Why homogenization should be the averaging method of choice in hydrodynamic lubrication

Rom, Michael; König, Florian; Müller, Siegfried; Jacobs, Georg

doi:10.1016/j.apples.2021.100055

Cited by 8 publications

(6 citation statements)

References 24 publications

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“…Almqvist et al compared the differences between the method of Patir and Cheng with the approach of homogenization, making clear that homogenization is promising approach (Almqvist et al , 2011). These findings are supported by Rom et al research (Rom et al , 2021). In this work flow factors were calculated using the commercially available software “Tribo-X”, which is based on the method of Patir and Cheng (Patir and Cheng, 1978).…”

Section: Flow Factorssupporting

confidence: 84%

About the change of flow factors during the run-in process of lubricated contacts

Holzer

Schmitz

2021

ILT

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Purpose This paper aims to increase the knowledge of the run-in process of lubricated contacts in hydraulical pumps. When performing EHL simulations of tribological contacts, the surface influence needs to be taken into account. This experimental measurement wants to investigate the amount of change of the flow factors in the first hour of run of tribological contacts. Design/methodology/approach An experimental test bench is used to run-in several samples. After several minutes of running, samples are removed and the surface structure is captured using a digital microscope. With the measured data, flow factors are calculated. Findings The findings were clear that flow factors are highly direction-dependent, especially shear flow factors in radial directions experience almost no change. Overall, influence of the surface structure of up to 30% compared to a flat surface can be registered. Originality/value This paper helps to choose application-oriented values for the simulation of tribological contacts.

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Section: Flow Factorssupporting

confidence: 84%

About the change of flow factors during the run-in process of lubricated contacts

Holzer

Schmitz

2021

ILT

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“…However, there are several challenges (computational cost, solution schemes, discretization of Couette term, density derivatives, numerical stability, etc.,) in employing deterministic models, which researchers are dealing with in different ways (Wang et al, 2020). Apart from the Patir and Cheng (Patir and Cheng, 1978) average flow model, the homogenization method (Bayada and Chambat, 1988) which also is a kind of averaging method, have received much attention due to its accurate averaging results and applicability for arbitrary oriented rough surfaces (Rom et al, 2021). Different forms of the homogenized Reynold's equations were derived to study both the stationary and transient lubricated contact problems (Bayada and Faure, 1989;Bayada et al, 2005;Almqvist and Dasht, 2006;Almqvist et al, 2007;Almqvist et al, 2011;Almqvist et al, 2012;Fatu et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Different forms of the homogenized Reynold's equations were derived to study both the stationary and transient lubricated contact problems (Bayada and Faure, 1989;Bayada et al, 2005;Almqvist and Dasht, 2006;Almqvist et al, 2007;Almqvist et al, 2011;Almqvist et al, 2012;Fatu et al, 2012). Unlike the Patir and Cheng average flow model (Patir and Cheng, 1978), the method of homogenization is not commonly used in tribology (Rom et al, 2021). In the past, the homogenized Reynold's equation was used to study surface roughness and texture effects in conformal contacts (Bayada et al, 2005;Sahlin et al, 2010;Rom et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Unlike the Patir and Cheng average flow model (Patir and Cheng, 1978), the method of homogenization is not commonly used in tribology (Rom et al, 2021). In the past, the homogenized Reynold's equation was used to study surface roughness and texture effects in conformal contacts (Bayada et al, 2005;Sahlin et al, 2010;Rom et al, 2021). Recently, the method has been employed in non-conformal contacts to study micro-EHL, and for the predicting the coefficient of friction in the ML regime (Hugo et al, 2019;Hansen et al, 2020;Hansen et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

An assessment of the effect of surface topography on coefficient of friction for lubricated non-conformal contacts

Prajapati,

Hansen,

Björling

2024

Front. Mech. Eng.

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Determining an accurate state of lubrication is of utmost importance for the precise functionality of machine elements and to achieve elongated life and durability. In this work, a homogenized mixed-lubrication model is developed to study the effect of surface topographies on the coefficient of friction. Various measured real surface topographies are integrated in the model using the roughness homogenization method. The shear-thinning behavior of the lubricant is incorporated by employing the Eyring constitutive relation. Several Stribeck curves are generated to analyze the effect of roughness lays and root mean square (RMS) roughness on the coefficient of friction. The homogenized mixed lubrication model is validated against experimental rolling/sliding ball-on-disc results, and a good agreement between simulated and experimental coefficient of friction is found.

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“…Homogenization techniques have received more attention in recent years than flow factor modifiers with the works of, among others, de Boer et al [21,22], de Boer and Almqvist [23], and Han et al [24]. In Rom et al [25], the reader can find the homogenization advantages that explain its greater development. However, flow factor modifiers seem to be more widely used to date, such as in [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Full and Hybrid Multiscale Lubrication Modeling

Francisco

Brunetière

2022

Lubricants

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The numerical solution for the lubrication of parallel rough surfaces cannot be obtained using the well-known flow factors of Patir and Cheng. Nor can it be determined using homogenization techniques. Is there an alternative, besides a purely long-term deterministic way of solving the problem? The present paper aims at proposing a multiscale approach in order to reduce the computing time, specific to deterministic resolutions, while maintaining good accuracy. The configuration is a parallel rough surface slider, with imposed hydrodynamic operating conditions. The domain consists of independent macro-elements, on which the Reynolds equation is solved. Then, the macro-element boundaries are adjusted to ensure global mass conservation. In its hybrid version, the algorithm replaces some well-chosen macro-elements by simple linear finite elements. The results clearly show the potential of our method. Because the lubrication of each macro-element can be processed independently, the multicore architecture of the processor is exploited. Even if the performance depends on the ratio roughness/height, the computing time is half than for the classical deterministic method, with a few percent errors. The work concludes with some recommendations on the configurations for which the multiscale method is best suited, such as surfaces with short correlation lengths.

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Why homogenization should be the averaging method of choice in hydrodynamic lubrication

Cited by 8 publications

References 24 publications

About the change of flow factors during the run-in process of lubricated contacts

About the change of flow factors during the run-in process of lubricated contacts

An assessment of the effect of surface topography on coefficient of friction for lubricated non-conformal contacts

Full and Hybrid Multiscale Lubrication Modeling

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