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This paper examines the effect of tire footprint and contact stress distribution under various combinations of tire pressures and tire loads on the pavement response through 3-D finite element static analysis with linear elastic material model. Analyzed footprints include a field-measured footprint and two cases of simplified ones. Our results indicate that factors including tire load, the distribution of contact stress, and the shape of footprint will affect the tensile strains at the bottom of the asphalt concrete layer as well as the compressive strains on the top of the subgrade. However, the compressive strains on the top of the subgrade are more sensitive to tire load than the shape of footprint. The research demonstrated that pavement response analysis could be carried out using field-measured footprints instead of the simplified approximations. Reduced tire pressure was effective in reducing the tensile strains at the bottom of asphalt concrete layer, but did not decrease significantly the compressive strains at the top of the subgrade. Key words: tire-pavement contact stress, tire footprint, tire pressure, pavement response, asphalt concrete pavement, strain, finite element analysis. Le present article etudie l'effet de l'empreinte des pneus et de la distribution de la contrainte de contact selon diverses combinaisons de pressions et de charges de pneus sur la reponse de la chaussee au moyen d'une analyse statique tridimensionnelle par elements finis selon une modelisation elastique lineaire du materiau. Les empreintes analysees comprennent une empreinte mesuree sur le terrain et deux cas d'empreintes simplifiees. Nos resultats indiquent que les facteurs telles la charge du pneu, la distribution de la contrainte de contact et la forme de l'empreinte auront un effet sur la contrainte de tension au bas de la couche de beton bitumineux et sur les contraintes de deformation sur le dessus de la couche de fondation. Toutefois, les contraintes de deformation sur le dessus de la couche de fondation sont plus sensibles a la charge du pneu qu'a la forme de l'empreinte. La recherche a demontre que l'analyse de la reponse de la chaussee pourrait etre realisee en utilisant des empreintes mesurees sur le terrain plutot que des approximations simplifiees. Une pression de pneu reduite a permis de reduire les contraintes de tension au bas de la couche de beton bitumineux, mais n'a pas reduit de maniere significative les contraintes de deformation sur le dessus de la couche de fondation. [Traduit par la Redaction] Mots-cles : contrainte de contact pneu-chaussee, empreinte de pneus, pression de pneu, reponse de la chaussee, chaussee en beton bitumineux, contrainte, analyse par elements finis., 1. Introduction The critical pavement damage mechanisms in flexible pavements are fatigue cracking in the asphalt concrete (AC) layer and rutting in the subgrade (Huang 1993). Fatigue cracking develops in [...]

A processing technology that facilitates quality injection molding without prior drying of polymer pellets has been proposed. The main idea is not to let the water evaporate to bubbles inside the mold. The polymer will be maintained hydrated as it was in the hopper of the injection molding machine throughout the entire molding processes by controlling the cavity pressure above the saturation pressure of water until solidified. In this work, the gas counter pressure (GGP) system has been designed and built to maintain the cavity pressure above the saturation pressure. The performance of the proposed method has been examined by checking the visual quality and the mechanical properties of the molded parts. The method has been tested with pellets of polymethyl methacrylate (PMMA), polycarbonate, polyethylene terephthalate, polybutylene terephthalate, and polyamide 66. The results show that the GCP prevents surface impairment incurred by the vapors without or with minor effects on the mechanical properties. Finally, the effects of energy saving has been examined by conducting the actual process for 1 day. POLYM. ENG. SCI., 52:2417-2423, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION A variety of polymer parts are manufactured by the injection molding process (1). These days, the injection molding industry is struggling with cost-down and quality improvement at the same [...]

