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Li, Jinxia
Publications (10 of 26) Show all publications
Westerberg, L.-G., Höglund, E., Li, J., Lugt, P. & Baart, P. (2016). Free-Surface Flow of Lubricating Greases (ed.). Paper presented at STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016. Paper presented at STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016.
Open this publication in new window or tab >>Free-Surface Flow of Lubricating Greases
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2016 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Grease lubrication is traditionally used in a great variety of mechanicalsystems such as rolling bearings, seals, and gears where it has beenshown more advantageous than oil, mainly due to its consistencyallowing the grease to stay inside the system and not leak out. Freesurface effects play an important role in rolling bearings and opengears as the configuration normally is filled with about 30% grease toavoid heavy churning. In this study an analytical model of thestationary uniform flow on a rotating disc is developed and validatedwith experiments. The model results in the velocity profile for the flowin the thin fully yielded viscous layer in connection to the surface aswell as an expression for the plug flow region on top of the viscouslayer. Experiments with two different greases having NLGI grade 1 and2 respectively shows it is possible to obtain a good fit with theanalytically obtained thickness using the rheological parameters foractual greases.

National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-34367 (URN)88a90512-6d63-4b60-9022-f0ea3070e1ba (Local ID)88a90512-6d63-4b60-9022-f0ea3070e1ba (Archive number)88a90512-6d63-4b60-9022-f0ea3070e1ba (OAI)
Conference
STLE Annual Meeting & Exhibition : 15/05/2016 - 19/05/2016
Note
Godkänd; 2016; 20160825 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-09Bibliographically approved
Westerberg, L.-G., Li, J., Höglund, E., Lugt, P. & Baart, P. (2015). Free-surface grease flow: influence of surface roughness and temperature (ed.). Paper presented at . Tribology letters, 59(1), Article ID 18.
Open this publication in new window or tab >>Free-surface grease flow: influence of surface roughness and temperature
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2015 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 59, no 1, article id 18Article in journal (Refereed) Published
Abstract [en]

Grease flow in grease lubricated systems can often be qualified as free-surface flow. It occurs for example in rolling bearings after the churning phase or on open gears. Here only a fraction of the bearing or gearbox volume is filled with grease. Part of the grease is flowing in relatively thin layers induced by centrifugal forces caused by rotation of the various components. In this paper a model problem is investigated in the form of a free-surface flow of grease on a rotating disc. Experiments have been performed where the onset of flow and remaining grease have been studied varying the surface roughness, temperature and the centrifugal forces. The experiments have been coupled to analytical models describing the flow and temperature distribution in the grease. It was found that the impact of surface roughness could be neglected. The flow is determined by the centrifugal forces and rheology of the grease. Temperature effects the rheology but also the oil separation creating low shear strength/low viscosity layers at the surface.

National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-8807 (URN)10.1007/s11249-015-0537-y (DOI)000356539000018 ()2-s2.0-84930656362 (Scopus ID)75ade837-7eab-45d5-9ec4-9cb64e09e705 (Local ID)75ade837-7eab-45d5-9ec4-9cb64e09e705 (Archive number)75ade837-7eab-45d5-9ec4-9cb64e09e705 (OAI)
Note
Validerad; 2015; Nivå 2; Bibliografisk uppgift: This article is part of the Topical Collection on STLE Tribology Frontiers Conference 2014; 20150414 (lgwe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Westerberg, L.-G., Farré-Lladós, J., Li, J., Höglund, E. & Casals-Terré, J. (2015). Grease flow in an elbow channel (ed.). Tribology letters, 57(3), Article ID 30.
Open this publication in new window or tab >>Grease flow in an elbow channel
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2015 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 57, no 3, article id 30Article in journal (Refereed) Published
Abstract [en]

The flow of lubricating greases in an elbow channel has been modeled and validated with velocity profiles from flow visualizations using micro-particle image velocimetry. The elbow geometry induces a nonsymmetric distribution of shear stress throughout its cross section, as well as varying shear rates through the transition from the elbow inlet to the outlet. The flow has been modeled both for higher flow rates and for creep flow. The influence of the grease rheology and flow conditions to wall slip, shear banding and an observed stick–slip type of motion observed for low flow rates are presented. The effect on the flow of the applied pressure is also modeled showing that the flow is sensitive to the pressure in the angular ( ϕ ) direction of the elbow. For high pressures, it is shown that the flow is reversed adjacent to the elbow walls.

