Modelling of fluid continuum considering 3D surface parameters in hydraulic assemblies
01 Jan 2009-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology (Elsevier)-Vol. 33, Iss: 1, pp 99-106
TL;DR: In this paper, a 3D surface modelling approach is presented using random process modelling as the basis to model the grinding and honing processes which are commonly employed for the manufacture of the hydraulic assemblies.
Abstract: Friction in servo hydraulic assemblies reduces the response characteristics of the system. The friction is influenced by various factors including the geometry (form and surface errors) of the sliding surfaces. In this work, functionally significant 3D surface parameters from the Birmingham parameters are investigated for reduced friction. A 3D surface modelling approach is presented using random process modelling as the basis. An exponential decay areal autocorrelation function is used to model the grinding and honing processes which are commonly employed for the manufacture of the hydraulic assemblies. Honed surface is modelled with the crosshatches of appropriate angle. Method of surface modelling is validated using the data obtained through measurements on a practical surface. Different surface maps with varying surface parameters of the ground and honed surfaces are generated. The fluid continuum gap geometries of the hydraulic assemblies are modelled using these surface maps as envelopes. Pressure distribution, velocity and viscous friction force are used as measurands of the frictional characteristics. Using computational fluid dynamics (CFD) approach, these measurands are evaluated for different functionally significant Birmingham parameters. Based on further analysis, negative skewness, lower kurtosis values, higher valley fluid retention index were found to have lower frictional characteristics.
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TL;DR: In this article, an algorithm is developed for the numerical generation of 3D anisotropic surfaces with prescribed 3D surface roughness parameters using either the Non-linear Conjugate Gradient Method (NCGM) or 2-D Digital Filter method.
Abstract: Three-dimensional surface roughness of mating parts of engineering assemblies has a significant influence on their functional behaviour. Studies on load bearing capacity in elastohydrodynamic contacts, gap flow analysis in precision hydraulic assemblies using modeled 3D fluid continuum micro gap geometry, etc., have made it possible to quantify the effect of certain 3D surface roughness parameters on frictional behaviour of the assemblies. This set forth the need for artificially generated three-dimensional engineering surfaces having prescribed roughness values for a better understanding and prediction of tribological problems. In this paper, an algorithm is developed for the numerical generation of three-dimensional anisotropic surfaces with prescribed 3D surface roughness parameters. The procedures employ either the Non-linear Conjugate Gradient Method (NCGM) or 2-D Digital Filter method. The results show that both the methods can adequately produce surfaces at small correlation distances, while at higher correlation distances the NCGM yields better results. Comparison between model-simulated output and measurement results of three-dimensional surface roughness of engineering surface show a good match, supporting the validity of the model.
95 citations
TL;DR: In this paper, a simulation model of material removal in 5-axis based on the N-buffer method and integrating the Inverse Kinematics Transformation is presented, which is linked with the velocity giving the surface topography resulting from actual machining conditions.
Abstract: Within the context of 5-axis free-form machining, CAM software offers various ways of tool-path generation, depending on the geometry of the surface to be machined. Therefore, as the manufactured surface quality results from the choice of the machining strategy and machining parameters, the prediction of surface roughness in function of the machining conditions is an important issue in 5-axis machining. The objective of this paper is to propose a simulation model of material removal in 5-axis based on the N-buffer method and integrating the Inverse Kinematics Transformation. The tooth track is linked with the velocity giving the surface topography resulting from actual machining conditions. The model is assessed thanks to a series of sweeping over planes according to various tool axis orientations and cutting conditions. 3D surface topography analyses are performed through the new areal surface roughness parameters proposed by recent standards.
57 citations
TL;DR: In this article, a simulation model for the prediction of machined surface patterns is developed based on the well-known N-buffer method, which can be coupled to a feed-rate prediction model.
Abstract: The paper deals with the prediction of the 3D surface topography obtained in 5-axis milling in function of the machining conditions. For this purpose, a simulation model for the prediction of machined surface patterns is developed based on the well-known N-buffer method. As in sculptured surface machining the feed rates locally vary, the proposed model can be coupled to a feed-rate prediction model. Thanks to the simulation model of 3D surface topography, the influence of the machining strategy on resulting 3D surface patterns is analyzed through an experimental design. Results enhance the major influence of the tool inclination on 3D topography. Surface parameters used in the study are strongly affected by the variation of the yaw angle. The effect of the feed rate is also significant on amplitude parameters. Finally, the analysis brings out the interest of using surface parameters to characterize 3D surface topography obtained in 5-axis milling.
54 citations
Cites background from "Modelling of fluid continuum consid..."
...For friction in servo hydraulic assemblies, surfaces with negative skewness, low kurtosis values, and high valley fluid retention index were found to have lower frictional characteristics [6]....
