Methods for the design of formed sheet metal parts with printed sensors
Recent developments in the field of production research focus on multifunctional components. One approach to manufacture such a component is the integration of electronics in formed sheet metal parts. Printing, in particular screen printing, is a suitable process to apply electrical structures on sheet metal previous forming. Due to its rapidity and low material requirement, screen printing is an economic production process. Another reason to favor the use of screen printing for the integration of electric structures is the application previous the forming process. This allows the integration on positions which are hard to access after the forming process, for example the inner surface of a tube. An example for printed electronics are printed strain gauges (Figure ).
The aim of the project is the manufacturing of formed sheet metal parts with printed strain gauges, which are capable to measure elastic deformation in the formed part. The investigations will be conducted exemplarily by means of roll forming. Particularly the influence of the parameters temperature, surface condition of the sheet metal, surface preparation, logarithmic strain, strain rate and stress condition (uni- and multiaxial) on the performance of strain gauges will be examined. With this knowledge suitable print layouts for printed strain gauges for varying forming processes and applications can be designed.
The first objectives of the project are the layout of the screen printing process and the determination of its reproducibility. Furthermore the identification of sufficient screen printing inks according to their ductility, adhesion strength and scratch resistance will be conducted. Subsequently, the behaviour of printed strain gauges for small strains will be characterized by tensile tests and the resulting gauge factor (relationship between relative change of resistance and strain). Afterwards the dependency of electrical conductivity and temperature in the range of 20 and 80 °C will be examined. The dependency of gauge factor and the aforementioned parameters temperature, surface condition of the sheet metal, surface preparation, logarithmic strain, strain rate and stress condition (uni- and multiaxial) will be analyzed with suitable experiments (for example a biaxial test to determine the strain gauge behavior during multiaxial stress condition). Finally the developed principles will be proven with the manufacturing of a roll formed demonstrator.
The research project is funded by Deutsche Forschungsgemeinschaft (DFG).