Abstract: The present invention provides a multi-range force sensor comprising a load cell made of a shape memory alloy, a strain sensing system, a temperature modulating system, and a temperature monitoring system. The ability of the force sensor to measure contact forces in multiple ranges is effected by the change in temperature of the shape memory alloy. The heating and cooling system functions to place the shape memory alloy of the load cell in either a low temperature, low strength phase for measuring small contact forces, or a high temperature, high strength phase for measuring large contact forces. Once the load cell is in the desired phase, the strain sensing system is utilized to obtain the applied contact force. The temperature monitoring system is utilized to ensure that the shape memory alloy is in one phase or the other.

Abstract: A sensor device for registering strain of a component, which comprises a sensor chip and a supporting substrate, which are connected to each other by a connecting layer such that they form a prefabricated sensor module. The sensor module is attached to the component by a durable creep-free connection such that the strain of the component is transferred to the sensor chip.

Abstract: The present invention relates to a piezo-electric stretching detector which is used for measuring the positive and negative stretching on the surfaces of rigid structures using electric signals, wherein said detector can be attached by a force connection onto said surfaces in a compressible or non-removable relation. This stretching detector has a high sensitivity in all stretching directions and is made of a piezo-ceramic material which is applied in a thin layer on at least one surface of a flexible metal sheet or which is fixedly attached to said metal sheet in the shape of a moulded body. At least one of said stretching detectors can be arranged on the free abutting end of at least one resilient pressure body which is imbedded in the reception housing of a stretching sensor. The stretching sensor further comprises members for pressing the reception housing onto the surface to be measured.

Abstract: The invention relates to a micromechanical sensor and to a corresponding production method that includes the following steps: a) preparing a doped semiconductor wafer ; b) applying an epitaxial layer that is doped in such a way that a jump in the charge carrier density in the interface between the semiconductor wafer and the epitaxial layer occurs; c) optionally etching ventilation holes traversing the epitaxial layer and optionally filling the ventilation holes with a sacrificial material; d) depositing at least one sacrificial layer, at least one spacing layer, a membrane and optionally a semiconductor circuit on the top side of the epitaxial layer using a technology known per se, wherein the semiconductor circuit may be applied after the membrane is formed or while depositing the layers required to form the membrane; e) etching a hole on the back part of the sensor, wherein the etching method is selected in such a way that etching advances in the direction of the top side and ceases in the interference bet

Abstract: A transducer body having a traditional single-axis envelope capable of multi-axis measurements. The transducer body includes coaxial base ends with an intermediate flexure element in the form of a ring having an internally centered stiffening web which reduces deflection and localizes strain for accurate high-capacity single-axis load measurements, as well as for bending and shear. The invention further includes a novel arrangement of strain gages on the transducer body, preferably including three sets: strain gages on the stiffening web to measure single-axis loading along the longitudinal axis of the transducer body; bending measurement strain gages spaced at 45° around the periphery of the ring element; and shear measurement strain gages located at 90° locations on the periphery of the ring.

Abstract: A two-layer structure composite material, by which it is possible to easily detect the occurrence of the cracks occurred in the structural material and to predict the possible destruction of the structural material before it actually occurs. To a structural material, a voltage generating material consisting of a ferroelectric material, a pyroelectric material or a piezoelectric material, is bonded to produce a two-layer structure material, and an electrode is provided for detecting voltage, which is generated owing to impact force.

Abstract: A strain gage assembly 10 includes a mounting substrate 12 having an adhesive surface 14 and a gage surface 16. The adhesive surface 14 of the mounting substrate 12 includes an adhesive layer 18 disposed thereon operable to affix the mounting substrate 12 to a component. The adhesive layer 18 is further operable to allow ready detachment of the mounting substrate 12 from the component. The gage surface 16 of the mounting substrate 12 includes a strain gage 20 disposed thereon. The mounting substrate 12 may be formed from a material operable to reduce a strain level received by the strain gage 20.

