Optimisation of composite castings by means of neutron measurements

The composite casting process is mainly used to produce composite engine blocks with in-cast liners. Due to different thermal expansion of the casting material and the material of the insert residual stresses occur during solidification. These residual stresses can reduce fatigue strength and lead to distortions of the part. They can be minimised by constructive measures. Casting simulation is a suitable method to predict residual stresses and distortions and thus to optimise design of parts. To improve the accuracy of stress simulation composite castings were designed and characterised using conventional and modern test methods such as neutron tomography and neutron diffraction. Neutron diffraction enables to measure, non-destructively, stress distributions within the bulk of the specimen. The results are used to verify and optimise the residual stress simulation. In the end this enables an optimised construction of composite castings.