Project description:

In the research project ‘The influence of pressure reduction rates on the damage behaviour of hydraulic components’, the crack propagation behaviour of a component in contact with hydraulic fluid at pressure reduction rates of up to 1,000,000 bar/s is being investigated. The core objective of the project is to generate an understanding of the effects that lead to premature failure due to high pressure reduction rates.

The current state of research is contradictory with its presented theories and results. The differences between the theories on a macroscopic and microscopic level are analysed. This allows the hypothesis of the wedge effect caused by oil in components with pressure-induced deformation to be verified or falsified.

This research project will provide the basis for developing a damage theory for these components. For this purpose, the effects occurring in the crack gap are simulated and analysed using simulation methods. The focus is on the investigation of crack closure behaviour during pressure reduction, taking into account realistic pressure change rates and crack geometries. A high-pressure measuring connection of an axial piston pump closed with a threaded plug is suitable as the object of investigation. A fluid-structure interaction model is used as a simulation approach, which can set the occurring mechanical and fluid-mechanical processes in interaction with each other. With the help of a fluid-structure interaction model, an understanding of the crack behaviour is developed and damage mechanisms are investigated. By applying similarity theories, substitute systems (variation of geometry and oil viscosity) are derived, which exhibit physically comparable behaviour under congruent loading while simultaneously reducing the required computing resources.

The results of the simulation serve to derive the analytical basis for a reliable prediction of the component load as a function of the pressure degradation rates and to gain knowledge of the underlying damage mechanisms for accelerated crack growth.

Funding of the project:

The research project is funded by the German Research Foundation (DFG) under the project number 449676223