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Showing papers on "Residual stress published in 1978"


Journal ArticleDOI
TL;DR: In this paper, a method for determining the residual microstress and macrostress in polycrystalline aggregate is presented, using the shift and broadening induced by residual stress, due to a transition in an atomic system.
Abstract: Using the R‐line fluorescence of trace Cr3+ in sintered Al2O3 as an example, a method of analysis is outlined for determining the residual microstress and macrostress in a polycrystalline aggregate. It uses the shift and broadening, induced by residual stress, of a line due to a transition in an atomic system dissolved in the aggregate. For sintered Al2O3 from three different manufacturers, but made for the same purpose, the isotropic and shearing components of the residual microstress and macrostress are listed in tabular form. For the isotropic component of the microstress a distribution is found, with a mean value of ∼2 kbar, in which tension and compression are equally probable.

241 citations



Book ChapterDOI
TL;DR: In this paper, the authors used computer simulation methods to estimate the fatigue crack initiation life of butt welds using strain-controlled fatigue concepts, and found that the initiation life was very sensitive to changes in Kf, but rather insensitive to strength level.
Abstract: The fatigue crack initiation life (cycles to obtain a 0.25-mm fatigue crack) was estimated for butt welds using strain-controlled fatigue concepts. Key developments which facilitated these estimates were the assumption of(K f ) m a x conditions (the largest value of Kf possible for a given weld shape), the use of computer simulation methods which modeled cyclic hardening and softening as well as mean stress relaxation effects, and the use of the fatigue properties of the actual weld zone in which the initial notch was located. The initiation life was found to be very sensitive to changes in Kf, but rather insensitive to strength level. The importance of residual stresses and mean stress varied with material as did the fraction of total life devoted to crack initiation. Mild steel (ASTM Specification for Structural Steel (A 36)) high strength, low alloy (ASTM Specification for High-Yield Strength, Quenched and Tempered Alloy Steel Plate, Suitable for Welding (A 514)) steel and aluminum alloy welds were considered.

91 citations


Book ChapterDOI
TL;DR: In this paper, the swelling behavior of a graphite/epoxy (AS/3501-5) is described by a model which is based on the assumption that the swelling is negligible until the moisture concentration reaches a threshhold value and then increases linearly thereafter.
Abstract: : The swelling behavior of a graphite/epoxy (AS/3501-5) is shown to be described by a model which is based on the assumption that the swelling is negligible until the moisture concentration reaches a threshhold value and then increases linearly thereafter. The model also provides a means of measuring the volume fraction of voids. The analytical results, which take into account the curing stresses, are compared with the experimental data for the transverse and thickness strains of symmetric laminates as well as for the warpage of unsymmetric laminates. The initial absorption on virgin specimens facilitates the subsequent diffusion and the residual stresses appear to be responsible for the absorption being slower than the desorption during the early stages of moisture conditioning. Warpage of unsymmetric laminates is discussed in light of the cracks found in constituent plies. Finally derived is a temperature-relative humidity relationship which renders the graphite/epoxy composite laminates free of residual stresses. (Author)

80 citations


Book ChapterDOI
TL;DR: In this paper, the authors present, in a single chapter, many of the recent instrumental advances and to explain the fundamental limitations associated with this measurement, and describe many current applications in those areas where the measurement has already proven to be useful.
Abstract: : The idea of measuring residual stresses by x-ray diffraction was first proposed by Lester and Aborn (1925). In this report the main aim is to present, in a single chapter, many of the recent instrumental advances and to explain the fundamental limitations associated with this measurement. Many current applications are described in those areas where the measurement has already proven to be useful.

69 citations


Journal ArticleDOI
TL;DR: In this paper, the volume dilatation in the absence of stress is assumed to be a linear function of the separate specific volumes and weight fractions of the constituents (pearlite, austenite and martensite).
Abstract: T he problems of quenching-stress analysis are critically reviewed and an adequate simple theory is discussed. The theory accounts for both plasticity and volumetric changes due to phase transformation accompanying the thermal-hardening of a group of simple steels that are characterized by C-shaped time-temperature-transformation diagrams. The volume dilatation in the absence of stress is assumed to be a linear function of the separate specific volumes and weight fractions of the constituents (pearlite, austenite and martensite). With use of the classical relationships of a formal theory of transformation kinetics, the amounts of pearlite and martensite are expressed in terms of the temperature and the temperature-history. The specific forms of such functions are given. In order to account for the influence of phase transformation on plastic properties, the non-isothermal plastic flow-rule is generalized, and a thermal-hardening parameter is introduced which is identified with the amount of pearlite. Variational principles and bounding inequalities associated with the fundamental rate-problem are considered. As an example, the problem for a rapidly, uniformly-cooled half-space is solved. The variations of the residual stress and the final amount of martensite with distance from the outer surface are given, for several values of the rate-of-cooling. The results suggest that the residual stress vanishes on the plane containing approximately 30–35 per cent of martensite.

