Theoretical and Experimental Contact Stiffness Characterisation of Nominally Flat Surfaces

2012 ◽  
Vol 186 ◽  
pp. 107-113 ◽  
Author(s):  
Iuliana Piscan ◽  
Agusmian P. Ompusunggu ◽  
Thierry Janssens ◽  
Nicolae Predincea
Keyword(s):  
Normal Load ◽  
Contact Stiffness ◽  
Contact Theory ◽  
Tangential Displacement ◽  
Tangential Contact ◽  
Flat Surfaces ◽  
Elastic Bodies ◽  
Order Of Magnitude ◽  
Theoretical Results ◽  
Good Agreement

In this study the tangential contact stiffness between two elastic bodies having nominally flat surfaces with different material combinations is investigated. The tangential contact stiffness between these two elastic bodies is first calculated based on the Greenwood-Williamson-McCool contact theory. Then, the tangential contact stiffness is determined by experimental investigation on a tribometer under the effect of different values of normal load and tangential displacement amplitude. The tangential contact stiffnesses obtained from the experimental data show a good agreement with the theoretical results, where the trends are similar and they are in the same order of magnitude.

scholarly journals Linear relationship of normal and tangential contact stiffness with load

2020 ◽  
Vol 476 (2243) ◽  
pp. 20200329
Author(s):  
K. S. Parel ◽  
R. J. Paynter ◽  
D. Nowell
Keyword(s):  
Surface Roughness ◽  
Linear Relationship ◽  
Normal Load ◽  
Contact Stiffness ◽  
Roughness Parameter ◽  
Image Correlation ◽  
Tangential Load ◽  
Normal Contact ◽  
Tangential Contact ◽  
Normal Contact Stiffness

Measurements with digital image correlation of normal and tangential contact stiffness for ground Ti-6Al-4V interfaces suggest a linear relationship between normal contact stiffness and normal load and a linear relationship between tangential contact stiffness and tangential load. The normal contact stiffness is observed approximately to be inversely proportional to an equivalent surface roughness parameter, defined for two surfaces in contact. The ratio of the tangential contact stiffness to the normal contact stiffness at the start of tangential loading is seen to be given approximately by the Mindlin ratio. A simple empirical model is proposed to estimate both the normal and tangential contact stiffness at different loads for a ground Ti-6Al-4V interface, on the basis of the equivalent surface roughness and the coefficient of friction.

Investigation of normal and tangential contact stiffness considering surface asperity interaction

2019 ◽  
Vol 72 (3) ◽  
pp. 379-388
Author(s):  
Hongping Yang ◽  
Xiaowei Che ◽  
Cheng Yang
Keyword(s):  
Contact Mechanics ◽  
Fractal Geometry ◽  
Contact Stiffness ◽  
Contact Theory ◽  
Normal Contact ◽  
Tangential Contact ◽  
Content Type ◽  
Elastic Plastic ◽  
Stiffness Model ◽  
The Relationship

Purpose This paper aims to propose a normal and tangential contact stiffness model to investigate the contact characteristics between rough surfaces of machined joints based on fractal geometry and contact mechanics theory considering surface asperities interaction. Design/methodology/approach The fractal geometry theory describes surface topography and Hertz contact theory derives the asperities elastic, elastic-plastic and plastic contact deformation. The joint normal and tangential contact stiffness are obtained. The experiment method for normal and tangential contact stiffness are introduced. Findings The relationship between dimensionless normal contact load and dimensionless normal and tangential contact stiffness are analyzed in different plasticity index. The results show that they are nonlinear relationships. The normal and tangential contact stiffness are obtained based on theoretical and experimental methods for milling and grinding machined specimens. The results indicate that the present model for the normal and tangential contact stiffness are consistent with experimental data, respectively. Originality/value The normal and tangential contact stiffness models are constructed by using the fractal geometry and the contact mechanics theory considering surface asperities interaction, which includes fully elastic, elastic-plastic and fully plastic contacts deformation. The present method can generate a more reliable calculation result as compared with the contact model no-considering asperities interaction.

scholarly journals SIMULATION OF FRICTIONAL DISSIPATION UNDER BIAXIAL TANGENTIAL LOADING WITH THE METHOD OF DIMENSIONALITY REDUCTION

