Subproject B3

The objective of subproject B3 is the integration of piezoceramic modules into metallic components by high pressure die casting. The main challenge is the control of thermo-mechanical loads during the highly dynamic mould filling and the cooling. A solution to a damage-free integration is the jacketing of the modules with a porous structure which supports the modules on the one hand and can be penetrated with liquid metal easily on the other hand.
In the first project stage, a novel supporting concept has been developed. The modules are surrounded by expanded metal consisting of Al99.5 (figure 1). This enables a complete integration and an eccentric module placement. 
 

Both structure and functionality of the module is retained in spite of the high loads (figure 2). Unfortunately, the interface strength between supporting structure and cast matrix is weak and the eccentric module placement is limited.

The aim of further research is the enhancement of the technology for a robust integration process suitable for mass production.
On the one hand, the interface strength between structure and cast matrix shall be improved. Therefore, a surface activation of the expanded metal is required to achieve a metallic continuity. On the other hand, the eccentric placement of the modules has to be modified to the end that the distance between module and neutral axis of the component is increased. This is essential for adaptronic applications.
The experimental studies are complemented by numerical simulations of the die filling and the infiltration of the expanded metal on the one hand and the thermo-mechanical response of the embedded PZT-module and the casting on the other hand. Melt flow simulations are carried out using the commercial VOF code Flow-3D. The numerical model (Fig. 3 and 4) enables the prediction of thermal and mechanical loads acting upon the module during the cavity fill and shall help to develop new module supporting strategies.
 

 

Thermally induced residual stresses and deformations of the composite that develop during the final cooling are modelled using the FE-software ABAQUS. Numerical investigations yield a significant influence of the polyimide insulation, which functions as a buffer, on the thermal and mechanical loads. The thermal expansion coefficient mismatch between the PZT-ceramic and the aluminium matrix leads to the formation of a small gap and thus to a measurable deformation of the component surface (Fig. 5).