09 Dec 2022

Cited by 1 | Viewed by 1137

Abstract

This work shows the atomic scale deformation behavior of crystalline multilayer coating comprising up to five Cr and Ni layers. A molecular dynamics simulation was conducted to visualize the atomic scale behavior of the multilayer during indentation/unloading and scratch. Normal and shear directional [...] Read more.

This work shows the atomic scale deformation behavior of crystalline multilayer coating comprising up to five Cr and Ni layers. A molecular dynamics simulation was conducted to visualize the atomic scale behavior of the multilayer during indentation/unloading and scratch. Normal and shear directional forces were recorded to compare repulsion and friction forces between the multilayer models during the indentation/unloading and scratch simulations. Dislocation lines within the layers were quantified to understand the deformation behavior of each model. Atomic scale deformation and dislocation lines after the indentation and scratch were visualized. Generation and movement of a single dislocation line during the indentation simulation were also visualized within a few picoseconds. The repulsion and friction forces of the five-layer model showed the lowest values among the models. The unloading stiffness of the five-layer model was calculated to be the lowest among the models. The amount of plastic deformation and the wear volume of the one-layer model after the indentation and scratch was calculated to be the highest among the models. The number of dislocation lines of the five-layer model showed an increasing trend during the indentation and scratch. The highest dislocation density of the five-layer model might aid in an enhancement of resistance to the plastic deformation to reduce the wear volume when scratched. Full article

(This article belongs to the Special Issue Friction and Wear of Coatings/Films)

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22 pages, 4834 KiB

Open AccessArticle

Piston Compression Ring Elastodynamics and Ring–Liner Elastohydrodynamic Lubrication Correlation Analysis

by Swagatika Biswal and Prakash Chandra Mishra

Lubricants 2022, 10(12), 356; https://doi.org/10.3390/lubricants10120356 - 09 Dec 2022

Cited by 1 | Viewed by 1369

Abstract

Friction loss in an internal combustion engine largely depends on elastohydrodynamic lubrication. The piston compression ring is a contributor to such parasitic losses in the piston subsystem. The complex elastodynamics of the ring are responsible for the transient and regime-altering film that affects [...] Read more.

Friction loss in an internal combustion engine largely depends on elastohydrodynamic lubrication. The piston compression ring is a contributor to such parasitic losses in the piston subsystem. The complex elastodynamics of the ring are responsible for the transient and regime-altering film that affects the elastohydrodynamic lubrication of the ring liner contact conjunction. The current paper will discuss the ring radial, lateral deformation, and axial twist, and its effect on the film profile of the compression ring and its subsequent effect on tribological characteristics like elastohydrodynamic pressure, friction, and lubricant. A finite difference technique is used to solve the elastohydrodynamic issue of elastodynamic piston compression by introducing the elastodynamically influenced film thickness into the lubrication model. The results show that consideration of the elastodynamics predicts a 23.53% reduction in friction power loss in the power stroke due to the elastodynamic ring compared to the rigid ring. The elastodynamic effect improves the lubricant oil flow into the conjunction. A finite element simulation predicts a von-Mises stress of 0.414 N/mm², and a maximum deformation of 0.513 µm at the core and coating interface is observed at the ring–ring groove contact. The sustainability of EHL in this case largely depends on the ring–liner elastodynamics. Full article

(This article belongs to the Special Issue Sustainable Elastohydrodynamic Lubrication)

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19 pages, 7004 KiB

Open AccessArticle

Thermo-Mechanical Modelling of Friction Stir Processing of AZ91 Alloy: Using Smoothed-Particle Hydrodynamics

by Roshan Vijay Marode, Srinivasa Rao Pedapati, Tamiru Alemu Lemma and Venkata Somi Reddy Janga

Lubricants 2022, 10(12), 355; https://doi.org/10.3390/lubricants10120355 - 08 Dec 2022

Cited by 11 | Viewed by 1424

Abstract

A thermo-mechanical model of friction stir processing (FSP) using the Altair based on meshless Smoothed-Particle Hydrodynamics (SPH) was developed and verified experimentally. Process parameters adopted for both experimentation and simulation during the FSP of AZ91 were 1000 rpm tool stirring speed, 40 mm/min [...] Read more.

