Abstract: A method and apparatus for ascertaining internal stresses in a hardened region to be tested for a component made of a predetermined material includes measuring coercive field strength and amplitude of magnetic Barkhausen noise as a function of mechanical stress and hardness in calibration samples of a predetermined material of known hardness and known internal stress. Calibration functions are ascertained from the measured values indicating the dependency of the hardness and the amplitude of the magnetic Barkhausen noise as functions of the hardness and mechanical stress. The coercive field strength and the amplitude of the magnetic Barkhausen noise is measured in a location-dependent manner over the region of the component to be tested. The measured values of the coercive field strength and the amplitude of the magnetic Barkhausen noise are converted in the region to be tested into location-dependent hardness and into location-dependent mechanical stress using the ascertained calibration functions.

Abstract: A method for manufacturing parts for rotary machines, especially turbine wheel disks, having a hub bore in a hub region, as well as turbine wheel disks manufactured by the method, includes pre-turning a contour at the hub region having a profile differing from a hub contour to be produced. At least the hub region is initially treated. At least the hub region having the pre-turned contour is cooled with a coolant fluid after the initial treatment to produce internal compressive strains in the hub region. The pre-turned contour is reduced after the cooling to the hub contour to be produced.