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Showing papers on "Residual stress published in 1990"


Journal ArticleDOI
TL;DR: In this article, a semi-infinite interface crack between two infinite isotropic elastic layers under general edge loading conditions is considered and the problem can be solved analytically except for a single real scalar independent of loading, which is then extracted from the numerical solution for one particular loading combination.
Abstract: A semi-infinite interface crack between two infinite isotropic elastic layers under general edge loading conditions is considered. The problem can be solved analytically except for a single real scalar independent of loading, which is then extracted from the numerical solution for one particular loading combination. Two applications of the basic solution are made which illustrate its utility: interface cracking driven by residual stress in a thin film on a substrate, and an analysis of a test specimen proposed recently for measuring interface toughness.

905 citations


Journal ArticleDOI
TL;DR: In this paper, the authors focus on the rheometric study of a physical gel exhibiting a yield stress and show how the determination of shear rheological properties can be affected by anomalous phenomena such as fracture and slip at the wall.
Abstract: This work particularly focuses on the rheometric study of a physical gel exhibiting a yield stress. The measurements were carried out in a cone—plate configuration using two different types of rheometer working under controlled torque or under controlled velocity. Shear creep, constant shear rate, and stress relaxation tests have been performed. Measurements of apparent viscometric properties were conducted at the same time as observation of the strain field in the sample. Observing the strain field enables us to confirm the reliability of the interpretation of the results and also to estimate the true shear rate in the fluid. It is shown how the determination of shear rheological properties can be affected by anomalous phenomena such as fracture and slip at the wall. The influence of roughness of the tool surfaces and of evaporation shows up. The results presented in this study show how some rheometrical measurements of the yeild stress and the microstructural interpretations given, may be erroneous. Some recommendations are made in order to improve current rheometrical tests and their interpretation. A log—log graph with typical shear stress-shear rate measurements and their corresponding strain fields is given: it should be used as a guideline in yield stress fluids rheometry. In addition it is made clear that visual observation of the sheared sample is a key technique. A protection which completely eliminates evaporation is suggested. It is shown that the measurement of residual stress in stress relaxation tests may be a convenient means of determining the value of the yield stress.

237 citations


Journal ArticleDOI
TL;DR: In this paper, the mechanical properties of six fiber-reinforced ceramics and glasses have been evaluated with the objective of critically assessing present understanding, and the results establish that the available mechanical property models correlate well with experiments, provided that independent measurements are made of the residual stress, interface sliding stress, and in situ strength properties of the fibers.
Abstract: The mechanical properties of a series of six fiber-reinforced ceramics and glasses have been evaluated with the objective of critically assessing present understanding. A major parallel theme has been the characterization of the interface and an assessment of the thermomechanical properties of the interfaces as they relate to composite behavior. The results establish that the available mechanical property models correlate well with experiments, provided that independent measurements are made of the residual stress, the interface sliding stress, and the in situ strength properties of the fibers. In addition, trends in the sliding stress are found to be qualitatively consistent with those expected for sliding along debonded surfaces.

234 citations


Journal ArticleDOI
TL;DR: Two-dimensional strains computed from the deformation of a slice after one radial cut were defined as the residual strains in that slice, and it was found that the distributions of the principal residual stretch ratios were asymmetric with respect to the radial cut.
Abstract: Residual stress in an organ is defined as the stress that remains when all external loads are removed. Residual stress has generally been ignored in published papers on left ventricular wall stress. To take residual stress into account in the analysis of stress distributions in a beating heart, one must first measure the residual strain in the no-load state of the heart. Residual strains in equatorial cross-sectional rings (2-3 mm thick) of five potassium-arrested rat left ventricles were measured. The effects of friction and external loading were reduced by submersing the specimen in fluid, and a hypothermic, hyperkalemic arresting solution containing nifedipine and EGTA was used to delay the onset of ischemic contracture. Stainless steel microspheres (60-100 microns) were lightly imbedded on the surface of the slices, and the coordinates of the microspheres were digitized from photographs taken before and after a radial cut was made through the left ventricular free wall. Two-dimensional strains computed from the deformation of a slice after one radial cut were defined as the residual strains in that slice. It was found that the distributions of the principal residual stretch ratios were asymmetric with respect to the radial cut: in areas where substantial transmural strain gradients existed, the distributions of strain components were different on the two sides of the radial cut. A second radial cut produced deformations significantly smaller than those produced from the first radial cut. Hence, a slice with one radial cut may be considered stress free.(ABSTRACT TRUNCATED AT 250 WORDS)