A thermo-mechanical model of friction stir processing (FSP) using the Altair based on meshless Smoothed-Particle Hydrodynamics (SPH) was developed and verified experimentally. Process parameters adopted for both experimentation and simulation during the FSP of AZ91 were 1000 rpm tool stirring speed, 40 mm/min tool advancing speed, and 0° tool tilt angle. The numerical analysis predicted the temperature distribution and material movement in the three phases: plunging, dwelling, and traversing. Simulated temperatures during the traversal phase were found to be greater than experimental temperatures using the Ti32 thermal camera as the heat was only transported by friction and plastic deformation. Peak temperatures for all three phases were observed to be in the range of 47% to 87% of the material’s melting point and are in accordance with the findings of the experiments. The SPH mesh-free model was proven to be capable of predicting the in-process thermal-mechanical state variables during and after the process by extracting morphology. The material movement around the tool has been predicted using SPH node tracking, which further anticipates that there was no complete flow of SPH nodes from RS to AS, leaving a gap that must be filled. Post-processed morphology shows inadequacy in the material flow due to lower compressive force. It formed the wormhole at the advancing side’s trailing and was verified experimentally. Full article

(This article belongs to the Special Issue Friction Stir Processing of Structural Metallic Materials)

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16 pages, 5268 KiB

Open AccessArticle

The Effects of Interval Uncertainties on Dynamic Characteristics of a Rotor System Supported by Oil-Film Bearings

by Jiaojiao Ma, Chao Fu, Zhaoli Zheng, Kuan Lu and Yongfeng Yang

Lubricants 2022, 10(12), 354; https://doi.org/10.3390/lubricants10120354 - 08 Dec 2022

Cited by 2 | Viewed by 1685

Abstract

Rotating systems equipped with oil-film bearings are critical and common in many industrial machines. There are various non-random uncertainties in such fluid-lubricated dynamic systems. It is important to quantify the effects of uncertainties without adequate statistical information on the dynamics of rotor-bearing systems. [...] Read more.

Rotating systems equipped with oil-film bearings are critical and common in many industrial machines. There are various non-random uncertainties in such fluid-lubricated dynamic systems. It is important to quantify the effects of uncertainties without adequate statistical information on the dynamics of rotor-bearing systems. In this paper, a rotor system with oil-film bearings at both ends is investigated considering many interval uncertainties. The rotating system is modeled in a deterministic sense. The Chebyshev interval method is used to track the propagation of different uncertainties. Deviations in the steady state responses, time history, and shaft orbits are calculated and comparatively discussed. Influence patterns of different interval parameters and dispersions in various dynamics are presented in detail. It is found that there can be global and local impacts as well as cumulative effects caused by multi-source uncertainties. The findings of the present study could be helpful for a more insightful dynamic analysis of rotor-bearing systems as well as their optimal design and maintenance. Full article

(This article belongs to the Special Issue Microstructure, Anti-wear Properties and Numerical Simulation of Lubricants)

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15 pages, 37416 KiB

Open AccessArticle

Experimental Study on the Lubrication Enhancement of Slider-on-Disc Contact by Stearic Acid Adsorption under Limited Lubricant Supply

by Yusheng Jian, Zhaogang Jing, Feng Guo, Pat Lam Wong and Xinming Li

Lubricants 2022, 10(12), 353; https://doi.org/10.3390/lubricants10120353 - 06 Dec 2022

Cited by 2 | Viewed by 2715

Abstract

The optimization of the lubricant supply quantity contributes to minimizing energy losses and wastage. To enhance the performance of hydrodynamic bearings running with limited lubricant supply (LLS), this study examined the effect of stearic acid as an additive. Stearic acid is commonly used [...] Read more.

The optimization of the lubricant supply quantity contributes to minimizing energy losses and wastage. To enhance the performance of hydrodynamic bearings running with limited lubricant supply (LLS), this study examined the effect of stearic acid as an additive. Stearic acid is commonly used for boundary lubrication as an organic friction modifier. How the stearic acid adsorption affects the hydrodynamic lubrication of a slider-on-disc contact under LLS was investigated using interferometry measurement and fluorescence observation in this study. Firstly, the oil reservoir of PAO10 with stearic acid adsorption was observed at the slider entrance. Secondly, the film thickness versus speed of PAO10 and PAO10 with 0.1% and 0.3% stearic acid, respectively, were measured. Finally, the morphology and surface properties of the glass and steel blocks with stearic acid adsorption were characterized by atomic force microscopy and Fourier transform infrared spectroscopy. The results show that the stearic acid adsorption layer weakens the wettability of the lubrication track and induces the ‘dewetting’ phenomenon of the lubricating oil. Thus, discrete oil distribution in the form of stripe or droplet can be generated, which leads to the accumulation of lubricating oil at the slider entrance to form a reservoir. An additional inlet pressure that is generated by the oil reservoir due to surface tension increases the oil film formation capacity. Furthermore, the morphologies of the adsorbed stearic acid layer on the glass and the steel blocks are, respectively, characterized by the nano-sized granular bulge and brush structure. This study reveals a new role of stearic acid adsorption in promoting LLS lubrication. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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19 pages, 7365 KiB

