Study of Microcontact Model for Hard Particles Between Rough Surfaces

2005 ◽  
Author(s):  
Jeng-Haur Horng ◽  
Shin-Yuh Chern ◽  
Chih-Hsien Chen ◽  
Ming-Yao Ku
Keyword(s):  
Contact Area ◽  
Rough Surfaces ◽  
Particle Diameter ◽  
Area Ratio ◽  
Contact Load ◽  
Body Contact ◽  
Hard Particles ◽  
Contact Situation ◽  
Three Body ◽  
Contact Area Ratio

Particles are often presented at contact interfaces. In this study, a three-body microcontact model Considering of hard particles and rough surfaces is proposed in order to understand the effects of particles between surfaces on contact characteristics. Both transitional surface-to-surface and particle-to-surface two-body microcontact simulations can be obtained according to the simplification of this model. In the three-body contact situation, the curves of contact area ratio versus dimensionless load are located in the range between two straight lines. The surface-to-surface two-body contact situation is the upper bound and the particle-to-surface two-body contact situation is the lower bound. The contact situation will approach to the pure particle-to-surface two-body contact situation as the value of particle diameter over roughness value of surface increases. The total contact area ratio increases when particle size or particles density decreases, and contact load increases. Contrary to the results for contact area ratio, the dimensionless separation increases when particle density increases or contact load decreases.

Three-Body Microcontact Model of Rough Surfaces and Its Application on Polishing of Wafer

2006 ◽  
Vol 505-507 ◽  
pp. 445-450 ◽  
Author(s):  
Jeng Haur Horng ◽  
Jian Shing Lee ◽  
D.C. Du
Keyword(s):  
Lower Bound ◽  
Contact Area ◽  
Rough Surfaces ◽  
Area Ratio ◽  
Body Contact ◽  
Contact Situation ◽  
Three Body ◽  
Straight Lines ◽  
Contact Area Ratio ◽  
Ratio Versus

In this study, a three-body microcontact model for rough surfaces is proposed in order to understand the effects of particles between surfaces on contact characteristics and its application on polishing of wafer. Both transitional surface-to-surface and particle-to-surface two-body microcontact simulations can be obtained according to the simplification of this model. In the three-body contact situation, the curves of contact area ratio versus dimensionless load are located in the range between two straight lines. The surface-to-surface two-body contact situation is the upper bound and the particle-to-surface two-body contact situation is the lower bound. As the value of D/σ increases, the contact situation will approach the pure particle-to- surface 2-body contact situation. The model also is used to study the wear mechanisms of the silicon wafer.

Effect of two-body and three-body microcontacts under dry friction on contact characteristics

2017 ◽  
Vol 232 (4) ◽  
pp. 706-719 ◽  
Author(s):  
Horng-Wen Wu ◽  
Yang-Yuan Chen
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Contact Area ◽  
External Load ◽  
Wear Debris ◽  
Elastoplastic Deformation ◽  
Particle Diameter ◽  
Body Contact ◽  
Wide Range ◽  
Three Body

The wear debris generation is unavoidable between the contact interfaces of moving components. In three-body contact instances, friction and wear occur at these separate contact points. This paper discusses the characteristics of the three-body contact comprising the abrasive particle in the interface compared to the two-body contact. The results show that for the wear debris or foreign particles present in the interface of the three-body contact, as external load initially increases, the external load is fully borne by the contact characteristics of particle-to-surface. Until the external load rises to a particular critical external load, it enters the real three-body situation, and the critical external load thus increases with an increase in the ratio of particle diameter to surface roughness. For two contact surfaces, the summit deformation is the elastoplastic deformation in a wide range of external loads. As the external load is lower than the critical external load value of the three-body contact, the contact surface is under the particle-to-surface two-body contact, and the elastic deformation of surface peak has the largest proportion of contact area. When the external load is higher than the critical external load value, the elastoplastic deformation contact area quickly dominates, and the total contact area ratio approximates to the surface-to-surface two-body contact situation. In the range of engineering surface roughness (σ = 50–400 nm), at each external load and surface roughness, the total friction coefficient decreases with the increase in the ratio of particle diameter to surface roughness under the three-body contact, and this shows that the friction coefficient of surface-to-surface contact is larger than that of the sphere wear debris between the contact interface. At the same surface roughness, the friction coefficient may increase or decrease with an increase in the external load because it is determined by particle diameter. At the same ratio of particle diameter to surface roughness and external load, the friction coefficient increases with the decreasing surface roughness.

