Study on the Normal Contact Stiffness of Rough Surface in Mixed Lubrication

2018 ◽  
Author(s):  
Huifang Xiao ◽  
Yunyun Sun ◽  
Xiaojun Zhou ◽  
Zaigang Chen
Keyword(s):  
Rough Surface ◽  
Contact Stiffness ◽  
Equivalent Model ◽  
Lubricant Layer ◽  
Asperity Contact ◽  
Normal Contact ◽  
Liquid Lubricant ◽  
Single Asperity ◽  
Rough Surface Contact ◽  
Film Stiffness

In this paper, a general contact stiffness model is proposed to study the mixed lubricated contact between a rough surface and a rigid flat plate, which is the equivalent model for the contact between two rough surfaces and is the general case for engineering contact interfaces. The total interfacial contact stiffness is composed of the dry rough surface contact stiffness and the liquid lubricant contact stiffness. The GW model is used for surface topography description and the contact stiffness of a single asperity is derived from the Hertz contact theory. The whole dry rough contact stiffness is obtained by multiple the single asperity contact stiffness with the number of contact asperities, which is derived based on the statistical model. The liquid film stiffness is derived based on a spring model. The stiffness contributions from the asperity contact part and lubricant layer part are separated and analyzed.

An Improved Elastic Contact Model Accounting for Asperity Interaction and Bulk Substrate Deformation

2009 ◽  
Author(s):  
Jungkyu Lee ◽  
Chang-Dong Yeo ◽  
Andreas A. Polycarpou
Keyword(s):  
Rough Surface ◽  
Contact Stiffness ◽  
Elastic Half Space ◽  
Contact Model ◽  
Asperity Contact ◽  
Single Asperity ◽  
Surface Contact ◽  
In Series ◽  
Bulk Substrate ◽  
Rough Surface Contact

An improved rough surface contact model is proposed accounting for bulk substrate deformation and asperity interaction. The asperity contact stiffness is based on Hertzian solution for spherical contact, and the bulk substrate stiffness on the solution of Hertzian pressure on a circular region of the elastic half-space. The contact behavior of a single asperity composed of hemi-spherical asperity deformation as well as bulk substrate deformation is calculated by introducing the concept of spring-in-series. Based on the single asperity model, the contact stiffness for the rough surface is calculated including the effect of asperity interaction. Analytical simulation results using the proposed rough surface contact model were compared with the CEB model and experimental measurements.

Contact Analysis of a Smooth Ball on an Anisotropic Rough Surface

1994 ◽  
Vol 116 (4) ◽  
pp. 850-859 ◽  
Author(s):  
C. Y. Poon ◽  
R. S. Sayles
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Stochastic Approach ◽  
Contact Analysis ◽  
Asperity Contact ◽  
Correlation Lengths ◽  
Real Contact ◽  
Rough Surface Contact ◽  
Contact Pressures ◽  
Contact Spots

The effects of surface roughness and waviness upon the real contact areas, gaps between contact spots, and asperity contact pressures were studied. The distribution of real areas, gaps, and contact pressures are presented for different surface roughness, σ and correlation lengths, β*. The load-area relationship is compared to Bush’s model of strongly anisotropic rough surface contact using a stochastic approach.

Comparative Contact Analysis Study of Finite Element Method Based Deterministic, Simplified Multi-Asperity and Modified Statistical Contact Models

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
A. Megalingam ◽  
M. M. Mayuram
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Rough Surface ◽  
Contact Area ◽  
Model Analysis ◽  
Contact Model ◽  
Contact Load ◽  
Asperity Contact ◽  
Single Asperity ◽  
Contact Models

The study of the contact stresses generated when two surfaces are in contact plays a significant role in understanding the tribology of contact pairs. Most of the present contact models are based on the statistical treatment of the single asperity contact model. For a clear understanding about the elastic-plastic behavior of two rough surfaces in contact, comparative study involving the deterministic contact model, simplified multi-asperity contact model, and modified statistical model are undertaken. In deterministic contact model analysis, a three dimensional deformable rough surface pressed against a rigid flat surface is carried out using the finite element method in steps. A simplified multi-asperity contact model is developed using actual summit radii deduced from the rough surface, applying single asperity contact model results. The resultant contact parameters like contact load, contact area, and contact pressure are compared. The asperity interaction noticed in the deterministic contact model analysis leads to wide disparity in the results. Observing the elastic-plastic transition of the summits and the sharing of contact load and contact area among the summits, modifications are employed in single asperity statistical contact model approaches in the form of a correction factor arising from asperity interaction to reduce the variations. Consequently, the modified statistical contact model and simplified multi-asperity contact model based on actual summit radius results show improved agreement with the deterministic contact model results.