Open AccessArticle

Dry Sliding Wear Features of an Al-20Sn-5Zn Alloy Affected by Microstructural Length Scales

by André Barros, Clarissa Cruz, Tamires Botelho, Adrina Silva, Luiz Casteletti, Amauri Garcia and Noé Cheung

Lubricants 2022, 10(12), 352; https://doi.org/10.3390/lubricants10120352 - 05 Dec 2022

Cited by 2 | Viewed by 1221

Abstract

Al-Sn-Zn alloys are attractive options for use as wear-resistant materials. While Sn promotes self-lubricating characteristics, Zn strengthens the Al-rich matrix. Conventionally, the manufacturing of these alloys involves casting. However, there is still a paucity of studies that associate the solidification microstructure with the [...] Read more.

Al-Sn-Zn alloys are attractive options for use as wear-resistant materials. While Sn promotes self-lubricating characteristics, Zn strengthens the Al-rich matrix. Conventionally, the manufacturing of these alloys involves casting. However, there is still a paucity of studies that associate the solidification microstructure with the wear resistance of these alloys. Inspired by such considerations, this work aims at investigating the wear behavior of an Al-20Sn-5Zn [wt.%] alloy produced by a directional solidification technique. A set of samples with different microstructure length scales was subjected to ball cratering tests using a normal contact load of 0.25 N and six test times. The results show that the dependence of the wear behavior on the microstructure length scale becomes more expressive for longer sliding distances. It was found that coarser microstructures provide an improved wear resistance. In view of that, a possible spectrum of specific wear rates was determined as a function of the sliding distance, considering different microstructure length scales. Finally, experimental equations are proposed to represent a possible range of wear volume and wear coefficient according to the dendrite arm spacings. Full article

(This article belongs to the Special Issue Tribological Characteristics of Bearing System)

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22 pages, 12107 KiB

Open AccessArticle

Influence of Si₃N₄ on the Dry Sliding Wear Characteristics of Stir-Cast Cu-10Sn/xSi₃N₄ Metal Matrix Composite for Bearing Applications

by Sooraj Satheesh, Gokul Krishna Gopakumar Priya, Govind Venugopal, Anuranjan Anil, Jayakrishna Ajithkumar Jayasree, Anandhan Ajan Vishnu, Karthik Venkitraman Shankar and Anil Kumar

Lubricants 2022, 10(12), 351; https://doi.org/10.3390/lubricants10120351 - 05 Dec 2022

Cited by 1 | Viewed by 1599

Abstract

Bronze metal matrix composites (MMCs) are futuristic materials that may find applications in automobile, aviation, and marine industries, specifically for propellers in submarines, bearings, and bushings for defence purposes. The present investigation studied the effect of Si₃N₄ (5, 10, 15 [...] Read more.

Bronze metal matrix composites (MMCs) are futuristic materials that may find applications in automobile, aviation, and marine industries, specifically for propellers in submarines, bearings, and bushings for defence purposes. The present investigation studied the effect of Si₃N₄ (5, 10, 15 wt%) ceramic particles on the physical, metallurgical, and tribological behaviour of Cu-10Sn/Si₃N₄ MMCs. Cast rods of three composites and a base alloy were fabricated using the liquid metallurgy route. The microstructural characterisation for the cast samples was conducted using FESEM (Field Emission Scanning Electron Microscope), EDS (Energy Dispersive Spectroscopy), XRD (X-ray diffraction), and TEM (Transmission Electron Microscope), which revealed that the Cu-10Sn alloy reinforced with 5 wt% of Si₃N₄ had homogeneous distribution and perfect bonding of the Si₃N₄ with the bronze MMC. The dry sliding wear test was performed by varying parameters such as the applied load (10, 20, 30 N) and sliding velocity (1, 2, 3 m/s). The specific wear rate (SWR) increased against an increased load. However, the SWR and coefficient of friction decreased and then increased against an increasing sliding velocity due to tribolayer formation. The primary wear mechanism observed at low and high loads was severe delamination. In contrast, the wear mechanism was adhesion wear at high and low velocities. Amongst the researched samples, Cu-10Sn/5 wt% Si₃N₄ composites revealed the least SWR at a load of 10 N and sliding velocity of 2 m/s and hence can be recommended for manufacturing bearings and bushings in the automobile and defence industry. Full article

(This article belongs to the Special Issue Friction and Wear in Composite Materials)

