Problem Statement and Motivation

Key Achievements and Future GoalsTechnical Approach

Sensor Technology for Non Destructive Assessment of Materials Degradation

J. Ernesto Indacochea & Ming L. Wang, Civil & Materials EngineeringNational 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.

• 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.

• 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.

Full creep

Intermediate creep

As-received