scholarly journals Effect of fluid inertia force on thermal elastohydrodynamic lubrication of elliptic contact

2021 ◽  
Vol 22 ◽  
pp. 13
Author(s):  
Fan-Ming Meng ◽  
Sheng Yang ◽  
Zhi-Tao Cheng ◽  
Yong Zheng ◽  
Bin Wang
Keyword(s):  
Fourier Transform ◽  
Film Thickness ◽  
Fast Fourier Transform ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Result ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Operation Conditions ◽  
Elliptic Contact ◽  
Inertia Forces

A non-Newtonian thermal elastohydrodynamic lubrication (TEHL) model for the elliptic contact is established, into which the inertia forces of the lubricant is incorporated. In doing so, the film pressure and film temperature are solved using the associated equations. Meanwhile, the elastic deformation is calculated with the discrete convolution and fast Fourier transform (DC-FFT) method. A film thickness experiment is conducted to validate the TEHL model considering the inertia forces. Further, effects of the inertia forces on the TEHL performances are studied at different operation conditions. The results show that when the inertia forces are considered, the central and minimum film thicknesses increase and film temperature near the inlet increases obviously. Moreover, the inertial solution of the central film thickness is closer to the experimental result compared with its inertialess value.

An Elastohydrodynamic Lubrication Model for Coated Surfaces in Point Contacts

2007 ◽  
Vol 129 (3) ◽  
pp. 509-516 ◽  
Author(s):  
Yuchuan Liu ◽  
W. Wayne Chen ◽  
Dong Zhu ◽  
Shuangbiao Liu ◽  
Q. Jane Wang
Keyword(s):  
Fourier Transform ◽  
Film Thickness ◽  
Fast Fourier Transform ◽  
Elastic Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Contact Radius ◽  
Point Contacts ◽  
Compliant Coating ◽  
Influence Coefficients ◽  
Coated Surfaces

An elastohydrodynamic lubrication (EHL) model for coated surfaces in point contacts has been developed by combining the elastic deformation formulation for the coated surfaces with an EHL model. Inverse fast Fourier transform (IFFT) is employed first to obtain the influence coefficients (ICs) from the frequency response function (FRF). The subsequent calculation of elastic deformation is performed using the efficient algorithm of discrete convolution and fast Fourier transform (DC-FFT). The coating EHL model is verified by the comparison to available numerical results. The effects of coating on lubrication under various loads, speeds, rheological models, and pressure-viscosity behaviors are numerically investigated. Similar to the observations from dry contact, stiffer coatings in EHL tend to reduce the nominal contact radius but increase the maximum contact pressure, and vice versa for more compliant coatings. However, as coating thickness increases, the influence of coatings on film thickness, including the central and the minimum film thicknesses, does not follow a monotonic variation, and therefore, cannot be predicted by any simple film thickness equation. The reason for that is the pressure viscosity effect which tends to counterbalance the effect of coating. The average friction coefficient in lubricant film increases in stiff coating cases but decreases for compliant coating cases. Furthermore, two possible approaches to improving the minimum film thickness thus reducing friction and wear in mixed lubrication are indicated: a thin stiff coating for conventional EHL and a thick compliant coating for soft EHL.

scholarly journals Roughness in lubricated rolling contact: The dry contact limit

2007 ◽  
Vol 221 (7) ◽  
pp. 787-791 ◽  
Author(s):  
A. V. Olver ◽  
D Dini
Keyword(s):  
Thin Films ◽  
Fourier Transform ◽  
Film Thickness ◽  
Fast Fourier Transform ◽  
Elastohydrodynamic Lubrication ◽  
Fourier Component ◽  
Rolling Contact ◽  
Perturbation Model ◽  
Rolling Contacts ◽  
Dry Contact

A difficulty with the standard fast Fourier transform (FFT) perturbation model of roughness in lubricated rolling contacts is that it does not necessarily converge towards the elastic case as the film thickness is reduced; rather it leads to a situation in which all the roughness is completely flattened. This is rarely the case for real engineering surfaces. Here, it is shown that this difficulty can be avoided by carrying out a Fourier transform of the elastostatically flattened roughness and using the resulting (complex) amplitude as the low-film thickness limit of each Fourier component in the elastohydrodynamic lubrication (EHL) analysis. Results give a plausible convergence to the elastostatic solution, which is nevertheless consistent with the expected near-full-film EHL behaviour and which becomes identical to the earlier model for roughness that, statically, can be fully flattened. As expected, hydrodynamic action persists at the finest scale, even for very thin films.

A Three-Dimensional Deterministic Model for Rough Surface Line-Contact EHL Problems

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Ning Ren ◽  
Dong Zhu ◽  
W. Wayne Chen ◽  
Yuchuan Liu ◽  
Q. Jane Wang
Keyword(s):  
Fourier Transform ◽  
Film Thickness ◽  
Fast Fourier Transform ◽  
Rough Surface ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Point Contacts ◽  
Transverse Roughness