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19 pages, 3663 KiB

Open AccessArticle

Characteristics of Hybrid Nanolubricants for MQL Cooling Lubrication Machining Application

by Syh Kai Lim, Wan Hamzah Azmi, Ahmad Shahir Jamaludin and Ahmad Razlan Yusoff

Lubricants 2022, 10(12), 350; https://doi.org/10.3390/lubricants10120350 - 05 Dec 2022

Cited by 7 | Viewed by 1517

Abstract

Efficient and effective lubricants have great application prospects in the manufacturing industries. Minimum quantity lubrication (MQL) machining with low flow rate of nanolubricants is investigated for cooling and lubrication during the process. This paper investigates the characterization of graphene-mixed aluminium oxide (G-Al₂ [...] Read more.

Efficient and effective lubricants have great application prospects in the manufacturing industries. Minimum quantity lubrication (MQL) machining with low flow rate of nanolubricants is investigated for cooling and lubrication during the process. This paper investigates the characterization of graphene-mixed aluminium oxide (G-Al₂O₃) hybrid nanomixture spent lubricants for MQL machining purposes. The main advantage of this method is to reduce the disposal lubricants to develop high-performance cooling-lubrication by using nanolubricants of G-Al₂O₃ nanoparticles in different volume composition ratios at a constant 1.0% volume concentration in a base liquid mixture of 40% spent lubricants. Before conducting the measurements of the nanolubricants’ thermal conductivity and dynamic viscosity, the nanolubricants were homogenous and stable. The tribological performance of all ratios was evaluated by using a four-ball wear tribotester machine. The thermal conductivity peak value for the G-Al₂O₃ hybrid nanolubricant was obtained and the highest enhancement, up to 29% higher than the base liquid solution, was obtained. The dynamic viscosity variation for all ratios was lower than the 40:60 ratio. The properties enhancement ratio suggests that G-Al₂O₃ hybrid nanolubricants with 1.0% volume concentration aid in the heat transfer, especially for ratios of 60:40 and 20:80. The lowest coefficient of friction (COF) for a ratio of 60:40 was obtained to be 0.064, with 45% enhancement as compared to the base liquid solution. In conclusion, optimum ratios for G-Al₂O₃ hybrid nanolubricants were determined to be 20:80 and 60:40. Regarding the properties enhancement ratio, the combination of enhanced thermophysical and tribological properties had more advantages for cooling lubrication application. Full article

(This article belongs to the Special Issue Minimum Quantity Lubrication: Environmental Alternatives in Processing)

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11 pages, 5702 KiB

Open AccessArticle

Structural Changes in Block-Shaped WEBAM’ed Ti6Al4V Samples after Friction Stir Processing

by Tatiana Kalashnikova, Andrey Cheremnov, Aleksander Eliseev, Denis Gurianov, Evgeny Knyazhev, Evgeny Moskvichev, Vladimir Beloborodov, Andrey Chumaevskii, Anna Zykova and Kirill Kalashnikov

Lubricants 2022, 10(12), 349; https://doi.org/10.3390/lubricants10120349 - 04 Dec 2022

Cited by 2 | Viewed by 1345

Abstract

In this paper, the structure and mechanical properties of workpieces made of Ti6Al4V alloy in the shape of blocks manufactured by wire-feed electron beam additive manufacturing and processed by friction stir processing were investigated. Samples were cut from the upper and lower parts [...] Read more.

In this paper, the structure and mechanical properties of workpieces made of Ti6Al4V alloy in the shape of blocks manufactured by wire-feed electron beam additive manufacturing and processed by friction stir processing were investigated. Samples were cut from the upper and lower parts of the additive block and processed in the layer deposition direction using different tool loading forces. Studies have shown that the processing of such material forms a clearly defined thermomechanically affected zone represented by nanosized α-grains. In the stir zone, the material is characterized by a fine-dispersed structure with a content of α- and nanosized α″-phase plates. The material after processing demonstrates 24% higher values of the ultimate tensile strength as compared to the base metal in the as-built state. Full article

(This article belongs to the Special Issue Friction Stir Processing of Structural Metallic Materials)

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14 pages, 10917 KiB

Open AccessArticle

Three-Body Abrasive Wear Performance of High Chromium White Cast Iron with Different Ti and C Content

by Mohammad Jobayer Huq, Kazumichi Shimizu, Kenta Kusumoto and Riki Hendra Purba

Lubricants 2022, 10(12), 348; https://doi.org/10.3390/lubricants10120348 - 04 Dec 2022

Cited by 5 | Viewed by 1535

Abstract

The need for better wear-resistant materials to reduce cost and save the environment is noteworthy. The striking wear resistance of high chromium white cast iron (HCCI) has made it industry’s predominant choice. The three-body abrasive wear resistance performance of HCCI was investigated based [...] Read more.

