Numerical Study on Effect of Dimples on Tribo-Characteristics in Non-Newtonian Thermal Elastohydrodynamic Lubrication Point Contacts With Different Mechanical and Thermal Properties

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Peiran Yang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Transient Behavior ◽  
Mechanical And Thermal Properties ◽  
Smooth Surfaces ◽  
Contact Surfaces ◽  
Micro Dimples

Abstract The transient behavior of tribo-characteristics caused by micro-dimples on point contact surfaces with different mechanical and thermal properties was investigated based on non-Newtonian thermal elastohydrodynamic lubrication (EHL) analysis. The dimples were assumed to exist on both contact surfaces and the surface shapes of the contact bodies were evaluated separately. It is pointed out that surface texturing due to the micro-dimples is not necessarily beneficial in EHL contacts under fully flooded conditions since the micro-dimples provide a high pressure and a thin minimum film thickness as compared with the case of contacts with smooth surfaces, although the friction coefficient of surfaces with micro-dimples is always lower than that of the smooth surfaces. In order to obtain relatively good tribo-characteristics, the velocity of the surface with low thermal conductivity should be faster than that with high thermal conductivity, and the wavelengths of micro-dimples in the direction of motion on both surfaces should be different.

Numerical study on the interaction of transversely oriented ridges in thermal elastohydrodynamic lubrication point contacts using the Eyring shear-thinning model

2016 ◽  
Vol 231 (1) ◽  
pp. 93-106 ◽  
Author(s):  
Jinlei Cui ◽  
Peiran Yang ◽  
Motohiro Kaneta ◽  
Ivan Krupka
Keyword(s):  
Friction Coefficient ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Solid Surfaces ◽  
Point Contacts ◽  
Transient Behaviour ◽  
Contact Surfaces ◽  
Thinning Effect

Transient behaviour of tribo-characteristics caused by transversely oriented ridges on point contact surfaces was investigated based on a thermal elastohydrodynamic lubrication analysis. The ridges were assumed to exist on both the contact surfaces with different velocities. Results show that the interaction of ridges gives a large influence on the local film thickness, pressure, friction coefficient, temperatures on both the solid surfaces and temperature in the oil film. It is also pointed out that the size of the contact bodies brings strong effect on the temperature distribution and shear rate as well as on the friction coefficient. Furthermore, it is revealed that under rolling-sliding conditions, the shear-thinning property of the lubricant is negligible when the size of the contact body is large enough. However, shear-thinning effect plays an important role when the size is extremely small.

Effects of Thermal Properties of Contact Materials and Slide-Roll Ratio in Elastohydrodynamic Lubrication

2021 ◽  
pp. 1-34
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Hiroshi Nishikawa
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Film Thickness ◽  
Thermal Inertia ◽  
Elastohydrodynamic Lubrication ◽  
Mechanical And Thermal Properties ◽  
Contact Materials ◽  
The Difference ◽  
Thermal Ehl

Abstract The effects of thermal conductivity, heat capacity, thermal inertia and slide-roll ratio on point elastohydrodynamic lubrication (EHL) are discussed with engineering ceramics and steel by a non-Newtonian thermal EHL analysis. When the thermal conductivities of contacting materials are significantly different, the film thickness is greatly affected by which material has the higher velocity. However, the film thickness is dominated by the heat capacity when the difference in thermal conductivity is not large. In contact of materials with the same mechanical and thermal properties, the central film thickness and friction coefficient are influenced by the thermal inertia.

Numerical Study on Effect of Thermal Conductivity in Point Contacts With Longitudinal Roughness on Abnormal Pressure Distribution

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Jing Wang ◽  
Peiran Yang
Keyword(s):  
Thermal Conductivity ◽  
Numerical Study ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Variation ◽  
Point Contacts ◽  
Contact Materials ◽  
Opposite Case ◽  
Abnormal Pressure ◽  
Longitudinal Roughness

Abstract In order to clarify the effect of thermal conductivity on non-Newtonian thermal elastohydrodynamic lubrication (EHL) in the point contact with longitudinal roughness on one surface or on both surfaces, numerical calculations are carried out. The contact is formed by ceramics and steel. The surface shapes of both contact solids are investigated separately. It was found that the pressure at ridges shows lower than that at grooves when the speed of a material with low thermal conductivity is faster than that of a material with high thermal conductivity. In the opposite case, such a phenomenon never occurs. This abnormal pressure variation is largely affected by the combination of contact materials and running conditions.

