This paper presents an integrated thermo-mechanical model for analyzing angular contact ball bearings (ACBBs) operating under oil-jet lubrication. The proposed approach enables a comprehensive analysis of both the mechanical and thermal behavior of the ACBB system. The proposed formulation employs a quasi-static approach to accurately calculate contact loads and heat generation, taking into careful consideration variations in internal clearance resulting from factors such as surface pressure, centrifugal forces, and thermal expansion. For the thermal analysis, a refined thermal network model is utilized. The proposed thermal model incorporates a newly derived correlation for the drag coefficient under oil-jet lubrication, which is obtained through high-fidelity computational fluid dynamics simulations. The validity of the proposed model is confirmed through comparison with experimental data. Furthermore, extensive simulations are conducted to investigate the impact of bearing fit-up and thermal variations on the performance of ACBBs.
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Study on the Effects of Operating Diametral Clearance Change on the Characteristics of Angular Contact Ball Bearings Patrick John Po, Gilbert Rivera, Jin-Hyeok Sa, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2024; 41(12): 997. CrossRef
The linear motion guideway (LM guide) is one of the key parts of precision motion and positioning, and it requires high straightness, form accuracy, stiffness, and surface quality. LM guides are actively used in manufacturing facilities for automobiles, aerospace, optics, semiconductors, robots, displays, and portable communication equipment. At present, most of LM guides are based on rolling contact, using either balls or rollers. Roller LM guides have been in high demand in recent years in various industrial fields that require high rigidity. In this study, the friction characteristics of ball and roller LM guides with the same rail width were compared, and friction behavior was analyzed. An experimental setup consisting of a driving unit, specimen, force sensor, and signal acquisition unit was constructed, and signals were collected under various conditions. Three lubrication conditions were used: no lubrication (dry surface), ISO-VG 32, and 68, and a wide feed-rate range from 1 to 100 mm/s was selected. The experimental results showed that the ball LM guide and the roller LM guide had significantly different friction characteristics, which were analyzed from the aspect of Stribeck curve components. In conclusion, friction behavior differed according to lubrication conditions in the no-payload state of the ball and roller LM guides, and the effect of lubrication conditions on friction behavior was shown.
Titanium alloys are used in various industries due to their superior mechanical strength and corrosion resistance. However, titanium is classified as a difficult-to-machine material due to its low thermal conductivity that consequently causes poor tool life. In this study, cryogenic+MQL milling was performed to improve the machinability of Ti-6Al-4V; a cryogenic coolant and a minimum quantity fluid were sprayed simultaneously. The machinability was analyzed according to the cooling and lubrication conditions, focusing on the cutting force and tool wear. When the minimum quantity fluid was injected using two nozzles during cryogenic machining, the cutting force remained low despite the increase in machining distance due to the effective lubrication. The average cutting force at the long machining distances (82-86 passes) was 14.8% lower than that under the wet condition. The tool wear progressed without chipping, and the flank wear length was 55.5% lower than that of the wet machining because the cryogenic cooling and minimum quantity lubrication reduced the tool temperature, friction, and thermal shock.
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Design and Development of a Real-Time AI-Based Tool Failure Prediction System for Machining Difficult-to-Cut Materials Mi-Ru Kim, Hoon-Hee Lee, Min-Suk Park, Wang-Ho Yun Journal of the Korean Society of Manufacturing Technology Engineers.2025; 34(4): 225. CrossRef
In this study, the mechanical and frictional properties of Polydimethylsiloxane (PDMS) were investigated. PDMS has received much attention because of its numerous advantages such as good formability, high transparency, light weight and low cost. However, PDMS has relatively poor mechanical properties compared to other materials, and it is vulnerable to surface damage or wear due to contact. As a result, there is a need to investigate the mechanical properties and enhance its tribological characteristics. In this study, PDMS specimens with different stiffnesses were prepared. The mechanical properties of PDMS were measured using a rigid spherical indenter. Sliding tests were performed to evaluate the frictional properties of the PDMS specimens under both dry and lubricated conditions. The effect of stiffness on the frictional properties of PDMS was assessed, In addition, sliding tests under various lubricated conditions were performed and the effect of the viscosity of the lubricant was also investigated. It was found that the mechanical and frictional properties of PDMS depended upon the stiffness of PDMS and the lubrication condition.
