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Modelings of the interface distribution and flow-induced residual stresses and birefringence in the sequential co-injection molding (CIM) of a center-gated disk were carried out using a numerical scheme based on a hybrid finite element/finite difference/control volume method. A nonlinear viscoelastic constitutive equation and stress-optical rule were used to model the frozen-in flow stresses in disks. The compressibility of melts is included in modeling of the packing and cooling stages and not in the filling stage. The thermally induced residual birefringence was calculated using the linear viscoelastic and photoviscoelastic constitutive equations combined with the first-order rate equation for volume relaxation and the master curves for the relaxation modulus and strain-optical coefficient functions of each polymer. The influence of the processing variables including melt and mold temperatures and volume of skin melt on the birefringence and interface distribution was analyzed for multi-layered PS-PC-PS, PS-PMMA-PS, and PMMA-PC-PMMA molded disks obtained by CIM. The interface distribution and residual birefringence in the molded disks were measured. The measured interface distributions and the gapwise birefringence distributions in CIM disks were found to be in a fair agreement with the predicted interface distributions and the total residual birefringence obtained by the summation of the predicted frozen-in flow and thermal birefringence., INTRODUCTION The co-injection process is known since its first introduction in the early 1970s. In co-injection molding (CIM), two different (dissimilar but chemically and Theologically compatible) polymers are injected into [...]

The simulation of the gapwise distribution of the thermally-induced residual birefringence and stresses in freely-quenched PS-PC-PS and PC-PS-PC multi-layered slabs in water was carried out to calculate the gapwise distribution of the transient and residual birefringence. The modeling was based on the linear viscoelastic and photoviscoelastic constitutive equations combined with the first-order rate equation for volume relaxation. The master curves for the Young's relaxation modulus and strain-optical coefficient functions obtained earlier for PS and PC were used in the simulations. The obtained numerical results provided the evolution of the thermally-induced stress and birefringence with time during and after quenching. The predicted gapwise residual birefringence distribution in these slabs was found to be in a fair agreement with the measured results. In addition, the gapwise distribution of the thermally-induced residual birefringence in the multi-layered PS-PMMA-PS, PMMA-PS-PMMA, PMMA-PC-PMMA, and PC-PMMA-PC slabs quenched from different initial temperatures was measured. Explanations were provided for the observed gapwise distribution of the thermal residual birefringence in each layer of these slabs including the effect of the initial temperature., INTRODUCTION During polymer processing, the polymer undergoes simultaneous mechanical and thermal influences in the fluid, rubbery, and glassy states. These effects introduce orientation, residual stresses, and shrinkage in the products [...]

Pipe extruded from polyethylene of strength class PE100 was tested using the ISO 13477 Small Scale Steady State 'S4' method, to investigate the effect of frozen-in stress on rapid crack propagation (RCP). It was found that the lower the residual stress, the lower the S4 critical temperature [T.sub.cS4] for RCP. Different experimental thermal treatments were used to independently modify residual stresses and crystallinity, to study the separate effects on RCP. It was found that the effect of crystallinity was less significant than that of residual stresses. It has previously been suggested that the residual stress influence on [T.sub.cS4] is determined by the balance of two mechanisms: additional stored strain energy prior to fracture helps to drive the crack, while the closing moment after fracture helps to close the flaring pipe wall. Tests on annealed specimens suggested that the first effect dominates, especially soon after crack initiation. However, the observed effect seems too large to be explained by this mechanism, and we suggest that the observed benefit from annealing may be better explained by a change in crack front shape. POLYM. ENG. SCI., 53:1217-1222, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Polyethylene (PE) pipes have been widely used for the last 50 years. Excellent properties such as corrosion and chemical resistance, low cost, toughness, durability, and ease of installation have [...]

Residual stresses and thermoviscoelastic deformation of a laminated film utilized for film insert molding was investigated through measurement of thermal expansion coefficient (CTE) and relaxation modulus. Thermoviscoelastic deformation of the film was also analyzed with numerical analysis by applying measured relaxation modulus, CTE, and residual stress to finite element method (FEM). Stress relaxation of the pristine film showed significantly different behavior from that of the unannealed film during annealing. Effects of the CTE and relaxation modulus on the thermoviscoelastic deformation were predicted by considering thermal shrinkage and structural relaxation. Moreover, numerical results on thermoviscoelastic deformation were in good agreement with experiments when initial stress distribution in the solid specimen was applied to the numerical analysis. POLYM. ENG. SCI., 52:1121-1127, 2012. © 2011 Society of Plastics Engineers, INTRODUCTION Film insert molding (FIM), known as in-mold decorating, is one of the various coating technologies to perform surface modification of injection molded parts. In general, a film is inserted [...]

