A Numerical Model for the Contact of Layered Elastic Bodies With Real Rough Surfaces

1992 ◽  
Vol 114 (2) ◽  
pp. 334-340 ◽  
Author(s):  
S. J. Cole ◽  
R. S. Sayles
Keyword(s):  
Numerical Model ◽  
Rough Surfaces ◽  
Surface Profile ◽  
Test Case ◽  
Measuring Instrument ◽  
Profile Data ◽  
Frictionless Contact ◽  
Varying Thickness ◽  
Pressure Distributions ◽  
Elastic Bodies

A numerical model for the two-dimensional dry, frictionless contact of two elastic bodies with real rough surfaces, where one body has a rigidly bonded surface layer, is presented. The model uses surface profile data directly recorded with a stylus measuring instrument and is suitable for use on a microcomputer. Verification of the accuracy of the model by reproduction of test case results is presented. Contact pressure distributions for layers of varying thickness and elastic modulus are presented.

Development of Theoretical Contact Width Formulas and a Numerical Model for Curved Rough Surfaces

2004 ◽  
Author(s):  
Shao Wang
Keyword(s):  
Numerical Model ◽  
Rough Surfaces ◽  
Contact Region ◽  
Roughness Parameter ◽  
Surface Profile ◽  
Root Mean Square Roughness ◽  
Load Parameter ◽  
Contact Parameter ◽  
Equivalent Radius ◽  
Contact Width

The apparent contact area of curved rough surfaces can be larger than that predicted by the Hertz theory due to asperity interaction outside the Hertzian region. In the present study, simple theoretical formulas for the contact semi-width and radius were derived, and a numerical contact model was developed based on an iterative scheme for the elastic deformation of the macroscopic surface profile and the asperity deformation. Both the theoretical formulas and the numerical model are based on a general power-law relationship between the local apparent pressure and real-to-apparent contact ratio. Numerical results of the contact semi-width agree well with the prediction of the formula. The apparent contact region becomes increasingly larger than the Hertzian region as the dimensionless roughness parameter increases, or as the dimensionless load parameter decreases, while the effect of the load exponent is relatively small. The ratio of the contact semi-width to the Hertzian semi-width is mainly determined by a dimensionless contact parameter involving the root-mean-square roughness, the equivalent radius and the Hertzian semi-width or radius. When applied to fractal regular surfaces, the present theory indicates that the influence of the fractal dimension on the contact behavior is due to its effects on both the area-load coefficient and the load exponent.

A Numerical Model for the Elastic Frictionless Contact of Real Rough Surfaces

1986 ◽  
Vol 108 (3) ◽  
pp. 314-320 ◽  
Author(s):  
M. N. Webster ◽  
R. S. Sayles
Keyword(s):  
Numerical Model ◽  
Rough Surfaces ◽  
Real Contact Area ◽  
Frictionless Contact ◽  
Random Process Theory ◽  
Surface Profiles ◽  
Rough Surface Contact ◽  
High Level ◽  
The Relationship ◽  
Sample Set

A computer model for the dry, frictionless contact of real rough surfaces is presented. The model uses data directly recorded from a stylus measuring instrument and as a confirmation of the model it is shown to reproduce “smooth case” results with a high level of accuracy. Results are given for two important applications of the technique. The first considers the analysis of the contact pressure and displacements for a bearing surface including a debris induced dent in the contact zone. The results go someway to providing an explanation of early life failure often associated with debris contaminated oil. Secondly the relationship between load and real contact area is studied for a sample set of surface profiles. The results obtained are compared with random process theory. It is proposed that the numerical model represents a different approach to rough surface contact allowing certain assumptions about the nature of surface roughness to be relaxed.

Measured and Predicted Static Friction for Real Rough Surfaces in Point Contact

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Jose M. García ◽  
Ashlie Martini
Keyword(s):  
Numerical Model ◽  
Yield Strength ◽  
Rough Surface ◽  
Rough Surfaces ◽  
Point Contact ◽  
Surface Profile ◽  
Static Friction ◽  
Cold Hardening ◽  
Quantitative Prediction ◽  
Statistical Parameters

A numerical model to predict static friction for metallic point contacts was developed and validated by comparison to experimental measurements using a specially designed test rig. Key aspects of the numerical model were the incorporation of a digitized real rough surface profile, application of discrete convolution fast Fourier transform (DC-FFT) to predict local asperity interference, and modification of the yield strength to capture the effect of cold hardening. It was found that these model features are critically important to quantitative prediction of static friction. The model significantly underestimated the static friction coefficient if randomly generated surfaces having statistical parameters the same as the measured rough surface were used; digitized real rough surfaces enabled accurate predictions. Further, the model was able to describe the static friction of worn surfaces after cold hardening was introduced through modification of material yield strength. This work illustrates the importance of incorporating the surface features and the change of those features with wear to accurately and reliably predict static friction.

A Two-Dimensional Adaptive Elasto-Plastic Contact Model of Rough Surfaces

2005 ◽  
Author(s):  
Tianxiang Liu ◽  
Geng Liu ◽  
Qin Xie
Keyword(s):  
Rough Surfaces ◽  
Computing Time ◽  
Surface Profile ◽  
Contact Problems ◽  
Contact Model ◽  
Computational Time ◽  
Real Contact Area ◽  
Asperity Contact ◽  
Pressure Distributions ◽  
Element Free

When contact problems are solved by numerical approaches, the surface profile is usually described by a series of discrete nodes with the same intervals along the coordinate axis. An adaptive-surface-based elasto-plastic asperity contact model is presented in this paper. Such a model is developed in order to reduce the computing time by removing the surface nodes that have little influence on the contact behavior of rough surfaces. The removed nodes are determined by setting a threshold. Thus, the contact problems can be described by fewer surface nodes but have similar results to the ones of the original surface. The adaptive asperity contact model is solved by using the element-free Galerkin-finite element (EFG-FE) coupling method because of its flexibility in domain descritization and versatility in node arrangements. The effects of different thresholds on the contact pressure distributions, real contact area, and the elasto-plastic stress fields in the contacting bodies are investigated and discussed. The results show that the computational time will dramatically reduce to about 50% when the relative error is about 5%.