2017 ◽  
Vol 15 (2) ◽  
pp. 295
Author(s):  
Andrey V. Dimaki ◽  
Roman Pohrt ◽  
Valentin L. Popov
Keyword(s):  
Dimensionality Reduction ◽  
Normal Load ◽  
Superposition Principle ◽  
Three Dimensional ◽  
Method Of Dimensionality Reduction ◽  
Elastic Bodies ◽  
Frictional Dissipation ◽  
Order Of Magnitude ◽  
Constant Normal Load ◽  
Numeric Solution

The paper is concerned with the contact between the elastic bodies subjected to a constant normal load and a varying tangential loading in two directions of the contact plane. For uni-axial in-plane loading, the Cattaneo-Mindlin superposition principle can be applied even if the normal load is not constant but varies as well. However, this is generally not the case if the contact is periodically loaded in two perpendicular in-plane directions. The applicability of the Cattaneo-Mindlin superposition principle guarantees the applicability of the method of dimensionality reduction (MDR) which in the case of a uni-axial in-plane loading has the same accuracy as the Cattaneo-Mindlin theory. In the present paper we investigate whether it is possible to generalize the procedure used in the MDR for bi-axial in-plane loading. By comparison of the MDR-results with a complete three-dimensional numeric solution, we arrive at the conclusion that the exact mapping is not possible. However, the inaccuracy of the MDR solution is on the same order of magnitude as the inaccuracy of the Cattaneo-Mindlin theory itself. This means that the MDR can be also used as a good approximation for bi-axial in-plane loading.

The influence of fluids on grain contact stiffness and frame moduli in sedimentary rocks

Geophysics ◽  
1992 ◽  
Vol 57 (12) ◽  
pp. 1571-1582 ◽  
Author(s):  
Azra N. Tutuncu ◽  
Mukul M. Sharma
Keyword(s):  
Contact Stiffness ◽  
Sedimentary Rocks ◽  
Separation Distance ◽  
Surface Forces ◽  
Contact Theory ◽  
Wave Velocities ◽  
Deformation Problem ◽  
Seismic Wave Velocities ◽  
Equilibrium Separation ◽  
Good Agreement

The frame moduli of sedimentary rocks are strongly influenced by the properties of the grain contacts. A modified Hertz contact theory is presented for the self consistent calculation of deformation, equilibrium separation distance (film thickness), and contact area of deformation for two spherical asperities in contact and subjected to an external load. We show that surface forces, i.e., electrostatic repulsion, Born, structural, and Van der Waals forces can be incorporated into the contact deformation problem. From the results presented, it is evident that surface forces play an important role in determining seismic wave velocities and attenuations at low confining stresses. The velocities and attenuations computed from the model are compared with measured values for glass beads, Navajo, Berea, Obernkirchner, and Fort Union sandstones. The velocities and attenuations calculated as functions of stress, frequency, fluid type, and saturation are in good agreement with reported experimental data.

Energy Dissipation in Contact Friction: Constant Normal and Cyclic Tangential Loading

1962 ◽  
Vol 29 (1) ◽  
pp. 17-22 ◽  
Author(s):  
L. E. Goodman ◽  
C. B. Brown
Keyword(s):  
Energy Dissipation ◽  
Normal Load ◽  
Tangential Force ◽  
Contact Friction ◽  
Surface Phenomenon ◽  
Tangential Displacement ◽  
Sphere Diameter ◽  
Flat Surfaces ◽  
Aisi 316 ◽  
Energy Dissipated

When a sphere is held between parallel flat surfaces by means of a constant clamping pressure and is then subjected to a cyclic tangential displacement parallel to the flats, energy is dissipated at the contacts. This occurs even when the maximum tangential force, T*, is less than Tmax, the force which will just produce slip over the entire contact surface. Measurements of the energy dissipated per cycle and of the hysteresis loop shapes have been found to agree well with the theory of Mindlin and Deresiewicz in the range investigated, 0.45 < δ*/δmax < 1. The sphere diameter and the normal load appear as parameters only in the way demanded by the theory. In the range investigated energy dissipation appears to be primarily a surface phenomenon and not one due to material damping. The material employed has been AISI 316 steel.

