Uniform Residual Stress Research Articles

Design and fabrication of submerged cylindrical laminates—I

This is the first of a two-part paper concerned with both structural and fabrication process design of a closed-end laminated composite cylinder intended for service in deep sea environment. The cylinder is made of many different orthotropic layers and is loaded by uniform, axisymmetric surface tractions. In addition, piecewise uniform eigenstrains and residual stresses may be caused in the layers during fabrication, by fiber prestress for waviness reduction and by piecewise uniform changes in temperature. The overall goal is to assure efficient use of the composite structure under a prescribed hydrostatic pressure, and to select fiber prestress distribution such that the total stresses in the plies do not exceed certain strength magnitudes. Mechanical and residual stresses in the layers are evaluated with mechanical and transformation influence functions. For the proportional loading applied by a hydrostatic pressure, a procedure is outlined for design of several layups such that the cylinder wall experiences an isotropic in-plane strain and, therefore, all layers support the same compressive normal stresses, regardless of fiber orientation. The results are applied in design and analysis stress fields in a specific structure. Fabrication process design is discussed in the second part of the paper ( Srinivas et al., 1999, Int. J. Solids Structures, 36, 3945–3976) .

The deformation models needed by the steel industry

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Melton K.N. 1999The deformation models needed by the steel industryPhil. Trans. R. Soc. A.3571531–1547http://doi.org/10.1098/rsta.1999.0388SectionRestricted accessThe deformation models needed by the steel industry K.N. Melton K.N. Melton British Steel, Swinden Technology Centre, Moorgate, Rotherham S60 3AR, UK Google Scholar Find this author on PubMed Search for more papers by this author K.N. Melton K.N. Melton British Steel, Swinden Technology Centre, Moorgate, Rotherham S60 3AR, UK Google Scholar Find this author on PubMed Search for more papers by this author Published:15 June 1999https://doi.org/10.1098/rsta.1999.0388AbstractThe steel supply chain generally comprises a steel producer, manufacturing semi–finished products, and a steel user, manufacturing formed components. A review is presented of the deformation models needed by the steel industry, considering the current and expected future requirements of the end users. A trend that is expected to accelerate is their increased use of automation. This imposes a tighter dimensional tolerance, which requires, among other things, models that predict rolling loads and physically based models being introduced, offering distinctive benefits that will be discussed. A narrow distribution of mechanical properties is needed, requiring techniques that link deformation parameters such as strain, time and temperature, through microstructure models to property prediction, and this should include toughness as well as yield strength. Being able to predict toughness at all points in a rolled product would significantly reduce waste and costs associated with destructive testing. The need for lightweight designs is leading to wider application of high–strength steels. Because of the requirements of lower cost and good weldability, the high strengths are being achieved through leaner chemistries, using controlled thermomechanical processing, where the transformation from austenite needs to be incorporated into the models. This is a major difference between steel and aluminium. Laser fabrication techniques are increasingly being used; these require high degrees of flatness in the steel, including after it has been cut, where non–uniform residual stress distribution can lead to distortion. Models that predict residual stresses are needed, and, since the customer might buy the steel in a coil and uncoil it himself, the residual stress model and data will need to be shared. Customers will become more than recipients of steel; they will share in the knowledge embedded in the steel, and the ability to do this, along the varying deformation processes used by the steel industry, is a challenge for those developing the modelling techniques. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by (2017) References Recrystallization and Related Annealing Phenomena, 10.1016/B978-0-08-098235-9.16001-X, (647-681), . Jáuregui A, Guerrero-Mata M, Monsalve A, Artigas A, Leduc L and Colás R (2013) Plastic deformation of low carbon steels, International Heat Treatment and Surface Engineering, 10.1179/1749514812Z.00000000041, 6:4, (164-167), Online publication date: 1-Dec-2012. (2004) References Recrystallization and Related Annealing Phenomena, 10.1016/B978-008044164-1/50023-2, (557-615), . Hurley P and Humphreys F (2003) Modelling the recrystallization of single-phase aluminium, Acta Materialia, 10.1016/S1359-6454(03)00192-7, 51:13, (3779-3793), Online publication date: 1-Aug-2003. Grong Ø and Shercliff H (2002) Microstructural modelling in metals processing, Progress in Materials Science, 10.1016/S0079-6425(00)00004-9, 47:2, (163-282), . Myhr O (2001) Modelling of the age hardening behaviour of Al–Mg–Si alloys, Acta Materialia, 10.1016/S1359-6454(00)00301-3, 49:1, (65-75), Online publication date: 1-Jan-2001. This Issue15 June 1999Volume 357Issue 1756Discussion Meeting Issue ‘Deformation processing of metals’ organized by M. F. Ashby, F. J. Humphreys, C. M. Sellars, H. R. Shercliff and M. J. Stowell Article InformationDOI:https://doi.org/10.1098/rsta.1999.0388Published by:Royal SocietyPrint ISSN:1364-503XOnline ISSN:1471-2962History: Published online15/06/1999Published in print15/06/1999 License: Citations and impact Keywordsthrough–process modelsteelhot rollingprocess controlfinite elementdeformation modelling

