Abstract: The invention relates to a method of measuring the biaxial shaping behaviour of metal materials, more particularly sheet metal. In the measuring method a flow locus curve comprehensively describing the shaping behaviour of the material is determined by determining the flow limits under tensile and compressive loading of secondary samples of a primary sample previously subjected to at least tensile, but preferably also to compressive loading. Preferably a number of flow locus curves of different preliminary loading of the primary sample are determined for each material. These flow locus curves, completely ascertained by tests, provide the further processor with a reliable ancillary means of selecting a material required for the particular shaping operation.

Abstract: The onset of rolling contact fatigue in an object may be detected by measuring the residual stresses in the surface of the object, and monitoring changes in their magnitude or their direction. The values of residual stresses in the surface are those averaged over a depth that may be in the range say 0.1 mm to 8.0 mm, for example about 2.5 mm. For ferromagnetic objects such as rails, the method may utilise an electromagnetic probe. Prior to rolling contact fatigue the surface stresses are compressive, and the onset of rolling contact fatigue may be characterised by a marked decrease of the stress in the generally transverse direction.

Abstract: The present invention provides a method of designing a high fatigue strength in high tensile strength steel, comprising: obtaining values of tensile strength &sgr;B (unit thereof is MPa) and Vickers hardness Hv of the steel; measuring a flaw area of an inclusion, when a fracture origin is located only at a surface of the steel; and estimating, in designing the high fatigue strength steel, that a fatigue limit &sgr;w (unit thereof is MPa) of the steel satisfies either &sgr;w≧0.5 &sgr;B or &sgr;w≧1.6 Hv, when a square root of the flaw area, (area)½ (unit thereof is m), contained in the steel is no larger than 45.8/&sgr;B2 or 4.47/Hv2. According to the present invention, a method of evaluating high fatigue strength in high tensile strength steel, in which method a relationship between a flaw dimension (area) of ODA and the fatigue strength is considered, and a high fatigue strength material can be provided.

Abstract: Focusing on the application of a predetermined relationship between the length of a fatigue damage detection sensor having a width of a specified shape and a required sensitivity or sensing accuracy (crack propagation rate), the present invention provides a fatigue damage detection sensor for structural materials and mounting method thereof, wherein when the length between a pair of fixing portions for fixing to a surface of a structural material M, both ends of a sensor body (2) sandwiching a notched portion (5) is defined as 2H, the length of a crack C that can propagate from a tip (5A) of the notched portion (5) is defined as (a), the number of times that a working load acts on the material is defined as N, and the crack propagation rate is defined as da/dN, the length 2H between said fixing portions is set so as to obtain a required sensitivity with which da/dN is proportional to H0.5m (m is a constant determined by a material).

Abstract: A method for estimating the life of an apparatus under a random stress amplitude variation, involving determining a probability density function of a cumulated damage quantity and estimating the life of the apparatus on the basis of the probability density function, characterized by: approximating a damage coefficient indicative of a damage quantity per unit by a linear expression when the random stress amplitude variation is in a narrow band; and representing the random stress amplitude variation &sgr;(t)(instantaneous) in terms of the sum of a time averaged value &sgr;(t)(mean) and a stochastic variation &sgr;′.

Abstract: A crack-type fatigue detecting sensor comprises: a foil substrate having a first surface and a second surface fixed to a member to be tested; and a foil fracture piece having a slit formed in a central portion between opposite end portions in a longitudinal direction thereof such that the slit extends from one side portion toward the other side portion in a width direction thereof perpendicular to the longitudinal direction, wherein the opposite end portions of the fracture piece are respectively fixed to the first surface of the substrate and a portion including the central portion having the slit has a thickness smaller than a thickness of the opposite end portions over a whole width.

Abstract: The present invention is a method and system for determining the residual stress within an elastic object. In the method, an elastic object is cut along a path having a known configuration. The cut creates a portion of the object having a new free surface. The free surface then deforms to a contour which is different from the path. Next, the contour is measured to determine how much deformation has occurred across the new free surface. Points defining the contour are collected in an empirical data set. The portion of the object is then modeled in a computer simulator. The points in the empirical data set are entered into the computer simulator. The computer simulator then calculates the residual stress along the path which caused the points within the object to move to the positions measured in the empirical data set. The calculated residual stress is then presented in a useful format to an analyst.

