A Statistical Account of Asperity Heating in a Rough Surface Contact

2007 ◽  
Author(s):  
K. Farhang ◽  
A. Elhomani
Keyword(s):  
Closed Form ◽  
Heat Generation ◽  
Rough Surfaces ◽  
Integral Form ◽  
Sliding Contact ◽  
Heat Generation Rate ◽  
Friction Heat ◽  
Single Asperity ◽  
Rough Surface Contact ◽  
Statistical Integral

When two rough surfaces are in sliding contact an asperity on a surface would experience intermittent temperature flashes as it comes in momentary contact with asperities on a second surface. The frequency of the flash temperatures, their strength and duration depend, in addition to the sliding speed, on the topology of the two surfaces. In this paper a model is developed for the work-heat relation with a consideration of the above-mentioned intermittent nature of contact. The work of friction on one asperity is derived in integral form and closed-form equations. The rate of generation of heat is found due to a single asperity. Using the statistical account of asperity friction heat generation, rate of heat generation between two rough surfaces is obtained both in statistical integral form and in the approximate closed form.

Friction Heat Due to Sliding of Rough Surfaces: Micro-Scale Interactions and Their Macro-Scale Effect

2008 ◽  
Author(s):  
K. Farhang ◽  
A. Elhomani
Keyword(s):  
Closed Form ◽  
Heat Generation ◽  
Rough Surfaces ◽  
Integral Form ◽  
Sliding Contact ◽  
Heat Generation Rate ◽  
Friction Heat ◽  
Single Asperity ◽  
Macro Scale ◽  
Statistical Integral

When two rough surfaces are in sliding contact an asperity on a surface would experience intermittent temperature flashes as it comes in momentary contact with asperities on a second surface. The frequency of the flash temperatures, their strength and duration depend, in addition to the sliding speed, on the topology of the two surfaces. In this paper a model is developed for the work-heat relation with a consideration of the above-mentioned intermittent nature of contact. The work of friction on one asperity is derived in integral form and closed-form equations. The rate of generation of heat is found due to a single asperity. Using the statistical account of asperity friction heat generation, rate of heat generation between two rough surfaces is obtained both in statistical integral form and in the approximate closed form.

Effects of Angular Motion on Planar Rough Surfaces Contact From Static to Sliding

2010 ◽  
Author(s):  
Ting Ni ◽  
Xi Shi
Keyword(s):  
Friction Coefficient ◽  
Rough Surfaces ◽  
Angular Displacement ◽  
Sliding Contact ◽  
Sliding Speed ◽  
Interfacial Forces ◽  
The Stability ◽  
Inclined Angle ◽  
Rough Surface Contact ◽  
Turn Over

Due to the friction moment, there is an angular displacement when two flat rough surfaces come to sliding contact or quasi sliding contact. A 2-DOF inclined rough surface contact model is presented in this work, and the effects of the angular displacement on the friction coefficient, interfacial forces and moments are investigated. The numerical simulations show that both interfacial forces and moments increase with the increasing inclined angle, while the friction coefficient decreases instead. In addition, for a given sliding mass block system, the effects of the friction coefficient and the base sliding speed on the stability of the sliding contact are also discussed. The simulations indicate that a larger friction coefficient and a higher base sliding speed tend to turn over the mass block during the sliding.

Investigation of Inclined Planar Rough Surfaces Contact From Static to Sliding

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Ting Ni ◽  
Xi Shi
Keyword(s):  
Friction Coefficient ◽  
Rough Surfaces ◽  
Angular Displacement ◽  
Sliding Contact ◽  
Sliding Speed ◽  
Interfacial Forces ◽  
The Stability ◽  
Inclined Angle ◽  
Rough Surface Contact ◽  
Turn Over

Due to the friction moment, when two flat rough surfaces come to sliding contact or quasi-sliding contact, there is an inclined angle between these two surfaces. A two degree-of-freedom inclined rough surface contact model is presented in this work and the effects of the angular displacement on the friction coefficient, interfacial forces, and interfacial moments for the elastic-plastic planar rough surfaces contact are investigated. The numerical simulations show that both interfacial forces and interfacial moments gain with the increase of the inclined angle while the friction coefficient decreases instead. In addition, for a given sliding mass block system, the effects of that friction coefficient and base sliding speed on the stability of the sliding contact are also discussed. The simulations indicate that a larger friction coefficient and a higher base sliding speed tend to turn over the mass block during the sliding.