National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-11713 (URN)10.1007/s11249-015-0469-6 (DOI)000351050800016 ()2-s2.0-84924865257 (Scopus ID)ab81f40f-f721-47b7-960d-a2a86f41f90b (Local ID)ab81f40f-f721-47b7-960d-a2a86f41f90b (Archive number)ab81f40f-f721-47b7-960d-a2a86f41f90b (OAI)
Note

Validerad; 2015; Nivå 2; 20140331 (lgwe)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Li, J., Westerberg, L.-G., Höglund, E., Lugt, P. & Baart, P. (2015). Lubricating Grease Shear Flow and Boundary Layers in a Concentric Cylinder Configuration (ed.). Paper presented at STLE Annual Meeting & Exhibition : 17/05/2015 - 21/05/2015. Paper presented at STLE Annual Meeting & Exhibition : 17/05/2015 - 21/05/2015.
Open this publication in new window or tab >>Lubricating Grease Shear Flow and Boundary Layers in a Concentric Cylinder Configuration
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2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study, grease flow is visualized using micro Particle Image Velocimetry (μPIV). The experimental setup includes a concentric cylinder configuration with a rotating shaft to simulate the grease flow in a double restriction seal geometry with two different grease pocket sizes. It is shown that the grease is partially yielded in the large grease pocket geometry and fully yielded in the small grease pocket. For the small grease pocket, it is shown that three distinct grease flow layers are present: a high shear rate region close to the stationary wall, a bulk flow layer, and a high shear rate boundary region near the rotating shaft. The grease shear thinning behavior and its wall slip effects have been identified. The μPIV experimental results have been compared with a numerical model for both the large and small gap size. It is shown that the flow is close to one-dimensional in the center of the small pocket. A one-dimensional analytical model based on the Herschel-Bulkley rheology model has been developed, showing good agreement with the measured velocity profiles in the small grease pocket. Furthermore, wall slip effects and shear banding are observed, where the latter imply that using the assumption of uniform shear in conventional concentric cylinder rheometers may result in erroneous rheological results.

National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-40719 (URN)ff4b02dd-4b8b-4e98-ba12-cb157c52ba19 (Local ID)ff4b02dd-4b8b-4e98-ba12-cb157c52ba19 (Archive number)ff4b02dd-4b8b-4e98-ba12-cb157c52ba19 (OAI)
Conference
STLE Annual Meeting & Exhibition : 17/05/2015 - 21/05/2015
Note
Godkänd; 2015; 20150602 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-03-09Bibliographically approved
Li, J., Höglund, E., Westerberg, L.-G. & Zhmud, B. (2015). Rheology of Lubricating Grease (ed.). Paper presented at . Lube Magazine, 126, 12-18
Open this publication in new window or tab >>Rheology of Lubricating Grease
2015 (English)In: Lube Magazine, ISSN 1744-5418, Vol. 126, p. 12-18Article in journal (Refereed) Published
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-10857 (URN)9bbdbcf8-2b73-48e0-b2e3-4b902baec6aa (Local ID)9bbdbcf8-2b73-48e0-b2e3-4b902baec6aa (Archive number)9bbdbcf8-2b73-48e0-b2e3-4b902baec6aa (OAI)
Note
Godkänd; 2015; 20150410 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-03-09Bibliographically approved
Li, J., Westerberg, L.-G., Höglund, E. & Lundström, T. S. (2014). Design of test rig for visualizations of cylindrical shear and pressure driven Couette flow using μPIV (ed.). Paper presented at International Conference on Experimental Fluid Mechanics : 12/08/2014 - 15/08/2014. Paper presented at International Conference on Experimental Fluid Mechanics : 12/08/2014 - 15/08/2014.
Open this publication in new window or tab >>Design of test rig for visualizations of cylindrical shear and pressure driven Couette flow using μPIV
2014 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Couette flow is often encountered in concentric cylinder application such as rheometers etc. Being able to visualize such flows is of interest both from a fundamental point of view to understand the dynamics of complex fluids, but also in specific applications such as lubricants flowing through seal geometries. In this study a concentric cylinder test rig has been designed to visualize Couette flow in both radial and axial direction using micro Particle Image Velocimetry. The rig allows for control of the flow motion; the rotating inner cylinder creates a peripheral flow and an applied pressure in the axial direction creates a pressure driven flow. Thus, a single flow direction or a combination of directions can be analyzed. To demonstrate the technique a flow of a non-Newtonian shear thinning fluid in the form of lubricating grease was investigated and discussed. It is found that it is possible to capture the yield behavior of the grease, with regions of fully and partially yielded flow visible. The influence of temperature creep flow is also presented. Grease with both high and low yield stress are measured and compared could be measured and compared in a pocket with variable size. Furthermore, non-homogeneous effects such as shear banding and wall slip can be visualized. The test rig has thus a high potential to investigate the influence of wall material and wettability between fluids and the housing on the flow and wall slip behavior as long as the fluid is optically transparent.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-28218 (URN)1f1671f6-0162-41b1-8e5a-9068ded9c6ad (Local ID)1f1671f6-0162-41b1-8e5a-9068ded9c6ad (Archive number)1f1671f6-0162-41b1-8e5a-9068ded9c6ad (OAI)
Conference
International Conference on Experimental Fluid Mechanics : 12/08/2014 - 15/08/2014
Note
Godkänd; 2014; 20140926 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-09Bibliographically approved
Li, J., Westerberg, L.-G., Höglund, E., Baart, P. & Lugt, P. (2014). Experimental study of free surface grease flow subjected to centrifugal forces (ed.). Paper presented at Nordic Symposium on Tribology : 10/06/2014 - 13/06/2014. Paper presented at Nordic Symposium on Tribology : 10/06/2014 - 13/06/2014.
Open this publication in new window or tab >>Experimental study of free surface grease flow subjected to centrifugal forces
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2014 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