Abstract: The apparatus and associated method of the present invention remotely detects structural defects in a workpiece by monitoring the electrical continuity of thin crack wires deposited on or within the workpiece in response to a communication from a remote interrogation device. As a crack, delamination or other structural defect forms or propagates in a structural member or other workpiece, a crack wire located in the vicinity of the crack breaks. In addition to the crack wires, the defect sensing apparatus includes a transponder and a discontinuity sensor for detecting a discontinuity along the crack wire. In order to inspect the workpiece, a maintenance technician positions a remote interrogation device in proximity with the workpiece under inspection. The interrogation signals provided by the remote interrogation device are received by the transponder and serve to power the defect sensing apparatus.

Abstract: A device for measuring strain parameters of a stem, shaft or other cylindrical member of virtually any size or diameter includes a pair of generally flexible holders, each holder supporting a substrate having at least one strain gage thereon. Each substrate is bonded in a predetermined aligned position on the cylindrical member relative to the other substrate to permit strain measurement of the cylindrical member. The holders each include at least one guide. A flexible tensioning band engages the guide on each of the holders for placement and retention of the substrates in the predetermined positions. The band is tightened to provide pressure on the substrates during bonding for proper bonding of the substrates to the cylindrical member to provide adequate transfer of strain. In an alternate embodiment a single holder having a single strain gage substrate thereon is employed.

Abstract: A method and apparatus for pre-straining a bolt-on strain sensor. The pre-strain is preferably adjusted by inserting a strain adjusting tool through strain adjusting holes in the sensor and the structural member. The portion of the tool engaging the sensor is preferably offset from the portion of the tool engaging the hole in the support structure to provide a camming function. After the strain has been adjusted to a desired value, a bolt adjacent the strain adjusting hold of the sensor is tightened to fixedly secure the sensor to the support structure and maintain the preadjust strain at the desired value.

Abstract: An apparatus for monitoring the vacuum of a vacuum switch having at least one vacuum switch tube with a switch chamber and switch contacts is provided. The apparatus has a remotely interrogatable pressure measurement sensor in the form of a piezocrystal or surface acoustic (SAW) device arranged in the interior of the vacuum switch tube and a remote interrogation device placed external to the vacuum switch for monitoring the vacuum via the sensor.

Abstract: A bending sensor of the invention is formed of a flexible segment, a pressure-sensitive electrically-conductive resin film formed on the flexible segment, and a pair of electrodes to be attached to the resin film. The resin film is made of pressure-sensitive electroconductive ink and coated on the segment. The resin film has a characteristic such that an electric resistance value is reduced as a pressure on the resin film increases. When the segment is bend-formed at an inflection point by receiving an outer force, the segment provides a pressure to the resin film at the inflection point to produce an inner stress in the resin film. When the segment is bent-deformed, the electrodes output a resistance change of the resin film to thereby detect bending of the flexible segment.

Abstract: Disclosed are a device for the measurement of stresses exerted on a mechanical part and a method for the fastening of this device. The device comprises at least one plate and one strain gauge, the gauge being fixed to the plate which is connected to the mechanical part by linking and coupling means, the strain gauge generating an electrical signal representing the stresses exerted. Application to the measurement of stresses exerted on all types of mechanical parts, notably on brake calipers.

Abstract: An electrical type strain gauge for measuring both micro and macro deformations. The gauge may be constructed from thin films of homogeneously conductive polymers, including soluble polyaniline-based conducting polymers and ion-implanted organic polymers. The gauges are characterized by unexpected piezoresistivity from materials having high bulk resistivity, thermal stability, good flexibility, photoimageability and without adding carbon or metal particulate material to the polymer.

Abstract: An optical fiber strain sensor is provided which remembers the maximum stn a structure has experienced in a given timeframe. A reflective surface is fixed at one location on the structure, and a multi-mode optical fiber with a flat end is fixed at another location on the structure and is positioned so that its flat end is in contact with the reflective surface. A microbore capillary tube attached to the reflective surface encloses the fiber at its flat end and frictionally retains it in contact with the reflective surface. Increasing strain in the structure pulls the fiber end away from the reflective surface in proportion to the amount of strain; however, when strain is decreasing, the fiber buckles rather than moving closer to the reflective surface. Therefore, the maximum strain is reflected as a maximum distance between the fiber end and the reflective surface.

