Abstract: The present invention provides an apparatus, system and method which enables a determination of pressure on a surface which is coated with a pressure sensitive paint which, when flashed with light, exhibits return light with a decay time constant as a function of surface pressure. The system controls a light source which is adapted to emit a train of light pulses directed at the coated surface and controls a camera adapted to collect light level data from the surface. Further, a synchronizer is used to provide timing and control of the light source and the camera in which the synchronizer enables the light source and subsequently enables the camera to collect light level data in first and second gate periods. The first gate period is set to a predetermined time period associated with a light pulse and the second gate period is set to a predetermined time period subsequent to the first gate period. A decay time constant is determined from the data collected in the first gate period and the second gate period.

Abstract: A method for monitoring a structure (10) for the formation of cracks (18) includes first pretreating a surface (14) of the structure by applying a first coating (30) to the structure which bonds uniformly to the surface of the structure and creates a uniform surface coat. A second coating (40) is applied over the first coating and contains microcapsules (44). The microcapsules rupture in response to cracking of the structure to release a dye or pigment which changes the color of the second coating about the crack. Cracked portions which form in the structure may then be identified by observing color changes (48) in the second coating resulting from eruption of the microcapsules.

Abstract: The subject invention relates to a strain-sensitive coating, a strain measurement system, and a method to determine strains on substrate materials. In a preferred embodiment of the subject invention, the system includes a luminescent strain-sensitive coating and a strain field mapping system which can be used to create a strain map of the mechanical strain on a substrate material. The luminescent strain-sensitive coating of the subject invention is preferably a polymer-based coating, and can incorporate one or more luminescent compounds. The subject coating can be applied to produce a thin film on a substrate material, such as aluminum, steel, polymer, or composite. One or more characteristics of the luminescence emanating from the coating can then vary in relation to the strain on the substrate material.

Abstract: A method for determining stress effects, or stress endurance of a film layer coated on a wafer during a scrubber clean process is disclosed. In the method, a wafer having a film layer coated on top is held in a stationary position while a high pressure water jet having a pressure larger than 60 kg/cm2 is scanned across a top surface of the film layer and through a center of the wafer. The total number of stress defects is then counted in the scanning path on top of the film layer as an indication of the stress endurance of the specific coating layer. The invention also discloses a method for scrubber cleaning a wafer surface which is coated with a film layer without causing stress defects in the film by rotating a silicon wafer, which has a film layer coated on top at a suitable rotational speed, and then scanning a water jet across a top surface of the film layer without passing through a center of the wafer. The water pressure utilized for the water jet may be suitably between 50 kg/cm2 and 75 kg/cm2.

Abstract: A method for measuring permanent length deformations in materials includes determining a change of an initial distance between two measuring points on the material surface. A first pair of impressions is formed on a portable impression body that corresponds to these two measuring points prior to the expected deformation and a second pair of impressions is formed after a critical loading of the material. The distances between the first and the second pairs of impressions are then compared. A device for carrying out the method uses a fixed portion arranged on the material being measured and a portable impression body. The fixed portion of the device is provided with a pair of measuring elements which correspond to the measuring points disposed at a mutual distance from each other, and the portable impression body of the device has an impression face adapted for receiving the impressions that are created by the measuring elements.

Abstract: An improved method for measuring residual stress in a material comprising the steps of applying a spot of temperature indicating coating to the surface to be studied, establishing a speckle pattern surrounds the spot of coating with a first laser then heating the spot of coating with a far infrared laser until the surface plastically deforms. Comparing the speckle patterns before and after deformation by subtracting one pattern from the other will produce a fringe pattern that serves as a visual and quantitative indication of the degree to which the plasticized surface responded to the stress during heating and enables calculation of the stress.

Abstract: A real-time imaging contact gauge for indicating the distribution of contact pressure over a surface includes a transparent base panel, a pressure-transmitting member at one face of the transparent base panel for receiving the contact pressure to be indicated, a birefringent member sensitive to mechanical pressure located between the pressure-transmitting member and the transparent base panel, a plurality of spaced, parallel electro-luminescent layers carried by the transparent base panel for illuminating the birefringent layer, and a polarizer for polarizing the light transmitted to the birefringent layer to produce optical interference patterns corresponding to the contact presssure distribution applied to the pressure-transmitting member, which patterns are viewable through the opposite face of the transparent base panel.