64 citations


Patent
13 Sep 1978
TL;DR: In this article, a method of developing compressive residual stresses in the surface region of a high carbon steel alloy article is disclosed, where the article is made of an alloy having 0.8-1.6% C, 0.2-5% Cr, 0-20% ingredients selected from the group consisting of MN, V, Mo, W, Si, and the remainder Fe.
Abstract: A method of developing compressive residual stresses in the surface region of a high carbon steel alloy article is disclosed. The article is made of an alloy having 0.8-1.6% C, 0.2-5% Cr, 0-20% ingredients selected from the group consisting of MN, V, Mo, W, Si, and the remainder Fe. The article is heated in a carburizing atmosphere at 800°-950° C. for 1-2.5 hours, and then quenched to cool the central core of the article at a rate sufficiently fast to suppress the formation of non-martensitic austenite decomposition products, thereby establishing a residual compressive stress gradient proceeding from the surface to a depth of 0.007-0.03 inches.

45 citations


Journal ArticleDOI
TL;DR: The residual stresses in case of carburized steels stem from two major sources, both of which are associated with the rapid cooling of the steels from elevated temperatures as discussed by the authors.
Abstract: Residual stresses in case carburized steels stem from two major sources, both of which are associated with the (rapid) cooling of the steels from elevated temperatures. The first source is the more rapid cooling rate of the surface of the body, as compared with the rate of the interior. The second is the time lag in the transformation of the austenite on cooling between the high carbon and low carbon portions of the carburized body. The as-carburized residual stress intensities and states are altered to varying degrees dur-ing the course of the tests used to measure the mechanical properties. The significant changes take place not only as the result of the strain of the measurement test itself, but also because of the transformation of any austenite retained in the case of the carburized part, and because of stresses developed within the part by virtue of the rheological inter-actions which occur within the part since it is, in essence, a composite material. The resultant observed mechanical performance of the carburized body is the summation of the intrinsic mechanical properties of the material itself, and the effects of the residual stresses as-carburized, and as-altered by the above phenomena.

43 citations


Book ChapterDOI
TL;DR: In this paper, the relationship of the mirror constant to fracture toughness is discussed, and the effects of grain size and internal stress on fracture are demonstrated, as well as application of fracture surface analysis to scientific and applied problems are enumerated.
Abstract: The development of fracture surface observations into a quantitative tool for analysis of brittle fracture is reviewed. The effect of temperature, strain rate, and residual stresses on the "mirror constant," A, is discussed through recent experimental results, as well as new analysis of established literature. The current theories of mirror formation in glasses, glass ceramics, single crystals, and polycrystalline ceramics are compared to the results of a number of investigators. The relationship of the mirror constant to fracture toughness, that is, K I c , is discussed. Methods to incorporate the effects of grain size and internal stress on fracture are demonstrated. Finally, application of fracture surface analysis to scientific and applied problems are enumerated.

43 citations


Journal ArticleDOI
TL;DR: In this paper, the residual stresses in a 50% cold-rolled high strength low alloy steel were examined in conjunction with strain-controlled fatigue tests, and the diffraction peak became sharper with increasing number of cycles.

41 citations


Journal ArticleDOI
Bryan Harris1
TL;DR: In this article, a simple model was used to calculate the residual stresses in polyester-resin/glass fibre composites that arise when the material is cooled from the post-curing temperature.
Abstract: A simple model has been used to calculate the residual stresses in polyester-resin/glass fibre composites that arise when the material is cooled from the post-curing temperature. An elementary elasticity solution for shrink-fit stresses gives a value of the order of 24 MNm−2 for interfacial pressures in a single fibre model, and it appears that this stress is between 10 and 20% lower if the matrix is a hypothetical material having the properties of a composite. The pull-out stress for a glass fibre in polyester resin is estimated to be 7.6 MNm−2, in good agreement with earlier experimental results.

