scholarly journals Cavitation Growth Phenomena in Pure-Sliding Grease EHD Contacts

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 75
Author(s):  
Takefumi Otsu ◽  
Romeo Glovnea ◽  
Joichi Sugimura
Keyword(s):  
High Speed ◽  
Cavity Growth ◽  
Growth Time ◽  
In Situ Observation ◽  
Oil Viscosity ◽  
Grease Lubrication ◽  
Base Oil ◽  
Lubrication Film ◽  
Initial Stage ◽  
Cavity Growth Rate

This article describes experimental and theoretical studies on the cavitation phenomena in the grease lubrication film under pure sliding elastohydrodynamic contact. In situ observation tests using the optical interferometry technique were conducted, and the growth of cavitation was captured using a high-speed camera. The results showed that the cavity grew in two stages, which was similar to the behavior in the base oil, and that the cavity growth rate in the initial stage was higher than that in the second stage. In the initial stage, the cavity growth time in the grease was longer than that in the base oil, and the cavity length after the growth depended on the base oil viscosity. It was also found in the test using diurea grease that small cavities were formed by the lumps of thickener. The cavity growth in the initial stage was discussed by numerical simulation of pressure distribution based on a simple rheological model.

Effects of Grease Types on Vibration and Acoustic Emission of Defective Linear-Guideway Type Recirculating Ball Bearings

2010 ◽  
Author(s):  
Hiroyuki Ohta ◽  
Shinya Hayashi ◽  
Soichiro Kato ◽  
Yutaka Igarashi
Keyword(s):  
Acoustic Emission ◽  
Acoustic Emissions ◽  
Experimental Results ◽  
Ball Bearings ◽  
Oil Viscosity ◽  
Grease Lubrication ◽  
Base Oil ◽  
Defect Angle

In this paper, vibrations and acoustic emissions (AEs) of defective linear-guideway type recirculating ball bearings under grease lubrication were measured. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the RMS values) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle are reduced when a grease with higher base oil viscosity is used.

Grease Performance in Tapered Roller Bearings

2005 ◽  
Author(s):  
Michael R. Hoeprich
Keyword(s):  
Sem Analysis ◽  
Rolling Element Bearing ◽  
Oil Viscosity ◽  
Grease Lubrication ◽  
Base Oil ◽  
Rolling Element ◽  
Post Test ◽  
Tapered Roller ◽  
Element Bearing ◽  
Tapered Roller Bearings

To gain insight into the physical aspects of grease lubrication, nine greases with different oil viscosity and thickener combinations were tested in a tapered rolling element bearing under a light thrust load at speeds of 1800 and 3600 RPM. Bearings were run for thirty days or until a 150°C rib temperature was reached. Using SEM analysis, thickener samples were taken after testing from the rib/roller and raceway contacts for comparison with the thickener in new grease. A post test infrared technique was also used to evaluate grease thickness at the rib/roller contact and was compared with calculated film thickness. Bearing operating temperatures were then compared with grease base oil viscosity and thickener type.

Vibration and Acoustic Emission Measurements Evaluating the Separation of the Balls and Raceways With Lubricating Film in a Linear Bearing Under Grease Lubrication

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Hiroyuki Ohta ◽  
Yuko Nakajima ◽  
Soichiro Kato ◽  
Hideyuki Tajimi
Keyword(s):  
Acoustic Emission ◽  
Ball Bearing ◽  
Linear Velocity ◽  
Oil Viscosity ◽  
Grease Lubrication ◽  
Base Oil ◽  
Lubricating Film ◽  
Contact Voltage ◽  
Film Parameter ◽  
Vibratory Acceleration

This paper deals with vibration and acoustic emission (AE) measurements evaluating the separation of the balls and raceways with lubricating film in a linear-guideway–type recirculating ball bearing (linear bearing) under grease lubrication. In the experiments, three types of commercial grease, AS2, LG2, and PS2, were used. The vibratory acceleration, AE, temperature, and electric conductivity (contact voltage) in the test bearing were measured, while a carriage of the test bearing was driven at a certain linear velocity. Experimental results showed that the measured vibratory acceleration, AE, and contact voltage of the test bearing were affected by the linear velocity and the base oil viscosity of the grease. Next, the rail side film parameter ΛR and the carriage side film parameter ΛC were examined for the test bearing in operation, and it was shown that the ΛR value was lower than the ΛC value. In addition, a condition for the separation of all the balls and raceways with lubricating film was presented. Finally, it was shown that the measured root-mean-square (RMS) values of vibratory acceleration or AE can be used for evaluating the separation of all the balls and raceways with lubricating film in the test bearing.

