Sensor Technology for Non Destructive Assessment of Materials Degradation

1. Intermediate creep Full creep As-received Sensor Technology for Non Destructive Assessment of Materials Degradation J. Ernesto Indacochea & Ming L. Wang, Civil & Materials Engineering National Science Foundation • Corrosion and creep damage of materials are among the most important challenges for engineers in selecting materials for operation in extreme environments. • Corrosion stands for loses of about 300 billion dollars per year only in the USA. • Creep assessment is a major concern for repair and life extension of infrastructure equipment in power plants. • Early detection and close monitoring of corrosion and creep by non-destructive examination (NDE) is most effective to extend the life of structures and insure the continuous operation of power plants. • The material is a key part of the sensor. A magnetic field is applied to the component being assessed and its magnetic response is monitored. • The hysteresis loop and magnetic saturation depend on the microstructure and cross section of the exposed material. • Corrosion is a surface phenomenon that reduces the cross section of materials due to mass loss. • During the different stages of creep, materials suffer changes in grain size, phases, crystallographic lattice, and voids appear. • The magnetoelastic response of metals due to corrosion or creep gradually changes and it is used to estimate the degradation level due to creep or corrosion. • Corrosion damage with 0.5% mass loss of ferromagnetic materials can be detected with a 95% confidence limit. • Microstructural changes are also detected during the sensing of corrosion and creep. • In the third stage of creep damage the material becomes magnetically harder and the hysteresis curve shifts. • Improve sensor sensitivity to detect less than 0.5% mass loss due to corrosion and subtle microstructure changes during creep. • Extend our studies to development of nanostructured hydrogen sensing MOS devices.