Journal ArticleDOI
TL;DR: In this paper, a sharp crack is introduced into bend-test specimens using a wedge indenter and residual stresses are relieved by removing the surface layer containing the indentation, and it is found that annealing is not a satisfactory way of removing residual stresses from specimens precracked by indentation since it produces effects that give too high a value for fracture toughness.
Abstract: A technique has been devised for precracking fracture-toughness specimens of hardmetals whereby a sharp crack is introduced into bend-test specimens using a wedge indenter and residual stresses are relieved by removing the surface layer containing the indentation. The technique is reproducible, simple to use, and does not suffer from the inaccuracies and difficulties of interpretation inherent in using the spark-machining and pyramid-indentation techniques. It is found that annealing is not a satisfactory way of removing residual stresses from specimens precracked by indentation since it produces effects that give too high a value for fracture toughness. Spark-machined specimens do not give reliable fracture-toughness data because there are practical problems in introducing a notch sufficiently narrow to simulate the effect of a thin crack and because thermal damage caused by the spark discharge probably alters the properties of the material at the notch root.

Journal ArticleDOI
TL;DR: In this paper, the residual stresses in cold-formed, circular, steel tubes were analyzed on the basis of mathematical plasticity and the correlation between this analytical prediction and test results was satisfactory.
Abstract: Residual stresses in cold-formed, circular, steel tubes are analysed on the basis of mathematical plasticity. The correlation between this analytical prediction and test results is satisfactory.

Journal ArticleDOI
TL;DR: In this paper, the velocity differences of acoustical, perpendicularly polarized waves are measured directly by a "sing-around" method using a 5-MHz shear-type transducer.
Abstract: The acoustoelastic stress analysis is based on the fact that an initially isotropic material becomes anisotropic under stress. The birefringent effect for polarized ultrasonic shear waves in the stressed material will then be similar to the photoelastic effect in which a light wave and a transparent model specimen are used. In this paper, the velocity differences of acoustical, perpendicularly polarized waves are measured directly by a ‘sing-around’ method using a 5-MHz shear-type transducer. The residual-stress distribution in a mild-steel circular plate with a concentrically patch-welded joint is measured by this method. The acoustoelastic coefficient is obtained separately by uniaxial testing of the base material. The results show that the acoustical stress measurement, carried out nondestructively, agrees well with those obtained by conventional destructive methods as well as with theoretical predictions.

Journal ArticleDOI
TL;DR: In this paper, two elastic models for the development of residual stresses due to cooling in rock bodies are presented, one describing the "locking in" of stresses on grain-to-grain (microstructural) scale and the other describing the locking in of stresses at macro-structural scale.
Abstract: Two elastic models for the development of residual stresses due to cooling in rock bodies are presented. The first describes the "locking in" of stresses on grain-to-grain (microstructural) scale and the second describes the locking in of stresses on a macrostructural scale. Application of the microstructural model to uniform cooling of solid granite from 300°C to 0°C leads to a self-equilibrating stress field and an average volumetric residual strain of −7050×10−6. Application of the macrostfuctural model to the cooling from 300°C to 0°C of an idealized granite pluton surrounded by metasedimentary country rock leads to residual radial and hoop stresses of −232×105 Pa in the granite and residual radial and hoop stresses of −232 and 116×105 Pa in the metasediment at its contact with the granite.

Journal ArticleDOI
TL;DR: In this article, the design, operation, and testing of a 7 to 11-kg hand-held X-ray device for measuring residual stresses are described, based on a miniature Xray tube and generator and a position-sensitive detector.
Abstract: The design, operation, and testing of a 7 to 11-kg hand-held X-ray device for measuring residual stresses are described. The instrument is based on a miniature X-ray tube and generator and a position-sensitive detector. No motion of the detector is needed to record a peak, eliminating the expensive and heavy gearing characteristic of a conventional diffractometer; the only mechanical motion during a measurement is one change of the orientation of the device to the object. An entirely portable instrument is therefore available for use in the plant or in the field. Tests are reported in which the stress is measured to ±40 MPa (± 6 ksi) or better in 4 to 20 s, depending on the specimen.

Journal ArticleDOI
S.M. Wong1
TL;DR: In this article, the residual stresses in chromium films vacuum deposited by electron beam evaporation onto beryllium substrates were measured by X-ray diffraction and a minute peak shift of the diffraction profile revealed the presence of strain and hence stress.

Journal ArticleDOI
TL;DR: In this article, the hygrothermal and mechanical aspects of free-edge effects in composite laminates by means of elastic finite element analysis were studied, where time-varying stress concentrations were found present near the free edge region.
Abstract: To describe the moisture sorption process in a long, finite-width com posite laminate, the two-dimensional diffusion equation is solved using a finite element method. The solution which describes the time-varying moisture concentration profile in the solid, is then incorporated in the calculation of the elastic stress field induced by moisture swelling. Time- varying stress concentrations are found present near the free edge region. The moisture sorption history is shown to be important in the evaluation of the laminate's residual stress field.This is the concluding paper in a series of three by the authors, which study the hygrothermal and mechanical aspects of free-edge effects in composite laminates by means of elastic finite element analysis.