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

2014 ◽  
Vol 782 ◽  
pp. 3-7
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Kohta Kadoi ◽  
Peng Wen
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Solidification Cracking ◽  
In Situ Observation ◽  
High Speed Video Camera ◽  
Varestraint Test ◽  
Solidification Cracks ◽  
Observation Method ◽  
Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

The Study of Thermal Raising and Transmission Torque of High Speed Ball-Screw Lubricated by Different Greases

2015 ◽  
Vol 642 ◽  
pp. 212-216
Author(s):  
Yi Haung ◽  
Chin Chung Wei
Keyword(s):  
Contact Area ◽  
Axial Load ◽  
High Speed ◽  
Performance Test ◽  
Vertical Motion ◽  
High Viscosity ◽  
Ball Screw ◽  
Frictional Heat ◽  
Motion Platform ◽  
Base Oil

Ball screw is a high-precision and high performance linear drive of mechanical elements. The frictional heat of internal components what is very significant impact for platform transmission in high speed and the high axial load and causes the thermal expansion of element. In this research , the influence of different greases on ball screw is investigated in thermal rising of nut and driving torque in high speed and high axial load. A vertical motion platform was used for driving performance test. Thermal rising of nut of ball screw and the variance of transmission torque whose lubricated by high viscosity base oil grease is significant larger than the lower one. High viscosity grease is not easy to carry out the friction heat generated at ball and raceway contact area due to the bad flowing properties. It also has more serious wear occurred at contact area and high friction force, whose causes the large variance of transmission torque.

Experimental Analysis of Water/Oil Displacement Tests in Horizontal Pipe

SPE Journal ◽  
2021 ◽  
pp. 1-18
Author(s):  
Roberto Fernando Leuchtenberger ◽  
Jorge Luiz Biazussi ◽  
William Monte Verde ◽  
Marcelo de Souza Castro ◽  
Antonio Carlos Bannwart
Keyword(s):  
Viscous Liquid ◽  
High Speed ◽  
Cold Water ◽  
Tap Water ◽  
Logistic Function ◽  
Oil Field ◽  
Injection Velocity ◽  
Internal Diameter ◽  
Oil Viscosity ◽  
Horizontal Pipe

Summary Production shutdowns occur often throughout the life cycle of an oil field. In offshore fields, shutdown situations are accompanied by an intense heat exchange between pipeline and cold water, which exponentially increases oil viscosity. Such an event may lead to serious difficulty to restart the production, or even render it unfeasible, especially for heavy oil fields. Therefore, a preventive procedure is required to remove the ultraviscous oil from pipelines and risers; for example, by pumping diesel or methanol in a flush procedure. Designing an efficient cleanup procedure is therefore essential in terms of time, amount of fluid injected, and pumping system requirements. However, the amount of research published in this area is limited. In this paper, we propose a comprehensive analysis on how the displacement of a viscous liquid by a less-viscous liquid occurs in a pipeline through footages in different segments, varying the injection velocity. Two mineral oils with different viscosities and tap water were used as working fluids for this study. The experimental setup was built with a horizontal 10-m-long acrylic pipe with 19-mm internal diameter. Two high-speed cameras were placed both in the inlet and outlet segments. Our results demonstrate how water displaces viscous oil in a pipeline, showing different flow configurations as superficial water velocity increases, depending on the oil viscosity and distance from the inlet. A dimensionless analysis was performed by a combination of the forces that govern the flow and dimensionless groups found in literature. The results show an expected area of optimum values regarding cleaning time according to flow configuration. A unidimensional model using a logistic function was proposed and showed a good agreement with the experimental data. The model itself proven to be an easy tool for industry and academic purposes, supporting even more robust and elaborated models in the future. NOTE: Supplemental material is available with this paper and is available online under the Supplementary Data heading at https://doi.org/10.2118/205356-PA.