The need for better wear-resistant materials to reduce cost and save the environment is noteworthy. The striking wear resistance of high chromium white cast iron (HCCI) has made it industry’s predominant choice. The three-body abrasive wear resistance performance of HCCI was investigated based on combined Ti and C. The Ti and C content varied in different percentages. The addition of Ti resulted in refined M₇C₃ carbides and TiC crystallization. The hardness was significantly affected by the addition of Ti. The increment in Ti content resulted in a decrease in the hardness, leading to a higher wear rate. However, the individual contribution of C led to higher hardness and, hence, better wear resistance, which is contrary to Ti. Out of the three specimens with 3, 3.5, and 4 wt.% C content, the 4 wt.% C series showed the highest hardness but the lowest wear rate and depth. This study found that the combination of a lower percentage of Ti with a higher percentage of C in HCCI can have a worthwhile result in abrasive wear. Full article

(This article belongs to the Special Issue Assessment of Abrasive Wear)

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19 pages, 6607 KiB

Open AccessArticle

Multiphase Computational Fluid Dynamics of Rotary Shaft Seals

by Jeremias Grün, Simon Feldmeth and Frank Bauer

Lubricants 2022, 10(12), 347; https://doi.org/10.3390/lubricants10120347 - 03 Dec 2022

Cited by 2 | Viewed by 1928

Abstract

The primary task of rotary shaft seals is to prevent an unwanted fluid transfer between two areas. In shaft passages of gearboxes, for example, rotary shaft seals avoid the leakage of transmission oil to ambient air. This means the flow in the lubricant [...] Read more.

The primary task of rotary shaft seals is to prevent an unwanted fluid transfer between two areas. In shaft passages of gearboxes, for example, rotary shaft seals avoid the leakage of transmission oil to ambient air. This means the flow in the lubricant film in the sealing gap between the sealing edge and the shaft surface consists of at least two phases. Taking the phenomenon of cavitation into account, the flow consists of three phases. This study aims to provide an in-depth understanding of the multiphase flow in the lubricant film of rotary shaft seals. As experimental studies of the flow processes on a microscale have proven to be quite difficult, a simulation-based approach is applied. Computational fluid dynamics (CFD) serves to compute the transient multiphase flows in the lubricant film in the sealing gap. The computational domain is a three-dimensional microscale model of the lubricant film. The results show the transient hydrodynamic pressure buildup and the dynamic phase interactions during operation. This study provides far-reaching insights into the multiphase flow processes in the lubricant film in the sealing gap and simulation-based evidence of the lubrication and sealing mechanism of rotary shaft seals. Full article

(This article belongs to the Special Issue Fluid–Structure Interaction in Bearings and Seals)

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23 pages, 1250 KiB

Open AccessArticle

Boundary Lubricity of Vegetable-Oil-Derived Trimethylolpropane (TMP) Ester

by Chiew Tin Lee, Mei Bao Lee, William Woei Fong Chong, Jo-Han Ng, King Jye Wong and Cheng Tung Chong

Lubricants 2022, 10(12), 346; https://doi.org/10.3390/lubricants10120346 - 02 Dec 2022

Cited by 2 | Viewed by 1862

Abstract

Vegetable-oil-based biolubricants are an excellent alternative to conventional lubricants. Instead of focusing on novel feedstocks, these biolubricants should be further elucidated based on their fatty acid composition, which influences their tribological properties. Therefore, the study utilises gene expression programming (GEP) to derive a [...] Read more.

Vegetable-oil-based biolubricants are an excellent alternative to conventional lubricants. Instead of focusing on novel feedstocks, these biolubricants should be further elucidated based on their fatty acid composition, which influences their tribological properties. Therefore, the study utilises gene expression programming (GEP) to derive a boundary lubricity model for vegetable-oil-derived trimethylolpropane (TMP) esters, considering the fatty acid composition (saturation and monounsaturation levels), load and speed. Neat vegetable oil and blends from seven feedstocks are selected following a wide range of fatty acid profiles to synthesise TMP esters using a two-stage transesterification process. The TMP esters are spin-coated on wear discs that are subsequently rotated against a ball using a purpose-built tribometer. The frictional performance of the TMP esters with balanced saturation and monounsaturation levels of fatty acid are measured to improve it at higher speeds. The GEP model is statistically evaluated by adopting the friction data, a showing good generalisation and predictability capability. The model demonstrates that friction decreases with increasing saturation levels of the TMP ester. The GEP model for vegetable oil TMP esters allows for the tribological performance prediction of TMP esters following the fatty acid profile, providing a platform to optimise such biolubricant for desired applications. Full article

