In a management system for an attachment state of an attachment object, a sensor capable of detecting a value equivalent to stress of stress loaded, or a predetermined value from which the value equivalent to stress can be calculated, a washer storage unit storing identification information of a sensing washer, and a washer control unit transmitting the value equivalent to stress and the identification information of the sensing washer via a communication unit, are provided in the sensing washer between a bolt and a nut that attach an attachment object to a structural object. A management processing device acquires the value equivalent to stress and identification information of the sensing washer transmitted from the sensing washer, and presents the value equivalent to stress of the sensing washer of the identification information, or a corresponding stress value, as relational information with respect to a reference value stored in a storage unit.

An instrumented, load-sensing washer that can be used on a bolted joint to facilitate determining an axial clamping load of the bolted joint. The washer includes an annular washer body having first and second oppositely disposed axial ends and an outer circumferential sidewall. At least one strain gauge is provided on the circumferential sidewall and is configured to sense a deformation of the washer body do to clamping forces of the bolted joint. The washer further includes a communication assembly operatively coupled with the at least one strain gauge. The communication assembly may include an integrated circuit adapted to receive electrical signals from the at least one strain gauge related to the axial load borne by the washer.

A detector is a detector that detects fastening axial force applied by a fastening unit in an axial direction. The detector includes a strain element that has a through hole through which a bolt portion that the fastening unit has is inserted, and a strain sensing sensor that senses strain of the strain element. The strain element has a block-like form and has a planar portion following the axial direction on a side face thereof. The strain sensing sensor is provided on the planar portion.

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.

A method for determining the state of at least one sensor whose mechanical behaviour is nonlinear as a function of the amplitude of the pressure exerted against the sensor, the sensor and an electromechanical transducer being able to be coupled to a support, the method comprising the steps of: applying an electrical signal at a first amplitude to the terminals of the first electromechanical transducer, and determining a first set of values of a parameter characteristic of the electrical impedance of the first electromechanical transducer in response to the application of the electrical signal; applying the electrical signal at a second amplitude to the terminals of the first electromechanical transducer, and determining a second set of values of the parameter characteristic of the impedance; measuring a deviation between the first set of values and the second set of values; determining a state of the sensor as a function of the deviation between the first set of values and the second set of values.

The invention relates to a solution for how to measure the strain in a washer mounted in a bolt assembly comprising a bolt, nut and washer. The invention concerns a strain measuring washer assembly comprising a plate shaped washer body, sound emitting means and sound detecting means, and a method for using such.

A reversible force measuring device for ascertaining the magnitude and/or direction of an applied load and having a cavity containing an indicating material such as a fluid, with the cavity configured such that when a load is applied to the device, it causes a reversible volumetric change to the cavity. This change causes the indicating material to move in or out of the cavity in a quantity which corresponds to the magnitude and/or direction of the applied load. By measuring the movement of the indicating material, a user can determine the magnitude and/or direction of the applied load. The device may include a component which generates an electrical signal from the measured movement and transmits this signal to another device to control the tensioning of one or more fastener components and or make other analytical measurements by combining this measurement with other measurements like torque and or angle.

A bolt clamping force sensing washer includes a sensing washer, connection line assembly, and signal processor. The sensing washer includes a body, sensing component, and bushing. The body has an axial hole that matches outer diameter of a bolt's thread. The circumferential surface of the body has a circumferential groove for receiving the sensing component which measures a deformation signal generated by the body under an axial load. Two end surfaces of the body are perpendicular to the axial hole and each have a loosening-proof structure. The bushing is made of metal or plastic or formed by plastic insulating material casting to enclose the sensing component. The signal processor has a signal amplifier, microprocessor, pairing switch, power circuit unit, signal transmission unit, memory unit, RF antenna and alert unit. The connection line assembly is disposed at the bushing to electrically connect the sensing component and signal processor.

A sensor arrangement includes a sensor collar where the sensor collar has a sensor sleeve for insertion into an anchor hole and has a sensor flange which is fixedly connected to the sensor sleeve and which radially protrudes from the sensor sleeve for abutting on a mouth of the anchor hole. A through hole extends through the sensor sleeve and through the sensor flange. The sensor arrangement further includes a sensor where a physical quantity of the sensor flange is determinable by the sensor.

There is provided a sensor unit for a fastener assembly, the sensor unit comprising a mounting arranged to rigidly attach the sensor unit to, or adjacent to, a fastener assembly; and a sensor, that is an optical flow sensor or an inductive sensor, configured to sense movement of the fastener assembly. The sensor unit may comprise a processor arranged to process the output of the sensor to detect loosening of the fastener assembly and to output a signal representing the status of the fastener assembly. The sensor unit may comprise a wireless communication unit arranged to communicate the signal.