Material processing and service loads in different lifecycle stages of a productranging from semi-finished goods to operating structures-lead to an unfavorable superposition of residual stresses, especially of micro-and macro-residual stresses. Whereas near-surface compressive stress is often desired as it prolongs the useful service life, undesired, steep stress gradients and tensile stress at the surface promote the occurrence of cracks and wear during operation, ultimately leading to expensive and possibly dangerous premature component failure. Reliable management of the residual stress condition significantly contributes to the assessment and optimization of a part's or component's lifetime. Therefore, the nondestructive evaluation of residual stress in objects of different scales reaching from laboratory samples over semi-finished products up to operating components and structures has gained significant importance in the latest decades. Micromagnetic and ultrasonic methods are based on the interaction of an external magnetic field or an ultrasonic wave, respectively, with the material's microstructure and residual stress fields on different scales and in different depths from the material surface. The present contribution provides an overview regarding the local and volumetric measurement, characterization and evaluation of macro-and micro-residual stress by means of micromagnetic and ultrasonic techniques.

The increasing number of requirements placed on the mechanical properties of cast components leads to an increasingly detailed specification of strengths. The mechanical properties of cast iron materials are not only determined by its matrix. The basic structure, but also type, shape and distribution of the embedded graphite influence its properties as well. In this context, chunky graphite represents a degeneration of the graphite spheres. Its occurrence mainly influences the ductility of the material. At present, there is no nondestructive testing method that can be used to inspect components with respect to chunky graphite. Therefore, Fraunhofer IZFP is developing a method to characterize the nodularity of graphite spheres. In a first step, it is to be shown that the occurrence of chunky graphite can be detected in different microstructures. As it is already known that differences in the matrix and different graphite shapes and sizes influence the scattering behavior of ultrasound, ultrasonic scattering will be used for the investigations. Two different types of cast iron, one ferritic and one pearlitic, will be investigated for chunky graphite and different effects will be compared.