229 citations


Journal ArticleDOI
TL;DR: In this article, the authors derived general relations between stored elastic energy and statistical averages (mean values and fluctuations) of residual stresses in two-phase composites and to materials where the fluctuations of elastic constants can be neglected.
Abstract: R esidual Stresses in heterogeneous materials may arise because of differential or anisotropic thermal expansion of constituents. The paper is concerned with thermoelastic solids whose material properties fluctuate on the microscopic scale. Rigorous general relations between stored elastic energy and statistical averages (mean values and fluctuations) of residual stresses are derived. These results are applied to two-phase composites and to materials where the fluctuations of elastic constants can be neglected. One obtains exactly the stored energy, certain conditional mean values and the covariance matrix of the residual stresses. Under the assumptions of statistical homogeneity and isotropy, the results hold for any type of heterogeneous microstructure.

166 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present the LTC-ARTICLE-1990-001: http://jcm.sagepub.com/ Record created on 2006-06-26, modified on 2016-08-08
Abstract: Reference LTC-ARTICLE-1990-001 URL: http://jcm.sagepub.com/ Record created on 2006-06-26, modified on 2016-08-08

163 citations


Journal ArticleDOI
TL;DR: The thermal properties of low-residual stress, low-pressure chemical-vapor-deposited (LPCVD), silicon nitride (Si 1.0 N 1.1 ) have been extracted f
Abstract: The thermal properties of low-residual stress, low-pressure chemical-vapor-deposited (LPCVD), silicon nitride (Si 1.0 N 1.1 ) have been extracted f

135 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated reaction-forming of silicon carbide by the infiltration of carbonaceous preforms using alloyed silicon melts, in order to synthesize composite materials free of the residual silicon phase that has previously limited mechanical properties and upper use temperatures.
Abstract: The authors have investigated reaction-forming of silicon carbide by the infiltration of carbonaceous preforms using alloyed silicon melts, in order to synthesize composite materials free of the residual silicon phase that has previously limited mechanical properties and upper use temperatures. In this approach, rejection of the alloying component(s) from the primary silicon carbide phase into the remaining melt results in the formation of a secondary refractory phase, such as a silicide, in place of residual free silicon. Experiments conducted in the Si-Mo melt system show that relatively dense ({gt}90%) silicon carbide-molybdenum silicide materials free of residual silicon and residual carbon can be obtained. A model for reactive infiltration based on time-dependent permeabilities is proposed. Processing variables important for control of the reaction rate relative to the infiltration rate, and associated processing flaws, are discussed.

135 citations



Journal ArticleDOI
TL;DR: In this article, the effects of residual stress fields on fatigue crack propagation were evaluated using two numerical methods, i.e., finite element method and the weight function method, allowing a detailed analysis of the experimental data to be obtained.

115 citations


Journal ArticleDOI
01 Oct 1990-Polymer
TL;DR: In this article, residual stresses arising from the curing process in a 3D-constrained epoxy resin were determined experimentally by a strain-gauge method using the theory of incremental elasticity for an ageing, linear thermoelastic material subjected to dimensional constraints.

