Comparison of Synchrotron Radiation Diffraction and Micromagnetic Stress Analysis in Straightened Steel Pipes

The use of magnetic Barkhausen noise (MBN) and harmonic analysis (HA) as non-destructiveevaluation (NDE) techniques in the industrial environment increased in the last years. In our study,we evaluated the potential of those methods to measure residual stress on the surface of straightenedsteel pipes. To study the influence of the pipe manufacturing process and the following straighteningprocess we used pipes of three different straightening levels. The straightening was done with differentparameters, which resulted in a plastic deformation that leaves a visible helix on the surface of thepipes. High energy diffraction experiments were performed to obtain absolute values of residual stresson the surface and in the bulk of the pipe samples. With these residual stress values our MBN and HAdata was calibrated. The surface of all pipes showed high compressive stresses while the highest tensilestresses were 0.5 to 1.4 mm under the surface. The stresses correlate to greater plastic deformationduring the straightening process.