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Showing papers on "Residual stress published in 1980"



Journal ArticleDOI
TL;DR: In this paper, the authors studied the simultaneous generation of residual stresses and occurrence of structural changes owing to cyclic rolling contact fatigue in deep-groove ball bearings, using an X-ray diffraction technique.
Abstract: Deep-groove ball bearings have been endurance tested at high stress levels. The purpose of the work was to study the simultaneous generation of residual stresses and occurrence of structural changes owing to cyclic rolling contact fatigue. During the investigation the decomposition of both retained austenite and parent martensite were followed. The residual stresses and the austenite decomposition were measured by an X-ray diffraction technique, using signal averaging. Optical and transmission electron microscopy were used to observe the transformed regions resulting from the martensite decay. Depth profiles of residual stress and of successive structural changes were constructed. The observations are discussed in terms of a qualitative model for residual-stress generation under cyclic rolling contact.

130 citations



Journal ArticleDOI
George W. Scherer1
TL;DR: A method of calculating the effects of residual thermal stresses in optical waveguide fibers and the influence of various dopants on the magnitudes of the stresses is presented.
Abstract: The residual thermal stresses in optical waveguide fibers can be large enough to cause substantial changes in the refractive-index profile and to create optical anisotropy. This paper presents a method of calculating these effects and illustrates the influence of various dopants on the magnitudes of the stresses.

111 citations


Journal ArticleDOI
TL;DR: In this article, the effect of residual contact stresses on the dynamic fatigue response of surfaces containing indentation-induced flaws is studied, and a general formulation is obtained for the fatigue strength at constant stress rate.
Abstract: The effect of residual contact stresses on the dynamic fatigue response of surfaces containing indentation-induced flaws is studied. Indentation fracture mechanics is used to analyze the growth of well-defined “median/radial” cracks in combined residual (elastic/plastic) contact and applied (uniform) tensile fields, and thence to determine strength characteristics. In this way a general formulation is obtained for the fatigue strength at constant stress rate. Experimental confirmation of the essential predictions of the theory is obtained from strength tests on Vickers-indented soda-lime glass disks in water environment. It is thereby implied that residual stresses can have a significant deleterious influence on the fatigue behavior of any brittle solid whose controlling flaws have a contact history. Such effects need to be considered in the design of structural ceramics, most notably where fracture-mechanics calibrations of crack-velocity parameters are used for lifetime predictions.

109 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used microprobe analysis, microhardness and residual stress measurements to investigate the physical state of the surface layers of technical surfaces dependent from machininq processes.

100 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the extent of cure as a function of position can be predicted from heat transfer calculations if the reaction kinetics and thermal properties are known and that the residual stress gradient is dependent upon the temperature gradient developed.
Abstract: The temperature gradient developed during casting of an unsaturated polyester for which the kinetics of reaction and the heat capacities, thermal conductivities, and densities were known from earlier work was measured experimentally as a function of time in a thick casting and compared with predicted values calculated from a mathematical model. Agreement was excellent. The castings were sectioned and the sections were examined by birefringence. These examinations show good agreement between the temperature gradient developed during cure and the residual stress gradient. This work demonstrates that the extent of cure as a function of position can be predicted from heat transfer calculations if the reaction kinetics and thermal properties are known and that the residual stress gradient is dependent upon the temperature gradient developed.

76 citations


Journal ArticleDOI
TL;DR: In this article, a simple analytical method was proposed to predict the residual stress state and the stress strain curves of Nb3Sn composites at 4.2 K. The method requires only a prior knowledge of the volume fraction of the composite components and the percentage of the Nb converted to Nb 3Sn.
Abstract: The critical current Ic as a function of applied tensile strain depends upon the residual stress state that exists in Nb3Sn bronze‐process composite conductors after cooling from the reaction temperature to 4.2 K. This paper presents a simple analytical method to predict the residual stress state and the stress‐strain curves of Nb3Sn composites at 4.2 K. The method requires only a prior knowledge of the volume fraction of the composite components and the percentage of Nb converted to Nb3Sn. Experimental results and analytically derived values are compared and good agreement is generally found.