This paper presents the results of a study on the behavior of three full-scale confined masonry walls subjected to combined axial loads and out-of-plane uniform pressures. The variable studied was the wall axial load. Analytical models were developed to predict out-of-plane cracking and maximum pressures. The former was predicted using the finite element method and the latter using the spring-strut method. This last method was modified to include the effect of the wall axial load. Experimental cracking and maximum pressures were compared with those obtained from analytical models. Based on the experimental results, it was concluded that as the axial load increases, the out-of-plane maximum pressure also increases. However, this latter value is limited by crushing of the masonry. By comparing experimental and analytical results, it was concluded that the out-of-plane cracking and maximum pressures are in general well predicted by the analytical models developed in this work. Key words: confined masonry, out-of-plane uniform pressure, axial load, spring-strut method, stiffness of confining elements. Cet article presente les resultats d'une etude sur le comportement de trois murs pleine grandeur en maconnerie confinee soumis a des charges axiales combinees et a des pressions uniformes hors plan. La variable a l'etude etait la charge axiale des murs. Des modeles analytiques ont ete developpes afin de predire la fissuration hors plan et les pressions maximales. La fissuration a ete predite par elements finis et les pressions ont ete predites en utilisant la methode des << amortisseurs >>. Cette methode a ete modifiee pour inclure l'effet de la charge axiale des murs. La fissuration et les pressions maximales des experiences ont ete comparees a celles obtenues a partir de modeles analytiques. Les conclusions basees sur les resultats experimentaux montraient que la pression maximale hors plan augmente avec l'augmentation de la charge axiale. Toutefois, cette augmentation est limitee par l'ecrasement de la maconnerie. En comparant les resultats experimentaux et analytiques, il a ete conclu que la fissuration hors plan et les pressions maximales sont, regle generale, bien predites par les modeles analytiques developpes dans le present travail. Mots-cles : maconnerie confinee, pression uniforme hors plan, charge axiale, methode des << amortisseurs >>, rigidite des elements de confinement. [Traduit par la Redaction], Introduction The behavior of confined masonry walls under out-of-plane uniform pressure has not been widely studied. Most of the effort to study out-of-plane behavior has focused on unreinforced walls (Drysdale [...]

Several studies have been carried out on the evaluation of wind-induced pressures on building envelopes. However, there is very limited research on wind-induced forces on the main structural elements of a building including its foundation. Thus, a full-scale monitoring research project was initiated to examine the wind-induced structural forces for a lowrise wood building. The field facilities include two weather stations and a test house equipped with load and pressure sensors. The house is resting on top of twenty-seven 3-axis load cells and is structurally isolated, i.e., the only points of contact between the foundation wall and the superstructure are the load cells. Simultaneously to the load monitoring, 40 pressure taps are recording the envelope pressures both on the roof and the wall surfaces. In addition to the field monitoring, a scaled model of the house was tested in a boundary layer wind tunnel using three different upstream terrain configurations that provided varying levels of turbulence characteristics suitable for comparisons with full-scale values. The analysis of the wind speed and direction field data confirmed the non-uniform variation of the basic terrain properties over the wind direction and this was also verified in the comparison of the field with the wind tunnel results. These comparisons were made in the form of both envelope pressures and total uplift forces at the foundation level and provided useful insight regarding the wind load path inside the structural elements of the building. Experimental findings were also compared to the Canadian Code and American Standard wind provisions and indicated an underestimation of the total uplift force when using the code and standard provisions in some cases. Key words: full-scale monitoring, wind tunnel experiments, low-rise wood building, envelope pressures, wind uplift forces, design implications. De nombreuses etudes sur l'evaluation des charges dues au vent sur les enveloppes de batiments ont ete realisees. Toutefois, tres peu de recherche a ete realisee sur les charges dues au vent sur les elements structuraux principaux d'un batiment, incluant sa fondation. Un projet de recherche a pleine echelle a donc ete entrepris pour examiner les charges structurales dues au vent sur un batiment en bois de faible hauteur. Les installations sur le terrain comprennent deux stations meteorologiques et un batiment d'essai muni de capteurs de charge et de pression. Le batiment d'essai est installe sur 27 cellules de charge triaxiales et est structurellement isole, c.-a-d. que les seuls points de contact entre le mur de fondation et la superstructure sont les cellules de charge. Quarante prises de pression enregistraient en meme temps les pressions sur l'enveloppe, soit sur le toit et sur les murs. En plus du suivi sur le terrain, un modele a l'echelle du batiment a ete mis a l'epreuve dans une soufflerie a couche limite en utilisant trois differentes configurations de terrain amont qui fournissaient divers niveaux de turbulence pouvant etre compares aux valeurs a pleine echelle. L' analyse de la vitesse et de la direction du vent sur le terrain a confirme la variation non uniforme des proprietes de terrain de base par rapport a la direction du vent; cela se verifie egalement lors de la comparaison des resultats sur le terrain et en soufflerie. Ces comparaisons ont ete realisees sous forme de pressions sur l'enveloppe et les forces totales de soulevement au niveau de la fondation et elles ont fourni un apercu utile du chemin de la charge due au vent a l' interieur des elements de structure du batiment. Les conclusions de l' experience ont aussi ete comparees aux dispositions concernant le vent dans le Code canadien et de la norme americaine et elles montrent une sous-estimation de la force totale de soulevement dans certains cas utilisant les dispositions concernant le vent dans le Code canadien et de la norme americaine. Mots-cles : suivi a pleine echelle, experiences en soufflerie, batiment en bois de faible hauteur, pressions sur les enveloppes, forces de soulevement dues au vent, consequences de la conception. [Traduit par la Redaction], 1. Introduction The majority of dwellings in North America are lightweight, low-rise structures of rather simple geometry and layout. Wind-induced loading is of major importance during the design of these [...]

