The analysis method was developed using a cylinder of a high-pressure pump operating at pressures up to 400 MPa. The pressure is produced by an axial piston pump acting as a hydraulic drive, which exerts not only high operating loads but also dynamic loads on the cylinder. Complex loads arise especially at the sealing faces, where high operating pressures are combined with contact loading. In order to withstand these conditions over an extended period of time, specific internal stresses are introduced into the component using different methods.
Joined components are subject to various types of wear which substantially affect their service life. Fretting wear, for example, often occurs in shaft-hub joints, on bearing backs or dovetail joints in turbine rotors. This type of wear is caused by high loads and small superimposed vibration amplitudes. The significance of this type of wear becomes clear in the light of the fact that 8% of all breakdowns due to wear are caused by fretting.
The project was aimed at analyzing the tribological process in terms of wear and its influence on fatigue. Work also involved integrating the experimental results into a numerical simulation, carrying out experiments on wear characterization and tribomechanical fatigue and evaluating the results in the context of operating strength.
The analysis of the complex effects on a cylinder under internal pressure provided the basis for investigating complex mechanisms of material strength and for developing a methodology for the consideration of contact loading effects (fretting). Fretting constitutes an operation-induced notch and has the same consequences. The methodology developed allows measures against fretting to be taken as early as the product design phase. A material model was developed to assess the effect of fretting wear on the material. The material model developed in this project is based on characteristic material parameters taking into account the tribological system. The optimization process developed enables engineers to carry out a structured analysis and derive appropriate solutions to prevent progressive fretting wear.
This project was successful in analysing fretting as a complex loading condition and in identifying key influencing factors on damage development. The extensive analyses were used to derive appropriate measures against fretting and to provide design engineers with a comprehensive optimisation tool. The material model developed enables the calculation of material strength under fretting loading conditions and eliminates the need for complex experiments.
The project was carried out by the Chair of Mechanical Engineering together with BHDT GmbH and Oerlikon Balzers Coating Austria GmbH.