Abstract: A multiaxial strain cycle (32, 72) is received that is described by a strain tensor that is a function of time. A hyperelastic constitutive model (34, 74) corresponding to the material is received. A fatigue crack growth curve (36, 76) is obtained. A cracking energy density is calculated (50, 90) based on the constitutive model (34, 74) and the multiaxial strain cycle (32, 72). The cracking energy density is a function of material plane (44, 84) and indicates the portion of the total elastic strain energy density that is available to be released on a selected material plane (48, 88). A cracking plane is determined (54, 98) based upon the cracking energy density. A fatigue life is estimated (60, 100) based on the cracking plane and the fatigue crack growth curve (36, 76).

Abstract: A method and apparatus are provided for the detection, through nonlinear manipulation of data, of an indicator of imminent failure due to crack growth in structural elements. The method is a process of determining energy consumption due to crack growth and correlating the energy consumption with physical phenomena indicative of a failure event. The apparatus includes sensors for sensing physical data factors, processors or the like for computing a relationship between the physical data factors and phenomena indicative of the failure event, and apparatus for providing notification of the characteristics and extent of such phenomena.

Abstract: A method to estimate the crack growth rate of HIPed cast IN718 material with various grain sizes and working environments comprising determining the average grain size diameter and duration of hold time and solving the following equation, ⅆ a ⅆ N = 1 &AutoLeftMatch; 1.19 × 10 5 × GS + 5.59 × 10 4 × Env - 1.

Abstract: A material test specimen design is taught for the determination of critical strain and stress states for multiaxial fracture. The objective of the specimen is to increase the amount of data obtained per specimen while retaining simplicity in testing procedure by using standard tension testing machines to generate the primary deformation of the specimen. The specimen, in conjunction with analytical or computational simulation, uses nonuniform deformation fields produced by secondary and tertiary strain concentrations to generate and track these multiaxial strain states to fracture. Typically, the primary deformation is uniaxial tension of a panel, the secondary strain concentration is a circular hole in the panel and the tertiary strain concentrations are areas of reduced thickness within the deformation field of the circular hole. Multiaxial strain ratios from −0.50 to −0.10 and control over fracture initiation sites may be generated by a test specimen design of the type taught by this invention.

Abstract: A method for easily and effectively preventing shattered-rim fracture in a railway wheel. Generally, the method comprises the steps of providing a railway wheel, measuring the maximum defect size within the rim of the railway wheel, and determining whether the maximum defect size is less than a predetermined maximum permissible defect size, the maximum permissible defect size being determined based on an analysis of the likelihood of Mode II crack propagation from the defect when the railway wheel has been subjected to the load. The disclosed invention also encompasses a method for grading railway wheels for maximum load suitability.

Abstract: A sheet metal component, obtained by press-forming a one-piece metal sheet comprised of two metal sheets into a desired shape, has an expanding portion having an external appearance varying in dependence on a weld state of a weld portion of the one-piece metal sheet at which the two metal sheets are welded at their confronting ends. In manufacturing the sheet metal component, the one-piece metal sheet is transferred between upper and lower dies of a pressing machine and is positioned such that its metal sheet section including part of the weld portion is disposed between a punch formed in the lower die and a recess formed in the upper die so as to face the punch. The metal sheet section is pressed by the punch to be subject to plastic deformation, whereby the expanding portion is formed.

Abstract: A system 10 for continuously monitoring the integrity of a structure 14 includes a sensor pad 16 having a surface 18. The surface 18 is provided with a set of first channels 22 and interspersed second channels 24. Surface 18 is sealed onto the surface 12 of structure 14 so that the channels 22, 24 together with surface 12 form respective sets of first and second cavities 26 and 28. The first cavities 26 are placed in fluid communication with a vacuum source 101 via a third channel 30. The second cavities 28 are vented to the atmosphere via a fourth channel 34, through hole 35, and conduit 36. A high impedance 102 is placed in series between the vacuum source 101 and the first cavities 26. A differential pressure transducer 103 is connected across the high impedance 102 and monitors for change in vacuum condition between the vacuum source 101 and the vacuum in the cavities 26.