Abstract: An optical fiber strain sensor is provided which remembers the maximum stn a structure has experienced in a given timeframe. A pair of multi-mode optical fibers with flat ends meet end-to-end within a microbore capillary tube with which the fibers have frictional contact. The fibers are fastened to the structure at two points a known distance apart on either side of the capillary tube. Increasing strain in the structure pulls the fiber ends apart in proportion to the amount of strain; however, when strain is decreasing, the fibers buckle rather than move closer together. Therefore, the maximum strain is reflected as a maximum distance between the fiber ends. When the maximum strain experienced is to be measured, the free end of one fiber is connected to a light source and the free end of the other fiber is connected to a detector.

Abstract: An apparatus, system and method for actuating or sensing strains in a substrate which includes at least one actuator/sensor element which has transverse and longitudinal axes. The actuator/sensor element is attached to the substrate in such a manner that the stiffness of the actuator/sensor element differs in the transverse and longitudinal axes. In this manner, it is possible to sense or actuate strains in the substrate in a desired direction, regardless of the passive stiffness properties of the substrate, actuator element or sensor element. An isotropic actuator/sensor element attached to a substrate in this manner can then operate in an anisotropic way. In a preferred embodiment, the actuator/sensor element is bonded to the substrate at an area of attachment occupying only the central third of the actuator/sensor element in its longitudinal axes. The actuator/sensor element may be a piezoelectric, magnetostrictive, thermally actuated lamina (including bi-metallic) or shape memory alloy element.

Abstract: For detecting strains or breaks in the surface of a boat hull or other structure, the surface is covered with non-intersecting lengths of tape adhered to the surface. The tape has an inner strip of conductive elastomer and an outer strip of the same material, and between them a corrugated layer of copper foil. Both strips and the foil are insulated from each other and the outside. The strips and foil layer are connected to electrical resistance and capacitance measuring devices, which monitor any changes in the electrical properties of the tape lengths, caused by strain or breaking of the surface. Because of the corrugations, the foil will not change its resistance when the tape is elongated or compressed.

Abstract: A multilayer flexible circuit for sensing physical properties of a structural surface 12 capable of surviving exposure in harsh environments through the use of isolation materials 70 disposed within the flexible circuit 10.

Abstract: A device for measuring strain in substrates at high temperatures in which the thermally induced apparent strain is nulled. Two gages are used, one active gage and one compensating gage. Both gages are placed on the substrate to be gaged; the active gage is attached such that it responds to mechanical and thermally induced apparent strain while the compensating gage is attached such that it does not respond to mechanical strain and measures only thermally induced apparent strain. A thermal blanket is placed over the two gages to maintain the gages at the same temperature. The two gages are wired as adjacent arms of a Wheatstone bridge which nulls the thermally induced apparent strain giving a true reading of the mechanical strain in the substrate.

Abstract: The present invention is intended to facilitate prediction of the life of a structure, such as a frame of a dump truck and so forth without requiring cumbersome calculations. A gauge (2, 3 or 4) for predicting a life of a structure comprises a gauge main body of a thin plate form having annular ring portions (5, 6) of substantially the same configuration at both ends and a strip-like connecting portion (7) integrally connecting the annular ring portions and formed with V-shaped cut-outs (8, 8) at the intermediate portion in opposition to each other. The gauge main body has a shorter life than the life of the structure (1) to be predicted. A crack gauge is fitted between the mutually opposing cut-outs. The gauge is fixed on a predetermined position on the structure by way of welding or so forth. A breaking time of the gauge can be obtained from a variation of a measured resistance of the crack gauge. Based on the breaking period, the life of the structure (1) is predicted.

Abstract: A strain sensor adapted for adhesive attachment to a device element such as a valve stem includes a sensor circuit coupon, a support for the coupon, and a clamp carried by the support for clamping the support around the device element.