Journal ArticleDOI
TL;DR: In this article, an extensive experimental investigation of the residual stresses in cold-formed steel members is presented, where the electrical discharge machining (EDM) technique is used to cut coupons for residual stress measurement.
Abstract: An extensive experimental investigation of the residual stresses in cold‐formed steel members is presented. The electrical discharge machining (EDM) technique is used to cut coupons for residual stress measurement. As compared to the conventional saw‐cutting method, the EDM technique greatly reduces the external disturbance during the machining of a thin‐walled section caused by heating, clamping, and vibration. The experimental results provide a further understanding of the magnitude and distribution of the residual stresses in cold‐formed steel sections, which are found to be quite different from the residual stresses in hot‐rolled steel shapes. Based on the experimental findings, an idealized distribution pattern of the residual stresses in a cold‐formed channel section is outlined. Finally, the yielding propagation in an axially compressed cold‐formed steel section is described, and an equation for predicting the extent of yielding is derived.

Journal ArticleDOI
TL;DR: In this article, Annealing was used to relax non-uniform tensile stress in boron-doped p + -Si cantilever beams and the optimum annealing condition was determined.
Abstract: Annealing was used to relax non-uniform tensile stress in boron-doped p + -Si cantilever beams. The optimum annealing condition was determined. A for

Journal ArticleDOI
TL;DR: In this paper, the authors used X-ray diffraction analysis to determine the actual lattice-spacing depth profiles in two different γ′-Fe4N1−x surface layers on α-iron substrates.
Abstract: Composition-depth and (residual) stress-depth profiles were investigated in two different γ′-Fe4N1−x surface layers on α-iron substrates. X-ray diffraction analysis was applied. Determination of the actual lattice-spacing depth profiles required correction for the effect of penetration of the X-rays. The dependence of the nitrogen content in γ′-Fe4N1−x surface layers on depth below the surface corresponds with that expected for diffusion-controlled layer growth. The formation of porous grain boundaries (channels) in the surface-adjacent part of the layers provides the possibility of nitrogen uptake at “internal” surfaces during nitriding, leading to the development of concave concentration-depth profiles in this part of the layers. Stress buildup in the massive interface-adjacent part of γ′-Fe4N1−x layers on a-Fe substrates originates from both the presence of a concentration-depth gradient and the difference in thermal contraction between layer and substrate on cooling from the nitriding temperature to the measurement temperature. Channel/pore development along grain boundaries in the surface-adjacent part of the layers provides a mechanism for stress relaxation during nitriding. On cooling, the channels can also accommodate part of the thermally induced misfit. Lateral strain gradients in the most severely porous part of the layers are revealed by the X-ray diffraction analysis.

Journal ArticleDOI
TL;DR: In this paper, the effects of several physical properties defining the performance of the constituent fiber, matrix, and interface are examined relative to their effect on composite's behavior, and it is shown that the initial transverse modulus for the composite will be the same regardless of whether there is a well-bonded or an unbonded interface.
Abstract: The mechanics of transversely loaded high-temperature composites with a thermally induced residual stress field and a vanishingly weak fiber-matrix interface strength was investigated using two analytical models. In particular, the effects of several physical properties defining the performance of the constituent fiber, matrix, and interface are examined relative to their effect on composite's behavior. Both models demonstrate that, if there is a thermally induced residual stress field in the composite, the initial transverse modulus for the composite will be the same regardless of whether there is a well-bonded or an unbonded interface. 10 refs.

Journal ArticleDOI
TL;DR: In this paper, the mechanical deflection of circular membranes of SiNx is presented as a technique for measuring the stiffness and residual stress of very thin, single-layer films.
Abstract: The mechanical deflection of circular membranes of SiNx is presented as a technique for measuring the stiffness and residual stress of very thin, single-layer films The dimensions of the membranes are controlled precisely using standard photolithography, dry etching and wet etching techniques Thicknesses vary between 009 μm and 027 μm and average diameters range between 1100 μm and 4100 μm A Nanoindenter is used to deflect the membranes with a point force at their centers, and to continuously record the applied forces and the resulting deflections The analysis of the force-deflection data yields the values of Young’s moduli and residual stresses for the films

