STRESS MEASUREMENT METHOD AND APPARATUS IN PRESTRESSING STRANDS USING INVERSE MAGNETOSTRICTION EFFECT AND INDUCED MAGNETIC FIELD

摘要

The present invention relates to a method to measure a degree of corrosion and tension stress applied to a PS steel material using a magnetic field passing through the PS steel material outside, and an inverse magnetostrictive phenomenon wherein magnetic permeability is changed depending on a stress state of a magnetic substance; and an electromagnetic device used for the tension stress measurement method. According to the present invention, an electromagnet device (1) to measure the degree of corrosion and tension stress of a PS steel material (21) arranged in a PC member (200) comprises: a yoke type core (10) equipped while each different stimuli (12) face in a transverse direction on both sides of a transverse direction of the PC member (200); a magnetization coil (20) to magnetize the yoke type core (10) by supplying power while winding the yoke type core (10); a power supply device (30) to supply power to the magnetization coil (20); and a hall sensor (11) equipped in the stimulus (12) to face a lateral surface in the transverse direction of the PC member (20), and to measure a strength of a magnetic field coming in each stimulus. Furthermore, provided is the method to measure a corrosion degree and tension stress of a PS steel material (21) by understanding a change in a cross section and a change in stress of the PS steel material by measuring a change in strength of a magnetic field using the electromagnet device.