Study of Residual Stress Distribution by a Combined Method of Moire´ Interferometry and Incremental Hole Drilling, Part I: Theory

A new method combining Moire´ interferometry and the incremental hole-drilling method is developed to determine both uniform and nonuniform residual stress distribution in depth. The study is reported in two parts. In this first part, the theoretical development of the moire´ interferometry hole-drilling method is presented. The relationship between the in-plane surface displacements produced by introducing a blind hole and the corresponding residual stresses is established by employing the existing theoretical solution containing a set of undetermined coefficients. The coefficients are calibrated by the three-dimensional finite element method and they are processed nondimensionally for general use. The whole field in-plane surface displacements data Ux and Uy produced by the relaxation of residual stresses are obtained from moire´ interferometry after each increment of hole drilling. The high signal-to-noise ratio provided by moire´ interferometry allows accurate determination of fringe orders near the hole boundary which is essential for enhancing fidelity of residual stress determination. The experimental procedure to determine the signs of residual stresses is described and the accuracy of the method is also discussed.

New Concept of Equivalent Inherent Strain for Measuring Axisymmetric Residual Stresses

A new concept, the equivalent inherent strain gθeq, is proposed for measuring axisymmetric residual stresses, based on the inherent strain theory. gθeq is a parameter obtained by incorporating the radial inherent strain component into the tangential inherent strain component in computing the axially uniform axisymmetric residual stresses. The application of this concept can avoid the restriction of radial inherent strain component estimation and hence leads to a more simple and accurate method for measuring axisymmetric residual stresses. Experimental measurement and numerical simulation were carried out to demonstrate that this method has both the simplicity of the Sachs method and the high accuracy of the inherent strain method. [S1087-1357(00)70402-3]

Residual stress in polycrystalline diamond/Ti6Al4V systems

Polycrystalline diamond coatings were deposited on Ti6Al4V alloy by HF-CVD, at fixed temperature (650 C) for different deposition times. During the process, thick titanium carbide layers were formed at the metal/diamond interface. X-ray diffraction (XRD) methods were used to assess coating quality, phase composition, texture, and residual macrostress of the diamond/TiC/Ti system. For a better evaluation of the residual stress present in each phase, three independent measurements were performed with synchrotron radiation (SR-XRD). The measured residual strain could be interpreted in terms of a simple axially uniform residual stress model: σ 11 = σ 22 , σ 33 = 0, σ ij = 0 ( i ≠ j ). Irrespective of film thickness, the residual stress was very intense, compressive both in the diamond layer (approx. −6.5 GPa) and in TiC (approx. −1.4 GPa), and tensile in Ti6Al4V (approx. 70 MPa). The high residual strain in the diamond layer affected the results of texture measurements using the traditional pole figure method; more reliable results were obtained by measuring the integrated intensity, rather than peak maximum intensity, as a function of tilting angles.

軸対称残留応力推定法としての相当固有ひずみ概念の提案

A new concept, the equivalent inherent strain g^eq_θ, is proposed for the measurement of axisymmetric residual stresses, based on the inherent strain theory. That is combining the radial and tangential inherent strain components gr, gθ into one parameter g^eq_θ in computing the axially uniform axisymmetric residual stresses. Based on this concept, the difficulty of estimating the value of gr is overcome and stress distribution in a long cylinder can be computed by merely estimating g^eq_θ and axial inherent strain component gz from measured strains in tangential and axial directions. Stress distribution in a thin disk or ring can be simply obtained by estimating g^eq_θ from measured strain in tangential direction. The concept was verified by the experiment of measuring residual stresses in a pipe with cladding. A numerical simulation was carried out to demonstrate that the measuring method based on g^eq_θ has both the convenience of the Sachs method and the high accuracy of the inherent strain method.