Abstract: A prefabricated, easily installable strain gage assembly (10) is provided which includes an elongated synthetic resin substrate (12) having adhesive (16) applied to the majority of one surface thereof while leaving a handling tab portion (18) adjacent one end of the substrate (12). A strain gage unit (28) is secured to the adhesive-bearing surface of substrate (12). A strippable protective film (56) is placed in covering, protective relationship to the strain gage (28) and the adhesive surface of substrate (12). Preferably, the substrate (12), adhesive (16) and film (56) are substantially transparent, and the substrate (12) is provided with perpendicular alignment marks (55, 55a) which are strategically located relative to the strain gage unit (28).

Abstract: A device for detecting fatigue of a monitored structure due to flexure comprises a fuse made of the same material as the monitored structure and formed with a failure portion designed to fail because of fatigue prior to failure of the monitored structure when the fuse and the monitored structure both experience the same stress history. An adhesive secures the fuse to the monitored structure and extends substantially over the entirety of a side of the fuse that is adjacent to the monitored structure. However, the adhesive is spaced apart from the failure portion. The adhesive ensures that the fuse and the monitored structure experience substantially the same stress history in both tension and compression yet does not inhibit failure of the failure portion. The device can be monitored locally by sight or can be used as part of a remote-monitoring system.

Abstract: A strain gauge and method of making same for use in certain medical applications, such as sensing the occurrence of an apnea event. The device is also applicable to monitoring mechanical motion associated with other medical conditions. The strain gauge actually measures the change in direct current resistance produced by stretching and compression of a number of carbon deposits coupled in series on a longitudinally extendible substrate. This extendibility is produced by suitably die cutting a flexible but inherently inelastic insulative substrate. The easily produced device may be used externally or encapsulated for implantation.

Abstract: An aircraft and a method and system for operating thereof as force/moment sensors integrated in elastic connecting joints of parts and units of the aircraft. The various force/moment components determined by the sensors are processed in order to generate control signals for optimizing the operation of the aircraft.

Abstract: A load sensing gasket having a gasket body defining a service opening for fluids and having a load sensor encased in a cavity in the body. The gasket body comprises a first gasket layer providing a first outer gasketing surface and a first inner surface, a second gasket layer providing a second outer gasketing surface and a second inner surface, the inner surfaces together defining the cavity and side walls for defining a perimeter for the cavity. The load sensor includes confronting electrodes and a pressure sensitive electrically resistive material between the electrodes and conductors extending outwardly of the perimeter. A seal between the first and second gasket layers around the load sensor seals the electrodes in the cavity from fluids when the gasket is in use.

Abstract: A strain gauge primarily designed for dynamic measurements and requiring very little force to produce a change in length. The strain gauge is alternately concave and convex in shape, such as a sinusoidal curve with nodes of low resistance on the convex portions and strain gauges of high resistance on the concave portions. The gauge is unbonded and can be stretched with very little force. The strain gauge is utilized in an instrument to monitor infant respiration and detect episodes of apnea.

Abstract: Sensors responsive to small changes in the concentration of chemical species are disclosed, comprising (a) a mechanochemically responsive polymeric film capable of expansion or contraction in response to a change in its chemical environment, operatively coupled to (b) a transducer capable of directly converting said expansion or contraction to a measurable electrical response.

Abstract: In the present apparatus, a system converting stress in a structural member into strain by positioning a body of lasing material (creating a coherent beam) on a structural member. The body has parallel end faces. One is opposite a mirror attached to the structural member. The member strain varies laser cavity spacing and modulates the laser beam as a function of strain.

Abstract: A strain gage comprising a strained-layer superlattice crystal exhibiting piezoelectric properties is described. A substrate upon which such a strained-layer superlattice crystal has been deposited is attached to an element to be monitored for strain. A light source is focused on the superlattice crystal and the light reflected from, passed through, or emitted from the crystal is gathered and compared with previously obtained optical property data to determine the strain in the element.

Abstract: An electrical resistance wire is mounted along a cable or a rod which can be subject to a tension load or strain. The wire is mounted so that it undergoes a variation of its resistance when there is a variation of the tension load in the cable or rod. The resistance in the resistance wire is measured on a periodic basis, which gives a measure of the tension load.