Foundation conditions are studied for a series of apartment buildings in a shore area reclaimed from the Nakdong River estuary delta west of Busan, South Korea, in full-scale field tests on two 600 mm, post-driving grouted, concrete cylinder piles instrumented with strain gages, driven through compressible layers and a short distance into underlying dense sand at depths of 56 m (Shinho) and 35 m (Myeongji). One test pile was provided with an O-cell so that after an initial Ocell test, a subsequent head-down test only affected pile shaft resistance. The purpose was to evaluate drivability of the piles, magnitude of the drag load due to consolidating soils, and potential settlement (downdrag) of the piled foundations. Early in the study, it became apparent that the internal process of heating and cooling of the grout during the hydration process and swelling from absorption of water affected the strain records and the assessment of residual load in the test piles during the wait time before the static loading test. The paper reports the measurements, analyses, and method for determining residual load, strain-dependent modulus of test piles, and actual load distribution in the test piles. The results are correlated to cone penetration test (CPTU) sounding data and effective stress analysis. Key words: concrete piles, concrete modulus, swelling, strain measurement, drag load, settlement. Les conditions des fondations d'une serie de blocs a appartements situes dans une region cotiere rehabilitee du delta de l'estuaire de la riviere Nakdong a l'ouest de Busan, Coree du Sud, ont ete etudiees a l'aide d'essais sur le terrain a l' echelle reelle sur deux pieux cylindriques en beton, instrumentes de jauges de deformation de 600 mm et cimentes apres la mise en place, enfonces a travers des couches compressibles et a travers une faible distance de sable dense sous-jacent, a des profondeurs de 56 m (Shinho) et de 35 m (Myeongji). Une cellule O a ete installee sur un des pieux, de sorte qu'apres l'essai en cellule O initial, un essai subsequent affecte seulement la resistance de l'arbre du pieu. L'objectif etait d'evaluer la facilite d' enfoncement des pieux, la magnitude de la charge de trainee causee par la consolidation des sols, et le tassement potentiel (trainee vers le bas) des fondations des pieux. Au debut de l'etude, il a ete observe que le processus interne de rechauffement et refroidissement du ciment durant l'hydratation et le gonflement cause par l'absorption d'eau affectent le register des deformations et l'evaluation de la charge residuelle dans les pieux d'essai durant la periode d'attente avant les essais en chargement statique. L'article presente les mesures, les analyses et une methode pour determiner la charge residuelle, le module de dependance des deformations des pieux, et la distribution des charges actuelles dans les pieux d' essai. Les resultats sont correles avec des resultats d'essai de penetration au cone (≪ CPTU ≫) et d'analyse des contraintes effectives. Mots-cles: pieux en beton, module du beton, gonflement, mesure des deformations, charge de trainee, tassement. [Traduit par la Redaction], Introduction The Nakdong River estuary delta area covers a large area west of the city of Busan, South Korea, and is composed of very thick deposits of compressible and, originally, [...]

Welded, thick-walled piping intersections are widely used in many engineering applications including the offshore and nuclear power industries. These components are often fabricated by multipass welding, which inevitably introduces undesirable residual stresses. In this paper, weld-induced residual stresses in a thick-walled piping intersection were predicted using a validated, full three dimensional, sequentially coupled thermomechanical finite element modeling technique. The moving heat source was simulated by imposing body heat flux onto the newly activated elements progressing along the circumferential weld path around the intersection during each pass. The effect of cooling rate on the final residual stress state, especially at critical areas where the peak residual stresses are located, was then investigated by applying different convective heat transfer coefficients to the exposed piping intersection surfaces. It was found that the magnitudes and overall spatial distributions of residual stresses were very sensitive to cooling rate. Residual stresses on the outer surfaces of the component can be significantly reduced by external cooling. On the other hand, cooling the inner surfaces can dramatically convert residual stresses from tensile to compressive in these regions. The results and modeling technique presented in this paper show that residual stress profiles in multipass welded complex geometries can be efficiently optimized through convenient cooling rate control. [DOI: 10.1115/1.4000634] Keywords: residual stress, multipass welding, cooling rate, finite element

At the end of 2006, defects were identified using ultrasonic testing in three of the pressurizer nozzle dissimilar metal (DM) welds at the Wolf Creek nuclear power plant. Understanding welding residual stress is important in the evaluation of why and how these defects occur, which in turn helps to determine the reliability of nuclear power plants. This paper presents analytical predictions of welding residual stress in the surge nozzle geometry identified at Wolf Creek. The analysis procedure in this paper includes not only the pass-by-pass welding steps, but also other essential fabrication steps of pressurizer surge nozzles. Detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. Case studies were carried out to investigate the change in the DM main weld stress fields resulting from different boundary conditions, material strength, weld sequencing, as well as simulation of the remaining piping system stiffness. A direct comparison of these analysis methodologies and results has been made in this paper. Weld residual stress results are compared directly to those calculated by the nuclear industry. [DOI: 10.1115/1.4000701]