Mechanical and Thermal Properties of Magnesia Binder Based on Natural and Technogenic Raw Materials

2021 ◽  
Vol 320 ◽  
pp. 181-185
Author(s):  
Elvija Namsone ◽  
Genadijs Sahmenko ◽  
Irina Shvetsova ◽  
Aleksandrs Korjakins
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Raw Materials ◽  
High Strength ◽  
Strength Properties ◽  
Waste Materials ◽  
Mechanical And Thermal Properties ◽  
Experimental Part ◽  
Technogenic Raw Materials ◽  
Caustic Magnesia

Because of low calcination temperature, magnesia binders are attributed as low-CO2 emission materials that can benefit the environment by reducing the energy consumption of building sector. Portland cement in different areas of construction can be replaced by magnesia binder which do not require autoclave treatment for hardening, it has low thermal conductivity and high strength properties. Magnesium-based materials are characterized by decorativeness and ecological compatibility.The experimental part of this research is based on the preparation of magnesia binders by adding raw materials and calcinated products and caustic magnesia. The aim of this study was to obtain low-CO2 emission and eco-friendly material using local dolomite waste materials, comparing physical, mechanical, thermal properties of magnesium binders.

Experimental and numerical study on cavitation under elastohydrodynamic lubrication point contact

2021 ◽  
pp. 135065012110527
Author(s):  
Mingfei Ma ◽  
Wen Wang ◽  
Wenxun Jiang
Keyword(s):  
Contact Area ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hertzian Contact ◽  
Pressure Area ◽  
Cavitation Pressure ◽  
Experimental Researches ◽  
State 1

As a common phenomenon in elastohydrodynamic lubrication, cavitation has an effect on the completeness of the oil film in the contact area. Many studies have therefore been conducted on cavitation. Experimental researches on cavitation usually rely on optical interference observation, which offers a limited resolution and observation range. In this paper, an infrared thermal camera is used to observe the cavity bubbles on a ball-on-disc setup under sliding/rolling conditions. The results show that the cavity length increases with an increases of the entrainment speed and the viscosity of the lubricants. These observations are explained by a numerical model based on Elrod's algorithm. Effects of entrainment speed and lubricant viscosity on the breakup of cavitation bubbles and the cavitation states are investigated. Both the simulation and experimental results show that a negative pressure area is present behind the Hertzian contact area. The ambient pressure plays a role in maintaining cavitation state 1. The cavitation pressure is close to the vacuum pressure when the entrainment speed is low and to the ambient pressure instead when the entrainment speed is high.

scholarly journals Bio-based rigid polyurethane foam prepared from apricot stone shell-based polyol for thermal insulation application – Part 2: Morphological, mechanical, and thermal properties

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 6080-6094
Author(s):  
Muhammed Said Fidan ◽  
Murat Ertaş
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Properties ◽  
Thermogravimetric Analysis ◽  
Polyurethane Foam ◽  
Flame Retardants ◽  
Compressive Modulus ◽  
Cell Diameter ◽  
Mechanical And Thermal Properties ◽  
Rigid Polyurethane Foam

The procedure for the liquefaction of apricot stone shells was reported in Part 1. Part 2 of this work determines the morphological, mechanical, and thermal properties of the bio-based rigid polyurethane foam composites (RPUFc). In this study, the thermal conductivity, compressive strength, compressive modulus, thermogravimetric analysis, flammability tests (horizontal burning and limited oxygen index (LOI)) in the flame retardants), and scanning electron microscope (SEM) (cell diameter in the SEM) tests of the RPUFc were performed and compared with control samples. The results showed the thermal conductivity (0.0342 to 0.0362 mW/mK), compressive strength (10.5 to 14.9 kPa), compressive modulus (179.9 to 180.3 kPa), decomposition and residue in the thermogravimetric analysis (230 to 491 °C, 15.31 to 21.61%), UL-94 and LOI in the flame retardants (539.5 to 591.1 mm/min, 17.8 to 18.5%), and cell diameter in the SEM (50.6 to 347.5 μm) of RPUFc attained from liquefied biomass. The results were similar to those of foams obtained from industrial RPUFs, and demonstrated that bio-based RPUFc obtained from liquefied apricot stone shells could be used as a reinforcement filler in the preparation of RPUFs, specifically in construction and insulation materials. Moreover, liquefied apricot stone shell products have potential to be fabricated into rigid polyurethane foam composites.