Abstract: A strain gauge sensor for sensing stresses and deformations in mechanical members or structures, comprising a support substrate in form of a thin plate, made of an electrically-insulating material, preferably ceramic material, bearing on one face at least one thick-film resistor; said support substrate being adapted to be firmly attached with its other face onto a member or structure of which stresses and deformations are to be locally sensed, so that said stresses or deformations determine through the substrate corresponding deformations of said at least one thick-film resistor.

Abstract: The deformation sensitive electroconductive knitted or woven fabric of the present invention is a knitted or woven fabric, which can be changed in electroconductivity at the deformed portion when the deformation of stretch or compression is applied thereon by maintaining in the certain ratio of the number of electrically insulating portions to the number of electroconductive portions at the intertwined portions of the fibers and/or the portions between the intertwined portions of the fibers. By using this knitted or woven fabric directly or a deformation sensitive electroconductive sheet having an elastomer laminated on at least one surface of the knitted or woven fabric, it can be utilized as an stretch sensitive electroconductive device or pressure sensitive electroconductive device provided electrodes capable of detecting the changes in electroconductivity corresponding to deformations as electrical characteristics such as electrical resistance.

Abstract: A method and device for monitoring large structures so as to detect defects, e.g. cracks. An electric current is supplied to a steel structure which is equipped with contact points between which are measured voltage drops caused by the impressed current. A relatively large number of fixed contact points are used all over the area which is to be monitored. The voltage drops are measured between selected pairs of contact points and these voltage drops are compared with corresponding voltage drops that have been measured previously in the same manner when the structure was in an initial condition, preferably without any defects. The monitoring can this be performed by means of robust and simple devices which are relatively impervious to rough environments.

Abstract: A novel transducer able to detect ultrasonic surface waves over a wide frency band. The transducer is essentially a grid or series of bars connected in parallel or series. The sensitivity of the transducer increases proportionally with frequency for constant surface wave amplitude. The transducer detects surface waves by providing a resistance change across the transducer output terminal proportional to the surface wave strain. The output voltage can be calibrated to give a direct reading of the surface wave amplitude. The coupling problems which are inherent in most transducer configurations are drastically reduced for this strain sensitive detector. The modulation of the grid excitation voltage provides a means for mixing two signals by giving the direct product of the signals in time. Complicated filtering functions can be built into the grid detector by varying the bar spacing in a manner analogous to the piezoelectric interdigital grid transducer.

Abstract: A transducer assembly for monitoring stress in flexible sheet material, by responding directly to stress in the sheet and providing an electrical output which is related to the magnitude of biaxial stresses in the sheet. A transducer, for example of a suitable epoxy, is cast as an inclusion through which the stresses from the material are transferred. According to a preferred embodiment, a hole is made in the fabric material and the coating, if present, is removed from adjacent yarns about the edge of the hole to form an annular region to which the transducer then is securely bonded. If a non-yarn material is used then the epoxy is formed about the material per se. One or more electrical strain gages are affixed to the transducer, to directly sense stresses in the material which are transmitted to the transducer. In other embodiments the transducer is an integral part of a piece of sheet material which in turn is spliced into the overall material to be monitored.

Abstract: A thin film strain gage is deposited on a flexure beam under controlled deposition conditions such that the dielectric parts thereof are normally in a compressive state. During use, when the strain gage is flexed in a manner tending to place parts thereof in tension, the dielectric parts are instead maintained either in compression, which is their more resistant state against mechanical fracture, or only in slight tension. Specifically, the dielectric films are deposited by sputtering with the substrate negatively biased, with the deposition rate and substrate temperature maintained at predetermined levels for enhancing compressive deposition.

Abstract: A method of, and apparatus for, determining the time dependency of the length of a fissure in a test specimen during a fracture test which comprises securing an electrically conductive, areal or surface-like element to the test specimen such that during the fracture test it tears at the region of the fissure. An electrical parameter, such as the electrical resistance is determined between two measuring locations of the element. The measuring locations are selected such that the measurement current between such measuring locations passes through the region of the fissure. The element which is employed has a compact measuring section which is free of openings and the element is secured at the test specimen in such a manner that the measuring section completely covers the surface region which is occupied, during the fracture test, by the fissure until the end of the measurement of the length of the fissure, so that the resistance substantially uniformly increases with the length of the fissure.