Steel corrosion in reinforced concrete (RC) structures leads to change of steel mechanical properties, longiludinal cracking in the concrete cover, and other related effects that weaken the serviceability and load capacity of the composites. It is therefore extremely important to have methods targeted to the evaluation of the structural damage reduced by corrosion for estimating the residual load capacity of a structure, and then for inspection procedures and strengthening the maintenance interventions. This paper presents a simplified methodology capable of providing estimates of the residual life of corroded RC beams. The proposed method uses damaged material properties, and accounts for the length of partial corrosion and the amount of corrosion, concrete loss and change of bond strength within this specified length. A comparison of the model predictions with the experimental results published in the literature shows the validity of the model. It is also concluded that the ultimate flexural moment of corroded RC beam will not significantly influenced by the partially corroded or unbonded length and the bond characteristics over this partial length as long as the tensile steel of the beam can reach its yield strength, in addition, although complete loss of bond over the partial length is assumed to asses the residual strength of corrosion-damaged RC beam, neglecting the influence of bond strength within the corroded length may lead to underestimate the ultimate flexural capacity of the damaged beam, especially when the corrosion level of tensile steel of the RC beam is not very high. DOI: 10.1061/(ASCE)CF.1943-5509.0000083 CE Database subject headings: Reinforced concrete: Concrete beams corrosion: Load bearing capacity; Residual strength. Author keywords: Partial length: Corrosion: Bond: Bearing capacity: Residual strength.

A mechanistic response model was recently developed at the University of Illinois to analyze geogrid base reinforced flexible pavements designed for low to moderate traffic volumes with a relatively thin hot-mix asphalt surface layer. This model utilizes the finite element approach and properly considers (1) the nonlinear, stress-dependent behavior of pavement foundation geomaterials, i.e., unbound aggregates and fine-grained soils; (2) anisotropic behavior of the granular base layer; and (3) the compaction and preloading induced unbound aggregate base residual stresses. To validate the developed mechanistic model, field response data were collected from instrumented full-scale pavements constructed with both geogrid reinforced and control test sections. The model predictions using the nonlinear and anisotropic characterizations of the granular base layer moduli were found to better capture the magnitudes and the trends in the measured response data. After trafficking to failure of the pavement test sections, pavement trench studies were conducted to gather constructed layer thicknesses and additional forensic data in an effort to provide refined inputs for the mechanistic response model. An increase in stiffness observed around the geogrid reinforcement in the field was properly modeled by the use of horizontal residual stresses above the geogrid, which resulted in a better match of the predicted with the measured pavement responses of the reinforced sections. As a result, the mechanistic model predictions computed at different locations in the test sections compared reasonably well with a large number of field measured responses under different load levels. DOI: 10.1061/(ASCE)TE.1943-5436.0000046 CE Database subject headings: Geogrids: Mechanistic models: Flexible pavements; Finite element method; Anisotropy; Nonlinear analysis: Residual stress.

Hard turning and grinding are precision processes in many cases for manufacturing various mechanical products. Product performance is highly dependent on the process induced residual stress. However, the basic differences in residual stress profiles generated by hard turning and grinding with and without the presence of a thermal white layer have not been well understood. This study aims to compare basic characteristics of the residual stress profiles using an extensive residual stress measurement for five surface types: hard turned fresh, hard turned with a white layer, ground fresh, ground with a white layer, and as heat treated. The X-ray diffraction data revealed distinct differences in the residual stress profiles for the five surface types. Hard turning with a sharp cutting tool generates a unique 'hook' shaped residual stress profile characterized by compressive residual stress at the surface and maximum compressive residual stress in the subsurface, while 'gentle' grinding only generates maximum compressive residual stress at the surface. The depth of compressive residual stress in the subsurface by hard turning is much larger than that by grinding. The high hertz pressure induced by the cutting tool in turning is the determining factor for the differences in residual stress. High tensile residual stress associates with the existence of a turned or a ground white layer The coupled effects of high hertz pressure and rapid temperature change induced by tool wear play an important role in the resultant tensile residual stress. In addition, residual stress by grinding is more scattered than that by turning. Compared with the deterministic influence of machining process on the magnitudes and profiles of residual stress, the effect of heat treatment is minor [DOI: 10.1115/1.3159046] Keywords: residual stress, hard turning, grinding, white layer

The influence of various assumptions on the modeling of cleavage fracture in the presence of residual stresses was investigated. Analyses were undertaken for modified single edge notched bend specimens, manufactured from A533B ferritic steel The influence of residual stress fields, introduced by a method of in-plane compression, was investigated through the use of a modified J-integral designed to retain path independence in the presence of initial stress and strain fields and nonproportional loading. Application of modified J values to predict fracture using probabilistic methods, and their use in a well-known structural integrity assessment code, showed that assumptions about levels of out-of-plane constraint, material hardening behavior, and the method of crack introduction have a significant influence on the conservatism of the resulting failure predictions. It was found that more realistic modeling of crack introduction had a major effect on the accuracy of failure predictions, with the effects of material hardening being of secondary importance. [DOI: 10.1115/1.3066938] Keywords: J-integral, residual stress, fracture, cleavage

To measure directly residual stresses by digital image correlation using hole drilling, the deformation pattern that is governed by the residual stresses is used to affine transform the image captured after the object is deformed. If the values of trial residual stress components are properly chosen, the image after affine transformation will have a maximum similarity to the original image. This turns the residual stress measurement issue into a pure numerical computational process, which leads to the direct output of residual stresses. Validation tests have proved the viability of the approach. The proposed concept and principle could be extended to other specific measurement tasks with known deformation patterns. OCIS codes: 100.2000, 120.4880.