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: A crack-type fatigue detecting sensor comprises: a foil substrate having a first surface and a second surface fixed to a member to be tested; and a foil fracture piece having a slit formed in a central portion between opposite end portions in a longitudinal direction thereof such that the slit extends from one side portion toward the other side portion in a width direction thereof perpendicular to the longitudinal direction, wherein the opposite end portions of the fracture piece are respectively fixed to the first surface of the substrate and a portion including the central portion having the slit has a thickness smaller than a thickness of the opposite end portions over a whole width.

Abstract: A sacrificial specimen for use in monitoring a long-term stress intensity of a structure including a main body made of a metal and having an artificial crack formed at a central region thereof, and a pair of metal or synthetic resin thin plates each having a slit formed at a central region, said pair of thin plates being cemented together with interposing the main body therebetween such that said artificial crack is exposed outside through the slits. The sacrificial specimen is cemented onto a structure whose long-term stress intensity has to be monitored such that a central portion corresponding to the central regions of the main body and thin plates is not secured to the structure surface. When the sacrificial specimen is subjected to stress, the slits formed in the thin plates are deformed largely and a fatigue crack is produced in the main body such that the fatigue crack extends from the artificial crack.

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: The invention relates to a process for checking a hollow body section, wherein the section, after being filled with a fluid, is subjected to a bursting test to demonstrate its brittle fracture resistance. After the open ends of the section are closed, the required bursting pressure is applied by the dynamic movement toward each other of two elements that reach in a sealing manner through the open ends. The dynamic movement of the two elements is achieved by accelerating a weight toward one of the two elements such that the weight impacts the one of the two elements at an impact velocity, causing the dynamic movement.

Abstract: A method of inspecting a crack in a ceramic substrate that is not exposed on the surface. The method can detect all cracks and make objective judgement possible by expressing the inspection result as numerical data. Conductors are disposed on both faces of a ceramic substrate, wherein one of the conductors is a conductive liquid; the insulation resistance value or an electric property dependent on the insulation resistance is measured with the conductive liquid or other conductors electrically connected to the conductive liquid which are used as electrodes.

Abstract: A device for detecting fractures or corrosion in a workpiece having a non-conductive outer surface. A thin film layer of metallic material comprising a plurality of separate crack detection wires is bonded to the non-conductive surface of the workpiece. A top coating of protective material is applied to the thin film layer to protect the detection wires from abrasion and corrosion. When an electrical current is transmitted through the detection wires, a predictable resistivity pattern is viewable on a monitor. As a fracture propagates through the workpiece causing the crack detection wires to break one-by-one, the change in resistivity of the wires can be monitored and the existence and extent of any fracture or corrosion to the wires determined.

Abstract: A system for, and method of, empirically determining stress in a molded package and a power module embodying the system or the method. In one embodiment, the system includes: (1) a sensor, having a magnetic core exhibiting a known complex permeability in a control environment, that is embedded within the molded package and therefore subject to the stress and (2) a measurement circuit, coupled to the sensor, that applies a drive signal to the sensor, measures a response signal received from the sensor and uses the drive signal and the response signal to determine a complex permeability under stress of the core. The magnitude of the stress can then be determined from the core's complex permeability under stress.

Abstract: Methods and apparatus for detecting the onset of stress corrosion cracking are described. In one aspect, the present invention is a passive detector for in-situ detection of the onset of stress corrosion cracking in a nuclear reactor. The detector includes a ceramic insulator mounting member. A first material sample and a second material sample are secured to the mounting member. In the one embodiment, a metal bolt extends through the first and second material samples and secures the samples to the mounting member. The first material sample is cold worked to induce residual tensile stress and the second material is not cold worked. A first electrical conductor is electrically connected to the first material sample and a second electrical conductor is electrically connected to the second material sample.