Mechanics and mechanisms of toughening of advanced ceramics

In addition to toughening induced by phase transformation, crack deflection and bridging, near-tip microcracking has been identified as being another important source of toughening of advanced ceramics. In this paper, attention is devoted to the examination and modelling of these toughening mechanisms using an appropriate discrete damage model in which the microcracking region is modelled as a zone containing discrete multiple microcracks interacting with a main crack. These interaction effects between a main crack and microcracks have been studied by a number of researchers; existing solutions, however, suffer from certain difficulties resulting from over simplifying the problem. We have recently obtained a general explicit solution to the corresponding antiplane and plane problems of an arbitrarily located and oriented elliptical hole in the vicinity of the main crack under generalized loading conditions. Two aspects of the current problem are examined. The first is concerned with shielding and amplification effects associated with the release of uniform or non-uniform residual stresses from a single microcrack, while the second is concerned with shielding effects associated with the formation of a microcracking region around a stationary and a steadily growing main crack.

Enhanced sensitivity residual-stress measurements using taper-hole drilling

A novel method for enhancing the strain sensitivity of the hole-drilling method for measuring uniform residual stresses is examined. Such enhanced strain sensitivity is important because it improves the accuracy of the residual-stress evaluation. The new method involves enlarging the effective hole size by drilling a reverse taper hole. A simple practical technique for drilling reverse taper holes is described. The strain sensitivity for this new method is compared with that of the conventional hole-drilling method. Experimental results show excellent correspondence with theoretical results. The reasons for the sensitivity improvement are explained.

Optimization of winding process for composite pressure vessels

The winding of composite pressure vessels and pipes is always realized with some pretensioning, and some external loads may be applied. It is important to determine an optimal preload regime that ensures the maximum load-carrying capacity of the vessel subjected to internal pressure. In the present paper the optimal preload distribution is analyzed in the winding process for cylindrical and spherical pressure vessels that are treated as growing viscoelastic bodies subjected to ageing. In the case of cylindrical pressure vessels, an explicit solution for the dependence of the optimal preload intensity on the polar radius is derived for a nonageing material, and an approximate analytical solution is obtained for an ageing ribbon material. The influence of the rheological characteristics of the material on the optimal pretensioning is studied numerically. In the case of spherical pressure vessels, the optimal regime of internal pressure applied during the winding process is obtained that ensures a uniform residual stress distribution over the vessel cross-section. Both ageing and nonageing viscoelastic materials, as well as the optimal loading of a spherical vessel at finite strains, are analyzed. The new solutions obtained and the formulated recommendations are of special practical interest and importance for the optimal design and manufacturing of composite pressure vessels and pipes.

Residual Stress Analysis of Different Microstructures in Alumina Microelectronic Substrates

AbstractX-ray residual stress analysis was used to investigate the role of various phases in the formation of residual stress in laser-scribed alumina microelectronic substrates. Previous work by our group shows that the stress induced in the vicinity of a laser-scribe line is 20 to 50 percent of the modulus of rupture of this multiphase material. Our concern with the resulting stress is fracture of the substrate during subsequent firing processes and in-service fracture of the finished microelectronic device.The phases investigated, in addition to the alumina matrix, included a glassy phase (7% by volume), a spinel structure (3%), and porosity (4%) in 96% alumina. Electron probe microanalysis (EPMA), electron spectroscopy for chemical analysis (ESCA). scanning electron microscopy (SEM), and quantitative metallography were used to characterize the microstructure and composition of these phases. A Nd:YAG laser was used to scribe lines which raised the state of stress in the substrate.X-ray residual stress analysis shows that a uniform residual stress exists across the laser-scribed substrate, contrary to expected results. X-ray composition analysis suggests that the spinel phase of the material is vitrified in the heat affected zone of the laser scribe. The formation of this brittle glass phase, mainly at triple points and grain boundaries, may act as a pathway for inter-granular fracture and lead to subsequent failure of the finished microelectronic device.

The effect of porosity and γ-γ′ eutectic content on the fatigue behaviour of hydrogen charged PWA 1480: Gayda, J., Dreshfield, R.L. and Gabb, T.P. Scr. Metall. Mater. Nov. 1991 25 (11) 2589–2594