Journal ArticleDOI
TL;DR: In this article, a study of the micromechanics of continuous silicon carbide fiber rein forced 6061 aluminum has been carried out using generalised plane strain non-linear finite element analysis.
Abstract: A study of the micromechanics of continuous silicon carbide fibre rein forced 6061 aluminum has been carried out using generalised plane strain non-linear finite element analysis. An interface element has been developed enabling separate shear and tensile strengths to be assigned, with a quadratic interaction equation. Residual stresses due to manufacturing were included in the analysis.The effect on transverse tensile strength of fibre packing geometry, fibre spacing, resid ual stresses, interface strengths and matrix material properties were investigated. It was found that the interface strength is the most important factor. Residual stresses are beneficial, these being largely controlled by the yield strength of the matrix material at the time the residual stresses are set up. Fibre packing and spacing and matrix strength do not significantly affect predicted strength.

Journal ArticleDOI
TL;DR: In this paper, a model including both primary and secondary cooling was developed to predict the effect of the substrate temperature on residual stress in thermally sprayed coatings, and the importance of primary cooling was confirmed.
Abstract: Post-fabrication cool down (secondary cooling) is said to be the major cause of the residual stress in thermally sprayed coatings. Primary cooling, the cooling of spray particles to substrate temperature after solidification, is seldom considered. The purpose of the present work is to demonstrate the importance of primary cooling. A model including both primary and secondary cooling was developed to predict the effect of the substrate temperature on residual stress. The following three sequential mechanisms were considered: (1) shrinkage of the spray particles after solidification; (2) deformation of the deposit during spraying; (3) deformation of the deposit after spraying. When the expansion coefficient of the coating is less than that of the substrate, the model predicts that a high substrate temperature induces compressive stress and that a low substrate temperature generates tensile stress. Therefore an optimum substrate temperature exists to minimize residual stress. The modelling results were confirmed by experiments. When the relation between expansion coefficients is reversed, the stress is always tensile throughout the spraying procedure. The present model explains the complicated behaviour of residual stress in sprayed coatings. The importance of primary cooling is confirmed.

Journal ArticleDOI
TL;DR: In this paper, the authors present the mathematical model ALSPEN, in which the thermally induced strains and stresses which develop during direct chill (DC) semicontinuous casting of aluminum billets are calculated by a finite-element method.
Abstract: This paper presents the mathematical model ALSPEN, in which the thermally induced strains and stresses which develop during direct chill (DC) semicontinuous casting of aluminum billets are calculated by a finite-element method. The metal is assumed to be an isotropic elasticviscoplastic material with strongly temperature-dependent properties. In the material description, the viscoplastic strain is treated in a “unified” manner, in which low-temperature (approximately) time-independent plasticity and creep at high temperatures occur as special cases. Furthermore, in the numerical time stepping procedure, all of these plastic material properties, which are present simultaneously in the solution domain as a result of the large temperature differences, are treated in a similar way. To demonstrate some of the capabilities of ALSPEN, we have modeled the casting of an AlMgSi alloy, AA6063. The material properties of this alloy have been studied in parallel with the development of the mathematical model.

Journal ArticleDOI
TL;DR: In this paper, the residual axial stresses generated by thermal cycling of an SiC-glass ceramic composite were measured and the results indicated that measurements of the force-displacement relation for an indenter loaded onto the end of a fiber can be used to calculate the magnitude of the residual stress in the fiber.
Abstract: Fiber sliding in the presence of residual stresses in ceramic composites is analyzed. The results indicate that measurements of the force-displacement relation for an indenter loaded onto the end of a fiber can be used to calculate the magnitude of the residual axial stress in the fiber. The technique is applied to measure residual stresses generated by thermal cycling of an SiC-glass ceramic composite.