Abstract: A double cantilever beam (DCB) assembly is disclosed, comprising a fracture specimen having a notch which defines first and second spaced, substantially parallel, outwardly extending beams, terminating at a closed end where crack growth occurs and extending to an open end. The beams are connected to each other along at least a portion of a facing surface of each beam by two, substantially parallel ligaments, spaced from each other on the facing surfaces of the beams. Another disclosed embodiment is a corrosive environment measuring apparatus, comprising a double cantilever beam assembly disposed in an aqueous portion of a reactor vessel, and including the features described above. The reactor vessel is often a constituent of a nuclear reactor, and the DCB assembly is often disposed in a tube which is selectively lowered into the aqueous portion of the reactor vessel. The tube is usually a local power range monitor tube.

Abstract: A process for improving fatigue resistance of a case hardened component having a case thickness "t", subjected to one or more of rolling, sliding, abrasion, bending and pitting includes determining the magnitude of fatigue strength at surface and at a plurality of pre-selected points along thickness "t" of a component. The applied fatigue stresses acting upon the component at the surface and at the plurality of pre-selected points along thickness "t" are also determined. Then, a compressive residual stress profile is tailored from the surface to thickness "t" of the component. The compressive residual stresses at the surface and at the plurality of the pre-selected points along thickness "t" respectively have a magnitude sufficient to attain a net resultant stress which is at least 25% lower than the fatigue strength at the surface and the corresponding plurality of pre-selected points.

Abstract: The system consists of a series of programs that enable a user to investigate possible toughening mechanisms against crack growth in composites and brittle materials consisting of different combinations of materials and containing planar interfaces and elliptically shaped microstructures. The programs begin with various materials, sizes and orientations of microstructures, distances of a crack from a material interface, and possible formulas for energy absorption mechanisms of interest to the user. They then allow a crack to advance toward an interface numerically integrate over a circular and microstructural regions and thus calculate the balance of various energy quantities during crack advance. They then transform the final calculations into a graph display of net energy per incremental length of crack advance versus crack distance from the microstructural entity in question.

Abstract: A nondestructive inspection method of inspecting a securing defect of a polymer insulator having an FRP core, an outer cover portion arranged around the FRP core, and at least one metal member secured to at least one end of the FRP core, includes the steps of; measuring an acoustic emission signal generated when the metal member is secured to the FRP core by using compression dies; and determining whether or not the securing defect is generated on the basis of the acoustic emission signal in process. Moreover, the disclosed apparatus performs the nondestructive inspection method mentioned above.

Abstract: Two electrical wires are connected to the surface of an electrically conductive solid body at two measurement points located on either side of a crack in the surface of the body. The two wires form a thermoelectric couple. A constant DC current is applied to the body. The two wires are connected to a device for measuring the extent of the crack and another device for measuring the temperature of the crack. By measuring the potential difference during application and interruption of the DC electric current to the body, it is possible to simultaneously obtain a measurement of the extent of the crack and a measurement of the temperature of the crack.

Abstract: A method of predicting crack initiation based fatigue life includes the steps of plotting the elastic finite element stress states of a stress history for a given component at a predetermined critical location in the stress space and determining the least square fit ellipsoid of the stress states by a straight line through the center of gravity. An aspect ratio .lambda..sub.2 /.lambda..sub.1 is defined where .lambda..sub.1 and .lambda..sub.2 are the two largest eigen values of the eigen system of matrix M which defines the least square fit ellipsoid and where .lambda..sub.1 .gtoreq..lambda..sub.2. A multiaxial fatigue analysis is performed where the aspect ratio exceeds a predetermined value.

Abstract: A method and system for detecting and preventing Stress Corrosion Cracking (SCC) in buried pipelines or other structures is presented. The basic principle of the invention is to use a plurality of test coupons which are placed in the same environment as a pipeline or other structure of interest as indicators of the development of SCC in the structure of interest. Loading and temperature of the test coupons are controlled. The test coupons are given a range of different Cathodic Protection (CP) levels, with the range of CP levels selected so as to encompass the CP level at which SCC would be expected to occur. The occurrence of cracking in a test coupon indicates levels of CP which will sustain SCC. SCC is prevented in the structure by application of a level of CP which did not sustain SCC.