(This article belongs to the Special Issue Advances in Boundary Lubrication)

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17 pages, 6535 KiB

Open AccessArticle

Probing the Dynamic Progression of Erosion–Corrosion of X65 Pipeline Steel Using the Electrical Resistance Method in Conjunction with Galvanostatic Polarization

by Kongzhong Liu, Wanheng Jiang, Wanbin Chen, Liang Liu, Yunze Xu and Yi Huang

Lubricants 2022, 10(12), 345; https://doi.org/10.3390/lubricants10120345 - 02 Dec 2022

Cited by 3 | Viewed by 1251

Abstract

The initiation of erosion and the coupled damage of erosion and corrosion on the surface of X65 pipeline steel with varying applied anodic currents were online monitored using the electrical resistance (ER) method. Results show that ER method in conjunction with anodic polarization [...] Read more.

The initiation of erosion and the coupled damage of erosion and corrosion on the surface of X65 pipeline steel with varying applied anodic currents were online monitored using the electrical resistance (ER) method. Results show that ER method in conjunction with anodic polarization was a highly effective approach for the investigation of the interaction effect between erosion and corrosion, which can be used to quickly and conveniently obtain the synchronously changed erosion and corrosion rates. The critical impact energy is a key parameter of sand particles to induce erosion damage on the steel surface, which can remove the flaky cementite at the edge of the pits. The threshold anodic current density that can cause a synergic effect between erosion and corrosion of X65 pipeline steel can be quantitatively fitted based on the erosion rates under varying anodic currents. Full article

(This article belongs to the Special Issue Erosion-Corrosion and Stress Corrosion Characteristics of Hydraulic and Marine Structures)

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12 pages, 5635 KiB

Open AccessArticle

Microstructure and Performance of Fe₅₀Mn₃₀Cr₁₀Ni₁₀ High-Entropy Alloy Produced by High-Efficiency and Low-Cost Wire Arc Additive Manufacturing

by Xibin Zhang, Yonggang Tong, Yongle Hu, Xiubing Liang, Yongxiong Chen, Kaiming Wang, Mingjun Zhang and Jiaguo Xu

Lubricants 2022, 10(12), 344; https://doi.org/10.3390/lubricants10120344 - 02 Dec 2022

Cited by 4 | Viewed by 1355

Abstract

High-entropy alloys exhibiting superior properties have great potential applications in various fields. The ability to achieve efficient and economical production of large size and complex structures of high-entropy alloy is of great significance to promoting its engineering application. Additive manufacturing is the key [...] Read more.

High-entropy alloys exhibiting superior properties have great potential applications in various fields. The ability to achieve efficient and economical production of large size and complex structures of high-entropy alloy is of great significance to promoting its engineering application. Additive manufacturing is the key method to produce the complex component; however, the current trend in additive manufacturing of high-entropy alloys focuses on laser additive manufacturing, which is expensive and time-consuming. Herein, we developed a wire arc additive manufacturing (WAAM) method with high-efficiency and a low-cost Fe₅₀Mn₃₀Cr₁₀Ni₁₀ high-entropy alloy was successfully produced. The as-produced alloy was composed of face-centered cubic (FCC) phase with minor σ phase. Its microstructure mainly exhibited dendritic and cytosolic dendritic crystals. Mechanical strength of the additive manufactured alloy reached about 448 MPa with a high fracture elongation up to 80%. The additive manufactured alloy had good corrosion resistance with a protecting layer formed on the surface after corrosion testing, which was much better than 45 steel. Additionally, the frictional performance of the additive manufactured alloy was characterized against the grinding parts of steel and Al₂O₃ balls, and the corresponding friction mechanism was discussed. Full article

(This article belongs to the Special Issue Corrosion and Tribocorrosion Behavior of Metals and Alloys)

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15 pages, 4685 KiB

Open AccessArticle

Tribological Properties of Polydopamine-Modified Ag as Lubricant Oil Additives

by Yanxin Zhang, Jun Cheng, Changfeng Lu, Hao Chen, Guoxin Xie, Lin Zhang and Jianbin Luo

Lubricants 2022, 10(12), 343; https://doi.org/10.3390/lubricants10120343 - 01 Dec 2022

Cited by 1 | Viewed by 1701

Abstract

Nanoparticles agglomerate easily because of their high surface energy, which seriously reduces their tribological properties as lubricant additives. In this work, the core-shell nanoparticles Ag@polydopamine (PDA) were successfully prepared by the self-oxidation of dopamine hydrochloride on the surface of Ag nanoparticles and the [...] Read more.

