Abstract: A magnetic detector includes permanent magnets that magnetize a wire rope W in the longitudinal direction, and a search coil that detects a change in the cross sectional area of the wire rope W magnetized by the permanent magnets. The magnetic detector is provided so as to surround a part of the wire rope W. Prior to inspection, the magnetic detector is moved back and forth at least three times across an inspection range of the wire rope W. After the magnetic detector is moved back and forth, the change in the cross sectional area, that is, damage to the wire rope W is inspected by using signals outputted from the search coil.

Abstract: A tension measuring method installs a reel having a cylindrical coil forming part on a cable to be measured, forms a coil by winding a conductor around the coil forming part, measures a magnetic hysteresis loop of the cable by supplying a current to the coil to generate a magnetic field, and computes a tension of the cable using a parameter determined from the hysteresis loop. A magnetic field sensor and a magnetic flux sensor are provided inside a through hole in the coil forming part, and the cable is positioned inside the through hole. The magnetic field is varied so that the hysteresis loop includes a near-saturation magnetization region, to measure the hysteresis loop using the sensors. The parameter is selected from a magnetic flux or a magnetic flux density, a remanent magnetization, a coercivity, a magnetic permeability, and a hysteresis loss in the near-saturation magnetization region.

Abstract: A tension measuring method installs a reel having a cylindrical coil forming part on a cable to be measured, forms a coil by winding a conductor around the coil forming part, measures a magnetic hysteresis loop of the cable by supplying a current to the coil to generate a magnetic field, and computes a tension of the cable using a parameter determined from the hysteresis loop. A magnetic field sensor and a magnetic flux sensor are provided inside a through hole in the coil forming part, and the cable is positioned inside the through hole. The magnetic field is varied so that the hysteresis loop includes a near-saturation magnetization region, to measure the hysteresis loop using the sensors. The parameter is selected from a magnetic flux or a magnetic flux density, a remanent magnetization, a coercivity, a magnetic permeability, and a hysteresis loss in the near-saturation magnetization region.

Abstract: A magnetic detector includes permanent magnets that magnetize a wire rope W in the longitudinal direction, and a search coil that detects a change in the cross sectional area of the wire rope W magnetized by the permanent magnets. The magnetic detector is provided so as to surround a part of the wire rope W. Prior to inspection, the magnetic detector is moved back and forth at least three times across an inspection range of the wire rope W. After the magnetic detector is moved back and forth, the change in the cross sectional area, that is, damage to the wire rope W is inspected by using signals outputted from the search coil.

Abstract: A magnetic detector includes permanent magnets that magnetize a wire rope W in the longitudinal direction, and a search coil that detects a change in the cross sectional area of the wire rope W magnetized by the permanent magnets. The magnetic detector is provided so as to surround a part of the wire rope W. Prior to inspection, the magnetic detector is moved back and forth at least three times across an inspection range of the wire rope W. After the magnetic detector is moved back and forth, the change in the cross sectional area, that is, damage to the wire rope W is inspected by using signals outputted from the search coil.

Abstract: A damage evaluation apparatus, to evaluate damage to a tendon embedded in concrete. The apparatus includes a magnetizer for generating magnetic force, and a detector for detecting change in magnetism produced from a damaged area of the tendon when magnetized. The magnetizer includes a excitation coil; an iron core passing through a center hole of the excitation coil; a pair of columnar yokes connected to respective ends of the iron core and extending toward the concrete; and a pair of plate-shaped yokes connected to the pair of columnar yokes at a distal end thereof for forming magnetic poles having spread along the surface of the concrete. By passing an electric current through the excitation coil, a magnetic circuit is formed by the yoke shaft, the pair of columnar yokes, the pair of plate-shaped yokes, and the tendon over a range thereof situated between the pair of plate-shaped yokes.

Abstract: A magnetic detector includes permanent magnets that magnetize a wire rope W in the longitudinal direction, and a search coil that detects a change in the cross sectional area of the wire rope W magnetized by the permanent magnets. The magnetic detector is provided so as to surround a part of the wire rope W. Prior to inspection, the magnetic detector is moved back and forth at least three times across an inspection range of the wire rope W. After the magnetic detector is moved back and forth, the change in the cross sectional area, that is, damage to the wire rope W is inspected by using signals outputted from the search coil.

Abstract: A damage evaluation apparatus, to evaluate damage to a tendon embedded in concrete. The apparatus includes a magnetizer for generating magnetic force, and a detector for detecting change in magnetism produced from a damaged area of the tendon when magnetized. The magnetizer includes a excitation coil; an iron core passing through a center hole of the excitation coil; a pair of columnar yokes connected to respective ends of the iron core and extending toward the concrete; and a pair of plate-shaped yokes connected to the pair of columnar yokes at a distal end thereof for forming magnetic poles having spread along the surface of the concrete. By passing an electric current through the excitation coil, a magnetic circuit is formed by the yoke shaft, the pair of columnar yokes, the pair of plate-shaped yokes, and the tendon over a range thereof situated between the pair of plate-shaped yokes.