The Effect of Transient Fuel Staging on Self-Excited Instabilities in a Multi-Nozzle Model Gas Turbine Combustor

2017 ◽  
Author(s):  
Wyatt Culler ◽  
Janith Samarasinghe ◽  
Bryan D. Quay ◽  
Domenic A. Santavicca ◽  
Jacqueline O’Connor
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Equivalence Ratio ◽  
Growth Time ◽  
Stable Operation ◽  
Time Constants ◽  
Decay Times ◽  
Fuel Staging ◽  
Passive Techniques

Combustion instability in gas turbines can be mitigated using active techniques or passive techniques, but passive techniques are almost exclusively used in industrial settings. While fuel staging, a common passive technique, is effective in reducing the amplitude of self-excited instabilities in gas turbine combustors at steady-state conditions, the effect of transients in fuel staging on self-excited instabilities is not well understood. This paper examines the effect of fuel staging transients on a laboratory-scale five-nozzle can combustor undergoing self-excited instabilities. The five nozzles are arranged in a four-around-one configuration and fuel staging is accomplished by increasing the center nozzle equivalence ratio. When the global equivalence ratio is φ = 0.70 and all nozzles are fueled equally, the combustor undergoes self-excited oscillations. These oscillations are suppressed when the center nozzle equivalence ratio is increased to φ = 0.80 or φ = 0.85. Two transient staging schedules are used, resulting in transitions from unstable to stable operation, and vice-versa. It is found that the characteristic instability decay times are dependent on the amount of fuel staging in the center nozzle. It is also found that the decay time constants differ from the growth time constants, indicating hysteresis in stability transition points. High speed CH* chemiluminescence images in combination with dynamic pressure measurements are used to determine the instantaneous phase difference between the heat release rate fluctuation and the combustor pressure fluctuation throughout the combustor. This analysis shows that the instability onset process is different from the instability decay process.

Numerical Analysis of the Effect of Diffusion and Creep Flow on Cavity Growth

2007 ◽  
Author(s):  
Frederick W. Brust ◽  
Joonyoung Oh
Keyword(s):  
Growth Rate ◽  
Numerical Method ◽  
Cavity Growth ◽  
Volume Growth ◽  
Numerical Results ◽  
Shape Evolution ◽  
Cavity Volume ◽  
Cavity Shape ◽  
Cavity Growth Rate ◽  
Fully Coupled

In this paper, intergranular cavity growth in regimes, where both surface diffusion and deformation enhanced grain boundary diffusion are important, is studied. In order to continuously simulate the cavity shape evolution and cavity growth rate, a fully-coupled numerical method is proposed. Based on the fully-coupled numerical method, a gradual cavity shape change is predicted and this leads to an adverse effect on the cavity growth rates. As the portion of the cavity volume growth due to jacking and viscoplastic deformation in the total cavity volume growth increases, the initially spherical cavity evolves to V-shaped cavity. The numerical results are physically more realistic compared to results in the previous studies. The present numerical results suggest that the cavity shape evolution and cavity growth rate based on an assumed cavity shape, whether spherical or crack-like, cannot be used in this regime due to transitional coupled growth mechanisms.

scholarly journals A Superhydrophilic Aluminum Surface with Fast Water Evaporation Based on Anodic Alumina Bundle Structures via Anodizing in Pyrophosphoric Acid

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3497 ◽  
Author(s):  
Daiki Nakajima ◽  
Tatsuya Kikuchi ◽  
Taiki Yoshioka ◽  
Hisayoshi Matsushima ◽  
Mikito Ueda ◽  
...  
Keyword(s):  
Contact Angle ◽  
Oxide Film ◽  
High Speed ◽  
Porous Alumina ◽  
Aluminum Surface ◽  
Water Evaporation ◽  
Water Contact ◽  
Initial Stage ◽  
Angle Measuring ◽  
Pyrophosphoric Acid

A superhydrophilic aluminum surface with fast water evaporation based on nanostructured aluminum oxide was fabricated via anodizing in pyrophosphoric acid. Anodizing aluminum in pyrophosphoric acid caused the successive formation of a barrier oxide film, a porous oxide film, pyramidal bundle structures with alumina nanofibers, and completely bent nanofibers. During the water contact angle measurements at 1 s after the water droplet was placed on the anodized surface, the contact angle rapidly decreased to less than 10°, and superhydrophilic behavior with the lowest contact angle measuring 2.0° was exhibited on the surface covered with the pyramidal bundle structures. As the measurement time of the contact angle decreased to 200–33 ms after the water placement, although the contact angle slightly increased in the initial stage due to the formation of porous alumina, at 33 ms after the water placement, the contact angle was 9.8°, indicating that superhydrophilicity with fast water evaporation was successfully obtained on the surface covered with the pyramidal bundle structures. We found that the shape of the pyramidal bundle structures was maintained in water without separation by in situ high-speed atomic force microscopy measurements.

Sign in / Sign up

Export Citation Format

Share Document