Journal ArticleDOI
TL;DR: In this article, a finite element program applicable to all axisymmetric shapes for the prediction of material behavior exposed to various heat treatments has been developed based on a thermodynamic and kinetic algorithm for predicting the hardenability of low alloy steels combined with the calculation of stress and distortion evolution.
Abstract: A comprehensive finite element program applicable to all axisymmetric shapes for the prediction of material behavior exposed to various heat treatments has been developed based on a thermodynamic and kinetic algorithm for predicting the hardenability of low alloy steels combined with the calculation of stress and distortion evolution. During the temperature field and stress calculations the microstructural contributions, like latent heat formation, influence on thermophysical properties, microstructural dependence of σ/e curve, transformation strain, and transformation plasticity are taken into account, which give more insight and more accurate predictions of the material response. Thus microstructural optimizations with respect to hardenability, hardness, residual stresses and distortion are made possible.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the behavior of fatigue crack growth and closure through a compressive residual stress field and found that partial opening of the crack occurs and this plays an important role in crack growth.
Abstract: Behaviour of fatigue crack growth and closure through a compressive residual stress field is investigated by performing fatigue crack growth tests on welded SEN specimens of a structural steel (JIS SM50A). Depending on the type of the initial residual stress in the region of crack growth, the growth and closure of the crack show different behaviour. In particular, in the transition region from a compressive residual stress field to a tensile residual stress field, the fatigue crack growth rates cannot be described by the effective stress intensity factor range ΔKeff, based on the measured crack opening stress intensity factor Kop. Also it is found that the R'-method using the data of da/dN vs ΔK for residual stress-free specimens, with the effective stress ratio R'[=(Kmax+Kr)/(Kmin+Kr)], gives non-conservative predictions of the growth rates in the transition region. Observations of crack closure behaviour in this study indicates that partial opening of the crack occurs and this plays an important role in crack growth through a compressive residual stress field. Based on the concept of a partial opening point (defined and measured in this work), fatigue crack growth behaviour can be better explained.

Journal ArticleDOI
TL;DR: In this article, the effects of fiber spacing, volume fraction and aspect ratio on residual stresses in metal-matrix composites are analyzed numerically, and the results show that the side-to-side spacing of fibers is the most important microstructural parameter affecting the distribution of residual stress and plastic deformation in the matrix.
Abstract: The effects of fiber spacing, volume fraction and aspect ratio on the residual stresses in metal-matrix composites are analyzed numerically. The composite is modeled as a periodic array of cylindrical cells, each consisting of the matrix alloy with a whisker embedded in the ceter. Account is taken of thermoelasticity both in the fiber and in the matrix and of temperature-dependent plasticity in the aluminum matrix. A general formulation, valid for finite strains and rotations, is discussed. Quenching is simulated by imposing a temperature history obtained from a macroscopic solution of the heat equation for a cylindrical bar to the surface of a cell. The resulting residual stress fields are calculated. The results show that the side-to-side spacing of fibers is the most important microstructural parameter affecting the distribution of residual stress and plastic deformation in the matrix. The overall level of plastic deformation in the matrix, measured by the volume average of effective plastic strain, depends primarily on fiber volume fraction. The fiber aspect ratio has little effect, apparently because the residual fields become essentially independent of axial position a short distance from the fiber corner.

Journal ArticleDOI
TL;DR: In this article, the interfacial shear strength of SCS-6 SiC-fiber-reinforced reaction-bonded Si3N4 (RBSN) composites was studied as a function of temperature.
Abstract: The interfacial shear strength of AVCO SCS-6 SiC-fiber-reinforced reaction-bonded Si3N4 (RBSN) composites was studied as a function of temperature. Fiber “push-through” experiments were conducted with a diamond indenter and a high-temperature microhardness tester. The interfacial shear strength was variable and depended mostly on interfacial bonding at low temperatures (5 to 18 MPa at room temperature) and frictional forces at high temperatures (12 to 32 MPa at 1300°C). The frictional component is attributed to the surface roughness of the fibers. The interfacial shear strength increased with temperature, because of the relief of residual stresses arising from the thermal expansion mismatch between fiber and matrix. Because of the composite nature of these fibers, a number of interfaces were tested in each experiment. The interface which debonded and slid was not always the same. Interfacial fracture took place either between the two outermost carbon layers of the SCS-6 fibers, or between the SiC core and the innermost of the two outer carbon layers. The outermost carbon layer of the fiber always stayed bonded to the Si3N4 matrix.