The partial admission technique is widely used to control the output power of turbines. In some cases, it has more merits than full admission. However, additional losses, such as expansion, mixing, or pumping, are generated in partial admission as compared with full admission. Thus, an experiment was conducted in a linear cascade apparatus having a partial admission region in order to investigate the effect of partial admission on a blade row. The admission region was formed by a spouting nozzle installed at the inlet of the linear cascade apparatus. Its cross section was rectangular and its size is 200 x 200 [mm.sup.2]. The tested blade was axial-type and its chord was 200 mm. Nineteen identical blades were applied to the linear cascade for the partial admission experiment. The blades moved along the rotational direction in front of the admission region, and then operating forces and surface pressures on the blades were measured at the steady state. The experiment was conducted at a Reynolds number of 3 x [10.sup.5] based on the chord. The nozzle flow angle was set to 65 deg with a solidity of 1.38 for performance test at the design point. In addition, another two different solidities of 1.25 and 1.67 were applied. From the experimental results, when the solidity was decreased, the maximum rotational force increased but the maximum axial force decreased. [DOI: 10.1115/1.4002468] Keywords: partial admission, turbine operating forces, surface pressure, linear cascade, axial-type blade

Sperm velocity is long known to be an important indicator of sperm quality but without much biophysical theory explaining it. Contact mechanics based modeling was developed here to determine the effects that sperm velocity ([v.sub.s]) and sperm head density ([[rho].sub.s])--which is an indicator of the stiffness of the head, have on the peak sperm-zona pellucida contact pressure ([p.sub.m]) during the early phase of sperm penetration. The modeling identified [v.sub.s] as being more influential on [p.sub.m] compared with the influence that [[rho].sub.s] has, which means that for spermatozoa competing on the same oocyte, greater [v.sub.s] is a more important advantage than higher [[rho].sub.s]. Specifically, [p.sub.m] was more sensitive by a power of 2 to changes in [v.sub.s] than to changes in [[rho].sub.s]. It was further demonstrated that each 0.1 g/cc increase in [[rho].sub.s] (within the physiologically relevant range of 1.3-1.7 g/cc) would be equivalent to just 3% rise in [v.sub.s], indicating again that faster swimming is a better strategy for spermatozoa compared with head stiffening. The modeling hence provided some useful insights regarding sperm biomechanics, which theoretically elucidate the well-recognized importance of sperm velocity measurements as being indicative of sperm quality. [DOI: 10.1115/1.4002857] Keywords: biomechanical cell model, cellular biomechanics, fertilization, motility, sperm quality