In order to improve the understanding of grease flow in various applications such as gears, seals and rolling bearings, the free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease was subjected to a centrifugal force. The grease flow and mass loss was measured for greases with different rheology on different surfaces and with surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type and yield stress, while the impact of the surface material and roughness is less pronounced. The mass loss is shown to be influenced both by the rheology of the grease and the surface material

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Fluid Mechanics and Acoustics
Research subject
Machine Elements; Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-37478 (URN)b866aeae-26f3-4d8c-9fed-d5678698efc5 (Local ID)b866aeae-26f3-4d8c-9fed-d5678698efc5 (Archive number)b866aeae-26f3-4d8c-9fed-d5678698efc5 (OAI)
Conference
Nordic Symposium on Tribology : 10/06/2014 - 13/06/2014
Note
Godkänd; 2014; 20140618 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-06-11Bibliographically approved
Westerberg, L.-G. & Li, J. (2014). Free surface Herschel-Bulkley flow on a rotating disc with application to lubricating greases (ed.). Paper presented at European Fluid Mechanics Conference : 14/09/2014 - 18/09/2014. Paper presented at European Fluid Mechanics Conference : 14/09/2014 - 18/09/2014.
Open this publication in new window or tab >>Free surface Herschel-Bulkley flow on a rotating disc with application to lubricating greases
2014 (English)Conference paper, Oral presentation only (Refereed)
National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-40070 (URN)f0ce83ee-098f-42cf-89ab-fab163bd77c1 (Local ID)f0ce83ee-098f-42cf-89ab-fab163bd77c1 (Archive number)f0ce83ee-098f-42cf-89ab-fab163bd77c1 (OAI)
Conference
European Fluid Mechanics Conference : 14/09/2014 - 18/09/2014
Note
Godkänd; 2014; 20140923 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-01-14Bibliographically approved
Westerberg, L.-G., Li, J., Höglund, E., Lugt, P. & Baart, P. (2014). Free-surface grease flow on a rotating plate (ed.). Paper presented at . Tribology letters, 56(2), 317-325
Open this publication in new window or tab >>Free-surface grease flow on a rotating plate
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2014 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 56, no 2, p. 317-325Article in journal (Refereed) Published
Abstract [en]

Grease lubrication is traditionally used in a great variety of mechanical systems such as rolling bearings, seals, and gears where it has been shown more advantageous than oil, mainly due to its consistency allowing the grease to stay inside the system and not leak out. Knowledge of the flow dynamics of grease is important for the understanding and prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. Free-surface effects play an important role in rolling bearings and open gears as the configuration normally is filled with about 30 % grease to avoid heavy churning. In this study, an analytical model of the stationary uniform flow on a rotating disc is developed and validated with experiments. The model results in the velocity profile for the flow in the thin fully yielded viscous layer in connection to the surface as well as an expression for the plug flow region on top of the viscous layer. Furthermore, the depth-averaged velocity is derived as is the shear stress value on the plate. From the latter, follows a condition for the grease to start moving and in turn yielding an expression for the viscous layer thickness as a function of the grease yield stress value, grease density, angular velocity, and radial position. In addition, an expression of the layer thickness containing the ratio between the flow rate and the layer width which in turn can account for effects not included in the model such as wall slip and surface adhesion and thus add another degree of freedom into the model. Experiments with two different greases having NLGI grade 1 and 2, respectively, shows it is possible to obtain a good fit with the analytically obtained thickness using the rheological parameters for actual greases.

National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-15967 (URN)10.1007/s11249-014-0411-3 (DOI)000344612900014 ()2-s2.0-84925532980 (Scopus ID)f8d7807a-34ee-4614-8f55-56dda6554617 (Local ID)f8d7807a-34ee-4614-8f55-56dda6554617 (Archive number)f8d7807a-34ee-4614-8f55-56dda6554617 (OAI)
Note
Validerad; 2014; 20140331 (lgwe)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Westerberg, L.-G., Farré-Lladós, J., Li, J., Höglund, E. & Casals-Terré, J. (2014). Grease flow in elbow channel (ed.). In: (Ed.), (Ed.), Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014: . Paper presented at STLE Annual Meeting & Exhibition : 18/05/2014 - 22/05/2014 (pp. 398-400). : Society of Tribologists and Lubrication Engineers, 1
Open this publication in new window or tab >>Grease flow in elbow channel
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2014 (English)In: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014, Society of Tribologists and Lubrication Engineers , 2014, Vol. 1, p. 398-400Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Society of Tribologists and Lubrication Engineers, 2014
National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Fluid Mechanics; Machine Elements
Identifiers
urn:nbn:se:ltu:diva-35563 (URN)a22e85d7-10fe-4d0e-9c52-0fa94f84c62a (Local ID)9781634391351 (ISBN)a22e85d7-10fe-4d0e-9c52-0fa94f84c62a (Archive number)a22e85d7-10fe-4d0e-9c52-0fa94f84c62a (OAI)
Conference
STLE Annual Meeting & Exhibition : 18/05/2014 - 22/05/2014
Note
Godkänd; 2014; 20140929 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-09Bibliographically approved
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