Method and system for measuring the volume loss of a metal substrate

A method for measuring the volume loss of a metal substrate comprising the steps of:

• inducing eddy currents in a test substrate;
• measuring the magnitude of the eddy current produced within the substrate at a plurality of locations on the surface of the substrate;
• and
• converting the measured eddy current magnitudes at each location to corresponding volume losses on the surface of the test substrate by multiplying the measured eddy current magnitude for a sector on the surface of a test substrate by a predetermined calibration factor (Cf) representing volume per unit area eddy current magnitude and by the surface area of the sector to provide measurements of the volume loss within the sector.

A method for measuring the volume loss of a metal substrate comprising the steps of:

• inducing eddy currents in a reference substrate;
• measuring the magnitude of the eddy current produced within the substrate at a plurality of locations of known volume loss on the surface of the substrate;
• determining a calibration factor (Cf) based on the measured magnitudes at the locations on the reference substrates;
• inducing eddy currents in a test substrate;
• measuring the magnitude of the eddy current produced within the substrate at a plurality of locations on the surface of the substrate;
• and
• converting the measured eddy current magnitudes at each location to corresponding volume losses on the surface of the test substrate using the calibration factor (Cf).

A method for measuring the volume loss of a metal substrate comprising the steps of:

• inducing eddy currents in a reference substrate having a surface comprising a plurality of sectors of predetermined surface area and predetermined volume loss such that at least a portion of the sectors have no volume loss and at least a portion of the sectors have a positive volume loss;
• measuring the magnitude of the eddy current produced within the reference substrate at a plurality of locations within each sector;
• averaging the eddy current magnitudes measured for the locations having no volume loss to provide a threshold level (T);
• normalizing the eddy current magnitudes for the locations in the sectors having positive volume loss by subtracting the threshold level (T) from the measured magnitudes at the locations;
• summing the normalized eddy current magnitudes measured at each of the locations in a sector to provide a normalized eddy current magnitude for the sector;
• determining a calibration factor (Cf) representing the measured volume per unit area eddy current magnitude by dividing the predetermined volume loss of the sector by the normalized eddy current magnitude for the sector and the surface area of the sector;
• inducing eddy currents in a test substrate;
• measuring the magnitude of the eddy current produced within the substrate at a plurality of locations on the surface of the substrate;
• and
• converting the measured eddy current magnitudes at each location to corresponding volume losses on the surface of the test substrate using the calibration factor (Cf).

A process for measuring the volume loss of a metal substrate comprising the steps of:

• inducing eddy currents in a metal reference substrate having a surface comprising a plurality of sectors of predetermined surface area and predetermined volume loss such that at least a portion of the sectors have no volume loss and at least a portion of the sectors have a positive volume loss;
• measuring the magnitude of the eddy current produced within the reference substrate at a plurality of locations within each sector;
• averaging the eddy current magnitudes measured for the locations in the sectors having no volume loss to provide a threshold level (T);
• subtracting the threshold level (T) from the measured magnitudes for the locations in the sectors having positive volume loss to provide a normalized eddy current magnitude for each location;
• summing the normalized eddy current magnitudes measured at each of the locations in the sector having the greatest volume loss to provide a normalized eddy current magnitude for the sector of greatest volume loss;
• dividing the predetermined volume of the sector of greatest volume loss by the normalized eddy current magnitude for the sector of greatest volume loss and the surface area of the sector of greatest volume loss to produce a calibration factor (Cf) representing the measured volume per unit area eddy current magnitude;
• inducing eddy currents in a metal test substrate;
• measuring the magnitude of the eddy current produced within the test substrate at a plurality of locations on the surface of the substrate and within sectors of predetermined surface area;
• subtracting the measured eddy current magnitudes at the locations by the threshold value (T) to produce normalized eddy current magnitudes at the locations;
• summing the normalized eddy current magnitudes for the locations within each sector to produce a normalized eddy current magnitude for each sector;
• multiplying the normalized eddy current magnitudes for each sector by the calibration factor (Cf) and by the surface area of the sector to provide volumetric measurements of the volume loss at the locations thereby providing a surface profile of volume loss on the test surface.

A system for producing a profile of the volume loss along the surface of a metal substrate comprising:

• means for inducing eddy currents in a test substrate;
• a measurement device for measuring the magnitude of the eddy current produced within the substrate at a plurality of locations on the surface of the substrate;
• and
• means for converting the measured magnitudes at the locations to corresponding volume losses at each location on the surface.

A system for producing a profile of the volume loss along the surface of a metal substrate comprising:

• means for inducing eddy currents in a test substrate, said test substrate having a surface comprising sectors of predetermined surface area;
• a measurement device for measuring the magnitude of the eddy current produced within the substrate at a plurality of locations on the surface of the substrate;
• and
• means for converting the measured magnitudes at the locations to corresponding volume losses on the surface, said converting means comprising:
• means for normalizing the eddy current magnitudes measured on the surface of the substrate,
• means for summing the normalized eddy current magnitudes within a sector to provide a normalized eddy current magnitude for the sector, and
• means for multiplying the normalized eddy current magnitude of the sector by the surface area of the sector and a calibration factor (Cf) representing the volume per unit area eddy current magnitude to calculate the actual volume loss on the surface of the substrate within each sector.