Previous biomechanical models of the penis simulated penile erections utilizing 2D geometry, simplified 3D geometry or made inaccurate assumptions altogether. These models designed the shaft of the penis as a one-compartment pressurized vessel fixed at one end when in reality it is a two-compartment pressurized vessel in which the compartments diverge as they enter the body and are fixed at two separate anatomic sites. This study utilizes the more anatomically correct two-compartment penile model to investigate erectile function. Simplified 2D and 3D models of the erect penis were developed using the finite element method with varying anatomical considerations for analyzing structural stresses, axial buckling, and lateral deformation. This study then validated the results by building and testing corresponding physical models. Finally, a more complex and anatomically accurate model of the penis was designed and analyzed. When subject to a lateral force of 0.5 N, the peak equivalent von Mises (EVM) stress in the twocompartment model increased by about 31.62%, while in the one-compartment model, the peak EVM stress increased by as high as 70.11%. The peak EVM stress was 149 kPa in the more complex and anatomically accurate penile model. When the perforated septum was removed, the peak EVM stress increased to 455 kPa. This study verified that there is significant difference between modeling the penis as a two- versus a one-compartment pressurized vessel. When subjected to external forces, a significant advantage was exhibited by two corporal based cavernosal bodies separated by a perforated septum as opposed to one corporal body. This is due to better structural integrity of the tunica albuginea when subjected to external forces. [DOI: 10.1115/1.4002794]

Traditionally, resultant force of lateral earth pressure serves as the basis for design of nearly vertical walls. Conversely, slopes are designed to be internally stable using a factor of safety approach. However, with the availability of heavy facing elements such as gabions, steep slopes are increasingly being constructed. Steep slopes are considered to be unstable unless supported; that is, such slopes require facings to resist lateral earth pressure. Extending Coulomb's formulation to such slopes may not be conservative as a planar slip surface may not be critical. Presented are the results of a formulation to find the resultant lateral force which utilizes a log spiral failure mechanism. Unlike Caquot and Kerisel or Coulomb, the soil-facing interface friction is assumed to act on segments of vertical surface only, thus replicating the geometry of stacked rectangular facing units. Given the batter, the backslope, the height, the interface friction, and the unit weight and design friction angle of the backfill, one can quickly determine the corresponding lateral earth pressure coefficient. Formulation assuming the interface friction is acting on an imaginary surface inclined at the batter angle, essentially equivalent to Coulomb and Caquot and Kerisel, is also presented. Its results show that for batters up to 20[degrees], the common approach of using the Coulomb method, including the assumed interface friction direction to coincide with the batter, yields results that are quite close to those stemming from the log spiral analysis. Hence, use of Coulomb's analysis for such small batters is reasonable as its formulation is simple. However, the lateral resultant is grossly underestimated for larger batters, especially when Coulomb analysis is used. DOI: 10.1061/(ASCE)GT.1943-5606.0000398 CE Database subject headings: Earth pressure; Limit equilibrium; Slope stability. Author keywords: Coulomb; Caquot and Kerisel; Lateral earth pressure; Limit equilibrium; Slope instability.

A multi-elbow piping system is adopted for the Japan sodium-cooled fast reactor (JSFR) cold-legs. Flow-induced vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7- and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study. [DOI: 10.1115/1.4002813] Keywords: fast reactor, cold-leg piping, elbow flow, flow-induced vibration, flow separation, pressure fluctuation

In this paper, the results of numerical simulation on the performance of a sudden expansion with fence viewed as a diffuser are presented. The two-dimensional steady differential equations for conservation of mass and momentum have been solved using the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The Reynolds number is in the range of 20-100 and fence subtended angle (FSA) between 10 deg and 30 deg. An aspect ratio of 2 is fixed for all the computations. The effect of each variable on average static pressure and diffuser effectiveness has been studied. Computations have revealed that for higher Reynolds number, the use of a fence always increases the effectiveness of the diffusion process when compared with a simple sudden expansion configuration. In low Reynolds number regime, depending on the positioning of the fence and the fence subtended angle, the fence may increase or decrease the diffuser effectiveness in comparison with sudden expansion without fence. [DOI: 10.1115/1.4000800] Keywords: sudden expansion with fence, Reynolds number, FSA, static pressure, diffuser effectiveness