This paper presents a novel viscous inverse method for blade design. In this method, viscosity is directly taken into account using a flow analysis code based on the Navier-Stokes equations. In this approach, the blade pressure loading and the blade thickness are prescribed and the corresponding blade profile is sought. By specifying the target pressure loading and the blade thickness, the camber line instead of the blade surface deforms. The prescription of the blade thickness ensures that a realistic blade shape with closed leading and trailing edges can be obtained. The redesign of an axial rotor and a stator blade, starting from an initial arbitrary profile in subsonic flow regimes, demonstrates the merits and robustness of this approach.

The influence of deposition temperature on the optical properties, microstructure, and residual stress of Yb[F.sub.3] films, deposited by electron-beam evaporation, has been investigated. The increased refractive indices and surface roughness of Yb[F.sub.3] films indicate that the film density and columnar structure size increase with deposition temperature. At the same time, higher packing density reduces absorption of moisture. The residual stress is related to deposition temperature and to substrate. For the samples deposited on BK7, the residual stress mainly comes from intrinsic stress, however, for those on fused silica, thermal stress is the dominant factor of total residual stress. OCIS codes: 310.0310, 310.3840, 310.6860.

Mg[F.sub.2] films with a columnar microstructure are obliquely deposited on glass substrates by resistive heating evaporation. The columnar angles of the films increases with the deposition angle. Anisotropic stress does not develop in the films with tilted columns. The residual stresses in the films depend on the deposition and columnar angles in a columnar microstructure. OCIS codes: 310.6870, 310.4925, 310.1860.

Titanium oxide (Ti[O.sub.2]) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 [degrees]C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. Ti[O.sub.2] films deposited by sputtering were generally more stable during annealing than those deposited by evaporation. OCIS codes: 310.0310, 310.1860, 310.6860, 310.6870.

Ta--Si oxide composite thin-film rugate filters were prepared by radio frequency ion-beam sputtering and their residual stress and substrate deflections were measured. The residual stress and substrate deflection of these composite film rugate filters were less than that of notch filters made from a series of discrete quarter-wave layers with alternate high and low indices because of the smooth modulation of composition and no interface structure of the rugate filter. OCIS codes: 310.6870, 310.1620.

A large-scale field-monitoring program for studying residual forces in long-driven piles is described. Eleven steel H-piles, 34.2-59.8 m in embedded length, were instrumented with vibrating-wire strain gauges, installed and subjected to static loading tests in a building site in Hong Kong. The residual forces in these piles during and after pile installation were recorded. The development of residual forces as it relates to the pile penetration depth during construction, and in time after the piles were installed, is presented. The measured load transfers in the piles from static loading tests are reported and the effect of the residual forces on the interpretation of load- transfer behavior is studied. The field measurements show that residual forces increase approximately exponentially with penetration depth. The residual forces continue to increase with time after pile driving due to secondary compression of disturbed soils around the pile shaft and other factors. The large residual forces in the long piles significantly affect the interpretation of the pile load distributions. The effect of residual forces on the shaft resistance is significant at shallow depths. Bearing-capacity theory tends to overpredict the true toe resistance of the long piles founded in weathered soils. DOI: 10.1061/(ASCE)1090-0241(2007)133:10(1216) CE Database subject headings: Driven piles; Full-scale tests; Load tests; Load transfer; Pile foundations; Residual stress; Time factors; Hong Kong; Weathering.

While it is generally assumed that global plate motions are driven by the pattern of convection in the Earth's mantle, the details of that link remain obscure. Bouyancy forces associated with subduction of cool, dense lithosphere at zones of plate convergence are thought to provide significant driving force, but the relative magnitudes of other driving and resisting forces are less clear, as are the main factors controlling long-term changes in plate motion. The ability to consider past as well as present plate motions provides significant additional constraints, because changes in plate motion are necessarily driven by changes in one or more driving or resisting forces, which may be inferred from independent data. Here we present for the first time a model that explicitly links global mantle convection and lithosphere models to infer plate motion changes as far back as Miocene time. By accurately predicting observed convergence rates over the past 10 m.y., we demonstrate that surface topography generated at convergent margins is a key factor controlling the long-term evolution of plate motion. Specifically, the topographic load of large mountain belts and plateaus consumes a significant amount of the driving force available for plate tectonics by increasing frictional forces between downgoing and overriding plates. Keywords: plate convergence, mountain building, resistive stresses, plate motion.