A Comparative Study on Equivalent Modeling of Rough Surfaces Contact

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Xi Shi ◽  
Yunwu Zou
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Contact Analysis ◽  
Contact Forces ◽  
Sliding Contact ◽  
Contact Model ◽  
Surface Model ◽  
Normal Contact ◽  
Surface Contact ◽  
Rough Surface Contact

Greenwood and Tripp (GT model) have proposed that the contact analysis of two rough surfaces (two-rough-surface contact model) could be considered as an equivalent rough surface in contact with a rigid flat (single-rough-surface contact model). In this paper, by virtue of finite element method, the normal contact analysis was performed with two-rough-surface contact model and its equivalent single-rough-surface contact model, and it was verified that the resultant normal contact forces are in good agreement with each other for these two models, meanwhile the equivalent stress is a little bit lower for two-rough-surface model due to shoulder-to-shoulder contact. In contrast, the sliding contact analysis was also performed with these two models, respectively, and the results show a great disparity with each other in all contact parameters due to the strong plowing effects in two-rough-surface model. Therefore, this equivalence approach proposed by Greenwood and Tripp is only valid for normal contact of rough surfaces and not valid for sliding contact.

Leakage Prediction in Mechanical Seals Under Hydrostatic Operating Condition

2007 ◽  
Author(s):  
S. Elhanafi ◽  
K. Farhang
Keyword(s):  
Closed Form ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rough Surfaces ◽  
Mechanical Seals ◽  
Operating Condition ◽  
Form Equation ◽  
Macro Scale ◽  
The Mean

This paper considers leakage in mechanical seals under hydrostatic operating condition. A contact model based on the Greenwood and Williamson contact of rough surfaces is developed for treating problems involving mechanical seals in which both the micron scale roughness of the seal face and its macro scale profile are used to obtain either a closed-form equation or a nonlinear equation relating mean plane separation to the mass flow rate. The equations involve the micron scale geometry of the rough surfaces and physical parameter of the seal and carriage. Under hydrostatic condition, it is shown that there is an approximate closed-form solution in which mass flow rate in terms of the mean plane separation, or alternatively, the mean plane separation in terms of the leakage mass flow rate is found. Equations pertaining to leakage in nominally flat seal macro profile is considered and closed form equation relating to leakage flow rate to pressure difference is obtained that contain macro and micron geometries of the seal.

A novel heat generation acquisition method of cylindrical battery based on core and surface temperature measurements

2021 ◽  
pp. 1-17
Author(s):  
Xiaoli Yu ◽  
Qichao Wu ◽  
Rui Huang ◽  
Xiaoping Chen
Keyword(s):  
Surface Temperature ◽  
Heat Generation ◽  
Discharge Rate ◽  
Total Heat ◽  
Temperature Measurements ◽  
Generation Rate ◽  
Air Cooling ◽  
Heat Generation Rate ◽  
Environmental Chamber ◽  
Average Heat

Abstract Heat generation measurements of the lithium-ion battery are crucial for the design of the battery thermal management system. Most previous work uses the accelerating rate calorimeter (ARC) to test heat generation of batteries. However, utilizing ARC can only obtain heat generation of the battery operating under the adiabatic condition, deviating from common operation scenarios with heat dissipation. Besides, using ARC is difficult to measure heat generation of the high-rate operating battery because the battery temperature easily exceeds the maximum safety limit. To address these problems, we propose a novel method to obtain heat generation of cylindrical battery based on core and surface temperature measurements and select the 21700 cylindrical battery as the research object. Based on the method, total heat generation at 1C discharge rate under the natural convection air cooling condition in the environmental chamber is about 3.2 kJ, and the average heat generation rate is about 0.9 W. While these two results measured by ARC are about 2.2 kJ and 0.6 W. This gap also reflects that different battery temperature histories have significant impacts on heat generation. In addition, using our approach, total heat generation at 2C discharge rate measured in the environmental chamber is about 5.0 kJ, with the average heat generation rate being about 2.8 W. Heat generation results obtained by our method are approximate to the actual battery operation and have advantages in future applications.

Sign in / Sign up

Export Citation Format

Share Document