Journal ArticleDOI
TL;DR: In this paper, a theoretical study of the stresses in an infinite circular solid cylinder subjected to rapid surface heating and cooling is presented, where a quasistatic, uncoupled, thermo-elastic analysis based on the incremental theory of plasticity is formulated, and a numerical procedure is developed for a method of successive elastic solutions.
Abstract: This paper presents a theoretical study of the stresses in an infinite circular solid cylinder subjected to rapid surface heating and cooling. A quasistatic, uncoupled, thermoelastoplastic analysis based on the incremental theory of plasticity is formulated, and a numerical procedure is developed for a method of successive elastic solutions. The material of the cylinder is assumed to have temperature-dependent properties and to be characterized by the Romberg-Osgood stress-strain relation. The transient and residual stress distributions are discussed in detail, along with variations of the equivalent stress and plastic strain with time.

Journal ArticleDOI
TL;DR: In this article, the current state of development of the RTR process for silicon ribbon growth is reviewed and a correlation may be obtained between minority carrier diffusion lengths, dislocation densities, and thermal stress levels.
Abstract: The current state of development of the RTR process for silicon ribbon growth is reviewed. Present growth capabilities, material characterization, and device performance are summarized. Specific process problems, such as poor laser coupling efficiencies, are discussed and approaches to their solution are described. Problems related to thermal stresses are discussed in some detail. Stress induced birefringence measurements are used to evaluate residual stresses. A linear temperature profile postheater is effective for reduction of residual stresses. A correlation may be obtained between minority carrier diffusion lengths, dislocation densities, and thermal stress levels.

Journal ArticleDOI
TL;DR: In this paper, cylinders of 2024 and 7075 Al alloy material were heat treated with a cold water quench to obtain high residual tensile stresses at the interior and internal cracks were given access to air, which produced tensile mode cracks.

Patent
David N. Jewett1
05 Sep 1978
TL;DR: In this article, a temperature profile controller is provided for cooling a crystal as it is pulled from a melt so that a substantially linear temperature gradient is established and maintained along the length of the crystal, whereby to prevent or reduce the occurrence of residual stresses in the crystal.
Abstract: A temperature profile controller is provided for cooling a crystal as it is pulled from a melt so that a substantially linear temperature gradient is established and maintained along the length of the crystal as it is cooled, whereby to prevent or reduce the occurrence of residual stresses in the crystal.

Journal ArticleDOI
TL;DR: In this paper, the behavior of composite beams consisting of a concrete slab attached to a steel beam by a shear connection is examined, and the effects of interface slip due to the flexibility of the connectors are included, as well as effects of residual stress and nonlinearity in the mechanical properties of the steel and concrete.
Abstract: The behavior is examined of composite beams consisting of a concrete slab attached to a steel beam by a shear connection. The effects of interface slip due to the flexibility of the connectors are included, as are the effects of residual stress and nonlinearity in the mechanical properties of the steel and concrete. Elastic methods of analysis are reviewed with the object of assessing the errors introduced by the conventional T-beam assumption. Comparisons are made with test reults on beams having adequate or inadequate shear connections, and having the relatively high width to span ratio of 0.35. In the nonlinear range, it was found that the combined effects of slip and residual stress were significant and could raise deflections by as much as 100%.


L. T. Shiembob1
01 May 1978
TL;DR: In this article, the effect of changing ZRO2/CoCrAlY ratios in the intermediate layers on thermal stresses was evaluated analytically with the goal of identifying the materials combinations which would minimize thermal stresses in the seal system.
Abstract: Development of the plasma sprayed graded, layered ZRO2/CoCrAlY seal system for gas turbine engine blade tip seal applications up to 1589 K (2400 F) surface temperature was continued. The effect of changing ZRO2/CoCrAlY ratios in the intermediate layers on thermal stresses was evaluated analytically with the goal of identifying the materials combinations which would minimize thermal stresses in the seal system. Three methods of inducing compressive residual stresses in the sprayed seal materials to offset tensile thermal stresses were analyzed. The most promising method, thermal prestraining, was selected based upon potential, feasibility and complexity considerations. The plasma spray equipment was modified to heat, control and monitor the substrate temperature during spraying. Specimens were fabricated and experimentally evaluated to: (1) substantiate the capability of the thermal prestrain method to develop compressive residual stresses in the sprayed structure and (2) define the effect of spraying on a heated substate on abradability, erosion and thermal shock characteristics of the seal system. Thermal stress analysis, including residual stresses and material properties variations, was performed and correlated with thermal shock test results. Seal system performance was assessed and recommendations for further development were made.


