Friction and Lubrication Behavior of a Selective Laser Melted Hydraulic Spool Valve Under Contaminated Conditions

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Hongqin Ding ◽  
Peng Lu ◽  
Chao Zhang ◽  
Yi Zhu ◽  
Huayong Yang
Keyword(s):  
Particle Concentration ◽  
Sample Surface ◽  
Valve Body ◽  
Small Surface ◽  
Lubrication Regimes ◽  
High Particle Concentration ◽  
High Particle ◽  
Spool Valve ◽  
Surface Pores ◽  
Friction And Lubrication

Abstract Selective laser melting (SLM) technology has a great potential to reduce size and weight of hydraulic valves. However, the tribological performance of an SLMed valve has not been studied which is crucial for the performance and reliability of the valve, especially under contaminated conditions. In this study, the friction and lubrication behavior between an SLMed valve body and a traditional spool were studied using a scaled reciprocating test rig under various contaminated conditions (frequency at 5 Hz and 25 Hz; particle concentration at 0.4 mg/ml and 4 mg/ml; particle size at 1.6 µm and 15 µm). Three types of SLMed samples were fabricated using different exposure times: one has many large surface pores (pores area > 1000 µm2 accounts for 7.167% of the sample surface); one has a few small surface pores (pores area between 100 µm2 and 1000 µm2 accounts for 0.574% of the sample surface); and one only has micropores (pores area < 300 µm2 accounts for 0.168% of the sample surface). The density, hardness, microstructures, and pore characterization of the SLMed samples were investigated. The results indicated that the frequency greatly influenced friction and lubrication behaviors by determining lubrication regimes. The influence of surface pores on the lubrication and friction depends on contact conditions: pores which served as particle containers to reduce friction are prominent under 5 Hz frequency and high particle concentration; extra lubrication by the surface pores is observed under 25 Hz frequency and low particle concentration.

scholarly journals Discordance between Circulating Atherogenic Cholesterol Mass and Lipoprotein Particle Concentration in Relation to Future Coronary Events in Women

2017 ◽  
Vol 63 (4) ◽  
pp. 870-879 ◽  
Author(s):  
Patrick R Lawler ◽  
Akintunde O Akinkuolie ◽  
Paul M Ridker ◽  
Allan D Sniderman ◽  
Julie E Buring ◽  
...  
Keyword(s):  
Particle Concentration ◽  
Cox Proportional Hazards ◽  
Health Study ◽  
Linear Regression Models ◽  
Apo B ◽  
Healthy Women ◽  
Lipoprotein Particle ◽  
High Particle Concentration ◽  
High Particle ◽  
Chd Risk

Abstract BACKGROUND It is uncertain whether measurement of circulating total atherogenic lipoprotein particle cholesterol mass [non–HDL cholesterol (nonHDLc)] or particle concentration [apolipoprotein B (apo B) and LDL particle concentration (LDLp)] more accurately reflects risk of incident coronary heart disease (CHD). We evaluated CHD risk among women in whom these markers where discordant. METHODS Among 27533 initially healthy women in the Women's Health Study (NCT00000479), using residuals from linear regression models, we compared risk among women with higher or lower observed particle concentration relative to nonHDLc (highest and lowest residual quartiles, respectively) to individuals with agreement between markers (middle quartiles) using Cox proportional hazards models. RESULTS Although all 3 biomarkers were correlated (r ≥ 0.77), discordance occurred in up to 20.2% of women. Women with discordant high particle concentration were more likely to have metabolic syndrome (MetS) and diabetes (both P < 0.001). Over a median follow-up of 20.4 years, 1246 CHD events occurred (514725 person-years). Women with high particle concentration relative to nonHDLc had increased CHD risk: age-adjusted hazard ratio (95% CI) = 1.77 (1.56–2.00) for apo B and 1.70 (1.50–1.92) for LDLp. After adjustment for clinical risk factors including MetS, these risks attenuated to 1.22 (1.07–1.39) for apo B and 1.13 (0.99–1.29) for LDLp. Discordant low apo B or LDLp relative to nonHDLc was not associated with lower risk. CONCLUSIONS Discordance between atherogenic particle cholesterol mass and particle concentration occurs in a sizeable proportion of apparently healthy women and should be suspected clinically among women with cardiometabolic traits. In such women, direct measurement of lipoprotein particle concentration might better inform CHD risk assessment.

