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.

Thermal Properties of Selected Timbers

2014 ◽  
Vol 982 ◽  
pp. 100-103 ◽  
Author(s):  
Dana Koňáková ◽  
Monika Čáchová ◽  
Eva Vejmelková ◽  
Martin Keppert ◽  
Robert Černý
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Moisture Content ◽  
Specific Heat ◽  
Heat Transport ◽  
Specific Heat Capacity ◽  
Open Porosity ◽  
Building Structures ◽  
The Difference

This article deals with thermal properties of selected kinds of timber. Wood, generally, is one of often used natural materials in building structures. For our research, woods were selected according to frequency of utilization in civil engineering branch. Four different timbers were chosen, and experimental determinations of their properties were performed. Basic physical properties as well as thermal properties belong among studied characteristics. From achieved results, it is obvious, that the bulk density of studied wood ranges between 373 kg m-3 and 649 kg m-3, the open porosity differ by 13%. Regarding thermal properties, values of the thermal conductivity as well as the specific heat capacity are influenced mainly by the open porosity and moisture content. The thermal conductivity in dry state varies by about 31% while in the case of the specific heat capacity the difference is about 19%. Obtained date will be used in the mathematical analysis of heat transport in building structures.

Effect of Nanosilica on Mechanical and Thermal Properties of Cement Composites for Thermal Energy Storage Materials

2015 ◽  
Vol 1131 ◽  
pp. 182-185
Author(s):  
Pongsak Jittabut
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Capacity ◽  
Compressive Strength ◽  
Thermal Properties ◽  
Thermal Energy ◽  
Energy Storage Materials ◽  
Mechanical And Thermal Properties ◽  
Storage Materials ◽  
Nanosilica Particle

This research article presents the mechanical and thermal properties of cement-based composite for thermal energy storage materials. The effects of nanosilica particle size and concentration determined by mixing nanosilica particle size of 50 nm, using nanosilica were of 1-5 wt%. Thermal properties coefficients were tested using a direct measuring instrument with surface probe (ISOMET2114). The influence of nanosilica on the performance, such as compressive strength, bulk density, thermal conductivity, volume heat capacity and thermal diffusivity of hardened composite cement pastes were studied for future solar thermal energy materials with better performance. According to the development of thermal storage materials and their application environment requirement in solar thermal power, the specimens were subjected to heat at 350, and 900°C. It were observed that, before heating, the compressive strength is optimized at nanosilica amount of 4wt% at the age of 28 days. Moreover, after heating at 350 oC and 900°C, the thermal conductivity and volume heat capacity of the cement paste enriched with nanosilica were significantly lesser than that of the before heating one.

Effects of the thermal conductivity of contact materials on elastohydrodynamic lubrication characteristics

2010 ◽  
Vol 224 (12) ◽  
pp. 2577-2587 ◽  
Author(s):  
M Kaneta ◽  
P Yang
Keyword(s):  
Thermal Conductivity ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Fluid Film ◽  
Contact Materials ◽  
Entrainment Velocity ◽  
Pressure Distributions ◽  
Traction Coefficient ◽  
Lubrication Characteristics ◽  
Lubricant Viscosity

Isothermal elastohydrodynamic lubrication (EHL) theory has brought the improvement in function, performance, and durability of machine elements with concentrated contacts. The main reason is that the theory can evaluate the lubrication characteristics, such as film thickness and pressure distributions, from the shape and size of contacting materials, lubricant viscosity at the entrance to the EHL conjunction, entrainment velocity, equivalent elastic modulus, and applied load. However, in order to estimate the film thickness and pressure distributions more accurately and to make clear the traction behaviour based on lubricant rheology, it is necessary to establish thermal EHL theory, which incorporates heat generation in the fluid film and heat transfer in the machine system on the foundation of isothermal EHL theory. The thermal conductivity of contact materials controls temperature in the fluid film and consequently the lubricant viscosity. Therefore, the EHL characteristics are affected remarkably by the thermal conductivity of contact materials. In this article, the effects of the thermal conductivity of contacting materials on the film thickness, pressure, and traction coefficient are described.

Effect of Nano-TiO2 on Mechanical and Thermal Properties of Cement Composites for Thermal Energy Storage Materials

2015 ◽  
Vol 804 ◽  
pp. 115-118
Author(s):  
Pongsak Jittabut
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Compressive Strength ◽  
Thermal Properties ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Energy Storage Materials ◽  
Mechanical And Thermal Properties ◽  
Storage Materials

This research article presents the mechanical and thermal properties of cement-based composite for thermal energy storage materials enriched with containing nanoTiO2 particle size (25 nm) and concentration (1-5 wt.%) were systematically investigated. Thermal properties coefficients were tested using a direct measuring instrument with surface probe (ISOMET2114). The influence of nanoTiO2 on the performance, such as compressive strength, bulk density, thermal conductivity, volume heat capacity and thermal diffusivity of hardened composite cement pastes were studied for future solar thermal energy materials with better performance. According to the development of thermal storage materials and their application environment requirement in solar thermal power, the specimens were subjected to heat at 350°C and 900°C. It was observed that, before heating, the compressive strength is optimized at nanoTiO2 amount of 2 wt%. Moreover, after heating at 350 °C and 900°C, the thermal conductivity and volume heat capacity of the cement paste enriched with nanoTiO2 were significantly lesser than that of the before heating one.