73 citations


Journal ArticleDOI
TL;DR: In this paper, a new X-ray method for the evaluation of three dimensional residual stress states is demonstrated by studies of the effect of grinding on Armco iron and a medium carbon steel.
Abstract: A new X-ray method for the evaluation of three dimensional (residual) stress states is demonstrated by studies of the effect of grinding on Armco iron and a medium carbon steel. Although the penetration depth of the Cr-radiation employed in this study is only 5 μm, there is evidence of residual stresses normal to the surface (normal and shear components). In the past it has been assumed that these stress components can be neglected. Shear stresses normal to the surface are small in Armco iron, but significant (± 60 MPa) in steel. From the sign of the shears, the direction of final grinding can be determined. Cooling decreases the tensile stresses parallel to the surface in steel; surprisingly, the opposite result is found in Armco iron.

73 citations


Journal ArticleDOI
TL;DR: In this paper, the residual stresses in injection molded bars of polypropylene have been examined using a stress relaxation method and by the layer removal technique, and a positive value for the internal stress parameter was obtained with newly molded specimens and was found to be retained by specimens stored at liquid nitrogen temperature.
Abstract: The residual stresses in injection molded bars of polypropylene have been examined using a stress relaxation method and by the layer removal technique. A positive value for the internal stress parameter was obtained with newly molded specimens and was found to be retained by specimens stored at liquid nitrogen temperature. The stress relaxation parameter reduced to zero both for specimens aged at room temperature and also for those aged at −40°C. Nevertheless the relaxation behavior of specimens aged at all three temperatures was quite distinct. The layer removal technique showed that the stresses near to the surface were compressive and those in the interior tensile, in apparent contradiction to the interpretation of Kubat and Rigdahl for the meaning of a positive internal stress parameter. A marked reduction in stress levels on aging at room temperature was confirmed, however. The relevance of the relaxation spectrum of polypropylene to these observations is discussed.

71 citations




Journal ArticleDOI
TL;DR: In this article, a method for evaluating residual stress in terms of elastic anisotropy has been tested and shown to provide a reasonable stress system; however, the texture must be known in detail, so as to calculate the effective anisotropic X-ray elastic constants.
Abstract: In residual stress measurements with X-rays, the interplanar spacing is often assumed to alter linearly with the orientation of the reflecting grains with respect to the stress system; the calculation of the stresses is based on this assumption when either the well-known two-tilt or sin2ψ methods are employed. But in materials with strong texture, large oscillations have sometimes been reported. A method proposed in the literature for evaluating stresses in such a situation in terms of elastic anisotropy has been tested and shown to provide a reasonable stress system; however, the texture must be known in detail, so as to calculate the effective anisotropic X-ray elastic constants. More importantly, the theory predicts that well-established standard methods (and measured or calculated isotropic X-ray elastic constants)can be used, and without knowledge of the texture,if hoo andhhh reflections are employed; this has been verified experimentally in this study. It is recommended that such reflections be employed in the future, rather than the common ones now utilized.

Journal ArticleDOI
TL;DR: In this paper, a residual stress system has zero resultant force, the body being in equilibrium, and the distance or range over which the stresses achieve this balance may be grouped into three classes as presented in Table 1.
Abstract: A stress maintained in the bulk of a material without application of an external traction (excluding gravity) or other sources, such as a thermal gradient, is called a residual stress. All residual stress systems have zero resultant force, the body being in equilibrium. The distance or range over which the stresses achieve this balance may be grouped into three classes as presented in Table 1. Also shown are the effects that the given examples exhibit using x-ray diffraction, the most popular technique to investigate residual stresses.

Journal ArticleDOI
01 Jan 1980-Wear
TL;DR: In this article, the residual stresses in hardened and tempered En 31 steel have been made after grinding under various conditions and three combinations of parameters were then selected to represent abusive, conventional and gentle grinding conditions.