This paper reports the development of a novel three-dimensional (3D) deterministic model (3D L-EHL) for rough surface line-contact mixed-elastohydrodynamic lubrication (EHL) problems. This model is highly demanded because line contacts are found between many mechanical components, such as various gears, roller and needle bearings, cams and followers, and work rolls and backup rolls in metal-forming equipment. The macro aspects of a line-contact problem can be simplified into a two-dimensional (2D) model; however, the topography of contacting rough surfaces, microasperity contacts, and lubricant flows around asperities are often three-dimensional. The present model is based on Hu and Zhu’s unified 3D mixed-EHL model (Hu and Zhu, 2000, “Full Numerical Solution to the Mixed Lubrication in Point Contacts,” ASME J. Tribol., 122(1), pp. 1–9) originally developed for point contacts and the mixed fast Fourier transform (FFT)-based approach for deformation calculation formulated by Chen et al. (2008, “Fast Fourier Transform Based Numerical Methods for Elasto-Plastic Contacts With Normally Flat Surface,” ASME J. Appl. Mech., 75(1), 011022-1-11). It is numerically verified through comparisons with results from the line-contact Hertzian theory and the conventional 2D line-contact smooth-surface EHL formulas. Numerical examples involving 3D sinusoidal and digitized machined surfaces are also analyzed. Sample cases indicate that transverse roughness may yield greater film thickness than longitudinal roughness. This observation is qualitatively in agreement with the trend predicted by Patir and Cheng’s stochastic model (1978, “Effect of Surface Roughness on the Central Film Thickness in EHL Contacts,” Proceedings of the Fifth Leeds-Lyon Symposium on Tribology, London, pp. 15–21). However, the roughness orientation effect does not appear to be quantitatively as great as that shown in the work of Patir and Cheng for the same range of λ ratio.

Application of the Amplitude Reduction Technique Within Probabilistic Rough EHL Models

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Laurentiu Moraru ◽  
Theo. G Keith
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Probabilistic Model ◽  
Elastohydrodynamic Lubrication ◽  
Reduction Technique ◽  
Operating Conditions ◽  
Single Parameter ◽  
Main Interest ◽  
Bulk Properties ◽  
Ehl Contact

Over the years, the deterministic elastohydrodynamic lubrication (EHL) approach has been widely used. This technique is very powerful in capturing details of asperity deformation and interaction. The probabilistic EHL methodology is still used when the main interest of the engineer is directed toward computations of bulk properties. During recent years, the results of many deterministic analyses have been published. The reduction of the waviness amplitude in EHL contacts under rolling-sliding was systematically studied and it was shown that the amplitude reduction is completely described by a single parameter that includes relative wavelength and the operating conditions. This approach, usually referred to as the amplitude reduction technique, has opened the way for developing improved probabilistic EHL models by incorporating the effects of fluid-induced roughness deformation, which is calculated using the fast fourier transform. In this paper we provide a review of the latest developments in the amplitude reduction technique and we present a probabilistic EHL algorithm for the computation of the load supported by the fluid, the elastically deformed asperities and the plastically deformed asperities, in a mixed EHL contact with either isotropic on nonisotropic roughness. The fluid-induced roughness deformation is incorporated into the probabilistic model via the use of the amplitude reduction technique.

Effects of fluid inertia forces in ferrofluid lubricated circular stepped squeeze films – Shliomis model

2016 ◽  
Vol 68 (6) ◽  
pp. 712-717 ◽  
Author(s):  
Jaw-Ren Lin ◽  
Tzu-Chen Hung ◽  
Shu-Ting Hu
Keyword(s):  
Load Capacity ◽  
Squeeze Film ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Content Type ◽  
Inertia Parameter ◽  
Machine Systems ◽  
Momentum Integral ◽  
Film Characteristics ◽  
Inertia Forces

Purpose This paper aims to study the inertia squeeze film characteristics between ferrofluid-lubricated circular stepped disks. Owing to the development of modern machine systems, the application of ferrofluids has received great attention. Because the circular disks are a special situation of circular stepped squeeze films, a further study of fluid inertia force effects on the ferrofluid-lubricated circular stepped squeezing mechanism is motivated. Design/methodology/approach On the basis of the ferrohydrodynamic flow model of Shliomis incorporating the momentum integral method, the effects of fluid inertia forces in ferrofluid-lubricated circular stepped squeeze films in the presence of external magnetic fields are investigated in this study. Analytical solutions of squeeze film performances are derived. Findings The fluid inertia force effects provide an increased load capacity and a longer squeeze film time for the ferrofluid-lubricated circular stepped squeeze film, especially for a larger value of the inertia parameter, the Langevin parameter and the volume concentration and a smaller value of the radius ratio and the step height ratio. Originality/value For engineering applications, numerical tables for squeeze film loads of circular stepped disks are also provided in this paper.

Design of the Power Parameter Measurement System Based on SOPC

2012 ◽  
Vol 503-504 ◽  
pp. 1338-1342
Author(s):  
Zhan Ying Tong ◽  
Jing Kui Mao
Keyword(s):  
Fourier Transform ◽  
Data Processing ◽  
Fast Fourier Transform ◽  
Measurement System ◽  
Parameter Measurement ◽  
Experimental Result ◽  
Time System ◽  
Power Parameter ◽  
Real Time System ◽  
Fpga Chip

In this paper the SOPC technology is applied to the power parameter measurement in a FPGA chip. The Fast Fourier Transform (FFT) algorithm implemented in the FPGA is the theory basis of the system, and the 32 bit NiosⅡ soft CPU nuclear is embedded in the FPGA, which can realize the functions of power signals samping, data processing, storage, display and so on. The experimental result shows that processing precision meets expectations, and achieving requirements of the real-time system, with advantages of high integration and flexible reconstruction.

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