Develpoment and verificatoin of a material model for prediction of containment safety of exhaust turbochargers

For predicting the containment safety of turbochargers against failure of rotors at elevated temperatures and dynamic loading the complex deformation and damage behaviour of the respective materials has to be determined by appropriate experiments and on the other hand the temperature and strain rate dependency has to be described by a material model to simulate the component behaviour under these complex loading conditions. The investigations focus on the cast iron alloy EN-GJS-400 with nodular graphite. Its mechanical behaviour under uniaxial and multiaxial tension as well as under compression and shear loading has been investigated for a variety of loading rates and temperatures. For the numerical modelling of the containment safety of turbochargers a material model has been developed with the capability to describe the specific deformation behaviour of casting materials, e.g. different properties under tension and compression, temperature and strain rate dependence. The deformation behaviour was described with a model for thermally activated flow and the damage behaviour with a Johnson-Cook type model and an extended failure model (bi-failure model) respectively. The material model has been verified by numerical simulations of penetration tests under highly dynamic impact loading conditions. Also a containment test on a turbocharger was simulated.