[...]
01 Jun 2011
TL;DR: A simulation model of material removal in 5- axis based on the N-buffer method and integrating the Inverse Kinematics Transformation is proposed and the tooth track is linked to the velocity giving the surface topography resulting from actual machining conditions.
Abstract: Within the context of 5-axis free-form machining, CAM software offers various modes of tool-path generation, depending on the geometry of the surface to be machined. Therefore, as the manufactured surface quality results from the choice of the machining strategy and machining parameters, the prediction of surface roughness in function of the machining conditions is an important issue in 5-axis machining. The objective of this paper is to propose a simulation model of material removal in 5- axis based on the N-buffer method and integrating the Inverse Kinematics Transformation. The tooth track is linked to the velocity giving the surface topography resulting from actual machining conditions. The model is assessed thanks to a series of sweeping over planes according to various tool axis orientations and cutting conditions. 3D surface topography analyses are performed through the new 3D roughness parameters proposed by recent standards.
44 citations
Cites background from "Modelling of fluid continuum consid..."
...For friction in servo hydraulic assemblies, negative Skewness and lower kurtosis values as well as the higher valley fluid retention index are found to have lower frictional characteristics [4]....
[...]
...According to previous work which try to link 3D surface roughness parameters to the part functionality [4,5,6], the study proposed is reduced to the more significant parameters for fatigue and friction applications....
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TL;DR: In this article, the correlation and regression analysis of parameters of textured surface topography was carried out, and the modeled surfaces were correctly matched to the measured surfaces in 90% of all analysed cases.
Abstract: Wear experiments were conducted on a block-on ring tester. The stationary block made from cast iron of 50 HRC hardness was ground. The rotated ground ring was made from 42CrMo4 steel of 32 HRC hardness. The rings were modified by a burnishing technique in order to obtain surfaces with oil pockets. Oil pockets of spherical and of drop shape were tested. The correlation and regression analysis of parameters of textured surface topography was carried out. Two sets of surfaces were analysed: after machining and after “zero-wear”. As the result of analysis, minimum number of parameters describing this surface kind was obtained. A simple truncation model of the ring surface change was used. Worn surface topographies, after a low wear, were also modeled in a different way. An idea of the proposed method of surface topography modeling is imposition of random surface of Gaussian ordinate distribution on the base surface (after burnishing). The modeled surfaces were correctly matched to the measured surfaces in 90% of all analysed cases. Basing on the simulation, the local wear values during a low wear process were calculated and compared with experimental ones.
37 citations
References
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Book•
01 Jan 1995
TL;DR: A Thomas's algorithm for the solution of a tridiagonal system of Equations is described in this paper, as well as a detailed discussion of the future of Computational Fluid Dynamics.
Abstract: Part I*Basic Thoughts and Equations 1 Philosophy of Computational Fluid Dynamics 2 The Governing Equations of Fluid Dynamics Their Derivation, A Discussion of Their Physical Meaning, and A Presentation of Forms Particularly Suitable to CFD 3 Mathematical Behavior of Partial Differential Equations The Impact on Computational Fluid Dynamics Part II*Basics of the Numerics 4 Basic Aspects of Discretization 5 Grids and Meshes, With Appropriate Transformations 6 Some Simple CFD Techniques A Beginning Part III*Some Applications 7 Numerical Solutions of Quasi-One-Dimensional Nozzle Flows 8 Numerical Solution of A Two-Dimensional Supersonic Flow Prandtl-Meyer Expansion Wave 9 Incompressible Couette Flow Numerical Solution by Means of an Implicit Method and the Pressure Correction Method 10 Incompressible, Inviscid Slow Over a Circular Cylinder Solution by the Technique Relaxation Part IV*Other Topics 11 Some Advanced Topics in Modern CFD A Discussion 12 The Future of Computational Fluid Dynamics Appendixes A Thomas's Algorithm for the Solution of A Tridiagonal System of Equations References
1,738 citations
Book•
01 Jan 2002TL;DR: In this article, the authors present a theory of the real area of contact (ROC) between two surfaces and show that the ROC can be represented as a triangle of a triangle.
