Functional Surfaces

  Surface Texturing for Tribology Optimization Copyright: © IBF

The surfaces of tools, semi-finished products and final goods play an essential role in fulfilling technical functions, e.g. with regard to tribology, flow behaviour and coatability.

The research topics embedded in this cross-sectional area are assigned to different research groups and are presented below.

 
 

Investigation of Skin-Pass Rolling With a Focus on Surface

Skizze des Nachwalzprozesses mit mill finish und EDT Oberfläche

An important characteristic of rolled aluminium strips for use in the automotive outer skin is the surface quality. The topography of the surface and in particular the number of roughness peaks as well as the volume of closed lubrication pockets influence the success of the subsequent process steps deep drawing and painting.
The work carried out so far has investigated the relationship between the process kinematics of skin-pass rolling and the transfer mechanisms. For this purpose, the kinematics of a process model of flat rolling was transferred to a mesomodel to describe the surface imprinting. With regard to the imprinting of the surface, a good correspondence between simulation and experiment could be shown.
In the medium term, the numerical model is intended to enable a knowledge-based design of the skin-pass process for aluminium alloys, taking into account global and local influences.

For further information, please contact Angela Quadfasel.


Image: Sketch of the skin-pass process with mill finish and EDT surface, Copyright: IBF
 
Simulation of Surface Indentation at Aluminium Skin-Pass Rolling
Simulation of surface indentation at aluminium skin-pass rolling
 
 
 

Efficient Machine Elements

Strukturierte Wellenhülse mit vergrößertem Ausschnitt der Struktur

Specially designed surfaces can reduce the coefficient of friction and shift hydrodynamic lubrication to lower rotational speeds and thus increase the efficiency of bearings. In this regard hemispherical surface structures with a depth and a diameter of 50 µm act as pockets for the lubricant and can store abrasive particles. Additionally, channel-like structures can guide lubricant to the tribological contact zone. The IBF has developed forming operations to manufacture such structures in collaboration with the Chair of Functional Materials, Universität des Saarlandes. The application of these structures on slide and roller bearings showed the beneficial tribological properties successfully.

For further information, please contact Conrad Liebsch.


Image: Structured shaft with magnified structure feature, Copyright: IBF
 
 

Riblet Rolling

Mit Riblets strukturiertes Aluminiumblech

Riblet rolling is an innovative and newly developed rolling process to manufacture so-called riblet surfaces from ductile metallic materials. A riblet surface consists of small microscopic grooves in the range of 50 µm in rolling direction and is inspired by the skin of sharks. When positioned in flow direction a riblet surface can reduce the frictional drag by approx. 5 %. In addition, a riblet surface has an enlarged surface area, which compared to a normal flat surface, can have certain advantages in terms of thermodynamic or tribological use. The aim of the riblet rolling process is to produce large quantities of durable metallic riblet surfaces in a cost-efficient manner and on a large scale.
To manufacture a riblet surface a work roll is structured using the “MicroWind” process. This creates a negative imprint on the work roll, which is transferred into the rolling stock during rolling. In one single pass the structure is imprinted into the rolling stock.

For further information, please contact Conrad Liebsch.


Image: Aluminium sheet with riblet structure, Copyright: IBF
 
 

Finite-Element Based Estimation of the Lifespan of Wear-Resistant Coating for Cold Rolling

TriboSim_Kaltwalzen

For cold rolling of steel, due to large plastic deformation, the periodic mechanical stress on work rolls is quite significant and often causes severe wear, which terminates the production and reduces the efficiency. To increase the lifespan of the work rolls, wear-resistant coatings are applied. However, the lifespan of work rolls with a specific coating category and thickness cannot be scientifically estimated, which causes difficulties in the coating selection and application for other forming technologies. In this project, multi-scale FE models are used to estimate the lifespan of coatings. In macro model the kinematics and stress in roll gap are simulated and afterwards transferred to a meso model as boundary conditions. In the meso model, the coating behaviour can be simulated using a bonding model under realistic forming condition as in the roll gap.

For further information, please contact Zhao Liu.


Image: Multiscale FE model for simulating coating behaviour during cold rolling, Copyright: IBF