Roughness Signature of Tribological Contact Calculated by a New Method of Peaks Curvature Radius Estimation on Fractal Surfaces

This paper proposes a new method of roughness peaks curvature radii calculation and its application to tribological contact analysis as characteristic signature of tribological contact. This method is introduced via the classical approach of the calculation of radius of asperity. In fact, the proposed approach provides a generalization to fractal profiles of the Nowicki's method [Nowicki B. Wear Vol.102, p.161-176, 1985] by introducing a fractal concept of curvature radii of surfaces, depending on the observation scale and also numerically depending on horizontal lines intercepted by the studied profile. It is then established the increasing of the dispersion of the measures of that lines with that of the corresponding radii and the dependence of calculated radii on the fractal dimension of the studied curve. Consequently, the notion of peak is mathematically reformulated. The efficiency of the proposed method was tested via simulations of fractal curves such as those described by Brownian motions. A new fractal function allowing the modelling of a large number of physical phenomena was also introduced, and one of the great applications developed in this paper consists in detecting the scale on which the measurement system introduces a smoothing artifact on the data measurement. New methodology is applied to analysis of tribological contact in metal forming process

Tribology of Machine Elements

Tribology is a branch of science that deals with machine elements and their friction, wear, and lubrication. Tribology of Machine Elements - Fundamentals and Applications presents the fundamentals of tribology, with chapters on its applications in engines, metal forming, seals, blasting, sintering, laser texture, biomaterials, and grinding

Roughness signature of tribological contact calculated by a new method of peaks curvature radius estimation on fractal surfaces

This paper proposes a new method of roughness peaks curvature radii calculation and its application to tribological contact analysis as characteristic signature of tribological contact. This method is introduced via the classical approach of the calculation of radius of asperity. In fact, the proposed approach provides a generalization to fractal profiles of the Nowicki's method [Nowicki. Wear Vol.102, p.161–176,1985] by introducing a fractal concept of curvature radii of surfaces, depending on the observation scale and also numerically depending on horizontal lines intercepted by the studied profile. It is then established the increasing of the dispersion of the measures of that lines with that of the corresponding radii and the dependence of calculated radii on the fractal dimension of the studied curve. Consequently, the notion of peak is mathematically reformulated. The efficiency of the proposed method was tested via simulations of fractal curves such as those described by Brownian motions. A new fractal function allowing the modelling of a large number of physical phenomena was also introduced, and one of the great applications developed in this paper consists in detecting the scale on which the measurement system introduces a smoothing artifact on the data measurement. New methodology is applied to analysis of tribological contact in metal forming process

Grinding and fine finishing of future automotive powertrain components

The automotive industry is undergoing a major transformation driven by regulations and a fast-paced electrification. A critical analysis of technological trends and associated requirements for major automotive powertrain components is carried out in close collaboration with industry – covering the perspectives of OEMs, suppliers, and machine builders. The main focus is to review the state of the art with regard to grinding, dressing, texturing and fine-finishing technologies. A survey of research papers and patents is accompanied by case studies that provide further insights into the production value chain. Finally, key industrial and research challenges are summarized