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.

Effects of Thermal Conductivity of Contacting Surfaces on Point EHL Contacts

2003 ◽  
Vol 125 (4) ◽  
pp. 731-738 ◽  
Author(s):  
M. Kaneta ◽  
P. Yang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Film Thickness ◽  
Temperature Variation ◽  
Optical Interferometry ◽  
The Other ◽  
Oil Film ◽  
Entrainment Velocity ◽  
Minimum Film Thickness ◽  
Thermal Ehl

With actual and virtual materials, the effects of the thermal conductivity of contacting surfaces on EHL are investigated through experimental analyses using the optical interferometry technique and the Newtonian thermal EHL analyses in consideration of the variation of oil properties in all directions within the film. A mineral bright stock is used as a lubricant. It is found that the distributions of pressure and film thickness, including the minimum film thickness, are influenced very much by the entrainment velocity and the slide-roll ratio. One of the causes is the temperature-viscosity wedge action produced by the temperature variation across the oil film, and the other is an increase in oil temperature at the entrance of the contact due to the heat produced by the compression work and the shearing of the oil. The degree of both influences depends on the thermal properties of contacting materials.

The Causes of Asymmetric Deformation of Surface Roughness Asperities in EHL Contacts

2021 ◽  
pp. 1-38
Author(s):  
Motohiro Kaneta ◽  
Kenji Matsuda ◽  
Hiroshi Nishikawa
Keyword(s):  
Thermal Conductivity ◽  
Surface Roughness ◽  
Contact Pressure ◽  
Elastic Moduli ◽  
Elastohydrodynamic Lubrication ◽  
The Other ◽  
Contact Materials ◽  
Oil Film ◽  
Asymmetric Deformation ◽  
The Difference

Abstract This paper provides the main causes of asymmetric or directional deformation of surface roughness based on a transient non-Newtonian thermal elastohydrodynamic lubrication (EHL) model, where the contact materials have different thermal conductivities and elastic moduli. It is clarified that the asymmetric deformation of the asperities appears due to two causes. One depends on the slide-roll ratio and the difference in thermal conductivity between contact materials, and the other is caused by the contact pressure between the asperities through the oil film.

scholarly journals Testing a Gypsum Composite Based on Raw Gypsum with a Direct Admixture of Paraffin and Polymer to Improve Thermal Properties

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3241
Author(s):  
Krzysztof Powała ◽  
Andrzej Obraniak ◽  
Dariusz Heim
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Phase Change ◽  
Large Scale ◽  
Building Materials ◽  
Residential Buildings ◽  
Energy Performance ◽  
Polymer Content ◽  
Volumetric Heat Capacity

The implemented new legal regulations regarding thermal comfort, the energy performance of residential buildings, and proecological requirements require the design of new building materials, the use of which will improve the thermal efficiency of newly built and renovated buildings. Therefore, many companies producing building materials strive to improve the properties of their products by reducing the weight of the materials, increasing their mechanical properties, and improving their insulating properties. Currently, there are solutions in phase-change materials (PCM) production technology, such as microencapsulation, but its application on a large scale is extremely costly. This paper presents a solution to the abovementioned problem through the creation and testing of a composite, i.e., a new mixture of gypsum, paraffin, and polymer, which can be used in the production of plasterboard. The presented solution uses a material (PCM) which improves the thermal properties of the composite by taking advantage of the phase-change phenomenon. The study analyzes the influence of polymer content in the total mass of a composite in relation to its thermal conductivity, volumetric heat capacity, and diffusivity. Based on the results contained in this article, the best solution appears to be a mixture with 0.1% polymer content. It is definitely visible in the tests which use drying, hardening time, and paraffin absorption. It differs slightly from the best result in the thermal conductivity test, while it is comparable in terms of volumetric heat capacity and differs slightly from the best result in the thermal diffusivity test.

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.

Determination of the Thermal Properties of a PCB by Coupled Numerical and Experimental Approach

2020 ◽  
Author(s):  
Yener Usul ◽  
Mustafa Özçatalbaş
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Numerical Analysis ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Analyses ◽  
Analysis Model ◽  
Linear Temperature ◽  
Coefficient Of Thermal Conductivity

Abstract Increasing demand for usage of electronics intensely in narrow enclosures necessitates accurate thermal analyses to be performed. Conduction based FEM (Finite Element Method) is a common and practical way to examine the thermal behavior of an electronic system. First step to perform a numerical analysis for any system is to set up the correct analysis model. In this paper, a method for obtaining the coefficient of thermal conductivity and specific heat capacity of a PCB which has generally a complex composite layup structure composed of conductive layers, and dielectric layers. In the study, above mentioned properties are obtained performing a simple nondestructive experiment and a numerical analysis. In the method, a small portion of PCB is sandwiched from one side at certain pressure by jaws. A couple of linear temperature profiles are applied to the jaws successively. Unknown values are tuned in the analysis model until the results of FEM analysis and experiment match. The values for the coefficient of thermal conductivity and specific heat capacity which the experiment and numerical analysis results match can be said to be the actual values. From this point on, the PCB whose thermal properties are determined can be analyzed numerically for any desired geometry and boundary condition.

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