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- Almqvist, Andreas, et al.
(författare)
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A new approach for studying cavitation in lubrication
- 2014
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Ingår i: Journal of tribology. - : ASME International. - 0742-4787 .- 1528-8897. ; 136:1
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Tidskriftsartikel (refereegranskat)abstract
- The underlying theory, in this paper, is based on clear physical arguments related to conservation of mass flow and considers both incompressible and compressible fluids. The result of the mathematical modeling is a system of equations with two unknowns, which are related to the hydrodynamic pressure and the degree of saturation of the fluid. Discretization of the system leads to a linear complementarity problem (LCP), which easily can be solved numerically with readily available standard methods and an implementation of a model problem in matlab code is made available for the reader of the paper. The model and the associated numerical solution method have significant advantages over today's most frequently used cavitation algorithms, which are based on Elrod-Adams pioneering work
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| 2. |
- Almqvist, Andreas, et al.
(författare)
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An Abbott curve based rough surface contact mechanics approach
- 2005
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Ingår i: Proceedings of the World Tribology Congress III - 2005. - New York : American Society of Mechanical Engineers. ; , s. 397-398
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Konferensbidrag (refereegranskat)abstract
- In this way all the height information of the surface profile is preserved and not only a few parameters, like Ra, Rq, Rz, Rsk, etc. The aim of this work is to investigate how classes of surfaces based on a single Abbott curve perform in terms of contact mechanical parameters like the real area of contact. The result shows that surfaces taken from a class of random surfaces generated from a specific Abbott curve behaves similar in a contact mechanics simulation. That is, the distribution of for example the real area of contact within such a class is compact, having a small deviation from its mean.This implies that it is possible to simulate classes of surfaces based on Abbott curves and to use the results to predict contact mechanical properties of real surface topographies.
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| 3. |
- Almqvist, Andreas, et al.
(författare)
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Development of a lubrication simulation model
- 2009
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Ingår i: Svenska mekanikdagarna. - Stockholm : Svenska nationalkommittén för mekanik. ; , s. 74-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
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| 5. |
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| 6. |
- Almqvist, Andreas, et al.
(författare)
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On the dry elasto-plastic contact of nominally flat surfaces
- 2007
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 40:4, s. 574-579
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Tidskriftsartikel (refereegranskat)abstract
- A model to be used for numerical simulation of the contact of linear elastic perfectly plastic rough surfaces was developed. Energy dissipation due to plastic deformation is taken into account. Spectral theory and an FFT-techique are used to facilitate the numerical solution process. Results of simulations using four two-dimensional profiles with different topographies in contact with a rigid plane for a number loads are reported. From the results it is clear that the real area of contact (Ar) changes almost linearly with load and is only slightly affected by the difference in topography. A plasticity index is defined as the ratio of plastically deformed area (Ap) and Ar. Plastic deformation occurs even at low loads and there is a significant difference in plasticity index between the surface profiles considered. An investigation on how the spectral content of the surface profile influences the results presented is also performed. This is to ensure that the metrological limitations of the optical profilerused to measure the surfaces do not have a significant influence. It is concluded that the highest frequencies of the measured profile have a negligible influence on the real area of contact.
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| 7. |
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| 8. |
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| 9. |
- Almqvist, Andreas, et al.
(författare)
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Simulation of piston ring : cylinder liner lubrication considering layered fluid films
- 2009
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Ingår i: Tribologia : Finnish Journal of Tribology. - 0780-2285. ; 28:3-4, s. 44-58
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Tidskriftsartikel (refereegranskat)abstract
- During the operation of hydrodynamically lubricated devices a fully formulated lubricant has the ability to form layers at the surfaces. A friction modifier's task is to adjust the interaction between lubricant and the surface so that friction is lowered. An antiwear additive creates a protective layer on the surface and this definitely influence the performance of the lubricated device. To gain fundamental understanding, models that address the modified liquid - solid interaction due to the formation of layers, but also models that may be used to study the effects of layers already formed on the contacting surfaces are required. In this paper, two non-Newtonian lubricant rheology models that may be used to simulate reacted layers resembling those created by lubricant additives are adopted for the simulation of the piston ring - cylinder liner lubrication problem. The possibility of layer to layer interaction, which is likely to occur in the convex conjunction between the ring and the liner, is considered and this extends the models found in the literature. The effects induced by this type of layering are studied by using a modified Reynolds' equation where the coefficients have been corrected with factors that accounts for the layer properties. This enables, effectively, studies of layers resembling those created by lubricant additives during the operation of the lubricated conjunction between a piston ring and a cylinder liner.
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| 10. |
- Almqvist, Andreas, et al.
(författare)
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Simulation of piston ring : cylinder liner lubrication considering layered fluid films
- 2008
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Ingår i: Proceedings of the 35th Leeds-Lyon Symposium on Tribology, 2008.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the operation of hydrodynamically lubricated devices a fully formulated lubricant has the ability to form layers at the surfaces. Such layers alter the interaction between the lubricant and the surface that definitely will influence the performance of the lubricated device.To gain fundamental understanding, models that address the formation of layers and the altered liquid – solid interaction, but also models that may be used to study the effects of existing layers are required. In this paper, non-Newtonian lubricant rheology models that may be used to resemble layers of variable shear strength – wall-slip specifically – are considered for the simulation of the piston ring - cylinder liner lubrication problem.The effects induced by this type of layering are studied by using a modified Reynold’s equation where the coefficients have been corrected with factors that accounts for layer properties. This enables, effectively, studies of immobile layers as well as wall-slip in the lubricated conjunction between a piston ring and a cylinder liner.
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