Nippon Telegraph and Telephone Corporation

Eri Matsunaga

Tadashi Minotani

Masahito Nakamura

Masayuki Tsuda

Soichi Oka

Takashi Sawada

A looseness detection sensor for detecting looseness of a bolt for fixing a component, including: a resonance unit arranged adjacent to a head portion of the bolt and made of an insulating material confining a high-frequency signal input externally; and a conductive member in conduction with the component across the resonance unit, wherein the conductive member is a cap put on the head portion of the bolt and includes a protrusion contacting a surface of the component.

Looseness detection sensor and method

A loosening detection device according to the present embodiment includes multiple washers having holes that allow bolts to pass therethrough, and including metals insulated from each other, a transmission line that electrically connects between the metals and between the metals of the washers, and a transmission line that includes a terminal pair at one end thereof, and that has the other end electrically connected to the metals of the washer. A resonance frequency is measured from the terminal pair to detect loosening of the bolts on the basis of a change in the resonance frequency.

Looseness detection device and looseness detection method

A bolt tightening torque management structure for a bolt for fastening a component includes: the bolt including a plurality of projections of different heights on a bearing surface of a head; a non-conductive film that is formed on the surface of the component, has a shaft hole through which a shaft of the bolt extends, and has a predetermined size; and a conductive film that has the shaft hole and a plurality of grooves, through which the projections extend, is formed on the non-conductive film, and has the same planar shape as the non-conductive film. The projections other than the projection having the smallest height are configured to be in contact with the surface of the component when the tightening torque of the bolt is appropriate. The base of each projection has a width dimensioned to close the corresponding groove.

Bolt tightening torque management structure and method

A looseness detection structure includes: a structure (transducer) T which is formed on a surface of a cable; a screw which tightens and fixes the cable in contact with the structure T; and a terminal (detection unit) which transmits a transmission signal to the structure T, receives a reception signal returning after propagating through the structure T, and detects the loosening of the screw based on a change in the reception signal.

Loosening detection structure and loosening detection method using said structure

A sensor for detecting looseness of a plurality of bolts and nuts fixing parts includes: a non-conductive film attached to a surface of the part, which is one of the parts, including holes H from which the bolts are inserted; and a conductive film attached to the non-conductive film, configured to receive supply of a high-frequency signal, and having a same planar shape as that of the non-conductive film, wherein the planar shape is a shape in which a resonance frequency of the high-frequency signal confined in the non-conductive film is different according to a position of a loosened bolt, and the planar shape of the conductive film is a shape in which a distance between a bolt and an end portion of the conductive film is different for each of the plurality of bolts.

Looseness detection sensor and how to identify loose bolts

An abnormality detection device and a fixing structure which are suitable for detecting an abnormality of a fastener such as a bolt or a nut are disclosed. An abnormality detection device detects an abnormality of a fixing structure, which includes a conductor and which fix steel plates to each other, and a spacer which includes an insulator and which is disposed between the steel plates and the washer. The abnormality detection device includes a transmission antenna that radiates electromagnetic waves to the fixing structure, a reception antenna that receives electromagnetic waves reflected by the fixing structure, and an abnormality detector that changes a frequency of the electromagnetic waves radiated from the transmission antenna to acquire frequency characteristics of standing waves received by the reception antenna. The abnormality of the fixing structure is detected by comparing the frequency characteristics with frequency characteristics in a normal state.

Abnormality detection device and fixing structure

A loosening detection structure used to detect loosening of a bolt includes a material that is disposed between a fixing subject steel plate and a head portion of a metal bolt for fixing the steel plate and either attached to a seating surface of the head portion of the bolt or attached to a washer disposed between the steel plate and the head portion of the bolt, and that has electrical characteristics that vary in response to variation in a force for fastening the bolt to the steel plate.

Loosening detection structure, loosening detection system and method

A transducer includes a conductive sheet installed on a sheath of a cable, an insulative sheet installed on the conductive sheet, holes being formed in predetermined positions of the insulative sheet, and a conductive sheet installed on the insulative sheet, holes being formed in predetermined positions of the conductive sheet. The transducer has structure in which, when the cable is tightened by the screw from the top of the conductive sheet and fixed, the distal end of the screw comes into contact with the conductive sheet passing through the holes formed in the insulative sheet and the conductive sheet, and the conductive sheet and the conductive sheet are electrically connected.

Transducer, loosening detection system and loosening detection method

Provided is a surface change detection body capable of detecting a change in the surface of an object only with passive components. The surface change detection body is disposed on a surface of an object to detect a change in the surface, and includes: a sensor unit that resonates with a high-frequency signal; a signal propagation unit that propagates the high-frequency signal to the sensor unit; and an incidence and reflection unit that receives the high-frequency signal from the outside and outputs a high-frequency signal reflected from the sensor unit to the outside, the sensor unit is a parallel plate resonator in which a dielectric is interposed, and the incidence and reflection unit is an antenna having a length which is an integral multiple of one fourth of an effective wavelength of a resonance frequency of the parallel plate resonator.

Surface change detector and surface change detection method using same

A looseness detection structure configured to detect looseness between a bolt and a nut that fix two components including a conductive film configured to be attached on a surface of the component, the surface of the component including a hole into which the bolt is inserted, the conductive film being attached such that the conductive film is not directly conductive to the component, a part of the conductive film having a dimension relating to a half wavelength of a high-frequency signal propagating inside the components, and a non-conductive film between a surface of the component and the conductive film in a case where surfaces of the components are conductors, and a second conductive film on a surface of the component in a case where the surfaces of the components are insulators, the second conductive film being opposite to the conductive film.

A crack detection device includes: a sensor unit that has a three-layer structure of conductor-insulator-conductor and is attached to a structure; a frequency characteristics acquisition unit that sweeps a predetermined frequency range to acquire a plurality of frequencies at which the impedance of the sensor unit is maximum or minimum; a crack presence/absence determination unit that determines the presence or absence of a crack based on a nonuniformity of the plurality of frequencies; a crack position table in which a relationship between crack positions and frequency shift directions is recorded; and a crack position detection unit that, when the crack presence/absence determination unit determines that there is a crack, takes a difference between two frequencies acquired by the frequency characteristics acquisition unit to determine a sign, and then refers to the crack position table in accordance with the sign to detect a crack position.

Crack detection device and method therefor

Provided are a crack detection system and a crack detection method that distinguish between a case where a crack is generated in a structure and other cases not to bring about erroneous detection. In a sensor terminal that detects, from a crack generated in a transducer provided on a structure, a crack in the structure, the transducer having a three-layered structure of conductor-insulator-conductor, the crack detection system including: an impedance measurement unit that measures impedance between the two conductors of the transducer; and a crack detection processing unit that calculates, from a frequency characteristic of the impedance, periodicity data regarding periodicity of a frequency at which impedance becomes a peak, and detects a presence of a crack in the structure in a case of periodicity data different from initially-measured periodicity data being included.

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Musashino, Japan

Eri Matsunaga