Nanoparticles agglomerate easily because of their high surface energy, which seriously reduces their tribological properties as lubricant additives. In this work, the core-shell nanoparticles Ag@polydopamine (PDA) were successfully prepared by the self-oxidation of dopamine hydrochloride on the surface of Ag nanoparticles and the dispersion of Ag nanoparticles in PAO6 was improved to promote anti-wear behaviors. The tribological properties of Ag@PDA nanocomposites as additives in poly alpha olefin (PAO) oil were studied under different concentrations, pressure and speed conditions by UMT-5 tribometer. It was demonstrated that the strong electrostatic repulsion of the PDA structure made the Ag nanoparticles better dispersed in PAO oil, thus playing a better lubricating role. When the concentration of the modified nanoparticles was 0.25 wt%, the friction coefficient of the lubricating oil decreased by 18.67% and no obvious wear was observed on the friction pair surface. When the Ag@PDA content was higher than 0.25 wt%, the tribological performance of the lubricating oil was weakened, which may be due to excessive Ag@PDA acting as an abrasive on the friction surface, thereby increasing friction and wear. The friction coefficient of the lubricating oil containing Ag@PDA decreased with the increase in load, but hardly changed with the increase in frequency. Full article

(This article belongs to the Special Issue State-of-the-Art of Tribology in China)

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13 pages, 6025 KiB

Open AccessArticle

Wear of TiAlCN Coating on HCR Gear

by Pavol Švec, Ľuboš Magdolen, Roman Protasov, Miroslav Bošanský and Ernest Gondár

Lubricants 2022, 10(12), 342; https://doi.org/10.3390/lubricants10120342 - 01 Dec 2022

Cited by 1 | Viewed by 2421

Abstract

Wear of TiAlCN coatings deposited on HCR (High Contact Ratio) gears was studied by the Niemann test during which the tested gears were loaded up to the 12th load stage. The resistance against scuffing was evaluated based on the criteria of allowable roughness [...] Read more.

Wear of TiAlCN coatings deposited on HCR (High Contact Ratio) gears was studied by the Niemann test during which the tested gears were loaded up to the 12th load stage. The resistance against scuffing was evaluated based on the criteria of allowable roughness (max. Rz 7 µm) and weight loss (max. 10 mg). The extent and character of wear were influenced by coating thickness, contact pressure and meshing frequency. The wear of thicker TiAlCN coatings on the tooth face started with the smoothing of surface protrusions. The next stage of wear was characterized by depletion of TiAlCN coating. After depletion to a thickness of about 2 µm, the layer was pressed into the soft substrate, and it subsequently cracked. At higher load stages, the layer was partially detached, but the critical roughness indicating scuffing was not exceeded. Thinner TiAlCN coating on the tooth flank cracked and fully detached at lower load stages compared to thicker layers and wear of uncoated soft substrate caused the increase in roughness above the critical value representing scuffing. Full article

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19 pages, 12262 KiB

Open AccessArticle

Experimental and 3D-Deform Finite Element Analysis on Tool Wear during Turning of Al-Si-Mg Alloy

by Imhade P. Okokpujie, Prince C. Chima and Lagouge K. Tartibu

Lubricants 2022, 10(12), 341; https://doi.org/10.3390/lubricants10120341 - 01 Dec 2022

Cited by 4 | Viewed by 1344

Abstract

Aluminum alloys are becoming increasingly significant in the manufacturing industry due to their light weight and durable properties. Widely applied in aerospace and construction, precision machining is required to ensure the best possible surface quality. The surface quality of a machined component is [...] Read more.

Aluminum alloys are becoming increasingly significant in the manufacturing industry due to their light weight and durable properties. Widely applied in aerospace and construction, precision machining is required to ensure the best possible surface quality. The surface quality of a machined component is directly affected by the tool wear incurred during machining. This research investigated the effect of process parameters and machining conditions on tool wear. The critical process parameters selected were cutting speed, feed rate, and depth of cut. Multi-walled carbon nanotube particles were dispersed in a base fluid of mineral oil to create a new lubricant applied during machining. Pure mineral oil was also used as a lubricant to reduce friction. Machining experiments were carried out with the two lubricants, and the tool wear incurred was measured and compared using a Dinolite microscope. All experiments were carried out with high-speed steel (HSS) cutting tools. Taguchi’s L9 orthogonal array was employed as a methodology to design the experiments. A finite-element 3D simulation was also carried out using DEFORM-3D to provide a scientific explanation of the turning process. Results showed a significant reduction in tool wear when machining with multi-walled carbon nanotubes (MWCNTs), with an average reduction of 14.8% compared to mineral oil. The depth of cut was also the most influential process parameter in terms of tool wear. Full article

