Integrating sensors in castings made of aluminum – new approaches for direct sensor integration in gravity die casting

Structural health monitoring relies on mechanical and thermal measurements of the component. Whereas for a strain gauge on the surface of a component a structural model is needed to gain knowledge of the internal state at the point of interest, integrated sensors can measure strain and temperature directly inside the component without the influence of adhesives required to mount the sensor on the surface. Integrating sensors in gravity die casting leads to certain requirements. The Sensors have to withstand the harsh conditions of the casting process at temperatures around 750 °C and a shrinkage of 1.1 % during solidification of the melt. The yield of embedded sensors can be increased, if the sensor-substrate is based on the same coefficient of thermal expansion, which reduces stress during the cooling phase and at the solidification point of the melt through shrinkage. Aluminum as substrate keeps the amount of foreign matter in the casting good at a minimum. In this paper we present the first approach to integrate sensors on aluminum substrates during gravity die casting. The design, fabrication and embedding of screen printed thick-film sensors is shown. The embedded sensors are examined before and after their integration into gravity die-cast aluminum in terms of thermal behavior and diffusion.