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]

scholarly journals Investigation of running-in process based on surface roughness parameters, real contact area ratio and tribological properties

2021 ◽  
Vol 49 (4) ◽  
pp. 988-996
Author(s):  
Jeng-Haur Horng ◽  
Dipto Biswas ◽  
A Adhitya ◽  
Qumrul Ahsan
Keyword(s):  
Surface Roughness ◽  
Contact Area ◽  
Roughness Parameter ◽  
Area Ratio ◽  
Real Contact Area ◽  
Stable Relationship ◽  
Real Contact ◽  
Shape Adjustment ◽  
Rigid Smooth ◽  
Contact Area Ratio

The running-in process is the initial process for the new moving parts wearing against each other to establish the shape adjustment that will regulate them into a stable relationship for the rest of their working life. The objective of this research is to investigate and evaluate the running-in process by using disk-on-block line contact device. Due to its empirical nature and well-ploughed analysis, an asperity micro-contact model is considered. The experiment is performed by varying the surface roughness of the block with rigid smooth sphere surface under specific condition. The effects of surface roughness, load, speed, and lubrication on the running-in behaviour is studied. The running-in process encourage plastic deformation of asperities and created microstructural changes on contact surfaces. The theoretical and experiment result shows that the plasticity index ps, surface roughness parameter b, real contact area ratio * A0 and specific film thickness l is influenced by the running-in process.

The Surface Parameters Analysis of Magnesium Alloys Sheet during Warm Isothermal Forming

2015 ◽  
Vol 642 ◽  
pp. 217-221
Author(s):  
Tung Sheng Yang ◽  
Z.X. Yang ◽  
Sheng Yi Chang
Keyword(s):  
Finite Element Analysis ◽  
Surface Roughness ◽  
Finite Element ◽  
Magnesium Alloys ◽  
Contact Area ◽  
Normal Pressure ◽  
Area Ratio ◽  
Element Analysis ◽  
Surface Parameters ◽  
Contact Area Ratio

This study uses the finite element method (FEM) to predict the workpiece surface parameters, including contact area ratio and surface roughness, of asperity flattening in indentation and sliding contact for magnesium alloys sheet during warm isothermal forming. Contact area ratio and surface roughness are investigated for different process and material parameters, such as sliding distance, temperature, normal pressure and bulk strain rate by finite element analysis. The predicted results of the surface parameters from the finite element analysis are in good agreement with the results obtained from experiments.

A Finite Element Based Study on the Elastic-Plastic Transition Behavior in a Hemisphere in Contact With a Rigid Flat

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
S. Shankar ◽  
M. M. Mayuram
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
Plastic Material ◽  
Plastic Region ◽  
Real Contact Area ◽  
Real Contact ◽  
Perfectly Plastic ◽  
The Difference ◽  
Elastic Perfectly Plastic ◽  
Green Model

An axisymmetrical hemispherical asperity in contact with a rigid flat is modeled for an elastic perfectly plastic material. The present analysis extends the work (sphere in contact with a flat plate) of Kogut–Etsion Model and Jackson–Green Model and addresses some aspects uncovered in the above models. This paper shows the critical values in the dimensionless interference ratios (ω∕ωc) for the evolution of the elastic core and the plastic region within the asperity for different Y∕E ratios. The present analysis also covers higher interference ratios, and the results are applied to show the difference in the calculation of real contact area for the entire surface with other existing models. The statistical model developed to calculate the real contact area and the contact load for the entire surfaces based on the finite element method (FEM) single asperity model with the elastic perfectly plastic assumption depends on the Y∕E ratio of the material.

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.

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.

Tribological Applications Considering Roughness Effects on Grain Flow

2011 ◽  
Vol 328-330 ◽  
pp. 837-842
Author(s):  
Hung Jung Tsai ◽  
Jeng Haur Horng ◽  
Hung Cheng Tsai ◽  
Pay Yau Huang
Keyword(s):  
Contact Area ◽  
Chemical Mechanical Polishing ◽  
Flow Theory ◽  
Area Ratio ◽  
Mechanical Polishing ◽  
Roughness Effects ◽  
Slider Bearings ◽  
Grain Flow ◽  
Contact Area Ratio ◽  
Cmp Model

The grain flow lubrication, based on Haff's grain flow theory and the Patir/Cheng flow factors method, is applied in the simulations of rough slider bearings and chemical mechanical polishing. In this paper, the results of flow factor, the performance of rough slider bearings and the mechanism of the CMP process for grain flow are briefly demonstrated. An improved CMP model, considering the partial hydrodynamic grain flow lubrication and elastic-plastic microcontact theory, is also proposed. The contact area ratio and the elastoplastic contact area ratio are presented to improve the understanding of CMP mechanisms.

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