Geometrical gauge factor of directional electric potential drop sensors for creep monitoring

Journal Article · Thu Jun 23 00:00:00 EDT 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3592123· OSTI ID:21511629

Madhi, E; Nagy, P B ^[1]

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1. School of Aerospace Systems, University of Cincinnati, Cincinnati, OH 45221 (United States)

Directional electric potential drop measurements can be exploited for in-situ monitoring of creep in metals. The sensor monitors the variation in the ratio of the resistances measured simultaneously in the axial and lateral directions using a square-electrode configuration. This technique can efficiently separate the mostly isotropic common part of the resistivity variation caused by reversible temperature variations from the mostly anisotropic differential part caused by direct geometrical and indirect material effects of creep. Initially, this ratio is roughly proportional to the axial creep strain, while at later stages, the resistance ratio increases even faster with creep strain because of the formation of directional discontinuities such as preferentially oriented grain boundary cavities and multiple-site cracks in the material. Similarly to ordinary strain gauges, the relative sensitivity of the sensor is defined as a gauge factor that can be approximated as a sum of geometrical and material parts. This work investigated the geometrical gauge factor by analytical and experimental means. We found that under uniaxial stress square-electrode sensors exhibit geometrical gauge factors of about 4 and 5 in the elastic and plastic regimes, respectively, i.e., more than twice those of conventional strain gauges. Experimental results obtained on 304 stainless steel using a square-electrode electric potential drop creep sensor agree well with our theoretical predictions.

• OSTI ID: 21511629
• Journal Information: AIP Conference Proceedings, Vol. 1335, Issue 1; Conference: Review of progress in quantitative nondestructive evaluation, San Diego, CA (United States), 18-23 Jul 2010; Other Information: DOI: 10.1063/1.3592123; (c) 2011 American Institute of Physics; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANISOTROPY
CAVITIES
CONFIGURATION
CRACKS
CREEP
ELECTRIC POTENTIAL
ELECTROCHEMISTRY
ELECTRODES
FORECASTING
GRAIN BOUNDARIES
METALS
MONITORING
NONDESTRUCTIVE TESTING
PLASTICS
SENSITIVITY
SENSORS
STAINLESS STEEL-304
STRAIN GAGES
STRAINS
STRESSES
ALLOYS
AUSTENITIC STEELS
CARBON ADDITIONS
CHEMISTRY
CHROMIUM ALLOYS
CHROMIUM-NICKEL STEELS
CORROSION RESISTANT ALLOYS
ELEMENTS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
MATERIALS TESTING
MEASURING INSTRUMENTS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
POLYMERS
STAINLESS STEELS
STEEL-CR19NI10
STEELS
SYNTHETIC MATERIALS
TESTING
TRANSITION ELEMENT ALLOYS