Investigating the Nonlinear Optical Response of Pepper Oil under Low Power Irradiation with Continuous Wave Visible Laser Beam

2020 ◽  
pp. 131-138
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Nonlinear Optical ◽  
Continuous Wave ◽  
Diffraction Integral ◽  
Visible Laser ◽  
Limiting Property ◽  
Kirchhoff Diffraction Integral ◽  
Theoretical Results ◽  
Good Agreement

The nonlinear optical properties of pepper oil are studied by diffraction ring patterns and Z-scan techniques with continuous wave beam from solid state laser at 473 nm wavelength. The nonlinear refractive index of the sample is calculated by both techniques. The sample show high nonlinear refractive index. Based on Fresnel-Kirchhoff diffraction integral, the far-field intensity distributions of ring patterns have been calculated. It is found that the experimental results are in good agreement with the theoretical results. Also the optical limiting property of pepper oil is reported. The results obtained in this study prove that the pepper oil has applications in nonlinear optical devices.

Studies of local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) crystals

2021 ◽  
Vol 76 (4) ◽  
pp. 299-304
Author(s):  
Fu Chen ◽  
Jian-Rong Yang ◽  
Zi-Fa Zhou
Keyword(s):  
Crystal Field ◽  
Elongation Ratio ◽  
Paramagnetic Resonance ◽  
Local Structures ◽  
Epr Parameters ◽  
Structure Constants ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic ◽  
Theoretical Results ◽  
Good Agreement

Abstract The electron paramagnetic resonance (EPR) parameters (g factor g i , and hyperfine structure constants A i , with i = x, y, z) and local structures for Cu2+ centers in M2Zn(SO4)2·6H2O (M = NH4 and Rb) are theoretically investigated using the high order perturbation formulas of these EPR parameters for a 3d 9 ion under orthorhombically elongated octahedra. In the calculations, contribution to these EPR parameters due to the admixture of d-orbitals in the ground state wave function of the Cu2+ ion are taken into account based on the cluster approach, and the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the studied EPR parameters with the local structures of the Cu2+ centers. Based on the calculations, the Cu–H2O bonds are found to suffer the axial elongation ratio δ of about 3 and 2.9% along the z-axis, meanwhile, the planar bond lengths may experience variation ratio τ (≈3.8 and 1%) along x- and y-axis for Cu2+ center in (NH4)2Zn(SO4)2·6H2O and Rb2Zn(SO4)2·6H2O, respectively. The theoretical results show good agreement with the observed values.

scholarly journals 41Ca Concentrations in Modern Bone and Their Implications for Dating

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 305-310 ◽  
Author(s):  
Roy Middleton ◽  
David Fink ◽  
Jeffrey Klein ◽  
Pankaj Sharma
Keyword(s):  
Mass Spectrometry ◽  
Accelerator Mass Spectrometry ◽  
Isotope Enrichment ◽  
Terrestrial Rock ◽  
Order Of Magnitude ◽  
Cow Bone ◽  
Good Agreement

We have made the first measurements without pre-enrichment of 41Ca in terrestrial rock and bone samples using accelerator mass spectrometry. Although the results in tufa deposits from Egypt are in good agreement with the saturation value of 8×10-15 predicted by Raisbeck and Yiou (1979), the average 41Ca:40Ca ratio of 2×10-15 (range: 0.6 to 4.2×10-15) that we measure in modern bone is an order of magnitude lower than that obtained previously by Henning, et al (1987) on a cow bone that was measured using AMS following isotope enrichment. The low value and the variability (more than a factor of seven) of the 41Ca:40Ca ratio in modern bone make the possibility of dating bones using 41Ca unlikely.

On the Flow Fields of Inertial Impactors

1974 ◽  
Vol 96 (4) ◽  
pp. 394-400 ◽  
Author(s):  
V. A. Marple ◽  
B. Y. H. Liu ◽  
K. T. Whitby
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Relaxation Method ◽  
Water Model ◽  
Navier Stokes ◽  
Visualization Technique ◽  
Navier Stokes Equations ◽  
Theoretical Results ◽  
Plate Distance ◽  
Good Agreement

The flow field in an inertial impactor was studied experimentally with a water model by means of a flow visualization technique. The influence of such parameters as Reynolds number and jet-to-plate distance on the flow field was determined. The Navier-Stokes equations describing the laminar flow field in the impactor were solved numerically by means of a finite difference relaxation method. The theoretical results were found to be in good agreement with the empirical observations made with the water model.

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