Abstract: A first aspect of the invention relates to an epoxy resin coating used in reflection photoelasticity, which is "black" in the infra-red part of the spectrum; another aspect to the use of an epoxy resin as a coating on at least one surface of a body to be subjected to cyclic loading and examined by thermoelasticity, and another aspect to a method of making thermoelastic measurements of a body when subjected to cyclic loading and hence measurements of stresses or strains, comprising, as an initial step, coating the surface(s) of the body to be measured with an epoxy resin whereby the surface(s) so coated represents a black body.

Abstract: A method and optical system is disclosed for measuring an amount of stress in a film layer disposed over a substrate. The method includes steps of: (A) applying a sequence of optical pump pulses to the film layer, individual ones of said optical pump pulses inducing a propagating strain pulse in the film layer, and for each of the optical pump pulses, applying at least one optical probe pulse, the optical probe pulses being applied with different time delays after the application of the corresponding optical probe pulses; (B) detecting variations in an intensity of a reflection of portions of the optical probe pulses, the variations being due at least in part to the propagation of the strain pulse in the film layer; (C) determining, from the detected intensity variations, a sound velocity in the film layer; and (D) calculating, using the determined sound velocity, the amount of stress in the film layer.

Abstract: A system (50) for determining strain includes: a stimulating light source (54, 56); a device (64) for placing stress on an object (58); a number of local strain gauges (66) attached to the object (58); and an image capturing device (62, 64). A controller (52) is coupled to the stimulating light source (54, 56) and has a signal that turns on the stimulating light source (54, 56). The controller (52) receives a strain signal from each of the local strain gauges (66) located on the object (58). The controller (66) has an image signal that determines when the image capturing device (62, 64) captures an image.

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: A method of estimating non-destructively the life expectancy of ceramic members, at least a surface layer of which is made of ceramics, is disclosed. The method comprises measuring a variation in at least one of physical characteristics of said ceramic members including color, grain size, electroconductivity and Young's modulus and estimating the life expectancy of the ceramic members on the basis of the predetermined relationship between the life of said ceramics and the physical characteristics. The method is excellent in estimation of the life expectancy of ceramic members of gas turbines or nuclear fusion reactor since the life expectancy of the members to be inspected can easily be estimated in a short time without fracturing the members.

Abstract: An apparatus for monitoring the fatigue strength of a structure comprises a longitudinal rib which is attached or integrated to the surface of the structure. The rib has a plurality of transverse notches of differing depths, each of the notches having a rounded end adjacent the surface of the structure and a pointed end extending toward an exterior edge of the rib.

Abstract: A force sensing assembly measures a magnitude of a force generated at the tabs in a product delivery system. The product delivery system can be one in which a force is produced at the tabs by the weight of the stack, by a paddle pushing an end of the stack, or by another similar type of advancing mechanism. In a preferred embodiment, the force sensing assembly has a pair of tabs connected to a cross-bar which extends across the stack and which is connected to the frame of the feeder through a bell crank at one end and a lever at the other end. The bell crank has one arm connected to the cross-bar and a second arm connected to a load cell. The force at the tabs causes the lever and bell crank to rotate, with the force being transmitted through the bell crank, through a spring, and then to the load cell. The load cell generates a force signal which is supplied to a controller for adjusting the amount of force at the tabs.

Abstract: A method for determining the residual stress in an unsupported region of a thin film. The method includes the steps of (a) optically exciting the film with a spatially and temporally varying optical excitation field to launch counter-propagating acoustic modes along at least one wavevector; (b) diffracting a portion of an optical probe field off the excited acoustic modes to generate a time-dependent signal field at the excitation wavevector; (c) detecting the signal field to generate a time-dependent, light-induced signal; (d) analyzing the light-induced signal to determine the frequencies of the acoustic modes; (e) partially determining the dispersion of at least one mode; and, (f) comparing the measured dispersion to that calculated using a mathematical model to allow the residual stress properties of the unsupported region of the film to be determined.

Abstract: A method and passive monitor for measurement of fatigue is provided. The method includes locating regions of high stress on a structure or material to be monitored, identifying the direction of principal stresses, and then aligning and bonding a specially fabricated passive fatigue monitor to the structure. After the structure has been subjected to a stress cycle, the passive fatigue monitor is removed and the striations formed in the monitor are evaluated. If necessary, contrast enhancement of striations can be performed prior to striation evaluation. Data from evaluations is assessed using rain flow cycle counting and Miners cumulative damage algorithms. The passive fatigue monitor is a small coupon of material fabricated from aluminum or other material known to form well-defined striations. The monitor is specially modified to contain a precrack which provides the location for striation formation.

