A three-dimensional fractal theory based on thermal contact conductance model of rough surfaces

2017 ◽  
Vol 232 (5) ◽  
pp. 528-539 ◽  
Author(s):  
Yongsheng Zhao ◽  
Cui Fang ◽  
Ligang Cai ◽  
Zhifeng Liu
Keyword(s):  
Rough Surfaces ◽  
Fractal Theory ◽  
Thermal Contact ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Engineering Application ◽  
Thermal Contact Conductance ◽  
Real Contact Area ◽  
Contact Conductance ◽  
Elastic Plastic

The thermal contact conductance is an important problem in the field of heat transfer. In this research, a three-dimensional fractal theory based on the thermal contact conductance model is presented. The topography of the contact surfaces was fractal featured and determined by fractal parameters. The asperities in the microscale were considered as elastic, elastic-plastic, or plastic deformations. The real contact area of the asperities could be obtained based on the Hertz contact theory. It was assumed that the rough contact surface was composed of numerous discrete and parallel microcontact cylinders. Consequently, the thermal contact conductance of the surface roughness was composed of the thermal constriction conductance of microcontacts and the air medium thermal conductance of microgaps. The thermal contact conductance of rough surfaces could be calculated by the microasperities integration. An experimental set-up with annular interface was designed to verify the presented thermal contact conductance model. Three materials were used for the thermal contact conductance analysis with different fractal dimensions D and fractal roughness parameters G. The numerical results demonstrated that the thermal contact conductance could be affected by the elastic-plastic deformation of the asperities and the gap thermal conductance should not be ignored under the lower contact load. The presented model would provide a theoretical basis for thermal transfer engineering application.

Modeling of Thermal Contact Conductance

2010 ◽  
Author(s):  
Mikhail V. Murashov ◽  
Sergey D. Panin
Keyword(s):  
Heat Transfer ◽  
Plastic Material ◽  
Rough Surfaces ◽  
Thermal Contact ◽  
Material Behavior ◽  
Thermal Contact Conductance ◽  
Nonstationary Temperature ◽  
Random Component ◽  
Contact Conductance ◽  
Elastic Plastic

Nowadays a new science direction has arisen from decades of experimental work carried out in 20th century — micromechanics of contact processes (deformation, heat transfer, electric conduction). To determine contact area a dynamic elastic-plastic deformation problem is to be solved even in the simplest case — butt contact of two rough surfaces under pressure. It is followed by the solution of spatial boundary heat transfer problem to obtain nonstationary temperature distribution for two bodies. In principal, this stage is not difficult to perform with finite element program ANSYS. Meanwhile the questions concerning deformation and conduction through oxide films of metals as well as directional effect remain. In the literature there are attempts to simulate thermal contact conductance numerically of such authors as M.K.Thompson, S.Lee et al, M. Ciavarella, M.M.Yovanovich and others. The disadvantages of existing spatial models are: - surfaces profiles has no random component; - only elastic or only plastic material behavior; - microroughness is not considered. In the present work the roughness before contact of two rough surfaces of copper bodies was presented as spatial two-level (roughness and microroughness) model with the use of fractal Weierstrass–Mandelbrot function. In quasistatic approach the 3D deformation and heat transfer problems of contacting bodies under pressure were solved within elastic-plastic material behavior. Contact ANSYS elements were used. Copper compression diagram was replaced by multilinear model of isotropic hardening. From the cycle of calculations real contact areas, shapes of contact spots, temperature and stress distributions were determined for the range of pressures. Good agreement with experimental data took place only when microroughness is considered.

A model of thermal contact conductance at high real contact area fractions

Wear ◽  
2010 ◽  
Vol 268 (1-2) ◽  
pp. 77-85 ◽  
Author(s):  
Przemysław Sadowski ◽  
Stanisław Stupkiewicz
Keyword(s):  
Contact Area ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Real Contact Area ◽  
Contact Conductance ◽  
Real Contact

Recent Developments in Contact Conductance Heat Transfer

1988 ◽  
Vol 110 (4b) ◽  
pp. 1059-1070 ◽  
Author(s):  
L. S. Fletcher
Keyword(s):  
Heat Transfer ◽  
Thermal Contact ◽  
Thermal Conductance ◽  
Thermal Contact Conductance ◽  
Contact Conductance ◽  
Thermal Rectification ◽  
Numerical Studies ◽  
Wide Range ◽  
Theoretical Investigations ◽  
Recent Developments

The characteristics of thermal contact conductance are increasingly important in a wide range of technologies. As a consequence, the number of experimental and theoretical investigations of contact conductance has increased. This paper reviews and categorizes recent developments in contact conductance heat transfer. Among the topics included are the theoretical/analytical/numerical studies of contact conductance for conforming surfaces and other surface geometries; the thermal conductance in such technological areas as advanced or modern materials, microelectronics, and biomedicine; and selected topics including thermal rectification, gas conductance, cylindrical contacts, periodic and sliding contacts, and conductance measurements. The paper concludes with recommendations for emerging and continuing areas of investigation.