Thermoacoustic transfer functions of a full-scale gas turbine burner operating under full engine pressure have been measured. The excitation of the high-pressure test facility was done using a siren that modulated a part of the combustion airflow. Pulsation probes have been used to record the acoustic response of the system to this excitation. In addition, the flame's luminescence response was measured by multiple photomultiplier probes and a light spectrometer. Three techniques to obtain the thermoacoustic transfer function are proposed and employed: two acoustic-optical techniques and a purely acoustic technique. The first acoustical-optical technique uses one single optical signal capturing the chemiluminescence intensity of the flame as a measure for the heat release in the flame. This technique only works if heat release fluctuations in the flame have only one generic source, e.g., equivalence ratio or mass flow fluctuations. The second acoustic-optical technique makes use of the different response of the flame's luminescence at different optical wavelengths bands to acoustic excitation. It also works, if the heat release fluctuations have two contributions, e.g., equivalence ratio and mass flow fluctuation. For the purely acoustic technique, a new method was developed in order to obtain the flame transfer function, burner transfer function, and flame source term from only three pressure transducer signals. The purely acoustic method could be validated by the results obtained from the acoustic-optical techniques. The acoustic and acoustic-optical methods have been compared and a discussion on the benefits and limitations of each is given. The measured transfer functions have been implemented into a nonlinear, three-dimensional, time domain network model of a gas turbine with an annular combustion chamber The predicted pulsation behavior shows a good agreement with pulsation measurements on a field gas turbine. [DOI: 10.1115/1.4000854]

Three-dimensional finite element analyses were performed to study the behavior of piles in sloping ground under undrained lateral loading conditions. Piles of different diameter and length in sloping cohesive soils of different undrained shear strength and several ground slopes were considered. Based on the results of the finite element analyses, analytical formulations are derived for the ultimate load per unit length and the initial stiffness of hyperbolic p-y curves. New p-y criteria for static loading of piles in clay are proposed, which take into account the inclination of the slope and the adhesion of the pile-slope interface. These curves are used through a commercial subgrade reaction computer code to parametrically analyze the effect of slope inclination and pile adhesion on lateral displacements and bending moments. To validate the proposed p-y curves, a number of well documented lateral load tests are analyzed. Remarkable agreement is obtained between predicted and measured responses for a wide range of soil undrained shear strength and pile diameter, length, and stiffness. DOI: 10.1061/(ASCE)GT.1943-5606.0000373 CE Database subject headings: Piles; Lateral loads; Clays; Finite element method; Numerical analysis; Lateral pressure; Soil-pile interactions; Slopes. Author keywords: Piles; Lateral loads; Clays; Finite-element method; Numerical analysis; Lateral pressure; Soil-pile interactions; Slopes; p-y curves; Adhesion.

Observations of the cross-shore variations of pressure gradients measured on a fixed barred beach in a large-scale laboratory wave flume are presented in this paper. The wave-induced components (0.1-1.0 Hz) of the free surface elevation, near- bottom vertical and cross-shore velocities, and pressure gradient are used in the analysis. The cross-shore variation of the pressure gradient showed the maximum value in the area of wave breaking over the bar, and the pressure gradients were considered to be influenced by the fluctuation of the water surface elevation, which are shown to be a rough proxy for the water surface slope. The cross correlation related to the vertical velocity showed no correlation in the wave breaking area. Surprisingly, although several measuring points were located in the wave breaking area or in the inner surf zone, the spatial variation of the pressure gradient and water surface elevation had a correlation coefficient greater than 0.8 with time lags approximately 0.1 of the wave period from offshore to onshore in both regular and irregular wave cases. This indicates that the near-bottom pressure gradient can be estimated using the water surface elevation over a complex barred bathymetry and through the inner surf zone. DOI: 10.1061/(ASCE)WW.1943-5460.0000055 CE Database subject headings: Pressure; Breaking waves; Laboratory tests; Barrier beaches; Surf zone. Author keywords: Pressure; Breaking waves; Laboratory tests; Barrier beaches.

