Based on stress and fatigue tests with specimens and structures, FEMM’s monitoring capabilities can be summarized as follows:
Relative Stress Monitoring Mechanical stress relative to an initial stress level. Sensitivity better than 1MPa has been demonstrated with carbon steel and super duplex specimens.
Absolute Stress Determination By using a different sensor FEMM has the potential to measure absolute stress.
Remanent Stress Determination Ferromagnetic steel “remembers” stress it has been exposed to, and maximum stress since last measurement can be measured.
Residual Stress Ability to measure residual stress variation in an area has been demonstrated. Monitoring of changes of residual stress caused by load variation.
Fatigue due to cyclic loads FEMM has shown high sensitivity to material changes caused by cyclic loads under high-cycle and low-cycle fatigue tests.
Crack detection FEMM’s sensitivity to fatigue development can be used to predict crack initiation. It has high sensitivity to detection of surface cracks and of crack growth.
Effects of loads exceeding yield High sensitivity to material changes caused by stress exceeding yield.
Metal loss detection and monitoring Localized or general wall thickness reduction caused by corrosion or erosion can be monitored with an accuracy of 0,1% (for general w.t. reduction and relative to remaining w.t.).
