Erhard Leidich

Numerical Investigation of Knurled Shaft-Hub Connections and Especially of the Joining Process

Faced with increasing cost pressures, manufacturers need to find new solutions for shaft-hub connections. One example is the knurled interference fit, where a shaft with knurls and interference is pressed in a soft hub with a cylindrical bore. At present the potential of the knurled interference fit is not fully used, because there are no general standards available for the design and for the joining process. But the joining process in particular has an important impact on the join strength. A predominantly forming joining process offers some advantages compared to cutting. Forming allows a clearly higher contact pressure over the groove because of the displacement of the hub material, which leads to greater axial reliability. Also, the natural material structure is preserved by the forming, and this, in combination with the hardening of the hub, should allow a higher transmittable torque. The Finite Element Method is used for detailed investigation of the joining process and the transmission behavior in the axial direction. With this method, the local loads, for example the hardening of the hub over the groove due to the formed join, are investigated as well as further parameter variations (e.g., chamfer angle, interference). Hence, an analytical approach for the determination of the necessary joining force was derived.

Fracture Behaviour of an Electron Beam Weld

This paper deals with cracks in an electron beam welded joint made of severely different materials. The motivation is to improve the design and reliability of an electron beam welded worm wheel, which may contain large cracks due to hot cracking. Material properties of the weld zones were determined by minitensile specimens. The fracture behaviour of the weld was investigated with CTSand SENB-specimen. So far, estimates of the threshold va lues for the fatigue crack growth can be presented. Further experimental and numerical investigations are pla nned.

Normen, Toleranzen, Passungen und Technische Oberflächen

Normen, Toleranzen und Technische Oberflachen haben eine grundlegende Bedeutung fur die Beschreibung und Definition von technischen Gegenstanden. Daher ist es notwendig sich mit diesem Inhalten vertraut zu machen, bevor einzelne Konstruktionselemente betrachtet werden.

Formulation and Characterization of PAI-PTFE-cg Antifriction Coatings

Polytetrafluoroethylene (PTFE) powder is used as a solid lubricant in commercial antifriction coatings. However, most of the matrix polymers are usually not compatible with virgin PTFE resulting in low dispersion and mechanical film stability and adhesion. In our research PTFE TF 2025 was irradiated by g-beam generating PTFE micropowder with persistant radicals and functional groups. These functional groups are able to perform a chemical grafting (cg) of polyamideimide (PAI) and modified PTFE-micropowder by reactive extrusion in melt. Based on grinded extrudates PAI-PTFE-cg dispersions were formulated followed by characterizing dispersion as well as film properties. It was found, that PAI-PTFE-cg dispersion comprises very small PTFE-particles at higher g-irradiation doses in homogeneous dispersions. In addition, all samples showed outstanding film flexibility. Basic tribological properties under mixed lubrication were studied by using a ring-on-disk tribometer. Finally, diluted dispersions were applied to a multi-surface sliding bearing (four segments) for testing in a hydrodynamic plain test bench.

IT-gestütztes Kosteninformationssystem als Instrument des Produktkostenmanagements am Beispiel der Auftragsfertigung im Werkzeug- und Formenbau

Stichwörter Entwicklungsbegleitende Kalkulation Kostencontrolling Kosteninformationssystem Produktkostenmanagement Produktkostenprognose Aufgrund der verschärften Wettbewerbssituation nimmt die Bedeutung einer genauen Angebotskalkulation sowie der Einhaltung von Kostenzielen bei der Auftragsfertigung zu. Um diesen Anforderungen gerecht zu werden, wurden in Kooperation mit einem Unternehmen des Werkzeugund Formenbaus ein Konzept für das Produktkostenmanagement und ein IT-gestütztes Kosteninformationssystem als dessen Kernstück entwickelt, die Gegenstand dieses Beitrags sind.

Produktkostenmanagement im Werkzeug- und Formenbau

Kurzfassung Der wachsende Kostendruck zwingt die Unternehmen des Werkzeug- und Formenbaus zum Aufbau eines Produktkostenmanagementsystems, mit dem Produktkosten effizient und verursachungsgerecht ermittelt sowie Kostenziele eingehalten werden können. Die TU Chemnitz entwickelt daher gemeinsam mit einem Werkzeug- und Formenbauer ein Produktkostenmanagementsystem auf Basis eines Regelkreismodells, in dem Methoden und Werkzeuge zur Produktkostenplanung, -kontrolle und -steuerung integriert sind.

Advanced Design of Worm Wheels Made of Dissimilar Materials

In order to provide the necessary wear and friction features in a worm gear, the worm wheels are often made of specific material, mainly bronze. Considerable material cost reduction is achieved by substituting the inner part of the wheel by a steel hub, which is joined with the bronze toothed rim by various means. In this paper, results of research to the optimum design and production of the wheel welded by the electron beam technology are presented. Namely, the crack distribution in the weld and residual stresses in the whole wheel were invetigated and an improved welding technology along with a modified weld geometry were proposed to eliminate the cracks considerably. The new welding technology is also applicable to gear wheels made of similarly related material combinations.Copyright