Rough Surface Normal Nanocontact Stiffness: Experimental Measurements and Rough Surface Contact Model Predictions

2017 ◽  
Vol 84 (3) ◽  
Author(s):  
Jungkyu Lee ◽  
Ali Beheshti ◽  
Andreas A. Polycarpou
Keyword(s):  
Thin Film ◽  
Rough Surface ◽  
Predictive Accuracy ◽  
Contact Stiffness ◽  
Flat Punch ◽  
Surface Contact ◽  
Contact Models ◽  
Rough Surface Contact ◽  
Contact Response ◽  
Good Agreement

This work presents experimental contact stiffness measurements for various thin films as well as homogenous materials through pressing a flat punch onto a nominally flat rough surface. These materials are typically used in micro/nano technological applications with thickness of the order of few nanometers. The experimental contact stiffness results are compared with predictions by different statistical rough surface contact models to assess their predictive accuracy for thin-film applications and, in addition, to get better insight to the physics of the contact. It is observed that rough surface contact models that account for asperity interaction show good agreement with the experimental results of the thin-layered specimens contact response. This indicates the importance of accounting for asperity interaction in surface roughness contact modeling of relatively smooth thin-film materials. It is verified that interfaces with compliant films on stiff substrates as well as homogeneous materials compare relatively well with statistical models accounting for asperity interactions.

Influence of lubrication starvation and surface waviness on the oil film stiffness of elastohydrodynamic lubrication line contact

2016 ◽  
Vol 24 (5) ◽  
pp. 924-936 ◽  
Author(s):  
Yuanyuan Zhang ◽  
Huaiju Liu ◽  
Caichao Zhu ◽  
Chaosheng Song ◽  
Zufeng Li
Keyword(s):  
Film Thickness ◽  
Contact Stiffness ◽  
Elastohydrodynamic Lubrication ◽  
Force Balance ◽  
Line Contact ◽  
Surface Waviness ◽  
Regular Surface ◽  
Normal Contact ◽  
Oil Film ◽  
Film Stiffness

Stiffness properties of interfacial engineering surfaces are of great importance to the dynamic performance of relevant mechanical systems. Normal contact stiffness and oil film stiffness of line contact problems are studied in this work analytically and numerically. The Hertzian contact theory and the Yang–Sun method are applied to predict the contact stiffness, while the empirical elastohydrodynamic lubrication (EHL) film thickness method and the complete numerical EHL model are used to predict the oil film stiffness. The numerical model mainly consists of the Reynolds equation; the film thickness equation, in which the regular surface roughness is taken into consideration; the force balance equation; and the viscosity-pressure equation. The effects of the normal load, rolling speed, regular surface waviness, and starved lubrication level on the oil film stiffness are investigated.

Rough Surface Contact of Curved Conformal Surfaces: An Application to Rotor–Stator Rub

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Rough Surface ◽  
Contact Force ◽  
Contact Stiffness ◽  
Point Contact ◽  
Contact Model ◽  
Industrial Society ◽  
Real Surface ◽  
Linear Elastic ◽  
Surface Contact ◽  
Rough Surface Contact

Rotating machines and associated triboelements are ubiquitous in industrial society, playing a central role in power generation, transportation, and manufacturing. Unfortunately, these systems are susceptible to undesirable contact (i.e., rub) between the rotor and stator, which is both costly and dangerous. These adverse effects can be alleviated by properly applying accurate real-time diagnostics. The first step toward accurate diagnostics is developing rotor–stator rub models which appropriately emulate reality. Previous rotor–stator rub models disavow the contact physics by reducing the problem to a single esoteric linear contact stiffness occurring only at the point of maximum rotor radial deflection. Further, the contact stiffness is typically chosen arbitrarily, and as such provides no additional insight into the contacting surfaces. Here, a novel rotor–stator rub model is developed by treating the strongly conformal curved surfaces according to their actual nature: a collection of stochastically distributed asperities. Such an approach is advantageous in that it relies on real surface measurements to quantify the contact force rather than a heuristic choice of linear contact stiffness. Specifically, the elastoplastic Jackson–Green (JG) rough surface contact model is used to obtain the quasistatic contact force versus rotor radial deflection; differences and similarities in contact force between the linear elastic contact model (LECM) and JG model are discussed. Furthermore, the linear elastic model's point contact assumption is assessed and found to be inaccurate for systems with small clearances. Finally, to aid in computational efficiency in future rotordynamic simulation, a simple exponential curve fit is proposed to approximate the JG force–displacement relationship.

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