scholarly journals Critical shoe contact area ratio for sliding on a tennis hard court

2017 ◽  
Vol 232 (2) ◽  
pp. 112-121 ◽  
Author(s):  
John Eric Goff ◽  
Luke Boswell ◽  
Daniel Ura ◽  
Mark Kozy ◽  
Matt J Carré
Keyword(s):  
Friction Coefficient ◽  
Contact Area ◽  
Sliding Friction ◽  
Static Friction ◽  
Area Ratio ◽  
Critical Ratio ◽  
Static Friction Coefficient ◽  
The Creation ◽  
Contact Area Ratio

Dimples have been used in the design of some modern tennis shoe outsoles to enhance sliding ability on hard courts. Experiments were performed with bespoke rubber samples possessing various numbers of holes, which served to simulate dimples in tennis shoe treads. The aim of the research was to assess the effect of contact area on sliding friction. As the ratio of holes to solid rubber increased, a critical ratio was reached whereby the static friction coefficient decreased by more than 11% for tread-to-court pressures comparable to real tennis play. Although this study analyzed bespoke rubber samples and not actual tennis shoe treads, shoe manufacturers should be interested in the existence of a critical dimple ratio that could aid them in the creation of tennis shoes suited for sliding on hard courts.

Partial Film Lubrication Characteristics of Inlet Zone in Cold Strip Rolling

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Kuo Fu ◽  
Yong Zang ◽  
Zhiying Gao
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Contact Area ◽  
Friction Stress ◽  
Area Ratio ◽  
Work Zone ◽  
Zone Length ◽  
Inlet Zone ◽  
Pressure Stress ◽  
Contact Area Ratio

According to the average flow Reynolds equation and rolling theory, a partial film lubrication model of inlet zone has been developed. The model mainly simulates and reflects the influence of surface topography on the inlet film thickness and inlet zone length. Based on the surface topography analysis, a method to judge the friction condition was proposed. All the calculation was conducted by a numerical method. The result shows that the transverse stripe increases the inlet film thickness and the inlet zone length, while the longitudinal stripe decreases them. The surface roughness will enhance this effect. The surface roughness and the stripe direction also have a significant influence on the contact area ratio and the distribution of stress and film thickness in work zone. Transverse stripe increases the lubricant film thickness and separates the roll and the sheet with a larger distance in work zone. It also decreases the contact area ratio, the pressure stress and friction stress of the work zone. Whereas longitudinal stripe decreases the film thickness and increases the contact area ratio, pressure stress and friction stress. The surface roughness increases the contact area ratio, pressure stress and friction stress.

FEM Analysis of Hydrostatic Pressure Generated Within Lubricant Entrapped Into Pocket on Workpiece Surface in Upsetting Process

1999 ◽  
Vol 122 (4) ◽  
pp. 822-827 ◽  
Author(s):  
Akira Azushima
Keyword(s):  
Hydrostatic Pressure ◽  
Contact Area ◽  
Plastic Material ◽  
Quantitative Relationship ◽  
Normal Pressure ◽  
Area Ratio ◽  
Real Contact Area ◽  
Bulk Deformation ◽  
Rigid Plastic ◽  
Contact Area Ratio