Adhesive Wear Phenomena in High Performance Polyaryletherketones (PAEK) Polymers

Adhesive wear is one of the most difficult types to study and is especially challenging for polymers. Such wear processes involve the mutual sticking of surface asperities followed by removal of debris from the bulk. This differs from abrasive wear in which debris is formed due to the penetration of hard rough asperities into the softer surface. Such descriptions have served the polymer tribology community for decades and are well suited for post-mortem analysis of wear surfaces. For instance, the presence of rippled features on the wear surface and large flake shaped debris are typical indicators of adhesive wear. However, this approach offers little insight into the underlying physics that occur at the interface. The overall objective of this research is to gain fundamental knowledge of adhesive wear phenomena in polyaryletherketone (PAEK) polymers. Ultimately, the hope is to correlate the observed surface damage and friction response with material science based explanations. Since no true adhesive wear test configuration exists, a top down approach was used in designing a set of experimental conditions. This was done with a multi-axis tribometer capable of being programmed to a wide array of displacements and trajectories. A catastrophic form of adhesive wear is termed fretting and results from the repeated slip of mutually loaded contacts. Using the multi axis tribometer PAEK polymers were studied in both multi directional sliding and fretting configurations with varied environmental conditions. An important aspect of PEEK tribology is the surface temperature reached during sliding. Infrared thermography was used to observe the full field temperature map of PEEK during ball-on-disc sliding. Additionally, friction studies were performed with steel and sapphire counterfaces. The results of this study illustrate the important role transfer films play in determining both the friction and temperature response of the PEEK wear interface. The formation of transfer films resembles a unidirectional drawing process. Polarized FTIR-ATR measurements were used to assess chain orientation in the friction formed PEEK on steel transfer films. The results of these studies serve to better elucidate underlying mechanisms involved in adhesive wear of PAEK polymers

Fundamentals of lubricated friction in deep drawing of zinc coated sheet metal considering contacting surface morphology and chemistry

Die vorliegende Dissertation beschäftigt sich mit dem tribologischen System beim Tiefziehen, das sich aus verzinktem Stahlblech, Werkzeugstahl und flüssigem Schmierstoff bei Raumtemperatur zusammensetzt. Der Schwerpunkt der Arbeit liegt insbesondere auf dem Zusammenhang zwischen dem Reib- und Verschleißverhalten des Tribosystems und der Zusammensetzung und der Topologie der Kontaktflächen. Die Beschreibung des Tribosystems basiert auf der Annahme, dass die Reibung und der Verschleiß durch Adhäsion und Furchung entstehen. Die Untersuchungen folgen einem modularen experimentellen Rahmen, der tribologische Versuche, Oberflächenanalysen und mechanisches Testen verbindet. Die Arbeit beginnt mit einer umfangreichen Übersicht des Stands der Technik, in der die wichtigsten Ansätze bezüglich der Charakterisierung von Reibung und Verschleiß, der Theorie des Reibmechanismus, die bestehenden Reibungsmodellierungsverfahren und das Konzept des dritten Körpers betrachtet werden. Es folgt die Beschreibung der angewendeten Vorgehensweise und der für die Untersuchung genutzten Materialien. Im Hauptteil der Dissertation werden die Ergebnisse der Versuche vorgestellt. Zunächst wird der Einfluss der Oberflächentopologie auf die Reibung betrachtet. Hierbei hängt die Topographie der Werkzeugoberfläche im Wesentlichen von der Art und der Genauigkeit des Endbearbeitungsprozesses ab. Die Ausgestaltung der Blechoberfläche wird durch das dem Walzprozess folgende Dressieren bestimmt. Anhand der Untersuchungen konnten die wesentlichen Eigenschaften der Kontaktoberflächen, die das Reibverhalten des Tribosystems beeinflussen, ermittelt werden. Es wurden Bleche von einem Coil mit stufenweise unterschiedlichen Dressiergraden in Streifenzieh- und Stiftscheibeversuchen untersucht, wobei Werkzeuge mit unterschiedlichen Oberflächenbeschaffenheiten eingesetzt wurden. Ein wichtiger Teil der Arbeit stellt die anschließende Ermittlung des Anteils der Oberflächenstruktur am Reib- und Verschleißverhalten des Tribosystems dar. Bei einem Vergleich zweier unterschiedlicher Arten von Zinkbeschichtung, nämlich der reinen Zinkbeschichtung und der Zink-Magnesium-Beschichtung konnte beobachtet werden, dass eine Änderung der chemischen Zusammensetzung der Beschichtung einen erheblichen Unterschied im Verhalten des jeweiligen Tribosystems zur Folge hat. Diese Erkenntnis ermöglicht weitere Einsichten hinsichtlich des Hauptmechanismus der Reibung beim Tiefziehen