In the present work a strategy for the qualitative and quantitative analysis of residual solvents in pharmaceutical products is reported. First, a low-resolution chromatogram is generated for the identification of the solvents present in the samples by means of headspace generation-fast gas chromatography--mass spectrometry (HS-fast GC/MS). From the plotting of this information by means of contour plots with time and mass/charge axes, it is decided whether quantification of such compounds can be accomplished without chromatographic separation or whether it should be done by fast gas chromatography. The nonseparative method is based on direct coupling of a headspace sampler with a mass spectrometer (HS-MS) and requires a signal recording time of only 3 min, while with fast gas chromatography the time required to obtain a chromatogram is 7.16 min. The use of headspace generation for introducing the sample and standard addition as a quantification technique provided satisfactory results and minimized the matrix effect. An important advantage of the methodologies used here is related to the fact that no prior treatment of the sample is required, thus minimizing the creation of analytical artifacts and the errors associated with this step of the analytical process. The methods were applied to the determination of residual solvents in 27 different pharmaceutical products. Detection and quantification limits were sufficiently low to enable the estimation of organic volatile impurities according to the International Conference on Harmonization (ICH) of Technical Requirements for the Registration of Pharmaceuticals for Human Use.

A comprehensive uncertainty analysis and order selection methodology, with detailed development for the slitting method is presented to measure the spatial variation of residual stresses. Using Monte Carlo numerical simulations, it is demonstrated that accurate uncertainty estimates require the estimation of model error, the ability of the chosen series expansion to fit the actual stress variation.

Cement stabilization of metallurgical residues is a frequently implemented option to reduce the associated environmental risks and thus simplify residue disposal procedures. As chemical stabilization is the first and main purpose of the process, physical testing of these stabilized residues is usually kept simple with unconfined compressive strength, permeability, and durability as the most frequently employed control tests. These tests are, however, unable to deliver a true image of the potentially complex mechanical behavior after stabilization of some important residues. One example is treated sludge. Stabilizing agents and fine residues are usually mixed at high water contents, resulting in a very porous microstructure, with fragile bonds. Under loading, rapid destructuration and compaction is possible and this process may be prone to material instabilities. These phenomena are experimentally and theoretically illustrated herein. The experimental illustrations are brought from a microstructural study and undrained triaxial campaign on a stabilized jarosite. The theoretical explanations are obtained from an elasto-plastic model previously employed for soft rocks. CE Database subject headings: Stabilization; Sludge; Elastoplasticity; Microstructure; Cement; Waste management; Waste disposal.

Byline: Ben D. MacArthur (1), Colin P. Please (1) Keywords: Growth induced stress; Necrosis; Multi-cell tumour spheroid; Continuum mechanics Abstract: We consider how cell proliferation and death generate residual stresses within a multi-cell tumour spheroid (MCTS). Previous work by Jones and co-workers [8] has shown that isotropic growth in a purely elastic MCTS produces growth induced stresses which eventually become unbounded, and hence are physically unrealistic. Since viscoelastic materials show stress relaxation under a fixed deformation we consider the effect of the addition of a small amount of viscosity to the elastic system by examining formation of equilibrium stress profiles within a Maxwell type viscoelastic MCTS. A model of necrosis formation based upon that proposed by Please and co-workers (see [16] [17] [18]) is then presented in which necrosis forms under conditions of adverse mechanical stress rather than in regions of extreme chemical stress as is usually assumed. The influence of rheology on necrosis formation is then investigated, and it is shown that the excessive stress generated in the purely elastic tumour can be relieved either by the addition of some viscosity to the system or by accounting for an inner necrotic interface with an appropriate stress boundary condition. Author Affiliation: (1) Faculty of Mathematical Studies, University of Southampton, SO171BJ, England Article History: Registration Date: 01/01/2004 Received Date: 05/04/2003 Online Date: 03/03/2004

Many models have already been developed to fit crack-growth data. Here, it is suggested that it can be useful to go a step further by examining residuals, which appear as differences between experimental and predicted values.

An analytical model is developed to analyze the effects of viscous flow on residual stresses in film-substrate systems. Compared to viscous flow in the film, viscous flow in the substrate results in slower stress relaxation in the system.

Thermal and thermoelastic effects in stressed solids were studied using a multimode approach.

