Patent ID: 6424149
Filing Date: 2002-07-23
Classification: G01N

Abstract:
A method for nondestructively determining fatigue of test ferromagnetic construction materials having a known, initial tensile stress (&sgr;0), by quantifying a change in effective tensile stress due to aging of materials, said method comprising the steps of:measuring a coercive force (Hc) and a magnetic susceptibility (&khgr;H) of a test material under a magnetic field having a coercive force (Hc); determining an effective tensile stress (&sgr;) by putting said, coercive force (Hc) and said magnetic susceptibility (&khgr;H) into the following first equation: &sgr;=a(Hc/&khgr;H)n where a and n are known constants determined by an internal structure of the test material; anddetermining a change in effective tensile stress of the test material, by comparing said effective tensile stress (&sgr;) of the test material with the initial tensile stress (&sgr;0) of the test material.