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 direct tension indicating washer apparatus includes a direct tension indicating washer; a base washer; and an anti-rotation feature to prevent rotation of the direct tension indicating washer relative to the base washer.

A monitoring system includes a fastener. A sensor is coupled to the fastener. A circuit board is electrically coupled to the sensor. An antenna electrically coupled to the circuit board.

A resilient washer has a one-piece washer body. The washer body has a central opening, an upper fastener interfacing section or bowl, a lower structure interfacing section or bowl and a resilient middle portion. The resilient middle portion connects the upper fastener interfacing section or bowl and the lower structure interfacing section or bowl. The resilient middle portion is configured to be locally collapsed when a fastener in the central opening is tightened into a structure. In one embodiment, the upper fastener interfacing section or bowl is annular, wherein the upper fastener interfacing section or bowl has a concavity for holding a head of the fastener. The concavity can be of a hemispherical shape. Preferably, the concavity has a smooth surface to allow polyaxial movement of a fastener.

An expansion bolt including an anchor bolt having an expansion section, and further including an expansion sleeve which surrounds the anchor bolt and which can be expanded by retracting the expansion section, and a spring element arranged on the anchor bolt. The spring element can be tensioned by inserting the anchor bolt into a bore hole and can retract the expansion section of the anchor bolt into the expansion sleeve when it is released. An indicator element indicates when a rated tension of the spring element is reached.

A nut, or a washer for a nut, in particular a wheel nut or axle nut for vehicles, having a body, having a central threaded hole, having a peripheral wall, having an abutment face at a lower side, wherein the nut also has a plurality of wrench faces on the peripheral wall of the nut body for tightening or releasing the nut by means of a tool which cooperates with the wrench faces. In order to be able to detect the loosening of wheel nuts or axle nuts of vehicles, and to indicate such loosening to a vehicle driver to avoid dangerous situations during driving, there is provided in the body at least one recess in which a sensor element is arranged, wherein the sensor element is connected to a wireless interface which is configured to transmit a sensor signal of the sensor element wirelessly to an external reception unit.

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.

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 direct tension indicating washer includes a first surface having a protuberance formed thereon; a second surface having an indentation formed opposite the protuberance; an indicating material positioned in the indentation; and a channel leading from the indentation to an outer diameter of the direct tension indicating washer; wherein the indicating material is weather-resistant.