A Numerical Model for Simulating Liquid Particles Deposition on Surface

2018 ◽  
Author(s):  
Zhenxia Liu ◽  
Fei Zhang ◽  
Zhengang Liu
Keyword(s):  
Particle Size ◽  
Numerical Model ◽  
Particle Deposition ◽  
Surface Profile ◽  
Leading Edge ◽  
Solid Particles ◽  
Liquid Particle ◽  
Aircraft Icing ◽  
Turbine Vane ◽  
Deposition Thickness

The deposition of liquid particles, which may be converted from solid particles due to high temperature gas heating, makes much more harm on turbine vane blades compared to solid particles, since it may block film-cooling holes, worsen the cooling efficiency and aerodynamic performance of the turbine vane blades. Due to the similarity between the deposition of liquid particles on a surface and the icing on a surface, a numerical model for simulating particles deposition was developed based on the Myers icing model, an extension of the Messinger model, which has been applied in predicting aircraft icing or aero-engine icing. Compared to the conventional liquid particle deposition model, the numerical model in this paper considers the heat transfer and the flow of liquid particles during the particles phase transition from liquid state to solid state. In this model, the change of the surface profile due to the particles deposition was also considered, which was implemented with dynamic mesh technique. To test this model, deposition distribution and thickness obtained from the numerical simulations were compared to the experimental results. Additionally, a numerical simulation was conducted for liquid particle deposition on a flat plate. The result showed that the deposition thickness at the leading edge was much larger than that on the upper surface where the deposition appeared mainly at the middle and rear of the plate. The deposition mass and thickness increased with the increasing in the particle size. The effect of the particle size on the deposition thickness was more notable on the upper surface compared to that at the leading edge.

Numerical Study on the Effect of a Submerged Breakwater Seaward of an Existing Breakwater for Climate Change Adaptation

2018 ◽  
Author(s):  
Athul Sasikumar ◽  
Arun Kamath ◽  
Onno Musch ◽  
Arne Erling Lothe ◽  
Hans Bihs
Keyword(s):  
Climate Change ◽  
Numerical Model ◽  
Transmission Coefficient ◽  
Numerical Study ◽  
Protective Measure ◽  
Test Case ◽  
Relative Width ◽  
Optimal Dimension ◽  
Submerged Breakwater ◽  
Design Storm

In coastal areas, climate change is causing mean sea level rise and more frequent storm surge events. This means the breakwaters are expected to withstand the action of more severe incident waves and larger overtopping rates than they were designed for. Therefore, these impacts may have a negative effect on the functionality such as overtopping above the acceptable limits, in addition to stability of these structures. A breakwater which has been partly damaged by a storm stronger than the design storm has weak spots that can easily be damaged further. One way of protecting these breakwaters subjected to climate change is to build a submerged breakwater on the seaward side. This study focuses on the use of numerical model for optimal dimension of a submerged breakwater to be used as a protective measure for an existing structure. Comparisons are made between transmission coefficient predicted in the numerical model and those calculated from different formulae in literature. The variation in transmission coefficient due to different relative submergence and relative width parameters for waves with different steepness is studied and curves showing the dependence of these parameters on wave transmission are made. These results are then used for a test case in Kiberg, Norway where a submerged breakwater is proposed in front of a existing damaged rubble mound breakwater. The optimal geometry generated on the basis of curves is then implemented in the local-scale finite element wave prediction model, CGWAVE.

scholarly journals A study on surface morphology and tension in laser powder bed fusion of Ti-6Al-4V

2020 ◽  
Vol 111 (9-10) ◽  
pp. 2891-2909
Author(s):  
Mahyar Khorasani ◽  
AmirHossein Ghasemi ◽  
Umar Shafique Awan ◽  
Elahe Hadavi ◽  
Martin Leary ◽  
...  
Keyword(s):  
Surface Tension ◽  
Process Parameters ◽  
Surface Profile ◽  
Test Case ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Data Set ◽  
Powder Bed ◽  
Case Morphology ◽  
Melting Pool

Abstract When reporting surface quality, the roughest surface is a reference for the measurements. In LPBF due to recoil pressure and scan movement, asymmetric surface is shaped, and surface roughness has different values in different measurement orientations. In this research, the influence of the laser powder bed fusion (LPBF) process parameters on surface tension and roughness of Ti-6AI-4 V parts in three orientations are investigated. To improve the mechanical properties, heat treatment was carried out and added to the designed matrix to generate a comprehensive data set. Taguchi design of experiment was employed to print 25 samples with five process parameters and post-processing. The effect and interaction of the parameters on the formation of surface profile comprising tension, morphology and roughness in various directions have been analysed. The main contribution of this paper is developing a model to approximate the melting pool temperature and surface tension based on the process parameters. Other contributions are an analysis of process parameters to determine the formation and variation of surface tension and roughness and explain the governing mechanisms through rheological phenomena. Results showed that the main driving factors in the variation of surface tension and formation of the surface profile are thermophysical properties of the feedstock, rheology and the temperature of the melting pool. Also, the results showed that while the value of surface tension is the same for each test case, morphology and the value of roughness are different when analysing the surface in perpendicular, parallel and angled directions to laser movement.

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