Abstract: An apparatus for monitoring the fatigue strength of a structure comprises a longitudinal rib which is attached or integrated to the surface of the structure. The rib has a plurality of transverse notches of differing depths, each of the notches having a rounded end adjacent the surface of the structure and a pointed end extending toward an exterior edge of the rib.

Abstract: A method for detecting stresses includes the steps of dispersing a fluorescent substance in a solid portion where stresses are to be detected, measuring fluorescence decay time of the fluorescent substance dispersed in the solid portion, and detecting stresses in the solid portion based on the measured fluorescence decay time. The method enables to non-destructively detect stresses in resin-molded products without impairing their mechanical properties.

Abstract: Applicant has discovered a new mechanism which induces the cracking and spalling of metal-reinforced concrete. Methods and compositions for preventing such cracking and spalling are provided. Methods of testing compositions or admixtures for effectiveness in preventing cracking and spalling are also provided.

Abstract: A device for monitoring the fatigue life of a structural member composed of a predetermined material, and a method of making same. The device is a substantially flat fuse composed of a material similar to the predetermined material and mountable on a structural member by adhesive during use. The fuse has cut out portions which define fuse elements and variable unbonded areas are formed about the fuse elements to effect failure at different times in sequence because of fatigue and prior to the failure of the monitored structural member when the fuse and the monitored structural member are subjected to substantially the same stress history.

Abstract: Disclosed is a device for selectively indicating strain comprising a layer of polymeric binder and, distributed in or adjacent to the binder layer, microcapsules containing an indicating means, whereby when the binder is stiff, minor flexure of the device causes rupture of the microcapsules and releases the indicating means. This device has a non-stiff state such that a given strain applied to the binder layer in the non-stiff state will not release the indicating means, and a stiff state such that the same given strain applied to the binder layer in the stiff state will release the indicating means. Also disclosed is a method for determining exposure of an article to a given low temperature.

Abstract: A device for monitoring the fatigue life of a structural member composed of a predetermined material, and a method of making same. The device is a substantially flat fuse composed of a material similar to the predetermined material and mountable on a structural member during use. The fuse has cut out portions which define fuse elements which also have reduced thicknesses to effect failure at different times in sequence because of fatigue and prior to the failure of the monitored structural member when the fuse and the monitored structural member are subjected to substantially the same stress history.

Abstract: The invention provides a method and means for detecting and giving warning of a predetermined status of cordage through the change of a warning element from one condition to a different condition in response to a change in the status of the cordage.

Abstract: A device for gauging the size of a bone socket comprising a hemispherical member having a pole on its axis at the distal end and having a bore on its axis at its proximal end; a handle releasably attached to the bore of the hemispherical member; and a pressure responsive surface on the hemispherical member to constitute a pressure responsive surface for changing characteristics when brought in contact with a bone socket to be gauged. The change in characteristics may be in color or shape. Also disclosed is the method for using the device.

Abstract: A technique for impregnating a fluid so that the impregnated fluid retains information about the highest pressure that has ever been exerted on it. This technique is particularly useful where normal pressure measurement methods are not practical.

Abstract: A device for gauging hoop stress in a female threaded connector member, the stress being caused by tightening of a tapered male threaded member into the female member, including an annular body dimensioned for surrounding the female member with a firm fit therebetween, the body including two discrete complementary half-sections. Each of the half-sections includes an overlapping segment on one end, and each segment has an aperture therein. A pin is provided for insertion through the aligned apertures. An anchor block is fixed to each of the otherwise free ends of the annular body, each of the blocks having a cutout portion therein. A weak link having a tensile strength less than that of the annular body is provided for insertion into the cutout portions for joining the blocks. The weak link clamps the body about the female member and breaks under the application of a predetermined hoop stress to the female member.

Abstract: A device for monitoring the fatigue life of a structural member is comprised of at least one and preferably a plurality of substantially flat, elongated coupons which are fabricated of the same material as that of the member being monitored. The coupons are secured in parallel to the member so that they all experience the same strain history as the member. Each of the coupons includes a different stress concentrating notch pattern so that the application of the same strain to all of the coupons results in the development of different stress concentrations within the coupons. The development of different stress concentrations within the coupons causes each coupon to have a different fatigue life, the fatigue life of each coupon being a predetermined percentage of the fatigue life of the structural member being monitored.

Abstract: A method of accelerating tests for the delayed failure of coatings and coated substrates caused by degradation is provided wherein the coated substrate is subjected to a controlled level of strain during testing.