Abstract: Flux-focusing electromagnetic sensor using a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks and material loss in high conductivity material. A ferrous shield isolates a high-turn pick-up coil from an excitation coil. Use of the magnetic shield produces a null voltage output across the receiving coil in presence of an unflawed sample. Redistribution of the current flow in the sample caused by the presence of flaws, eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal.Maximum sensor output is obtained when positioned symmetrically above the crack. By obtaining position of maximum sensor output, it is possible to track the fault and locate the area surrounding its tip.

Abstract: A method and apparatus for applying a force, displacement, or both to specimens, components, or systems by using a remote variable load/deflection device. The method enables testing of materials under actual in-service conditions. A displaceable container with a heating or heating and cooling element inside is provided. As heat is applied to the element, it expands thermally and causes the container to displace and apply force to specimens, components, or systems. The load/displacement of the container is modified by heating or cooling the element material. The container may be attached to in-service specimens, components, or systems and used to study the material behavior during in-service operation.

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 rising step-load test apparatus for subjecting the notched region of a fracture specimen to tension by applying four-point bending to the specimen, and having an adaptor that can fit into the test apparatus in four-point bending and convert the bending load to an axial tensile load on a second specimen for which the adaptor serves as a fixture. The test apparatus applies four-point bending to either the fracture specimen or the adaptor through two oppositely situated simple supports at one end of the fracture specimen or adaptor and two other oppositely situated simple supports at the other end of the fracture specimen or adaptor. The adaptor employs two pivotally attached linking members attached to the two ends of the second specimen to transfer a pure axial tension to the second specimen for testing in axial-tension mode. A chemical bath is provided for an accelerated test of hydrogen embrittlement.

Abstract: A corrosion monitoring apparatus and method for determining the corrosive effects of a chemical environment, having an environmental pressure, on a vessel containing the chemical environment. A probe is exposed to the environment and is made of a material substantially similar to that of which the vessel is made. The probe has a sealed internal chamber which contains a pressurized fluid which is monitored. A pressure transducer is in communication with the sealed internal chamber of the first probe for translating any pressure change within the chamber into a (preferably electrical) signal which is indicated by an electrical meter or similar device. Stress corrosion cracking of the probe causes fluid leakage and, therefore, a pressure change.

Abstract: A corrosive environment sensor comprises an elongate metal member having a pair of beam portions, each extending in a length direction between first and second ends of the metal member, and having a crack growth portion formed therein and extending in the length direction of the metal member from a crack starting end toward the second end, wherein the crack starting end is at an intermediate position between the first and second ends of the metal member and is between the pair of beam portions, a changeable load member having an expansible chamber disposed between the beam portion around the first end of the metal member and a means for supplying pressurized fluid to the expansible chamber. The changeable load member applies a load to the crack growth portion and the means for supplying pressurized fluid to the expansible chamber is responsible for ensuring that the displacement of the beam portions is accomplished in such a manner so as to provide a constant stress intensity factor at a crack growing point.

Abstract: An apparatus for preventing, detecting, and predicting the formation and propagation of cracks in structural members. The apparatus includes a plurality of strain sensors integrally formed with a patch to be fixed to an area on the surface of a structural member. The patch operates to reduce stress levels in the patch-covered area for deterring the formation or propagation of a crack therein. The sensors monitor changes in the strain field in the patch-covered area for detecting crack formation and detection. The apparatus may also include a temperature-compensating strain sensor and a temperature sensor both integrally formed with the patch for detecting and predicting crack formation and propagation, respectively.

Abstract: An apparatus for monitoring the growth of surface cracks in materials includes a means for applying a load to a specimen to simulate actual use of the specimen, means for illuminating the specimen, means for capturing images of the specimen, and means for processing the images to monitor crack growth in the specimen. Optionally, the means for processing can be used to control the other means.

