Target Material Impact on Inductive Sensing Distance Reduction Factors
Target material conductivity and permeability set inductive sensing distance reduction factors, reducing nominal operating range by up to seventy percent.
Cold Working Phase Shift
Deformation Response
Mechanical stress applied to a metal below its recrystallization temperature alters both its grain structure and its electromagnetic properties. Measuring the cold working phase shift provides a non-destructive method to assess the degree of plastic deformation in stainless steel components. As the crystal lattice undergoes strain, the electrical conductivity and magnetic permeability of the metal drift from their baseline values.
This change alters the phase angle of the impedance vector in an eddy current test coil.
Impedance Vector
Analyzing the phase displacement of the coil voltage relative to the excitation current reveals the depth and severity of the mechanical treatment. The sensor detects the cold working phase shift by comparing the phase angle of the returned signal against an annealed reference specimen. This metric helps separate structural alterations from simple lift-off variations.
Calibration Standard
Industrial metrology systems calibrate phase-sensitive instruments using reference blocks with known deformation percentages. Handheld or automated eddy current probes measure the phase angle at high frequencies to isolate the surface layers where strain is concentrated.
Physical Source
Microstructural transitions under stress lead to the formation of magnetic phases that drive the shift in the phase angle. Localized permeability changes create a complex impedance shift that increases with greater plastic strain. The measurement is verified by magnetic balances or metallographic analysis.