Abstract: The invention relates to a fatigue indicator for mechanical parts subjected to repeated stresses, which comprises two thick elements spaced apart from one another and joined together by a thin web having a slit, these two elements being incorporated in the part or fixed thereto so as to move with respect to one another upon application of stress on the mechanical part in a plane which is parallel to the plane of the web, the thin web being thus subjected to a shearing stress in its plane, and wherein the slit of the thin web extends from one of the edges of the web in the direction of relative movement to a blind end so that, when the part is stressed, two cracks appear from corners of the blind end of the slit, extend progressively in the web and finish by reaching the opposite edge of the web or joining cracks coming from this opposite edge, the web thus being detached or practically detached.

Abstract: The present invention relates to an improved fatigue damage indicator for a echanical member subjected to repetitive stress, comprising two thick elements which are spaced from one another and are connected one to the other by a thin web or plate formed with a slot and at least one pair of free opposite edges, the two elements being so connected with the mechanical member or fixed to the latter so that they are displaceable relative to one another in a plane parallel to the plane of the thin plate, the thick elements being disposed so as to be separated from one another in a direction substantially perpendicular to their direction of relative displacement by such stress, the thin plate being placed under shear force in its plane by such relative displacement, the slot of the thin plate extending from one of the edges of the web in the said direction and terminating short of the opposite edge in a blind end of the slot having two corners so that, with application of stress, two cracks develop at corners of the

Abstract: An apparatus for the approximate determination of forces acting on a support frame which has a compression member disposed between two pressure plates. The compression member has a coating of a material such as enamel which separates from the member as a function of the members' deformation under compressive forces and thus is an indicator of the magnitude of such forces.

Abstract: A fatigue damage indicator includes a thin plate mounted between or integral with two members to which a stress is to be applied, the disposition of the two members being such that the thin plate is stressed in shear.Slots extending in the direction of the applied stress may be provided to ensure that cracks formed by fatigue stress propagate in a desired direction and the crack propagation is designed to ensure that a part of the plate becomes detached or is bent substantially away.

Abstract: A method of detecting flaws in a printed circuit board laminate having drilled holes wherein a penetrating solution containing a UV fluorescing dye is applied to the laminate to fill the drilled holes and flaws. Excess penetrating solution is removed from the drilled holes and the surface of the laminate. The penetrating solution remaining in the flaws is cured into an insoluble solid and then the laminate is cross-sectioned to provide at least one sample carrying the cured solution. The sample is encapsulated in a clear epoxy and the encapsulated sample is ground and polished to provide a surface which is examined under UV light.

Abstract: An improved grid for computer-aided strain analysis of a deformed metal sheet comprises a preferred grid pattern of noncontacting uniform solid circles formed of thin plated copper and surrounded by exposed sheet surface. The copper circles are applied to the sheet surface and the sheet is deformed, whereupon the circles are stretched into ellipses. After sheet deformation, the ellipse pattern is oxidized to enhance contrast between the copper ellipses and the surrounding sheet metal and thereby enable the pattern to be reliably photographed for computer analysis.

Abstract: Fatigue in structural elements is determined by measuring the loss in specular reflection in a foil of polished metal secured to an exposed surface of the tested object, the elastic limit of the foil material under shearing stresses being lower than that of the tested object, and the foil consisting either of a single crystal or of polycrystalline material of uniform, small grain size.

Abstract: A method of detecting very small structural flaws at loads below those which cause the flaws to propagate is disclosed. Certain phenomena and relationships of fracture mechanics are utilized in conjunction with the generation, detection and interpretation of thermal emission signals indicative of plastic deformation of the tested material.

Abstract: A body electrode including a visual indicator to ensure optimal parallel positioning and electrical current distribution between the electrode and the body. The indicator comprises a flap imprinted with alternating areas of green and red indicia, and an exterior sheet overlying the flap and defining three windows. The flap and the exterior sheet are attached at longitudinally spaced locations to a stretchable, insulating cover sheet. Stretching the electrode to a predetermined optimal degree of tension aligns green indicia with the windows, and presence of red indicia in the windows indicates either excessive or insufficient applied tension.

Abstract: A method for measuring pressures which comprises allowing a material whose pressure is to be measured to press against a recording sheet to form a color image due to the pressure, and evaluating the changes in the optical color density of the color hue of the resulting color image on the recording sheet, the color image formation due to the pressure being effected by contacting a synthetic polymer microcapsule layer containing a color former with a color developer layer under pressure, said microcapsule layer and said color developer layer being coated on the same surface of the support.