Journal ArticleDOI
TL;DR: In this paper, an experimental investigation of the residual stresses in severely cold-bent high-strength steel plates is presented, where both the sectioning and hole-drilling methods are used for residual stress measurement; the two sets of results are found to be in good agreement.
Abstract: An experimental investigation of the residual stresses in severely cold‐bent thick high‐strength steel plates is presented. Both the sectioning and the hole‐drilling methods are used for residual stress measurement; the two sets of results are found to be in good agreement. Tension residual stresses on the inside surface of the bend range from 46% to 92% of the yield stress of the material. In addition, residual stresses through the plate thickness are measured using the sectioning method. A zigzag‐type residual stress distribution pattern through the plate thickness is observed. The test results are then compared to the values predicted by equations proposed by Dat in 1980. The cold‐bending behavior of the thick steel plates is also studied and the results are presented in a companion paper.

Journal ArticleDOI
TL;DR: In this article, the effects of peening and re-peening upon the fatigue fracture behavior of metallic components in the presence of shot peening residual stresses were examined. But, only the steel specimens showed further life enhancement.

Journal ArticleDOI
TL;DR: In this paper, the residual stresses in a SiC-TiB-2 particulate composite were measured using X-ray diffraction and shown to be consistent with stress-induced microcracking.
Abstract: Residual stresses in a SiC-TiB_2 particulate composite before and after stressing have been measured using X-ray diffraction. Tensile residual stresses in the TiB_2 drop by 60% after bending stresses of 250 MPa are applied. Likewise, the compressive residual stresses in the SiC phase decrease accordingly. Such behavior is consistent with stress-induced microcracking.

Journal ArticleDOI
TL;DR: In this paper, the single fiber pull-out test has been used to measure interfacial properties of SiC fibers in soda-borosilicate glass matrices, and two parameters were examined: the SiC to free carbon ratio at the surface of the siC fiber was varied to test the effect of interfacial chemistry and the glass expansion is varied to investigate the impact of residual stresses.

Journal ArticleDOI
R. Langman1
TL;DR: In this article, the authors examined various magnetic nondestructive evaluation (NDE) methods for residual stress that might be applied to low-carbon structural steels, some magnetization characteristics of 0.13%-C steel are presented for a range of applied fields and stresses.
Abstract: As part of a project examining various magnetic nondestructive evaluation (NDE) methods for residual stress that might be applied to low-carbon structural steels, some magnetization characteristics of 0.13%-C steel are presented for a range of applied fields and stresses. The range of stresses is uniaxial to 160 MPa (tensile and compressive, parallel to magnetization) and equal biaxial up to 160 MPa (tensile and compressive). The range of applied fields is 100-500 A/m. Quantities presented (graphically) are peak flux density, remanent flux density, coercive field, and differential permeability. Some anhysteretic magnetization results are given for equal biaxial stresses in addition to a brief description of the equipment that was used to make the measurements. >

Journal ArticleDOI
TL;DR: In this article, the residual stresses in Ti3Al/SiC composites were measured using two methods: X-ray diffraction and the change in their length when the matrix was entirely removed by etching.
Abstract: Residual stresses in Ti3Al/SiC composites have been measured using two methods. The compressive residual stresses in the fibers were inferred from measurements of the change in their length when the matrix was entirely removed by etching. The stresses were found to vary substantially from fiber to fiber. The longitudinal and transverse stresses in the matrix were measured by X-ray diffraction. Repeated measurements were made as the outer layer of alloy was removed by electropolishing as far as the first row of fibers. In one composite of lower fiber volume fraction, the matrix stresses were thus found to be approximately uniform throughout the specimen. In a higher volume fraction material, on the other hand, the matrix stresses increased significantly with depth from the outer surface: the longitudinal matrix stresses among the fibers were found to be about 60 pct larger than they were on the specimen surface. The implications of these measurements for processing and reliability of thin sheet titanium aluminide composites are discussed.