Book ChapterDOI
BM Kapadia1
TL;DR: In this article, an investigation of fatigue crack propagation behavior in air of as-deposited electroslag welds in two hot-rolled structural steels, prepared according to ASTM specification for Structural Steel (A 36) and ASTM Specification for High-Strength Low Alloy Structural STEEL with 50 000 psi Minimum Yield Point to 4 in.
Abstract: An investigation of fatigue crack propagation behavior in air of as-deposited electroslag welds in two hot-rolled structural steels, prepared according to ASTM Specification for Structural Steel (A 36) and ASTM Specification for High-Strength Low-Alloy Structural Steel with 50 000 psi Minimum Yield Point to 4 in. Thick (Grade A) (A 588), has shown that the crack-growth rates (da/dN) in the welds were similar to or up to five times slower than the rate in the base steels. The retardation in crack-growth rate was observed to be substantially greater for crack propagation in the coarse-grained heat-affected-zone (HAZ) and bond-line regions than in the weld metal, but this was not consistently observed. Moreover, marked variations in the microstructure of the weld metal and HAZ did not significantly influence crack propagation. These crack-growth data for the weldments, described in an earlier paper, have been analyzed in the present paper in terms of residual stresses causing the observed retardation in crack-growth rate. In the present work, quantitative comparisons of the crack-growth behavior of the welds were based on a cyclic-life parameter (N 1 ), which was defined as the number of cycles required for precracking the IT wedge-opening-loading (WOL) specimens to a total crack length of 2.54 cm (1 in.). This parameter gave results that were consistent with those based on incremental crack-growth (da/dN) data in the earlier paper. The observed retardation in crack-growth rate in the welds is attributed to compressive residual stresses introduced by welding. This effect was analyzed in the present paper in terms of a stress-intensity-range suppression concept, whereby the applied stress-intensity-factor range is decreased to some lower effective value. The results showed that the beneficial effect of compressive residual stresses on crack propagation appears to be of a variable nature and would diminish following a stress-relief heat treatment.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the mechanical properties of polycarbonate are controlled by the state of stress of the test specimen and that the tendency of the material to microcavitate is strongly dependent on the residual stresses in the surfaces of a test specimen.
Abstract: It is shown that the mechanical properties of polycarbonate are controlled by the state of stress of the test specimen. Whereas the yield stress of the material is relatively insensitive to the state of stress, the tendency of the material to microcavitate is strongly dependent on the residual stresses in the surfaces of a test specimen. The effects of quenching, annealing, post notching, solvent swelling and rate of testing on the modulus of toughness are all related to the state of compression on the free surfaces. The mechanism of deformation is shown by cinematography to consist of the nucleation of a shear band followed by microcavitation along the propagating band. Maximum toughness is obtained by suppressing microcavitation so as to promote shear yielding. When microcavitation occurs, it is the competition between propagating the microcavitation throughout the material and the generation of microcracks in the advancing shear band that controls the ultimate elongation.

21 Sep 1978
TL;DR: In this paper, the significance of residual stresses is analyzed with reference to depth of penetration of cold work, relaxation of residual stress by cyclic loads and to some other practical aspects.
Abstract: Flight simulation tests on 2024-T3 and 7075-T6 lug specimens indicated significant fatigue life improvements obtained by expanding the holes in accordance with the split-sleeve cold work method. Geometrical distortions induced by the expansion were measured. The significance of residual stresses is analysed with reference to depth of penetration of cold work, to relaxation of residual stress by cyclic loads and to some other practical aspects.

Journal ArticleDOI
TL;DR: Carrier mobility, threshold voltage and drain leakage current are investigated for MOS devices fabricated on (001)Si on (012) sapphire substrates with special emphasis on crystalline defects and residual stress in silicon films as mentioned in this paper.
Abstract: Carrier mobility, threshold voltage and drain leakage current are investigated for MOS devices fabricated on (001)Si on (012) sapphire substrates with special emphasis on crystalline defects and residual stress in silicon films. Mobility anisotropies which are ascribed to electron mass anisotropies caused by lateral compressive stress in SOS are observed in E-type and D-type MOS devices in the temperature range from 1.4 to 300 K. Moreover, mobility humps which resulted from marked changes in the electron configuration among energy valleys are found on curves at 1.4 and 4.2 K in the devices with a certain combination of silicon film thickness and channel directions. This can be explained by changes in conductivity-effective-mass and surface roughness scattering. In deep D-type MOS devices, the scattering due to space charge regions around dislocations is found to be predominant over other carrier scattering processes from results on the in-depth distribution of Hall mobility and carrier concentration.