Abstract: A nondestructive test method determines the degree of metal fatigue of test ferromagnetic construction materials by quantifying a change in effective stress due to aging of the test materials. The disclosed method is to measure the coercive force Hc and the magnetic susceptibility &khgr;H of the test materials at the field of the coercive force Hc. A current tensile stress &sgr; by putting the coercive force Hc and the magnetic susceptibility &khgr;H into the following first equation: &sgr;=a(Hc/&khgr;H)n. where a and n are known constants determined by the internal structure of the test materials. A change in current tensile stress of the test materials is determined by comparing the effective tensile stress &sgr; of the test materials with the initial tensile stress &sgr;0 of the test materials.

Abstract: A nondestructive test method determines fatigue of a test ferromagnetic construction material by quantifying a change in effective stress due to aging of the test material, in which the magnetic susceptibility (&khgr;c) of the test material is measured in its aged state under a magnetic field having a specified intensity (H) according to a relation as expressed by a first equation: c=&khgr;c H3. The magnetic susceptibility (&khgr;c) so measured and the magnetic field intensity (H) are put into the first equation, to obtain a susceptibility coefficient (c) of the test material. The susceptibility coefficient (c) so obtained is put into a second equation: &sgr;={log (c)−a}/b, where a and b are known constants determined by an internal structure of the test material, to obtain a current tensile stress (&sgr;) of the test material.

Abstract: The triazine thiol derivative having a perfluoro group of the present invention is represented by the following chemical formula: ##STR1## in which "n" is an integer of 1-12, "R" is represented by the following general formula;C.sub.m H.sub.2m+1wherein m is an integer of 0-24, and M.sub.1 and M.sub.2 respectively represent H or an alkali metal. Such triazine thiol derivative having a perfluoro group is excellent in reactivity, solubility and surface activity.