The aim of this investigation was to ascertain the relative changes in residual stress profile after the post-treatment of thermal spray WC–NiCrBSi coatings and relate these changes to the microstructural and tribo-mechanical properties. Residual strain measurements were performed using neutron diffraction technique in vertical scan mode. Functionally graded HVOF (JP5000) WC–NiCrBSi coatings were thermally sprayed on AISI 440C steel substrate discs, some of which were given different post-treatments i.e. HIPing at two different temperatures of 850 °C and 1200 °C, and heat-treatment in inert atmosphere at 1200 °C. Changes in microstructure due to heat-treatment were identified using SEM, XRD and light microscopy and correlated with tribo-mechanical properties determined using microhardness, Young’s modulus and fatigue testing. It was found that whilst simple models based upon the differences in coefficient of thermal expansion can be adapted to predict the approximate average residual stresses after the post-treatment, refined models based upon microstructural change, substrate plasticity, influence of heating/cooling rate, and pressure during the post-treatment are necessary for the reliable prediction of residual stress fields. Such models may then be utilised to tailor the residual stress profile during the post-treatment for specific industrial applications. Improvement in coating fatigue performance was related to the attenuation of stress gradient within the coating layers, and to the homogenisation of stress profile at the coating substrate interface at the higher HIPing temperature of 1200 °C. The presence of isostatic pressure during the HIPing post-treatment produced a more uniform residual stress and Young’s modulus profile, and hence a reduced stress concentrations that exacerbate fatigue failure.

On the effect of the release of residual stresses due to near-tip microcracking

This article provides a comprehensive theoretical treatment of the interaction effects associated with the release of a general residual stress field as a result of the formation of microcracks in the vicinity of a main crack. The theoretical formulations are based upon the use of the complex potentials of Muskhelishvili and an appropriate superposition procedure. The induced stress intensity factor at the main crack is obtained in a series form and the leading order closed form solution was utilized to elucidate two interesting features of the study. The first is concerned with shielding and amplification effects associated with the release of a uniform residual stress field from a single microcrack. The second is concerned with shielding effects due to the formation of a microcracking zone in the vicinity of a stationary and a steadily growing main crack. The results for the case of a single microcrack reveal that, depending upon the location and orientation of the mirocrack, shielding and amplification effects may become prevalent. In the case of a microcracking zone, equivalence between the current interaction model and the contiuum mechanics approach was established based upon similar microcrack nucleation criteria.

Stacking fault probability in β-SiC grown by chemical vapour deposition

The stacking fault probability in β-SiC, grown by chemical vapour deposition (CVD), was measured using the X-ray diffraction method. Stacking faults on the {111} planes shifted the {111} and {200} X-ray diffraction peaks from which the stacking fault probability can be directly determined. The stacking fault probability increased with decreasing deposition temperature owing to low surface atomic mobility at lower deposition temperatures. At a low hydrogen flow rate, the stacking fault probability increased as a result of decreasing the probability of combination of the silicon and carbon atoms. A methyltrichlorosilane flow rate higher than 10 cm3 min−1 had little effect on the stacking fault probability. Increasing the free silicon content also increased the stacking fault probability. A uniform residual stress effect was observed in the transparent deposit using a polarization microscope.

Measuring Residual Stresses by Hole-Drilling and Coherent Optics Techniques: A Numerical Calibration

Hole-drilling is a widely accepted method for determining residual stresses from the relaxation data obtained by a strain-gage rosette. Several researchers have recently investigated the alternative of employing interferometric techniques to reveal the displacement field produced by hole-drilling. As in the case of the standardized hole-drilling strain-gage method, proper calibration constants must be assessed so that this procedure can be effectively employed. This paper reports the displacement calibration constants derived from the results of an extensive numerical analysis. The constants proposed enable a uniform residual stress field to be determined, whatever the displacement component detected. The most commonly employed coherent optics techniques have been considered; computer-generated fringe patterns are reported and criteria are suggested to derive the stress field from fringe readings taken around the edge of the hole.

A note on the influence of residual stress on measured hardness

The influence of uniform residual stresses on measured hardness value is investigated experimentally, using samples containing a known cylindrical stress value. It is shown that realistic values of this stress have a first order effect on the hardness number obtained in a Vickers pyramidal indenter test.

Forest Products Laboratory Technical Notes

Advanced compressor designs today often include blade integrated disc (blisk) rotors, with high demands on aerodynamic performance, resistance againsthigh load levels and foreign object damage (FOD).To increasethe highcycle fatigue (HCF) strength, compressive residual stresses are introduced into the surface and subsurface layer of aerofoil, fillet (transient area between aerofoil and disk) and annulus (intermediate area between aerofoils). For generatingcompressive residual stresses several different industrial production processes are used, beside ultrasonic shot peening, laser shock peening, deep rolling and shot peening wet and dry with glass or ceramic media is shot peening with steel media the mostly used technology. However, depending on the size of the componentaccessibility for tools might be limited and the set-up of economical production techniques challenging for blisk shot peening.This paper gives an introduction into blisk shot peening, a sophisticated mechanical surface technology for treating aerofoil surfaces of blisk rotors using special designed calliper nozzles assolution for introducing uniform residual compressive stress states, as well as consistentshot peening coverage levels.