Der Einflu� von Druck und Temperatur auf die effektive Viskosit�t in geschmierten kontra-formen Kontakten

Ehlert, J.; Bartz, W. J.

doi:10.1007/bf01517228

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…Instead of a phenomenological SLS with the well known bulk modulus of the kind: (5) (N gives the number of particles and c defines a parameter connected with the volume of an individual particle) and a subsequent Young's modulus time dependency like we have a resulting phenomenological Young's modulus structure of the form: (6) With a known principle structure for the temperature distribution function deduced from the shear stress distribution (adiabatic approach) such an approach seems to be manageable by the means of iterations. With a typical dependency for the temperature dependent relaxation time like [37,38]: (7) (with a constant W A and the T = T 0 -viscosity η 0 and the Boltzmann-constant k B ) one can evaluate the mechanical contact situations applying the techniques elaborated in [2] (theory part II) under the assumption of completely adiabatic temperature fields resulting from shear and completely following the second stress invariant distribution. Please note, the positive sign in the exponential function for the relaxation time assuring decreasing viscosity η with increasing temperature.…”

Section: First Principle Based Interatomic Potential Description Of Mmentioning

confidence: 99%

Completely Analytical Tools for the Next Generation of Surface and Coating Optimization

Schwarzer¹

2014

Coatings

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Usually, some severe efforts are required to obtain tribological parameters like Archard's wear depth parameter k d . Complex tribological experiments have to be performed and analyzed. The paper features an approach where such parameters are extracted from effective interaction potentials in combination with more physical-oriented measurements, such as Nanoindentation and physical scratch. Thereby, the effective potentials are built up and fed from such tests. By using effective material potentials one can derive critical loading situations leading to failure (decomposition strength) for any contact situation. A subsequent connection of these decomposition or failure states with the corresponding stress or strain distributions allows the development of rather comprehensive tribological parameter models, applicable in wear and fatigue simulations, as demonstrated in this work. From this, a new relatively general wear model has been developed on the basis of the effective indenter concept by using the extended Hertzian approach for a great variety of loading situations. The models do not only allow to analyze certain tribological experiments, such as the well known pin-on disk test or the more recently developed nano-fretting test, but also to forward simulate such tests and even give hints for structured optimization or result in better component life-time prediction. The work will show how the procedure has to be applied in general and a small selection of practical examples will be presented.

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Section: First Principle Based Interatomic Potential Description Of Mmentioning

confidence: 99%

Completely Analytical Tools for the Next Generation of Surface and Coating Optimization

Schwarzer¹

2014

Coatings

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“…When smooth walled capillary or rotational rheometers are applied, this effect causes that the measured viscosities do not correspond to that of bulk material (too low viscosities are measured). The postulation by Jastrzebski [1] that the slip velocity mainly depends on the wall shear stress is generally accepted, although Ehlert et al state that the wall normal pressure has an additional influence [2].…”

Section: Introductionmentioning

confidence: 99%

Wall Slip Effect in Couette Rheometers

Harboe

Modigell

Pola

2012

SSP

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Wall slip of suspensions in confined flow is caused by segregation of a thin layer of liquid phase adjacent to the walls. This causes the bulk phase to slide along the walls, which means that the fluid flow velocities respective to the walls are not zero. In rheometers this affects the evaluation of the rheological properties. Despite the importance of understanding and controlling segregation effects, little research has been done on this subject area. Indeed in industrial casting, the die filling behaviour, and therefore the product quality, may depend on the segregation phenomena. It is important to understand the wall slip phenomenon’s correlation with experimental parameters, as a step towards casting process optimization. Two issues are handled in the present work, the first is the evaluation of different methods to investigate the wall slip effect, the second is the investigation of the wall slip effect dependency on the suspension parameters particle size and solid fraction, respectively. The suspensions employed for the investigations were the aluminium alloy A356 in semi-solid form and a “synthetic suspension” built up of glass spheres in silicon oil. As a result of the above described investigations, influence of suspension parameters are found, and a validated method to avoid the wall slip effect is suggested.

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Scale Invariant Mechanical Surface Optimization

Schwarzer

2017

Applied Nanoindentation in Advanced Materials

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Der Einflu� von Druck und Temperatur auf die effektive Viskosit�t in geschmierten kontra-formen Kontakten

Cited by 5 publications

References 2 publications

Completely Analytical Tools for the Next Generation of Surface and Coating Optimization

Completely Analytical Tools for the Next Generation of Surface and Coating Optimization

Wall Slip Effect in Couette Rheometers

Scale Invariant Mechanical Surface Optimization

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