Stress induced magnetization changes of steel pipes--Laboratory tests

Magnetometer surveys above gas pipelines show stress induced magnetic anomalies at pipe bends. This suggests a potential technique for the noninvasive monitoring of stress in buried pipelines, etc. Laboratory measurements of the magnetic field changes due to the elastic bending of 110 mm diameter pipe are presented. The effects of orientation with respect to the earths field and of internal pressure are reported. Hysteretic effects are found to be important.