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Kang, Shaojie
Publications (4 of 4) Show all publications
Kang, S., Furustig, J., Almqvist, A. & Larsson, R. (2013). A running-in model for the boundary lubricated contact (ed.). Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013. Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013.
Open this publication in new window or tab >>A running-in model for the boundary lubricated contact
2013 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

During the running-in period of a boundary lubricated contact, the surface roughness will be dramatically changed, involving large plastic deformation and wear on the asperity summits. This paper presents a running-in model. The model is based on the Boundary Element Method (BEM) and will focus on the investigation of large plastic deformations. The BEM model is based on the minimization of the complementary potential energy and deals with the contact at interfaces. The BEM model used in this paper previously adopted a linearly elastic- perfectly plastic material model and was frictionless, therefore a correction factor is needed for the model to improve its ability to account for high friction and large plastic deformation. The correction factor is made by improving the yield criterion and is derived with the assistance of the Finite Element Method (FEM). Both the friction and the strain hardening mechanism taken from the real material are implemented in the FEM model; the load and the contact area are required to match in both simulations. With the correction factor, results are promising for the current model to simulate the running-in process.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-36914 (URN)abc2b758-fe67-4e26-b3e3-f0fc429a076e (Local ID)abc2b758-fe67-4e26-b3e3-f0fc429a076e (Archive number)abc2b758-fe67-4e26-b3e3-f0fc429a076e (OAI)
Conference
International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013
Note
Godkänd; 2013; 20130815 (kang)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-01-14Bibliographically approved
Kang, S. (2013). Colliding asperities: a tribological event on micro scale (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Colliding asperities: a tribological event on micro scale
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In order to predict and optimize energy efficiency, fuel consumption and service life, friction and wear need to be predetermined with higher accuracy than what is possible today. This prediction and optimization is crucial for the development of sustainable mechanical components and systems with excellent environmental performance.Better and more reliable models for predicting friction, wear and scuffing risk in boundary lubricated contacts will be developed in this project. This includes a model for asperity-asperity collision with components of contact mechanics, thermodynamics and physics.In the boundary lubricated contact, loads are mostly carried by asperities. This makes the real area of contact is so different from the nominal contact area, a small fraction of the nominal contact area supporting the load will cause high contact stress and large deformation. Surfaces of machine components operating under high stress in long period can easily cause damage. Therefore, an elastoplastic analysis of asperity collision was conducted with the Finite Element Method. The contact area and contact stress were studied based on the change of parameters as adhesive friction coefficient, interference and collision velocity. The plastically deformed area and residual stress after collision were also depicted in figures.Friction will generate heat in the sliding contact, and eventually cause a temperature rise. Due to the heat is generated at asperities, heat flux is not continuous and the temperature both increase to a relatively high value and decrease to a small value in very short time. This kind of temperature is often called flahtemperature, and it is important to study because it can affect the viscosity of the lubricant, the formation of tribolayer and in turn it will affect the mechanical properites of the surface. The flash temperature was analyzed based on the previous study of the elastoplastic asperity collision, the times for flash temperature to reach maximum value were given and thermal expansion was also included.The FEM model can conduct a study regardless of the geometry and material properties of the surface asperity, but due to the very fine mesh required at the interface, it is not suitable to carry out an analysis of the rough surface contact. Therefore the Boundary Element Method was adopted to have a thorough study of the rough surface contact. The features of the analysis coudcuted in the FEM model, such as strain hardening and friction, should be replicable in the BEM model. In the end, an Engineering tool for the rough surface contact will be developed.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013. p. 75
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-17656 (URN)47706516-98c3-44ef-972b-ada881be1b18 (Local ID)978-91-7439-728-4 (ISBN)978-91-7439-729-1 (ISBN)47706516-98c3-44ef-972b-ada881be1b18 (Archive number)47706516-98c3-44ef-972b-ada881be1b18 (OAI)
Note
Godkänd; 2013; 20130815 (kang); Tillkännagivande licentiatseminarium 2013-09-27 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Shaojie Kang Ämne: Maskinelement/Machine Elements Uppsats: Colliding Asperities: a Tribological Event on Micro Scale Examinator: Professor Roland Larsson, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Ph.D Stefan Björklund, Kungliga Tekniska Högskolan, Stockholm Tid: Fredag den 18 oktober 2013 kl 10.00 Plats: E632, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-01-10Bibliographically approved
Kang, S., Orellana, R. F., Almqvist, A. & Jonsén, P. (2013). Deformation in silicon compressed by a steel ball (ed.). Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013. Paper presented at International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013.
Open this publication in new window or tab >>Deformation in silicon compressed by a steel ball
2013 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

Most of the studies dealing with contact mechanics are focused on the pressure and the deformation at the surfaces of the contacting bodies. However, the stress and deformation in the material underneath the actual surface are also important to study. In this work, the elastic deformations arising in a silicon block that is compressed by a steel ball is studied. More precisely, an optical metrology technique is employed to obtain the deformation in the substrate at a fixed depth. A finite element based model, is also developed in order to numerically estimate the elastic deformation of the silicon block. Moreover, the deformation and corresponding stress fields are also analysed with closed form analytical solutions. Comparisons of the results obtained from the experiments, the numerical simulations and analytical solution show that a good prediction of the deformation can be obtained by the finite element model.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Machine Elements; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-29281 (URN)2b3de021-fc96-44ba-b74b-abb498bebf11 (Local ID)2b3de021-fc96-44ba-b74b-abb498bebf11 (Archive number)2b3de021-fc96-44ba-b74b-abb498bebf11 (OAI)
Conference
International Tribology Symposium of IFToMM : 19/03/2013 - 21/03/2013
Note
Godkänd; 2013; 20130815 (kang)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-01-14Bibliographically approved
Kang, S., Almqvist, A. & Larsson, R. (2010). Two-dimensional finite element analysis of elastic-plastic deformation in asperity-asperity collision (ed.). In: (Ed.), (Ed.), 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010. Paper presented at Nordic Symposium on Tribology : 08/06/2010 - 11/06/2010. Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Two-dimensional finite element analysis of elastic-plastic deformation in asperity-asperity collision
2010 (English)In: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Conference paper, Published paper (Refereed)
Abstract [en]

The collision of cylindrical asperities is simulated by means of a commercial multiphysics software in this paper. The model combines a computational structure mechanics approach with a contact algorithm. Numerical results are first compared to classical Hertzian theory. Effects of the bulk material under the mating surfaces have been included in the simulation. Materials of top and bottom surfaces have been assigned different properties. Development of plastic deformation and friction are presented along the process of collision. Strain hardening is included in the elastic-plastic deformation. The effect of interference change and friction coefficient variation on deformation and friction has been studied. Deformed shape and subsurface residual stress in asperity are output parameters from this study.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2010
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-40193 (URN)f39748b0-834e-11df-ab16-000ea68e967b (Local ID)978-91-7439-124-4 (ISBN)f39748b0-834e-11df-ab16-000ea68e967b (Archive number)f39748b0-834e-11df-ab16-000ea68e967b (OAI)
Conference
Nordic Symposium on Tribology : 08/06/2010 - 11/06/2010
Note
Godkänd; 2010; Bibliografisk uppgift: CD-ROM; 20100629 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-01-14Bibliographically approved
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