In an attempt to strengthen the surface of materials, the potential of using a cavitating jet to form compressive residual stress has been investigated. Introducing compressive residual stress to a material surface provides improvement of the fatigue strength and resistance to stress corrosion cracking. In general cavitation causes damage to hydraulic machinery. However, cavitation impact can be used to form compressive residual stress in the same way as shot peening. In the initial stage, when cavitation erosion progresses, only plastic deformation, without mass loss, takes place on the material surface. Thus, it is possible to form compressive residual stress without any damage by considering the intensity and exposure time of the cavitation attack. Cavitation is also induced by ultrasonic, high-speed water tunnel and high-speed submerged water jet, i.e., a cavitating jet. The great advantage of a cavitating jet is that the jet causes the cavitation wherever the cavitation impact is required. To obtain the optimum condition for the formation of compressive residual stress by using a cavitating jet, the residual stresses on stainless steel (JIS SUS304 and SUS316) and also copper (JIS CllO0) have been examined by changing the exposure time of the cavitating jet. The in-plane normal stresses were measured in three different directions on the surface plane using the X-ray diffraction method, allowing for the principal stresses to be calculated. Both of the principal stresses are found changing from tension to compression within a 10 s exposure to the cavitating jet. The compressive residual stress as a result of the cavitating jet was found to be saturated after a certain time, but it starts decreasing, and finally, it approaches zero asymptotically. It could be verified in the present study that it was possible to form compressive residual stress by using a cavitating jet, and the optimum processing time could also be realized. The great difference between the water jet in water and air has also been shown in this regard.

Controlled orthogonal and controlled oblique machining of annealed AISI 4340 have been undertaken in a design of experiments framework to investigate the machining-induced residual stresses resulting from these processes. The experimentation demonstrates significant simplifications in the machining-induced residual stress problem when the stresses are expressed in a coordinate system fixed in the tool and also indicates that the directions along the cutting edge and normal to the cutting edge of the tool are principal directions of the machining-induced residual stresses. Based on the experimental results, a plane strain thermoelastoplastic model of metal flow under the flank of a cutting tool is developed to predict the full in-plane biaxial residual stress profiles existing at and beneath the newly created surface. Calibrated results show favorable agreement with the experimental machining-induced residual stresses in annealed AISI 4340.

Analysis of residual stress in welding joints by direct measurements and computed distributions reveal that the methods agree well with each other and they are suitable for evaluating both internal stress and surface stress.

The development of surface thermal stresses for a rectangular trigonal crystal rod having zero average stress on each of its lateral surfaces into Fourier series is presented. Ordinary stress solutions were utilized in an attempt to zero the balance of the surface stress. A computer code has been developed to add the generated correcting stresses to the original. The iteration of a stress correction technique has resulted in almost zero remaining lateral surface stress.

Research was conducted to evaluate the error introduced by the use of acoustoelastic coefficients defined with the natural coordinates for the estimation of residual stresses. Two approaches were considered to estimate the differences between the acoustoelastic coefficients in function of the system of coordinates. A comparison of theoretical and experimental results show that the value of some coefficients can vary significantly according to the used system of coordinates.

Aluminum alloys are used in a variety of structural engineering applications, such as transportable and lightweight bridges, due to their high strength-to-weight ratio and durability. However, the heat of welding may reduce their strength significantly and necessitate the inclusion of strength reduction factors in design calculations. Theoretical procedures for predicting ultimate shear and patch resistance, which include material strength reduction factors to allow for welding, are now incorporated in BS8118, the code of practice for aluminum structures, and EC9, the Eurocode of practice for aluminum structures. However, when compared with available test results, theoretical predictions in accordance with BS8118 and EC9 appear unduly conservative. Experimental and theoretical studies of the behavior and strength of welded aluminum alloy plate girders, subjected to shear and patch loading, are reviewed and discussed. Theoretical predictions of the ultimate resistance, based on modified and developed theories, are compared and show consistent and improved correlation with experimental results.

Research was conducted to examine the residual stress distribution in the direction of the film normal in thin diamond films deposited on Si substrate along with the distribution of Young's modulus. The microwave chemical vapor deposition method was used to deposit the films on the substrate. Results provide evidence that something quite different from the rest of the film growing mechanism is occurring near the interface at the very early stage of deposition where the region of interest is even far thinner than the thickness of thin films.

Research was conducted to characterized the crystallinity of laser-recrystallized Si films on insulators using micro-Raman imaging. To probe the structure at various depths, a small-angle bevel made by angle lapping of the SOI film was used. The depth profile of the Raman feature reveals that the defect density is high in the region near the interface of Si and SiO2 and that the stress increases toward the top surface of the silicon film.

Research was conducted to examine a metal-oxide-silicon capacitor under constant voltage using tunneling Fowler-Norheim bidirectional electron injections. Defects generated within the oxide were found to be of the same physical nature and are mainly composed of neutral traps. Results demonstrate that the saturation of interface state generation is linked to the polar bonds at the silicon/oxide interface.

Research was conducted to examine the mechanical stresses in tungsten lines on a silicon substrate using x-ray diffraction. Micro-Raman spectroscopy was used to investigate the stress state in the silicon substrate which, when induced in the silicon substrate, were compressive under the lines but tensile in between the lines. Results demonstrate that the combined micro-Raman spectroscopic and x-ray diffraction studies were effective in testing the validity of the assumptions.

