Numerische und versuchstechnische Beurteilung geschmierter Kontakte inhomogener Werkstoffe

Translated title of the contribution: Numerical and experimental investigation of lubricated contacts of heterogeneous materials

Herbert Krampl

Research output: ThesisDoctoral Thesis


To meet the extensive requirements on operating behaviour and fatigue life of materials in tribological applications, materials of heterogeneous type are often used. Joining the properties of several components, an optimized tribomaterial for use in the respective application is formed. The design of tribological lubricated contacts is still mostly based on experienced data and tribometric results. A combinatory method consisting of tribometric and numeric tools means an improvement of the process chain for the design of lubricated contacts. The present work deals with the combination of tribometric and numeric methods for the characterization of lubricated contacts related to local loadings and minimization of friction losses. For the metrological achievement of the coefficient of friction (COF) at selected operating parameters in lubricated contacts, a two disc test cell was designed. This allows a high-precision measurement of friction forces in disc contacts as well as the achievement of a contact potential (CP) between the disc samples. Giving a measure for the surface separation, the CP is used to estimate the lubrication regime existent in the lubricating gap. The numerical investigation of conformal and non conformal lubricated contacts is carried out with the finite element software COMSOL Multiphysics in the course of this work. For the consideration of heterogeneous material properties in these investigations, a method was developed. Based on microscopy as well as artificial phase distributions, the method allows an investigation of local stress concentrations in materials for tribological applications. A just as important as for the trend of reducing performance losses ongoing topic concerning lubricated contacts is the calculation of the COF. For the numerical treatment, common lubricant yield models are used to mimic the rheological properties. For a precise achievement of the COF in two disc contacts, the developed test rig has proven to provide reproducable as well as reliable results. From the measured data achieved, characteristic tendencies of the COF in dependency on slide to roll ratio, oil entry temperature, contact pressure and rotational frequency were derived. The built-up numerical models for the journal bearing and the two disc contact allow a detailed investigation of the lubricating film parameters such as pressure, temperature rise due to fluid friction, shear stress (COF) and lubricating gap geometry. Using the developed methodology for the consideration of heterogeneous material properties, the local stress concentrations as well as their affects on the build-up of lubricating films in the investigated contacts were achieved with high efficiency.
Translated title of the contributionNumerical and experimental investigation of lubricated contacts of heterogeneous materials
Original languageGerman
  • Brand, Clemens, Assessor B (internal)
  • Grün, Florian, Assessor A (internal)
  • Godor, Istvan, Co-Supervisor (internal)
Publication statusPublished - 2012

Bibliographical note

no embargo


  • heterogeneous
  • tribomaterials
  • lubricating film calculation
  • numerical assessment of coefficient of friction

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