Browsing by Subject "Texture design"

Now showing 1 - 4 of 4

Open Access
Homogenization-based design of surface textures in hydrodynamic lubrication
(John Wiley and Sons Ltd, 2016) Waseem, A.; Temizer, İ.; Kato, J.; Terada, K.
An optimization framework is developed for surface texture design in hydrodynamic lubrication. The microscopic model of the lubrication interface is based on the Reynolds equation, and the macroscopic response is characterized through homogenization. The microscale setting assumes a unilateral periodic texture but implicitly accounts for the bilateral motion of the surfaces. The surface texture in a unit cell is described indirectly through the film thickness, which is allowed to vary between prescribed minimum and maximum values according to a morphology variable distribution that is obtained through the filtering of a design variable. The design and morphology variables are discretized using either element-wise constant values or through first-order elements. In addition to sharp textures, which are characterized by pillars and holes that induce sudden transitions between extreme film thickness values, the framework can also attain a variety of non-standard smoothly varying surface textures with a macroscopically isotropic or anisotropic response. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.
Open Access
Homogenization-based microscopic texture design and optimization in hydrodynamic lubrication
(2016-08) Waseem, Abdullah
The aim of this thesis is to develop an optimization framework for the texture optimization in hydrodynamic lubrication using multi-scale homogenization technique. In hydrodynamic lubrication the asperities do not come into contact due to fluid film present between the surfaces and normal load is carried by the viscous fluid. The Reynolds equation can be used with confidence for such problems. For two-scale separation, a basis for optimizing the surface textures is established through an asymptotic expansion based homogenization scheme, which delivers a macroscopic Reynolds equation containing homogenized coefficients. These homogenized coefficients depend on the fluid film thickness directly and by controlling these coefficients a desired macroscopic response can be obtained. Design variables are introduced to control the fluid film thickness indirectly through an intermediate filtering stage. Both microscopic and macroscopic objectives are defined for texture optimization. The quality of the designed textures are evaluated numerically as well as aesthetically and optimization parameters are selected accordingly. Isotropic and anisotropic textures can be designed by using the proposed optimization scheme. For both microscopic and macroscopic objectives optimization surface textures are reconstructed as a sanity check. Texture optimization for prescribed load bearing capacity and maximum load bearing capacity in temporal and spatial variations are then carried out for squeeze film flow and wedge problem, respectively. Finally, to reduce the computational cost, Taylor’s expansion is proposed for the optimization problem. Overall, the methodology developed in this thesis froms a basis for a comprehensive micro-texture design framework for computational tribology.
Open Access
Micro-texture design and optimization in hydrodynamic lubrication via two-scale analysis
(Springer Verlag, 2017) Waseem, A.; Temizer, İ.; Kato, J.; Terada, K.
A novel computational surface engineering framework is developed to design micro-textures which can optimize the macroscopic response of hydrodynamically lubricated interfaces. All macroscopic objectives are formulated and analyzed within a homogenization-based two-scale setting and the micro-texture design is achieved through topology optimization schemes. Two non-standard aspects of this multiscale optimization problem, namely the temporal and spatial variations in the homogenized response of the micro-texture, are individually addressed. Extensive numerical investigations demonstrate the ability of the framework to deliver optimal micro-texture designs as well as the influence of major problem parameters. © 2017, Springer-Verlag Berlin Heidelberg.
Open Access
Microscopic design and optimization of hydrodynamically lubricated dissipative interfaces
(John Wiley & Sons, Ltd., 2019) Çakal, Berkay Alp; Temizer, İlker; Terada, K.; Kato, J.
A homogenization‐based topology optimization framework is developed, which can endow hydrodynamically lubricated interfaces with a micro‐texture, to achieve optimal macroscopic responses by addressing both dissipative and nondissipative physics at the interface. With respect to the homogenization aspects of the problem, the thermodynamic consistency of the two‐scale formulation is explicitly analyzed and verified. With respect to the topology optimization aspects, a variational approach to sensitivity analysis is pursued. Subsequently, these are employed in micro‐texture design studies, which address microscopic and macroscopic objectives. The influence of dissipation on the optimization results is demonstrated through extensive numerical investigations, which also highlight the importance of working in a sufficiently flexible design space that can deliver nearly optimal micro‐texture geometries.