A fastening device may include a hollow void. The hollow void may contain an inner coil proximate to a first end of the device, a sensing portion to sense a characteristic associated with the fastening device during a sensing time window, and a controller. The controller may rectify an alternating current from the inner coil during a charging time window, store energy associated with the rectified alternating current, and use the stored energy to charge the sensing portion during the sensing time window. An outer coil outside the fastening device may be located proximate to a second end of the device as compared to the inner coil. An interface portion outside the fastening device may provide an alternating current to the outer coil during the charging time window, detect the sensed characteristic via the outer coil during the sensing time window, and transmit an indication of the detected characteristic value.

A fastener and a system, apparatus, and method for monitoring a fastener are described. The fastener includes a head portion, a shank portion, a transponder, and a compression spring, wherein the head portion includes a mounting portion, and wherein the transponder is disposed in the mounting portion of the head portion. The transponder is arranged to monitor the shank portion, and includes an ultrasonic sensor and a signal processing circuit. The ultrasonic sensor is affixed to a transducer hosting surface, and is urged against the transducer hosting surface by placement of the printed circuit board in the head portion with the compression spring intervening therebetween. The ultrasonic sensor communicates with the signal processing circuit via the compression spring. The signal processing circuit captures a signal from the ultrasonic sensor and transforms the signal into a parameter corresponding to a tensile force being exerted by the fastener.

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.

A bolt (100) which is deformed when subjected to strain includes a cavity (104), intelligence and means (105) for determining strain and to alert at specific values.

A head of a bolt includes a deformed portion that has a smaller thickness in an axial direction of a shank or a smaller value of Young's modulus than other portion of the head, and that is configured to be deformed more than the other portion by axial force of the shank. A detection unit of the bolt is configured to detect strain on the deformed portion depending on the axial force of the shank. The deformed portion includes a thin portion that has a thickness smaller than a largest thickness of the head in the axial direction of the shank. The head includes a recessed portion having a bottom plate serving as the thin portion. The bottom plate is positioned on an axis of the shank. The detection unit is positioned on the axis of the shank and is configured to detect strain on the bottom plate.

Low cost transducer bonding tooling and techniques are provided which can be used to duplicate the quality of factory manufactured load indicating members, and to allow transducers to be attached to fasteners irrespective of their orientation. The bonding tooling and techniques can also be used to bond other small objects requiring precise placement and reliable bonding such as, for example, the bonding of identification labels to manufactured components or structures.

The invention relates to a screw connection, which comprises a screw body with an external thread, a mating piece with an internal thread which is matched to the external thread and into which the screw body is screwed, a spacer sleeve for clamping between a screw head of the screw body and the mating piece, and a sensor system which is configured to determine a stress state acting in the screw body. The sensor system comprises a transmitter, which is arranged in the spacer sleeve, and a receiver, which is arranged in the spacer sleeve, wherein the transmitter is configured to convert electrical energy into mechanical surface waves, the receiver is configured to convert mechanical surface waves into electrical energy, and the sensor system is further configured to draw conclusions about the stress state acting in the screw body and/or the spacer sleeve.

A rapid ultrasonic dual-wave calibrated detection method includes: numbering a plurality of high strength bolts; searching, in a database in equipment, a calibrated empirical value R.sub.0e of initial ratios R.sub.0 of ultrasonic transverse wave transit time to ultrasonic longitudinal wave transit time for bolts with entirely or partially same specification data, or a calibrated empirical value k.sub.e of a slope k of variation of a bolt tension with a ratio of transverse wave transit time to longitudinal wave transit time; measuring ratios R.sub.i of the ultrasonic transverse wave transit time to the longitudinal wave transit time for the plurality of high strength bolts; acquiring a pretightening axial force value, and using the pretightening axial force value in place of an average value of tensions of the plurality of high strength bolts, calculating calibrated another parameter k.sub.e or R.sub.0e; and calculating axial forces of the high strength bolts.

An assembly screw including at least a threaded part and a non-threaded part, the non-threaded part being equipped with a strain gage sensitive to the instantaneous elongation of the non-threaded part and with an RFID tag connected to the strain gage by a wired link, the assembly allowing the wireless transmission of an electrical resistance value of the strain gage representative of the instantaneous elongation.

A female fastener for receiving and engaging with a threaded male fastener, the female fastener comprising a threaded body, a load measuring device having an electrical switch mechanism disposed sealed and contained inside the threaded body for measuring compressive load on the female fastener and for communicating a signal representing said measured compressive load to an external system.