Tribological Aspects in Manufacturing Processes of Microstructured Components and their Tribological Behavior in Operation

Abstract

An ever increasing mobility and a shortage of resources lead to restrictive politically driven limits for fuel consumption as well as an increasing demand of customers for efficient vehicles. Though electrification of cars proceeds, combustion engines will play an important role for conventional and hybrid concepts within next decades. Thus, for a contribution to increasing energy efficiency of vehicles it is vital to trace sources of friction losses and to identify possibilities for friction reduction in combustion engines. Therefore, the follower as a main contributor to friction losses in valve trains was chosen as a demonstrator for friction reduction effects by microstructured components. However, the realization of theoretically advantageous microstructures with filigree geometries is challenging for manufacturing technologies. The present study focuses on the elaboration of a technological basis for a repeatable production of components with microstructured surfaces by a combined cup backward extrusion micro coining process, coping with the demands of large-lot production. For realization of a high accuracy the influence of friction on geometry of microstructured components was investigated. In addition, running-in of components is decisive for final geometry and tribological behavior of microstructured surfaces and hence considered as well.

Investigation of Production Limits in Manufacturing Microstructured Surfaces Using Micro Coining

“…Such a process can be integrated into the backward extrusion process commonly used for manufacturing tappets and applied in the cam-tapped-contact of the valve train. Based on the fact that already minor geometrical deviations of discrete structure elements lead to significant changes of the tribological conditions [ 10 ], the production limits need to be investigated to make use of the full potential of the micro coining process. Within this study, the process limits of tooling and the micro coining process itself are determined.…”

Untersuchungen zur Wirkungsweise von Mikrotexturen in elastohydrodynamischen Gleit-/Wälzkontakten

“…Die Steigung der Texturränder wiederrum kann entweder, trotz Prägen mit einem Prägepin mit steilen Flanken, das Resultat des Materialflusses beim Präge-prozess sein oder aus der Abformung eines Prägepins mit geneigten Seitenflächen resultieren. Der Übergang von der glatten Oberfläche in die Textur ist vermutlich vergleichsweise kantig, da die endgültige Texturtiefe nicht durch das Prägen selbst sondern durch einen nachgeschalteten Schleif-und Polierprozess bestimmt wird[327].…”