(This article belongs to the Special Issue Matching Ability and Anti-Wear Properties of Lubricants)

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8 pages, 2063 KiB

Open AccessArticle

Effects of Hot Isostatic Pressing on the Properties of Laser-Powder Bed Fusion Fabricated Water Atomized 25Cr7Ni Stainless Steel

by Arulselvan Arumugham Akilan, Ravi K Enneti, Vamsi Krishna Balla and Sundar V. Atre

Lubricants 2022, 10(12), 340; https://doi.org/10.3390/lubricants10120340 - 01 Dec 2022

Cited by 2 | Viewed by 1235

Abstract

25Cr7Ni stainless steel (super duplex stainless steels) exhibits a duplex microstructure of ferrite and austenite, resulting in an excellent combination of high strength and corrosion resistance. However, Laser-Powder Bed Fusion fabrication of a water-atomized 25Cr7Ni stainless steel of novel chemical composition resulted in [...] Read more.

25Cr7Ni stainless steel (super duplex stainless steels) exhibits a duplex microstructure of ferrite and austenite, resulting in an excellent combination of high strength and corrosion resistance. However, Laser-Powder Bed Fusion fabrication of a water-atomized 25Cr7Ni stainless steel of novel chemical composition resulted in a purely ferritic microstructure and over 5% porosity. The current study investigated the effects of two hot isostatic pressing parameters on the physical, mechanical, and corrosion properties as well as microstructures of water-atomized 25Cr7Ni stainless steel of novel composition fabricated by L-PBF for the first time in the literature. The corrosion behaviour was studied using linear sweep voltammetry in a 3.5% NaCl solution. The Hot Isostatic Pressing-treated sample achieved over 98% densification with a corresponding reduction in porosity to less than 0.1% and about 3~4% in annihilation of dislocation density. A duplex microstructure of ferrite 60% and austenite 40%was observed in the X-Ray Diffraction and etched metallography of the HIP-treated samples from a purely ferritic microstructure prior to the HIP treatment. With the evolution of austenite phase, the HIP-treated samples recorded a decrease in Ultimate Tensile Strength, yield strength, and hardness in comparison with as-printed samples. The variation in the morphology of the evolved austenite grains in the HIP-treated samples was observed to have a significant effect on the elongation. With a reduction in porosity and the evolution of the austenite phase, the HIP-treated samples showed a higher corrosion resistance in comparison with the as-printed samples. Full article

(This article belongs to the Special Issue Corrosion and Tribocorrosion Behavior of Metals and Alloys)

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13 pages, 3639 KiB

Open AccessArticle

Reduction in the Volumetric Wear of a Ball Polishing Tool Using Ultrasonic-Vibration-Assisted Polishing Process

by Fang-Jung Shiou, Zhao-Li Ding and Sun-Peng Lin

Lubricants 2022, 10(12), 339; https://doi.org/10.3390/lubricants10120339 - 30 Nov 2022

Cited by 2 | Viewed by 1392

Abstract

Ultraprecision freeform polishing using a bonnet or a felt ball mounted on a polishing head plays an important role in the mold and lens production industries. The volumetric wear of a bonnet or a felt polishing ball is still a problem to be [...] Read more.

Ultraprecision freeform polishing using a bonnet or a felt ball mounted on a polishing head plays an important role in the mold and lens production industries. The volumetric wear of a bonnet or a felt polishing ball is still a problem to be solved. The objective of this study was to develop an ultrasonic-vibration-assisted ball polishing process on a CNC machining center to improve the surface roughness of a STAVAX mold steel and to reduce the volumetric wear of the polishing ball. The optimal combination of the ultrasonic-vibration-assisted ball polishing parameters for a plane surface was determined by conducting the Taguchi L18 matrix experiments, ANOVA analysis, and verification experiments. The surface roughness of the polished specimens was improved from the burnished surface roughness of Ra 0.122 μm to Ra 0.022 μm. In applying the optimal plane surface ball burnishing and vibration-assisted spherical polishing parameters sequentially to a fine-milled and burnished aspherical lens surface carrier on a five-axis machining center, the surface roughness of Ra 0.014 μm was obtainable. The improvement in the volumetric wear of the polishing ball was about 62% using the vibration-assisted polishing process compared with the nonvibrated polishing process. Full article

(This article belongs to the Special Issue Assessment of Abrasive Wear)

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Lubricants, Volume 10, Issue 12 (December 2022) – 45 articles

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