Evaluation of second order residual stresses in iron carbon steels and white cast iron using micromagnetic methods
The paper presents two methods for a nondestructive determination of thermally induced residual stresses in iron carbon steels and white cast iron. The magnetic Barkhausen noise is measured in the temperature range between room temperature and +250øC under load stress. From the variation of load stress sensitivity of the micromagnetic parameters as a function of temperature, second order residual stresses can be concluded. The second approach is based on the application of micromagnetic sensors with very high spatial resolution. Using such sensors e.g. modified videoheads, measurements can be carried out with a local resoution of some micrometers. Based on this principle a magnetic microscope has been developed by moving the sensor stepwise over the polished surface of the specimen.