Patent ID: 6345534
Filing Date: 2002-02-12
Classification: G01N

Abstract:
A method for nondestructively determining fatigue of a test ferromagnetic construction material having a known, initial tensile stress (&sgr;0), by quantifying a change in effective stress due to aging of the material, said method comprising the steps of:measuring a magnetic susceptibility (&khgr;c) of the test material in an aged state thereof, under a magnetic field having a predetermined intensity (H), according to a relation as expressed by a first equation: c=&khgr;cH3; determining a susceptibility coefficient (c) of the test material, by putting the magnetic field intensity (H) and the measured magnetic susceptibility (&khgr;c) of the test material into the first equation; determining a current tensile stress ((T) of the test material, by putting the so-determined susceptibility coefficient (c) into a second equation: &sgr;={log (c)âˆ’a}/b where a and b are known constants determined by an internal structure of the test material; andcomparing the current tensile stress (&sgr;) of the test material with said initial tensile stress (&sgr;0), so as to determine a change in effective tensile stress of the test material.