Features of an underexpanded pulsed impact gas-dispersed jet with a high particle concentration

2017 ◽  
Vol 62 (1) ◽  
pp. 18-23 ◽  
Author(s):  
D. V. Sadin ◽  
S. D. Lyubarskii ◽  
Yu. A. Gravchenko
Keyword(s):  
Particle Concentration ◽  
High Particle Concentration ◽  
High Particle

scholarly journals Microparticle Concentration and Electrical Conductivity of a 700 m Ice Core from Mizuho Station, Antarctica

1988 ◽  
Vol 10 ◽  
pp. 38-42 ◽  
Author(s):  
Yoshiyuki Fujii ◽  
Okitsugu Watanabe
Keyword(s):  
Electrical Conductivity ◽  
Southern Hemisphere ◽  
Large Scale ◽  
Particle Concentration ◽  
Environmental Changes ◽  
Ice Core ◽  
Depth Interval ◽  
Preliminary Results ◽  
High Particle Concentration ◽  
High Particle

The present paper gives the preliminary results of the analyses on microparticle concentration and electrical conductivity of a 700.56 m ice core from Mizuho Station, Antarctica. Concentration of microparticles coarser than 0.63 μm in diameter increases more than twofold at the 240-440 m depth interval compared with that below 440 m in depth. The higher particle concentration is well associated with higher electrical conductivity and lower δ18O. Periods of high particle concentration are estimated to be 3000-6000 years B.P. A visible volcanic dirt band was found at 500.7 m below the surface. This dirt band may be isochronous with the shallowest ash band of the Byrd Station core, found at 799 m depth. The present study indicates that large-scale environmental changes possibly occurred in the Southern Hemisphere in the middle of the Holocene.

Surface Modification Approach to TiO2 Nanofluids with High Particle Concentration, Low Viscosity, and Electrochemical Activity

2015 ◽  
Vol 7 (37) ◽  
pp. 20538-20547 ◽  
Author(s):  
Sujat Sen ◽  
Vijay Govindarajan ◽  
Christopher J. Pelliccione ◽  
Jie Wang ◽  
Dean J. Miller ◽  
...  
Keyword(s):  
Surface Modification ◽  
Particle Concentration ◽  
Electrochemical Activity ◽  
High Particle Concentration ◽  
Low Viscosity ◽  
High Particle ◽  
Tio2 Nanofluids

Particle-Cluster Formation and Vorticity in Gas-Solid Flows

2017 ◽  
Author(s):  
Sai Satish Guda ◽  
Ismail B. Celik
Keyword(s):  
Fluidized Beds ◽  
Particle Concentration ◽  
Numerical Study ◽  
Cluster Formation ◽  
Injection Velocity ◽  
Discrete Phase Model ◽  
High Concentration ◽  
Ansys Fluent ◽  
High Particle Concentration ◽  
High Particle

Fluidized beds are widely used in industry for combustion, gasification, catalytic cracking and several other purposes. Pneumatic conveying of air is popularly used in industry to transport materials such as pulverized coal through pipelines. A common observation in gas-solid flow dynamics in both of the above systems is the formation of high concentration regions of particles; known as clusters in fluidized beds and rope like structures in pipe bends and ducts. Both the clustering and roping phenomenon were clearly observed in some experiments and in simulations of both fluidized beds and gas-solid flows in pipe bends. It has been found from these simulations that there is a strong correlation between vorticity and concentration. The high particle concentration regions are bounded by vortices of clockwise and counter clockwise direction of roughly the same order of magnitude and there is very low vorticity at the high concentration regions. The goal of this study is to find the cause and effect relation between the gas vorticity and the high particle concentration regions; in particular whether the gas vorticity causes particle agglomeration into clusters or vice-versa. Numerical study has been performed on a vertical pipe by creating a vortex field. In this regard, very large eddy simulations with Lagrangian Discrete Phase model have been performed using Ansys FLUENT and MFIX software packages. The influence of particles on the vorticity has been studied. Influence of several factors such as particle size, injection velocity etc. have also been studied. Correlations among turbulent kinetic energy, vorticity, and particle clustering and/or roping are illustrated.

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