Journal ArticleDOI
TL;DR: In this paper, the effect of the quenching rate on strength and residual stress was investigated and a "quenching window" was defined for aluminium alloys, where numerical models were used to determine the optimum quench cooling that leads to maximum strength and no residual stresses.

Book ChapterDOI
01 Sep 1980
TL;DR: In this paper, the development of residual stress and its partial relaxation by diffusion are described and the evolution of microcracks within the residual stress fields are examined, with particular attention devoted to considerations of the critical microstructural dimension at the onset of micro cracking.
Abstract: Brittle materials are subject to microcrack formation at grain boundaries and at second phase particles. These cracks are induced by residual stress that results from incompatibilities in thermal contraction. The development of residual stress and its partial relaxation by diffusion (at elevated temperatures) are described. The evolution of microcracks within the residual stress fields are then examined. Particular attention is devoted to considerations of the critical microstructural dimension at the onset of microcracking.

Journal ArticleDOI
TL;DR: In this paper, the authors explored the relationship between microstructure and prestrain void nucleation and found that voids resulting from a pre-strain-anneal treatment form preferentially at the ends of carbides on grain boundaries oriented roughly parallel to the prestrains tensile axis or rolling direction.
Abstract: Dyson and co-workers have shown that the creep life of a nickel base superalloy can be greatly shortened if the material is strained at room temperature before the creep test is carried out. They found that a prestrain followed by a short annealing time produces small grain boundary cavities, and it is the presence of these prenucleated voids which so seriously degrades service life at elevated temperatures. The present work explores the relationship between microstructure and prestrain void nucleation. Samples of the nickel base superalloy astroloy were given various heat treatments which led to significantly different microstructures. It was found that voids resulting from a prestrain-anneal treatment form preferentially at the ends of carbides on grain boundaries oriented roughly parallel to the prestrain tensile axis or rolling direction. Void spacing in the various microstructures is proportional to (but larger than) carbide spacing. The growth of these cavities during annealing is attributed to the presence of tensile residual stresses arising from the difference in deformability between grain boundary regions and the relatively soft matrix.


Journal ArticleDOI
TL;DR: In this paper, the authors used X-ray diffraction angles to measure residual and applied stresses in polymers and reinforced polymeric composites by diffracting from filler particles that are embedded before curing.
Abstract: X-rays can be used to measure residual as well as applied stresses in polymers and reinforced polymeric composites by diffracting from filler particles that are embedded before curing. We have investigated various fillers that exhibit suitable stress-induced shifts of diffraction angle when embedded in uniaxial graphite fiber/epoxy composites. Stresses in the particles determined by X-rays are proportional to the corresponding composite stresses, in agreement with the model of H. T. Hahn. Results indicate that the stress sensitivity (change in X-ray strain per MPa applied to the composite) increases in the order W, CdO, Ni, Ag, Nb, Al. The elastic range terminates at a yield point beyond which the stress sensitivity is markedly reduced for metallic fillers, but no such yield point has appeared with CdO particles. Oppositely directed particle strains are seen after unloading from stress levels that have exceeded the yield point. Theoretical predictions for these findings are discussed. Residual stresses in the particles were determined after curing and storage under ambient conditions. In the fiber direction the residual stresses were always found to be positive and larger than the principal stresses orthogonal to these.

Patent
27 Oct 1980
TL;DR: In this article, a method of prestressing the working surface of pressure chambers or cylinders comprising the steps of first shot peening their working surfaces to form compressive residual stresses, and then applying fluid pressure at a predetermined magnitude to cause tensile stresses in the working surfaces.
Abstract: A method of prestressing the working surface of pressure chambers or cylinders comprising the steps of first shot peening their working surfaces to form compressive residual stresses, and then applying fluid pressure at a predetermined magnitude to cause tensile stresses in the working surfaces. The magnitude of compressive residual stresses established on their outer working surfaces is made substantially equal to the tensile stress applied to these surfaces during the pressure phase of the process.