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Synergistic effect of sharkskin-inspired morphologies and surface chemistry on regulating stick-slip friction Liguo Qin, Xiaodong Huang, Zongsheng Sun, Zeyu Ma, Fagla Jules Mawignon, Baohua Lv, Lei Shan, Guangneng Dong Tribology International.2023; 187: 108765. CrossRef
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This paper discusses flow characteristics of nanofluid minimum quantity lubrication (MQL) in the milling process of a titanium alloy by usingnumerical analysis. A mist of nanofluids including nanodiamond and hexagonal boron nitride (hBN) particles is sprayed into a tool-workpiece interface with conditions varying by spray angle and flow rate. The milling. Are experimentally measured and minimized by the determined optimal spray angle and flow rate. The subsequent numerical analysis based on a computational fluid dynamics (CFD) approach is conducted to calculate the penetration ratios of the nanofluid droplets into a tool. At the experimentally obtained optimal spray angle and flow rate of the nanofluids’ mist, the calculated ratio of penetration is highest and, therefore, the optimal spray conditions of the nanofluids are numerically validated.
This paper presents a numerical study on the thermal characteristics of a milling process of titanium alloy with nanofluid minimum-quantity lubrication (MQL). The computational fluid dynamics (CFD) approach is introduced for establishing the numerical model for the nanofluid MQL milling process, and estimated temperatures for pure MQL and for nanofluid MQL using both hexagonal boron nitride (hBN) and nanodiamond particles are compared with the temperatures measured by thermocouples in the titanium alloy workpiece. The estimated workpiece temperatures are similar to experimental ones, and the model is validated.
Recently, titanium alloys have been widely used in aerospace, biomedical engineering, and military industries due to their high strength to weight ratio and corrosion resistance. However, it is well known that titanium alloys are difficult-to-cut materials because of a poor machinability characteristic caused by low thermal conductivity, chemical reactivity with all tool materials at high temperature, and high hardness. To improve the machinability of titanium alloys, cryogenic cooling with LN2 (Liquid Nitrogen) and nanofluid MQL (Minimum Quantity Lubrication) technologies have been studied while turning a Ti-6Al-4V alloy. For the analysis of turning process characteristics, the cutting force, the coefficient of friction, and the surface roughness are measured and analyzed according to varying lubrication and cooling conditions. The experimental results show that combined cryogenic cooling and nanofluid MQL significantly reduces the cutting forces, coefficients of friction and surface roughness when compared to wet condition during the turning process of Ti-6Al-4V.
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Current research trends in coolant application for machining Ti-6Al-4V alloy: a state-of-the-art review Prianka B. Zaman, N. R. Dhar Advances in Materials and Processing Technologies.2024; : 1. CrossRef
Comprehensive analysis of cutting temperature, tool wear, surface integrity and tribological properties in sustainable milling of Ti6Al4V alloy: LN2, nanofluid and hybrid machining Emine Şirin, Çağrı Vakkas Yıldırım, Şenol Şirin, Turgay Kıvak, Murat Sarıkaya Journal of Manufacturing Processes.2024; 131: 1360. CrossRef
Recent advancements in nano-lubrication strategies for machining processes considering their health and environmental impacts Kishan Zadafiya, Prassan Shah, Alborz Shokrani, Navneet Khanna Journal of Manufacturing Processes.2021; 68: 481. CrossRef
Determination of Flow Stress and Cutting Force Prediction of Ti-6Al-4V Material for 3D Printer using S-K Constitutive Equation Dae-Gyoun Park, Tae-Ho Kim, Eon-Chan Jeon Journal of the Korean Society of Manufacturing Process Engineers.2018; 17(6): 68. CrossRef
Friction and Wear Characteristics of Surface-Modified Titanium Alloy for Metal-on-Metal Hip Joint Bearing Hyeon-hwa Lee, Sungcheul Lee, Jong-Kweon Park, Minyang Yang International Journal of Precision Engineering and Manufacturing.2018; 19(6): 917. CrossRef
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