Abstract: A closed system, impact-fatigue test machine for grinding balls comprised of a vertically extending guide member and a lift conveyor wherein the guide member lies above a recessed anvil and defines in its center a longitudinal opening. Each grinding ball is carried upwardly by the conveyor to an opening in the upper portion of the guide member and then is dropped into the guide member to land laterally supported, upon an earlier dropped grinding ball which rests on the anvil below. The earlier dropped ball is then pushed from the anvil toward the conveyor causing the dropped ball to impact the anvil below. The number of dropping cycles that each ball can tolerate without fracture is counted by a counter. Fracture of the balls is detected by a fracture detector.

Abstract: A crack susceptibility test for weld metals such as the alloys of titanium, luminum and copper comprises filling a triangular pattern of grooves in a plate with weld metal wherein the groove arrangement provides the degree of restraint necessary to generate cracks in the weld metal. The grooves, which are fully contained in the plate, intersect to form a 30.degree.-60.degree.-90.degree. triangle, wherein the groove depth to plate thickness ratio is between about 0.2 and 0.8.

Abstract: Equipment for testing materials for the effects of stress corrosion cracking, which includes more than two tensioning units, each consisting of a base plate, two guide bars, an upper and a lower cross-beam, a locking system for the guide of the lower cross-beam and a connecting flange between the cross-beam and a threaded bar for causing elongation of a test sample. The power drive supply block drives the threaded bar. A motor power unit is included in the power drive supply block and vertically-slippable gearing is inserted between the motor gearing and the block. The motor power unit consists of two stepping motors driving sun gears. The sun gears drive planetary gears which, by means of an arm, drive the drive shaft operatively associated with the threaded bar. In particular, the invention relates to equipment with six tensioning units comprising an automatic limit switch-off means and a lift system in the power drive supply block for separating the drive gears from the rest of the system.

Abstract: A method for measuring crack propagation in samples as a function of the number of load cycles is proposed wherein changes in the frequency response of a mechanical impedance of a sample which is to be tested is registered. At a pulsation frequency, which corresponds to the resonant frequency of the sample, there is a rise in the resonance of the mechanical impedance, defined as the quotient of the speed of movement of the sample and the applied pulsating force. Since, when a crack grows in the sample, its elastic constant decreases along with the cross-sectional area, the frequency response of the sample shifts towards lower frequences.

Abstract: A dual element strain gauge is placed near a welded or otherwise constrained joint on a structural member so as to provide a constraint factor. The location for the strain gauge must be selected to provide constraint factor that is preferably near either maximum or minimum value. The strain gauge is monitored to detect a change in the initial constraint factor, which indicates failure has begun or is imminent.

Abstract: The present invention involves a new method for measuring plane strain fracture toughness (K.sub.Ic) of a somewhat non-elastic material uniquely suitable for use on specimens that are smaller than have formerly been required for performing valid K.sub.Ic tests. The present invention involves selecting a short-rod specimen configuration in which the specimen material at a crack front or tip therein would be constrained during loading to a plane strain state and, from the measurement and anelastic analysis of a load-displacement curve that includes at least two unloading slopes the energy per unit crack area that is required to slowly advance a steady state crack can be determined, which data, along with measurement of the critical load when the crack passes through a known location, and considering the specimen geometry, is used to determine the fracture toughness, K.sub.Ic, of the specimen.

Abstract: The gauge of the present invention consists of a three-pronged spring clip for arrangement between the grips of a conventional grip-loading fracture specimen loading machine, which grips are inserted into the mouth of a standard slotted fracture toughness test specimen, the gauge to monitor the specimen mouth opening displacement thereof during a test for fracture toughness. The spring clip preferably is formed from a single sheet of material that is bent appropriately to produce two aligned legs or prongs with a center leg or prong there between. In operation the outside prongs are essentially stationary while the center prong is arranged to flex with respect to grip movement apart, which center movement is sensed electrically by a strain gauge secured thereto at its point of bending.

Abstract: A method is disclosed for detecting the onset of cracking in an article subjected to dynamic loading. The article is subjected to a dynamically changing load, and additionally is loaded and vibrated at its natural frequency. The onset of a crack in the article is determined by noting a change in its natural frequency.

Abstract: Two radial cuts are made in a disc-shaped solid, the wedge (or sector) thereby produced is removed, and the exposed faces of the radial cuts are forced into contact with each other. By bonding (or welding) together the faces of the radial cuts, a self-stressed disc, capable of propagating a pure mode 1 crack, is created.

Abstract: A crack gauge for monitoring the progress of fatigue crack propagation in a conductive substrate is made by applying an inorganic insulating layer and then a metallic conductor. The conductor is laid in a geometry which results in a change in a measured electrical property of the conductor (e.g., resistance) as a fatigue crack propagates through the substrate and breaks the conductor. The adherent crack gauge is especially reliable in hostile environments. A special conductor geometry is useful for especially fatigue resistant substrates.

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 constant point of load application fracture specimen loading machine for applying a load between grips that engage opposite grip groove faces of a slotted specimen that preferably has as a remainder portion in that slot a "V" shaped slot root whereby, when the machine grips are moved apart, they rotate so as to apply a constant point of load application to pull the specimen apart at that slot root. The machine of the present invention is useful for measuring the fracture toughness, fatigue-crack growth resistance, or stress corrosion crack growth resistance of slotted specimens providing a unique force application system whereby sliding friction losses are minimized, and other introduced effects, such as from specimen grip machining tolerances, or the like, are largely automatically compensated for.

Abstract: Crack initiation in metallic structural members subject to cyclic loading is predicted by sensing metallurgical changes taking place as a result of the cyclic loading. Fatigue loading produces a cycle comprising a condition described as fatigue relaxation followed by fatigue intensification. By monitoring this cycle, measured strain for a known applied load will increase or decrease. By monitoring the change in strain load, crack initiation can be predicted as fatigue relaxation becomes fatigue intensification. In a preferred embodiment, the strain gauge is mounted beneath a patch excluding ambient atmosphere during monitoring of the structural members.

Abstract: An apparatus for detecting crack length of a test piece in a fatigue test wherein crack length is automatically detected and the tip of the crack is displayed on a monitor.A test piece having a crack thereon is irradiated by a Strobo light through an optical-scope. Reflected beams from the test piece are focused on a camera tube by passing through the optical-scope thereby forming an image of the crack on the camera tube.The image is then picked up by a scan converter memory so as to be memorized for an extended period.The memorized image is then introduced into an image analyser while monitored on a monitor screen. The tip of the crack is analysed and calculated in the image analyser and the position of the optical-scope is adjusted accordingly.A command controller is employed to control an overall time sequence of the entire apparatus.

Abstract: A flaw growth correlator for monitoring flaw growth potential in a structural body. The correlator providing a major increase in the sensitivity of flaw growth when compared to current designs of constant thickness crack gauges.

Abstract: The present invention relates to a method for measuring the fracture toughness of rock as it would exhibit in its natural down-hole setting. Practicing the method of the present invention involves internally pressurizing a rock specimen while simultaneously exerting an increasing external horizontal stress thereon, raising simultaneously the internal pressure to maintain a desired relationship of exterior to interior pressures until the specimen fractures, which pressure, in relationship to the stress intensity factor and specimen geometry, provides the specimen fracture toughness as it would exist in a down-hole situation.

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.