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Multiskalenansatz mit Mikrostrukturanalyse zur Drallbeurteilung von Dichtungsgegenlaufflächen: Dissertation

. Institutsbericht (2011)434.

Abstract

The sealing of rotating shafts by means of radial lip seals (RLS) against the environment is essential and a challenge for the engineering. The failure of a small and relatively inexpensive sealing element can provide an immense material damage. A growing environmental consciousness results in increasing requirements for the engaged sealing systems. Leakage, tolerated 20 years ago, is in now intolerable. The radial lip seal is part of a tribology system. This system includes the sealed fluid, the sealing counter surface and the radial lip seal. All system partners affect the goodness of sealing, wear and friction. The sealing counter surface is one of the most important partners in this system. It has to be neutral in fluid transport capability. Microstructures (Twist) on the surface cause an axial fluid transport against the direction of rotation. This leads to sealing system failure. The standard manufacturing method for sealing counter surface is twist free grinding. However, this standard process could also fail. The quality control of twist is hard to handle. Twist can be divided into macro‐ and microtwist. The standard roughness parameters like Ra or Rz are unsuitable for an adequate functional characterisation of twist. There are special twist measurement methods like the hairline method or the CARMEN‐analysis. But they have some weak points. The focus of these measurement methods is macrotwist or they afford only a quantitative view on twist. In the today’s industrial practice, you might faith in the goodness of the manufacturing process and on the recommended roughness parameters. The fine microtwist is mainly not observed. But this microstructures raise leakage in the sealing systems. Investigations at institute of machine components (IMA) at university of Stuttgart demonstrated this clearly. Such microstructures have a clear pumping ability. But there are no applicable measurement methods for this. The intention of this work was to develop a method for analysing the sealing counter surface for microtwist. In this work a method for measuring and analysing microstructures on sealing counter surfaces has been developed. New parameters for the characterisation of microtwist are established. Some examples showed that this analysis method is able to do a better characterisation of microtwist. An integral analysis of twist is possible in combination with the existing twist measurement methods. For this a procedure plan was developed in this work.

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