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: An apparatus for monitoring the growth of surface cracks in materials includes a servo-hydraulic test machine which applies a load to a specimen according to a predetermined loading regime designed to induce crack growth in the specimen, a UV laser for illuminating the specimen with a light having a frequency greater than the frequency of incandescent light, a UV video camera and a two dimensional imaging computer. Optionally, the two dimensional imaging computer can be used to control the servo-hydraulic test machine.

Abstract: A device and method are provided which non-destructively detect crack length and crack geometry in thin metallic plates. A non-contacting vibration apparatus produces resonant vibrations without introducing extraneous noise. Resulting resonant vibration shifts in cracked plates are correlated to known crack length in plates with similar resonant vibration shifts. In addition, acoustic emissions of cracks at resonance frequencies are correlated to acoustic emissions from known crack geometries.

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: Devices and methods for determining the fatigue status of a metallic specimen are provided. The methods include contacting the specimen with-a cell containing an electrode and an electrolyte in contact with the specimen. A voltage is then applied, or galvanically created, between the specimen and the electrode, and the current is measured passing through the electrolyte during a period in which the specimen is subjected to cyclic stresses. A signature is then prepared which is representative of a measured current at the electrode, and the signature is analyzed to determine the fatigue status of the specimen.

Abstract: An apparatus and method for inducing and measuring crack growth in a solid by using a double cantilever beam assembly which includes a fracture specimen with a notch that defines a pair of spaced outwardly extending beams terminating at an end where growth of a crack occurs, and a spring assembly for continuously urging the spaced beams apart with a substantially constant pressure that creates a spreading pressure at the end where crack growth occurs to stress the fracture specimen at the end. An electromagnet assembly is used to cyclically apply and remove the spreading pressure caused by the spring assembly.

Abstract: A corrosive environment sensor comprises an elongate member having a pair of elongate beam portions and a crack growth portion formed between the pair of beam portions so as to extend axially, and a wedge inserted between the pair of beam portions, wherein the crack growth portion has width thereof defined by quadratic curves extending axially so as to decrease from an axially intermediate portion of the sensor member to an axially intermediate portion of the crack growth portion and increase from the axially intermediate portion of the crack growth portion toward an end of the sensor member. The quadratic curves each consist of a first circular arc with first radius between the axially intermediate portion of the sensor member and the axially intermediate portion of the crack growth portion and a second circular arc with second radius less than the first radius between the axially intermediate portion of the crack growth portion and around the second end of the sensor member.

Abstract: A double-cantilever beam crack growth sensor made from welded alloy, e.g., nickel-based alloy, and a method for fabricating such sensors. The method includes the steps of forming a strongback from a block of a first nickel-based alloy; depositing a suitable thickness of nickel-based weld alloy on top of the strongback to form a bi-metallic test block; welding a second block of the first nickel-based alloy on top of the weld alloy; and machining the final three-layer block to form a double-cantilever beam crack growth sensor consisting of cantilever beams made of the first nickel-based alloy, a crack growth section of weld alloy having a microstructure wherein the direction of dendritic growth is parallel to the direction of crack growth and a third section made of the first nickel-based alloy.

Abstract: Notching methods and machines are provided by this invention for preparing notches in mechanical testing specimens. The notching machines razor element for creating a notch in the specimen and mechanical actuation elements for substantially linearly contacting the razor element with the specimen in a direction which is either substantially normal to the surface of the specimen receiving the notch or substantially normal to a stress created in the specimen during testing. This actuation forms a notch without any significant residual stresses forming ahead of the notch.

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: A corrosive environmental crack length measuring apparatus including a double-cantilever beam type test piece having a tapered portion in a portion where the crack grows, a slit, and at least two holes, with the test piece being placed within a corrosive environment. Leads inserted in the holes of the test piece to be spot-welded thereto to supply a direct current to the holes. A current polarity switching device is provided with, a stabilized direct current power supply connected with the direct current supplying leads through the current polarity switching device. Potential difference measuring leads are inserted in holes formed in two outer faces of the double-cantilever beam type test piece parallel to a section of a crack growing portion at a plurality of points along the crack growing direction so as to be spot-welded thereto.