Abstract: Foreword. Preface. 1 Introduction. 1.1 De.nition and History of Tribology. 1.2 Industrial Signi.cance of Tribology. 1.3 Origins and Signi.cance of Micro/Nanotribology. 1.4 Organization of the Book. References. 2 Solid Surface Characterization. 2.1 The Nature of Surfaces. 2.2 Physico-Chemical Characteristics of Surface Layers. 2.3 Analysis of Surface Roughness. 2.4 Measurement of Surface Roughness. 2.5 Closure. References. Suggested Reading. 3 Contact between Solid Surfaces. 3.1 Introduction. 3.2 Analysis of the Contacts. 3.3 Measurement of the Real Area of Contact. 3.4 Closure. References. Suggested Reading. 4 Adhesion. 4.1 Introduction. 4.2 Solid-Solid Contact. 4.3 Liquid-Mediated Contact. 4.4 Closure. References. Suggested Reading. 5 Friction. 5.1 Introduction. 5.2 Solid-Solid Contact. 5.3 Liquid-Mediated Contact. 5.4 Friction of Materials. 5.5 Closure. References. Suggested Reading. 6 Interface Temperature of Sliding Surfaces. 6.1 Introduction. 6.2 Thermal Analysis. 6.3 Interface Temperature Measurements. 6.4 Closure. References. 7 Wear. 7.1 Introduction. 7.2 Types of Wear Mechanisms. 7.3 Types of Particles Present in Wear Debris. 7.4 Wear of Materials. 7.5 Closure. References. Suggested Reading. 8 Fluid Film Lubrication. 8.1 Introduction. 8.2 Regimes of Fluid Film Lubrication. 8.3 Viscous Flow and Reynolds Equation. 8.4 Hydrostatic Lubrication. 8.5 Hydrodynamic Lubrication. 8.6 Elastohydrodynamic Lubrication. 8.7 Closure. References. Suggested Reading. 9 Boundary Lubrication and Lubricants. 9.1 Introduction. 9.2 Boundary Lubrication. 9.3 Liquid Lubricants. 9.4 Greases. 9.5 Closure. References. Suggested Reading. 10 Micro/Nanotribology. 10.1 Introduction. 10.2 SFA Studies. 10.3 AFM/FFM. 10.4 Atomic-Scale Simulations. 10.5 Closure. References. Suggested Reading. 11 Friction and Wear Screening Test Methods. 11.1 Introduction. 11.2 Design Methodology. 11.3 Typical Test Geometries. 11.4 Closure. References. Suggested Reading. 12Tribological Components and Applications. 12.1 Introduction. 12.2 Common Tribological Components. 12.3 Microcomponents. 12.4 Material Processing. 12.5 Industrial Applications. 12.6 Closure. References. Suggested Reading. Problems. Appendix Units, Conversions, and Useful Relations. A.1 Fundamental Constants. A.2 Conversion of Units. A.3 Useful Relations. Index.
1,375 citations
01 Jan 1971
TL;DR: In this paper, the waveform of a random signal is used as a representation of the profile of a surface, which is completely defined by two parameters, a height distribution and an auto-correlation function.
Abstract: In recent work it has been shown that many types of surfaces used in engineering practice have a random structure. The paper takes, as a representation of the profile of such a surface, the waveform of a random signal; this is completely defined by two parameters, a height distribution and an auto-correlation function. It is shown how such a representation can be transformed into a model, appropriate for the study of surface contact, consisting of an array of asperities having a statistical distribution of both heights and curvatures. This theory is compared with the results of an analysis of surface profiles presented in digital form. The significance of these findings for the theory of surface contact and for the measurement and characterization of surface finish is discussed.
762 citations
TL;DR: In this article, the waveform of a random signal is used as a representation of the profile of a surface, which is completely defined by two parameters, a height distribution and an auto-correlation function.
Abstract: In recent work it has been shown that many types of surfaces used in engineering practice have a random structure. The paper takes, as a representation of the profile of such a surface, the waveform of a random signal; this is completely defined by two parameters, a height distribution and an auto-correlation function. It is shown how such a representation can be transformed into a model, appropriate for the study of surface contact, consisting of an array of asperities having a statistical distribution of both heights and curvatures. This theory is compared with the results of an analysis of surface profiles presented in digital form. The significance of these findings for the theory of surface contact and for the measurement and characterization of surface finish is discussed.
737 citations
Book•
15 Jun 2002
TL;DR: In this article, an integrated approach to the assessment of 3D micro-topography is presented. Butler et al. present a detailed analysis of the effects of quantization on 3D topography characterisation.
Abstract: 1. Updating introduction to this revised reprint 2. An integrated approach to the assessment of 3-D micro-topography 3. Techniques and fidelity of data collection 4. Measurement strategy of the stylus instrument 5. Effects of stylus geometry and loading 6. Fidelity of the measurement datum 7. The selection of sampling conditions 8. Specification for a unified data file format 9. Reference for 3-D topography characterisation 10. Digital filtering of 3-D surface topography 11. Characterisation techniques 12. Parameters for characterising 3-D surfaces 13. The effects of quantisation on 3-D topography characterisation 14. Functional characterisation of engineering surfaces 15. Calibration of surface topography instruments.
656 citations