Elastoplastic Contact Conductance Model for Isotropic Conforming Rough Surfaces and Comparison With Experiments

1996 ◽  
Vol 118 (1) ◽  
pp. 3-9 ◽  
Author(s):  
M. R. Sridhar ◽  
M. M. Yovanovich
Keyword(s):  
Rough Surfaces ◽  
Thermal Contact ◽  
Material Behavior ◽  
Thermal Contact Conductance ◽  
Elastic Model ◽  
Time Data ◽  
Contact Conductance ◽  
Plastic Model ◽  
Elastoplastic Contact ◽  
Wide Range

A New thermal elastoplastic contact conductance model for isotropic conforming rough surfaces is proposed. This model is based on surface and thermal models used in the Cooper, Mikic, and Yovanovich plastic model, but it differs in the deformation aspects of the thermal contact conductance model. The model incorporates the recently developed simple elastoplastic model for sphere-flat contacts, and it covers the entire range of material behavior, i.e., elastic, elastoplastic, and fully plastic deformation. Previously data were either compared with the elastic model or the plastic model assuming a type of deformation a priori. The model is used to reduce previously obtained isotropic contact conductance data, which cover a wide range of surface characteristics and material properties. For the first time data can be compared with both the elastic and plastic models on the same plot. This model explains the observed discrepancies noted by previous workers between data and the predictions of the elastic or plastic models.

Thermal Contact Conductance of Spherical Rough Metals

1997 ◽  
Vol 119 (4) ◽  
pp. 684-690 ◽  
Author(s):  
M. A. Lambert ◽  
L. S. Fletcher
Keyword(s):  
Nuclear Reactor ◽  
Combustion Engine ◽  
Fundamental Problem ◽  
Thermal Contact ◽  
Thermal Conductance ◽  
Thermal Control ◽  
Cryogenic Liquid ◽  
Thermal Contact Conductance ◽  
Thermomechanical Model ◽  
Contact Conductance

Junction thermal conductance is an important consideration in such applications as thermally induced stresses in supersonic and hypersonic flight vehicles, nuclear reactor cooling, electronics packaging, spacecraft thermal control, gas turbine and internal combustion engine cooling, and cryogenic liquid storage. A fundamental problem in analyzing and predicting junction thermal conductance is determining thermal contact conductance of nonflat rough metals. Workable models have been previously derived for the limiting idealized cases of flat, rough, and spherical smooth surfaces. However, until now no tractable models have been advanced for nonflat rough “engineering” surfaces which are much more commonly dealt with in practice. The present investigation details the synthesis of previously derived models for macroscopically nonuniform thermal contact conductance and contact of nonflat rough spheres into a thermomechanical model, which is presented in an analytical/graphical format. The present model agrees well with representative experimental conductance results from the literature for stainless steel 303 and 304 with widely varying nonflatness (2 to 200 μm) and roughness (0.1 to 10 μm).

Fractal modeling of elastic-plastic contact between three-dimensional rough surfaces

2018 ◽  
Vol 70 (2) ◽  
pp. 290-300 ◽  
Author(s):  
Rufei Yu ◽  
Wei Chen
Keyword(s):  
Rough Surfaces ◽  
Fractal Theory ◽  
Three Dimensional ◽  
Geometrical Model ◽  
Contact Model ◽  
Radial Clearance ◽  
Content Type ◽  
Elastic Plastic ◽  
Fractal Roughness ◽  
Conformal Contact

Purpose This paper aims to propose a semi-analytical model to investigate the elastic-plastic contact between fractal rough surfaces. Parametric studies have been performed to analyze the dependencies between the contact properties and the scale-independent fractal parameters. Design/methodology/approach A modified two-variable Weierstrass-Mandelbrot function has been used to build the geometrical model of rough surfaces. The computation program was developed using software MATLAB R2015a. The results have been qualitatively validated by the existing theoretical and experimental results in the literature. Findings In most cases, a nonlinear relation between the load and the displacement of the rigid plane is found. Only under the condition of larger loads, an approximate linear relation can be seen for great D and small G values. (D: fractal dimension and G: fractal roughness). Originality/value The contact model of the cylindrical joints (conformal contact) with radial clearance is constructed by using the fractal theory and the Kogut-Etsion elastic-plastic contact model, which includes purely elastic, elastic-plastic and fully plastic contacts. The present method can generate a more reliable calculation result as compared with the Hertz contact model and a higher calculation efficiency as compared with the finite element method for the conformal contact problem.

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