Modelling of metalic seal seats

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Static sealing seats are machine elements of high importance in a number of fluid applications. Their essential task is to prevent unwanted leakage. Sealing seats can be classified into soft sealing, mostly based on elastomers, and hard sealing contacts, i.e. metallic contacts. Even though the composition of a hard sealing metallic contact is very simple, it is impossible to reliably predict the leakage based on design- and operating parameters to this date.An important application for hard sealing components can be found in seat valves. One common use of this valve type is in mobile hydraulics as load holding valves in order to prevent accidental safety relevant machine movements. The design of a seat valve is based on expert know-how and experience. This leads to a dimensioning towards the safe side and therefore to an oversizing of the sealing seat regarding it´s force and geometry. The result is an unnecessary large installation space, decreased dynamics and most times a limited fatigue strength of the valve.A new approach to describe two contact partners was developed by Dr. Bo Persson. The so-called contact mechanics theory is able to model soft sealing contacts and predict the resulting leakage correctly.Goal of this project is to apply the contact mechanics theory for hard sealing contacts and derive a general model to describe metallic sealing seats. The result is a theoretical concept with a physical motivation which includes parameters such as plastic deformation and surface roughness. For the development and validation of the general contact model, test rigs will be designed and built in order to investigate varying parameters separately and to compare the measurements with the model. Additionally, multi-dimensional FEM and CFD simulations are performed to obtain parameters for the validation, which cannot be measured. The results lead to an enhanced model describing hard sealing contacts, which is validated consecutively by a real application test rig.Scientifically, the description of the contact mechanics between two contact partners is advanced on the one hand. On the other hand the basis for a profound development of metallic sealing seats and the holistic advancement of seat valves is established. This is achieved by the development of a method which describes the contact mechanics of hard-hard-contacts. This method together with the resulting findings is expected to be applicable to other engineering fields with similar contact areas (interference fit, bolted connections etc.).