This paper presents part of a rigorous numerical study of the geometry changes in cylindrical shells due to localized fabrication misfit and the associated consistent residual stress field. The search for practically useful and credible modes of imperfections has led to this study of the geometric imperfections arising from misfits of construction. These are treated here by using a geometrically nonlinear analysis to study the effect of a mismatch in geometry at a point or a seam in a cylinder, or alternatively to explore the role of weld shrinkage in the formation of geometric imperfections. The imperfect geometries arising from these misfits are demonstrated, and some simplifications are given so that their shape may later be used in methods for characterizing imperfection patterns that can be applied to measurements of structures in service. It is found that the geometrical changes are essentially linear for most of the shrinkages considered.

An evaluation system for calculating the residual vibration caused by a HDD (Hard Disk Drive) mounting system is presented. It contains both the elements for measurement and analysis. The PES (Position Error Signal) of an ideally balanced rigid rotary actuator depends on the rotational vibration of the HDD, specifically at lower frequencies. First, this evaluation technique obtains a measurement of the transfer function of the HDD rotational acceleration over actuator current. Next, using the measured power spectrum of the actuator in combination with the HDD's tracking error transfer function, the response of the entire HDD and mount system is calculated in the frequency domain. Finally the time domain system response is calculated by computation of the Inverse Fast Fourier Transform (IFFT) of the frequency response solution, assuming a random phase of the input force. Good correlation is obtained between measured and calculated system responses. Experimental result show that the dominant residual vibration is caused by the mounting mechanism response and that both the HDD and HDD mount system need to be evaluated and understood as a system, in order to achieve higher TPI (Track per inch) in the future.

Differences in the glass transition temperatures ([T.sub.g]) of epoxy resins were observed when their samples for differential scanning calorimetry (DSC) measurements were prepared by two different methods. The differences (in [T.sub.g]) are believed to be due to the effects of interfacial residual stress, which is present only in the samples of lower [T.sub.g] prepared with the formation of a 'chemical' contact between epoxy resin and aluminum (pan) which have mismatched thermal expansion coefficients. Both types of the samples also showed, respectively, lower [T.sub.g] when they were prepared by a fast-cooling process than when they were prepared by a slow-cooling process. This suggests that matrix residual stress, which is present in both types of the samples, as well as interfacial residual stress, has similar effects on the [T.sub.g] of epoxy resins. This conclusion is substantiated by the results of the change of contact pattern and the freezing stress experiments., INTRODUCTION Residual stresses include interfacial residual stresses and matrix residual stresses (matrix residual internal stresses or matrix internal stresses). In epoxy resins, residual stresses are produced as a result of [...]

Residual stress distributions due to plating and polishing were determined for nickel-phosphorus plated aluminum alloy disks. Knowledge of these stresses provides insight into the material deformation and removal processes, information as to the effects of processing conditions on residual stress magnitude and can also serve as a basis for development of models of material deformation and removal in polishing. Measured disk shape data was fitted to an analytical solution for plate displacement due to bending moments, and residual stresses were calculated. Plating and polishing residual stresses were separated. Polishing residual stress is compressive indicating differential plastic deformation between the surface and interior regions of the workpiece. Residual stresses produced in polishing operations in which process motions were constrained so that polishing was unidirectional were measured. The results show large differences between amounts of deformation in the polishing direction and the direction perpendicular to it.

Stress-relief annealing (SR treatment) is often applied to relieve welding residual stresses in the fabrication process of pressure vessels, etc. This study aims at development of an efficient method as simple as hand calculation to estimate reduction of residual stresses of very thick welded joint by SR treatment. In the first report, an estimating method was developed for relaxation tests, in uniaxial stress state, at changing and constant temperatures because the stress relaxation phenomenon is considerably similar to that observed in the SR treatment of a joint. In this report, the stresses relaxed by SR treatment in a very thick welded joint are analyzed accurately by the finite element method based on thermal elastic-plastic-creep theory. The characteristics of the changes of the welding residual stresses in multiaxial stress state are studied in detail for further development of the estimating method to SR treatment of a very thick welded joint, of which the stress state and boundary condition are very complex.

BACKGROUND Compression Molding Jog (1) offers a good review of compression molding of neat thermoplastic resins. Polymeric powders are compression molded because melt flow polymer processing, like injection molding, does [...]

Theoretical considerations and observations of residual stress suggest that geometric remodeling in the heart may also alter residual stress and strain. We investigated whether changes in left ventricular geometry during physiologic growth were associated with corresponding changes in myocardial residual strain. In anesthetized rats from eight age groups ranging from 2-25+ weeks, the heart was arrested and isolated, and equatorial slices were obtained. The geometry of the intact, unloaded state was recorded, as well as the 'opening angle' of the stress-free configuration after radial resection of the tissue slice. The tissue was fixed and embedded for histological examination of collagen area fraction. Heart weight increased 10-fold with age and unloaded internal radius increased almost 4-fold. However, wall thickness increased only 66 percent, so that the ratio of wall thickness to internal radius decreased significantly from 2.22 [+ or -] 0.29 (mean [+ or -] SD) at 2 weeks to 0.81 [+ or -] 0.47 at 25 weeks. Opening angle of the stress-free slice decreased significantly from 87 [+ or -] 16 deg at 2 weeks to 51 [+ or -] 16 deg, and correlated linearly with wall thickness/radius ratio. Collagen area fraction increased with age. Hence physiologic ventricular remodeling in rats decreases myocardial residual strain in proportion to the relative reduction in wall thickness-radius ratio.