Journal ArticleDOI
TL;DR: In this paper, the average internal stresses in each constituent phase of plastically deformed α-γ two-ductile-phase Fe-CrNi steels are studied.

Journal ArticleDOI
TL;DR: In this paper, the essential equivalence of three loading conditions for thin-walled tubes was demonstrated, i.e., pure bending moment relaxation, pre-stressed, and steady-state temperature distribution.
Abstract: Thick-walled tubes are frequently pre-stressed (autofrettaged) in order to produce an advantageous stress distribution, and may be subsequently subjected to a steady-state temperature distribution. The cutting of, or appearance of defects within, such tubes may cause a relaxation in the form of pure bending moment. This note demonstrates the essential equivalence of each of these three loading conditions.

Journal ArticleDOI
TL;DR: In this article, the characterization of GaP crystals, grown by the liquid encapsulated Czochralski method, has been accomplished by means of a quantitative photoelastic technique, and two kinds of radiation with wavelengths, 0.55 and 1.1 μm, are effectively used to determine the isochromatic line corresponding to the zeroth order of retardation.

Journal ArticleDOI
TL;DR: In this paper, an experimental study of the residual stresses and fatigue properties of ground En 31 steel specimens is described, and individual grinding parameters (wheel types and speed, feed, dressing, and lubricant) are grouped into three categories: abusive, conventional, and gentle grinding.
Abstract: An experimental study of the residual stresses and fatigue properties of ground En 31 steel specimens is described. The individual grinding parameters (wheel types and speed, feed, dressing, and lubricant) are grouped into three categories: abusive, conventional, and gentle grinding. In the absence of high temperature-gradients, the mechanical strain in the workpiece is dominant, giving small compressive residual stress and long fatigue life. It is more common, however, for high temperatures to be generated at the surface. Quenching of the bulk steel produces martensite, which is then tempered, and the accompanying volume change can leave high tensile stress in the surface, resulting in greatly reduced fatigue life. Surface roughness is found to be much less important than the residual stress.


Journal ArticleDOI
TL;DR: In this article, the effect of position of the flaw, mean stress and post-weld heat treatment have been included together with an assessment of the validity of using small compact tension specimens to predict rates of growth in large joints.


Journal ArticleDOI
TL;DR: In this article, the impact strength and tensile properties of glassy amorphous polycarbonates were measured as a function of strip thickness reduction and it was shown that the residual tensile stresses at the surface decreased with increasing thickness reduction.
Abstract: The influence of cold working on the toughness improvement in glassy amorphous polycarbonates was studied. Cold working processes, namely rolling and. Steckel rolling were used to produce thickness reductions up to 40 percent in flat-strip specimens. The notched Izod impact strength and tensile properties were measured as a function of strip thickness reduction. It was shown that the toughness enhancement in polycarbonates cold worked to low thickness reductions was due to the residual stress state present as opposed to molecular orientation which becomes significant at higher degrees of cold work. Residual stress measurements were made by using the layer removal technique. Residual tensile stresses as high as 2100 psi were present in 1/4-in. cold-rolled polycarbonate at the surface. The maximum stress in the center of the specimen was 1100 psi in compression. The residual stresses at the surface decreased with increasing thickness reduction. The residual stress state for Steckel rolled. 1/2-in. polycarbonate was also measured and found to be more complex than for the thinner samples, The results demonstrated that surface tensile stresses and interior compressive stresses can produce large values of impact strength if the notch is to be machined after cold working. Thus, the values of impact strength measured from the notch Izod specimen are sensitive to the residual stress state in the polymer. This behavior is in contrast to earlier studies on thermally quenched material in which the material was quenched after notching. The thermal quenching produced surface compressive stresses which were also present at the notch tip. The presence of compressive residual stresses at the center of the notch suppressed the formation of a craze leading to toughness enhancement in cold worked polycarbonate strips. It is shown that by control of residual stresses in polycarbonate, strips at least 1/2 in. in thickness can be made to exhibit ductile failure in the notched Izod impact test.