scholarly journals Physical, mechanical and thermal properties of Crushed Sand Concrete containing Rubber Waste

2018 ◽  
Vol 149 ◽  
pp. 01076
Author(s):  
Guendouz Mohamed ◽  
Boukhelkhal Djamila
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Flexural Strength ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Bulk Density ◽  
Mechanical And Thermal Properties ◽  
The Past ◽  
Rubber Waste ◽  
And Performance

Over the past twenty years, the rubber wastes are an important part of municipal solid waste. This work focuses on the recycling of rubber waste, specifically rubber waste of used shoes discharged into the nature and added in the mass of crushed sand concrete with percentage (10%, 20%, 30% and 40%). The physical (workability, fresh density), mechanical (compressive and flexural strength) and thermal (thermal conductivity) of different crushed sand concrete made are analyzed and compared to the respective controls. The use of rubber waste in crushed sand concrete contributes to reduce the bulk density and performance of sand concrete. Nevertheless, the use of rubber aggregate leads to a significant reduction in thermal conductivity, which improves the thermal insulation of crushed sand concrete.

A numerical study on the blow-off limit of premixed hydrogen/air flames in a cylindrical micro-combustor

2020 ◽  
pp. 095441002097144
Author(s):  
Saeed Naeemi ◽  
Seyed Abdolmehdi Hashemi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Flow Velocity ◽  
Equivalence Ratio ◽  
Numerical Study ◽  
Flame Stability ◽  
Convection Coefficient ◽  
Inlet Flow ◽  
Micro Combustor ◽  
Emissivity Coefficient

In the current work, a numerical study on combustion of premixed H2–air in a micro-cylindrical combustor was carried out and the critical velocity of inlet flow that causes the blow-off was obtained. Furthermore, the effects the equivalence ratio, wall thickness, geometry of combustor and thermal properties of walls on the critical blow-off velocity were studied. The numerical results showed that, increasing the equivalence ratio results in higher critical blow-off velocity. A micro combustor with thicker wall had better flame stability. As the combustor dimeter is decreased the blow-off occur in lower inlet flow velocity. Higher thermal conductivity of walls increases the critical blow-off velocity. In addition, with varying heat convection coefficient (h) and emissivity coefficient [Formula: see text] of the walls from 1 to 60 W/m2.K and 0.2 to 0.8 respectively, the critical blow-off velocity is reduced and shows the importance of wall thermal properties in the design and operation of micro-combustors.

scholarly journals Experimental investigations into mechanical and thermal properties of rapid manufactured copper parts

2019 ◽  
Vol 234 (1) ◽  
pp. 82-95 ◽  
Author(s):  
Gurminder Singh ◽  
Pulak M Pandey
Keyword(s):  
Thermal Conductivity ◽  
Tensile Strength ◽  
Thermal Properties ◽  
Ultimate Tensile Strength ◽  
Heating Rate ◽  
Sintering Temperature ◽  
Mechanical And Thermal Properties ◽  
Surface Porosity ◽  
Soaking Time ◽  
Ultrasonic Assisted

In the present paper, mechanical and thermal properties of rapidly manufactured copper parts were studied. The combination of three-dimensional printing and ultrasonic assisted pressureless sintering was used to fabricate copper parts. First, the ultimate tensile strength and thermal conductivity were compared between ultrasonic assisted and conventional pressureless sintered samples. The homogenously mixing of particles and local heat generation by ultrasonic vibrations promoted the sintering driving process and resulted in better mechanical and thermal properties. Furthermore, response surface methodology was adopted for the comprehensive study of the ultrasonic sintering parameters (sintering temperature, heating rate, and soaking time with ultrasonic vibrations) on ultimate tensile strength and thermal conductivity of the fabricated sample. Analysis of variance was performed to identify the significant factors and interactions. The image processing method was used to identify the surface porosity at different parameter levels to analyse the experimental results. High ultimate tensile strength was obtained at high sintering temperature, long soaking time, and slow heating rate with low surface porosity. After 60 min of soaking time, no significant effect was observed on the thermal conductivity of the fabricated sample. The significant interactions revealed less effect of soaking time at low sintering temperatures for ultimate tensile strength and less effect of heating rate at low sintering temperatures for thermal conductivity. Multi-objective optimization was carried out to identify parameters for maximum ultimate tensile strength and maximum thermal conductivity.

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