Structural remodeling during acute myocardial infarction affects ventricular wall stress and strain. To see whether acute myocardial infarction alters residual stress and strain in the left ventricle (LV), we measured opening angles in rat hearts after 30 minutes of left coronary artery occlusion. The mean opening angle in 18 ischemic hearts (51 [+ or -] 20 deg) was significantly greater than in five sham-operated controls (29 [+ or -] 11 deg, P < 0.05). To determine whether these alterations in residual strain may be associated with strain softening caused by systolic overstretch of the noncontracting ischemic tissue, we also measured opening angles in isolated hearts that had been passively inflated to high LV pressures (120 mmHg). The mean opening angle of the strain-softened hearts was not significantly different from the sham-operated hearts (34 [+ or -] 27 deg, P = 0.74). Mean collagen area fractions in the myocardium were not significantly different between ischemic hearts (0.027 [+ or -] 0.014) and the nonischemic group (0.022 [+ or -] 0.011). Although there were significant differences in opening angles measured with ischemia, they do not appear to be a result of altered extracellular collagen content or softening associated with overstretch. Thus, there is a significant change in residual strain associated with acute ischemia that may be related to changes in collagen fiber structure, myocyte structure, or metabolic state.

In comparison with conventional heat treatment, high-temperature rapid thermal annealing (RTA) in a radio frequency (RF) induction-heated system can reduce or eliminate residual stresses in thin films in a few seconds. In this work, changes in the stress level due to the RTA of polycrystalline silicon thin films were studied as a function of annealing time and temperature. The corresponding variations in the microstructure and surface layer of the thin films were experimentally investigated by a variety of analytical tools. The results suggest that the residual stress evolution during annealing is dominated by two mechanisms: 1) microstructure variations of the polysilicon thin film and 2) effects of a surface layer formed during the heat treatment. The fact that the microstructure changes are more pronounced in samples after conventional heat treatment implies that the effects of the formed surface layer may dominate the final state of the residual stress in the thin film. [337] Index Terms - Polysilicon thin films, rapid thermal annealing, residual stress.

A sticking (stiction) model for a cantilevered beam is derived. This model includes the effect of the bending moment, which stems from stress gradient along the vertical direction of structural polysilicon, and the temperature during the release process. The bending moment due to the stress gradient will play an important role to evaluate antisticking efficiency since liquid tension and surface energy of microstructures tend to become smaller by newly developed antisticking techniques. The effects of stress gradient and temperature were analyzed and verified with surface-micromachined polysilicon cantilevers. By modifying the substrate polysilicon with grain-hole formation technique, the effects of residual stress gradient in polysilicon on stiction could be observed in the condition of low work of adhesion. Index Terms - Grain hole, polysilicon, sticking, stress gradient, surface micromachining.

A plane-strain load-deflection model for long plates clamped to a rigid support is developed. The analytical model describes the nonlinear deflection of plates with compressive or tensile residual stress and finite flexural rigidity under uniform load. It allows for the extraction of the residual stress and plane-strain modulus of single-layered thin films. Properties of compressively and weakly prestressed materials are extracted with an accuracy achieved previously only with tensile samples. Two approximations of the exact model are derived. The first reduces the plates to membranes by neglecting their flexural rigidity. Considerable errors result from this simplification. The second approximation provides an exact expression for the linear plate response. Using the model, mechanical properties were extracted from two plasma-enhanced chemical-vapor deposition (PECVD) silicon nitride films with weakly tensile and compressive prestress, respectively. Measured residual stresses are 1.3 [+ or -] 3.8 and -63 [+ or -] 12.4 MPa, respectively. Corresponding plane-strain moduli are 134.4 [+ or -] 3.9 and 142 [+ or -] 2.6 GPa, respectively. Index Terms - Load-deflection method, mechanical properties, PECVD silicon nitride, plate theory, rectangular membranes, residual stress, thin films, Young's modulus.

This article is designed to be a step in creation of the 'contact and crack calculus.' This term is introduced to denote a mathematical description of the infinitesimal variations in the elastic fields due to infinitesimal variation of domain of contact or crack, respectively. Rice has created foundations of this apparatus for cracks. Here, similar results were obtained for normal contact problems. It is also shown that the relationships between the stress intensity factors and displacements in tangential crack problems can be made a working apparatus in both directions.

The true temperature field and the transient residual stress field were studied by using the orthogonal-expansion technique. Analyses of the thermal barrier coating (TBC)/bond coat/superalloy system indicated that the elasticity solution and results from finite element stress studies correlated well in predicting thermal residual stresses in various layers and interfaces. The highest stresses were found to occur at the bond coat/TBC interface. At this interface, results showed a biaxial stress field due to high axial and tangential stress.