In order to investigate into the quantitative relationship between the hydrostatic pressure generated within the surface pocket of the workpiece and the normal pressure acting on the real contact area at the interface of metal forming such as drawing, rolling, forging and so on, the hydrostatic pressure is calculated accompanied with reduction in height in upsetting of cylinders having a central conical impression or a central conical dent filled with lubricant on the top surface, using the rigid-plastic finite element method. The formulated is based on the plasticity theory. The material is assumed to be rigid perfectly plastic material. It is assumed that the hydrostatic pressure is generated accompanied with a volume change in the surface pocket for compressible lubricants. The results obtained from the calculation are as follows: (1) The hydrostatic pressure generated within the lubricant in a central conical impression in cylindrical upsetting approaches the yield stress at a reduction in height of about 4 percent; (2) The hydrostatic pressure generated within the lubricant in a central conical dent in cylindrical upsetting having an annular asperity increases linearly and abruptly with increasing height reduction when the contact area ratio is small and the bulk deformation is elastic, and it increases gradually and the maximum value approaches the normal pressure acting on the contact area when the contact area ratio becomes large and the bulk deformation is plastic. [S0742-4787(00)00503-8]

A fractal model of contact between rough surfaces for a complete loading–unloading process

2020 ◽  
Vol 234 (14) ◽  
pp. 2923-2935
Author(s):  
Yuan Yuan ◽  
Kuo Xu ◽  
Ke Zhao
Keyword(s):  
Size Distribution ◽  
Contact Area ◽  
Rough Surfaces ◽  
Contact Process ◽  
Distribution Functions ◽  
Contact Load ◽  
Elastic Behavior ◽  
Loading Process ◽  
True Contact Area ◽  
True Contact

The mechanical properties of contact between rough surfaces play an important role in the reliability of the electromechanical system. In order to improve the design accuracy of precision instruments, an elastic-plastic contact model for three-dimensional rough surfaces based on the fractal theory is developed for a complete loading–unloading process based on the Majumdar and Bhushan model. The truncation size distribution functions of asperities for different values of asperity level in the loading process are given. Relationships between true contact area and total contact load in the complete loading–unloading process are obtained according to the truncation size distribution functions of asperities. The results show the range of asperity levels has significant effects on contact mechanical behaviors of fractal rough surfaces. When the first six levels of asperities do not exceed the critical elastic level, the fractal rough surfaces exhibit elastic behavior in a complete contact process, and the load–area relationships in the loading and unloading processes are coincident approximately. When the critical elastic level is less than the minimum level of asperity, the inelastic deformation begins to appear in fractal rough surfaces and the true contact area during the unloading process is always greater than the true area during the loading process for a given total contact load. In comparison with the K-K-E model, the present model is proved to be reasonable.

scholarly journals Dynamic contact area ratio in shoulder instability: an innovative diagnostic technique measuring interplay of bony lesions

2019 ◽  
Vol 28 (7) ◽  
pp. 2361-2366
Author(s):  
Hanneke Weel ◽  
Peter R. Krekel ◽  
Nienke Willigenburg ◽  
W. Jaap Willems ◽  
Pietro Randelli ◽  
...  
Keyword(s):  
Contact Area ◽  
Shoulder Instability ◽  
Diagnostic Technique ◽  
Dynamic Contact ◽  
Area Ratio ◽  
Ct Scans ◽  
Anterior Shoulder Instability ◽  
Control Group ◽  
Level Of Evidence ◽  
Contact Area Ratio

Abstract Purpose The hypothesis of this study is that Dynamic Contact Area Ratio of the humerus and glenoid, measured with CT scans, is significantly reduced in patients with anterior shoulder instability compared to the Dynamic Contact Area Ratio in a control group of people without shoulder instability. Methods Preoperative CT scans of patients who underwent surgery for anterior shoulder instability were collected. Additionally, the radiologic database was searched for control subjects. Using a validated software tool (Articulis) the CT scans were converted into 3-dimensional models and the amount the joint contact surface during simulated motion was calculated. Results CT scans of 18 patients and 21 controls were available. The mean Dynamic Contact Area Ratio of patients was 25.2 ± 6.7 compared to 30.1 ± 5.1 in healthy subjects (p = 0.014). Conclusion Dynamic Contact Area Ratio was significantly lower in patients with anterior shoulder instability compared to controls, confirming the hypothesis of the study. The findings of this study indicate that calculating the Dynamic Contact Area Ratio based on CT scan images may help surgeons in diagnosing anterior shoulder instability. Level of evidence III.

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