Magnetic Barkhausen noise (MBN) is a nondestructive method for residual stress analysis. A great advantage over most complementary residual stress analysis techniques is that measurements can be performed very fast. Barkhausen noise is affected by residual stress to the same extent as by the microstructure of the analyzed sample. Thus, a careful calibration considering the microstructure has to be carried out for quantitative residual stress determination. In the present work, the influence of slight changes in microstructure (i. e. grain size) was investigated for a mild steel. Calibration curves were determined by means of 4-point bending tests. Afterwards, the calibration curves were validated using tensile test samples with known applied stress. The tensile samples were manufactured from a different batch attaining a smaller average grain size than the calibration sample. The stress determined significantly differed from the nominal applied stress due to the differences in the grain size. After consideration of the grain size effect, satisfactory agreement between determined and nominal stress could be achieved. Finally, an MBN residual stress analysis was performed on a deep rolled sample. Complementarily, the residual stress state was determined by means of X-ray diffraction (XRD). Significant differences between the XRD and MBN results could be observed. The results indicate that the microstructure of the calibration sample must be identical with the microstructure of the sample to be analyzed to avoid erroneous residual stress results. Furthermore, the load direction during MBN calibration must be correctly chosen.

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The incremental hole-drilling method is a well-known mechanical measurement procedure for the analysis of residual stresses. The newly developed PRISM® technology by Stresstech Group measures stress relaxation optically using electronic speckle pattern interferometry (ESPI). In case of autofrettaged components, the large amount of compressive residual stresses and the radius of the pressurized bores can be challenging for the measurement system. This research discusses the applicability of the measurement principle for autofrettaged cylinders made of steel AISI 4140. The residual stresses are measured after AF and after subsequent boring and reaming. The experimental residual stress depth profiles are compared to numerically acquired results from a finite element analysis (FEA) with the software code ABAQUS. Sample preparation will be considered as the parts have to be sectioned in half in order to access the measurement position. Following this, the influence of the boring and reaming operation on the final residual stress distribution as well as the accuracy of the presented measurement setup will be discussed. Finally, the usability of the FEA method in early design stages is discussed in order to predict the final residual stress distribution after AF and a following post-machining operation.