Reduced order structural models for the calculation of wet contact forces due to impacts in hydraulic valves

Impacts in hydraulic valves generate structure-borne sound. Numerical methods are applied to calculate the contact forces, which are related to the acoustic noise generation. The fluid between the moving valve stem and the end stop creates a squeeze film force. A model order reduction technique in two steps is applied to capture the flexibility of the impact bodies in a multi-physics system simulation. The first reduction step is based on modal truncation using normal and attachment modes. The second step aims to select the important states or modes within the model bandwidth based on Hankel singular values, where two selection procedures are compared. The squeeze film effect is represented by an analytical formula which is closely incorporated to the compliant contact model. This contact deformation relation for the wet impact has to account for the transition between the pure squeeze motion and the structural collision. Measurements are used to support the calculation results. The coupled calculation of elastic and hydraulic effects leads to improved models for predicting the noise design and the functionality of hydraulic valves.