The clarification of creep damage mechanism and the establishment of remaining life prediction methods of longitudinal welded piping of P91 steel are important subjects to maintain a reliable operation of boilers in thermal power plants. Internal pressure creep tests were conducted on P91 steel longitudinal welded tubes to characterize the evolution of creep damage with time and to evaluate a life prediction method. Interrupted creep tests were performed for damage observation in addition to rupture tests. Three dimensional finite element creep analyses of the longitudinal welded tube specimens were conducted to identify the stress and creep strain distributions within the specimen during creep. Failure occurred at a heat affected zone (HAZ) without a significant macroscopic deformation. It was found that the initiation of creep voids had concentrated at the midthickness region in the HAZ rather than in the surface. The creep analysis results indicated that the triaxial tensile stress yielded at the midthickness region in the HAZ due to difference of creep deformation property among the base metal, the HAZ, and the weld metal. It was suggested that the triaxial stress state caused acceleration of the creep damage evolution in the HAZ, resulting in internal failure of the tube specimens. A rupture time prediction method of the welded tube is proposed based on the maximum principal stress and the triaxial stress factor in the HAZ. The void growth behavior in the HAZ was well predicted by the previously proposed void growth simulation method by introducing a void initiation function to the method. [DOI: 10.1115/1.4001688] Keywords: internal pressure creep, P91 steel, longitudinal welded tube, life prediction, void growth simulation

Simple and accurate approaches to predict failure pressures in corroded pipelines are outlined in this work. It is shown that failure pressures for corroded pipelines can be predicted from the solution for undamaged pipelines using an equivalent wall thickness. Three different yield criteria (Tresca, ASSY (average shear stress yield), and von Mises) are reviewed in the light of reported experimental burst pressures. At first, failure pressures for cylindrical vessels with an infinitely long groove are studied by means of numerical simulations. The effect of groove size (depth and width) over the pipeline performance is quantified through a model. Finally, the scheme is extended to estimate the failure pressure of thin walled vessels with irregular finite defects. [DOI: 10.1115/1.4001801] Keywords: failure pressure, infinitely long groove, burst test, damaged and undamaged pipelines

In this paper, the modified formulae have been provided. They can be used to calculate the stress in layers with gaps of a layered cylinder In order to obtain the modified formulae, a detailed derivation process has also been presented in this paper. Meanwhile, we have clarified the derivation process and application range of Pimshtein's formulae and corrected the errors. We have also indicated the shortcomings of the formulae given by Huang, Chen and Lai, and the ASME code. Finally, a practical example is presented to show how the modified formulae are applied. Calculation results obtained from the modified formulae have been compared with those obtained by finite element method and above mentioned formulae; it shows that the results from the modified formulae are in accordance with finite element results. [DOI: 10.1115/1.4001658] Keywords: layered vessel interlayer gaps, modified formulae, stress calculation

The effect of oxygen partial pressure on crack growth rates in Alloy 617 has been studied using both static and fatigue loadings at 650[degrees]C over the oxygen partial pressure range [10.sup.-19] - [10.sup.-3] atm. Tests were conducted at either the constant stress intensity factor K for static conditions or the constant [DELTA]K in fatigue. Oxygen concentration was measured on both the inlet and outlet of the test retort as well as in situ with a probe located directly at the specimen surface. For fatigue loading the crack path was observed to be transgranular but crystallographic with a decreasing growth rate as the oxygen concentration decreased. However, for static loading the crack path shifted to intergranular at the same [K.sub.max] (fatigue) and exhibited what appears to be an increasing crack growth rate with decreasing oxygen concentration. [DOI: 10.1115/1.3155793]

The postcyclic reconsolidation response of low-plastic Fraser River silt was examined using laboratory direct simple shear testing. Specimens of undisturbed and reconstituted natural low-plastic Fraser River silt and reconstituted quartz powder, initially subjected to constant-volume cyclic loading under different cyclic stress ratios (CSRs) and then reconsolidated to their initial effective stresses ([[sigma]'.sub.vo]), were specifically investigated. The volumetric strains during postcyclic reconsolidation ([[epsilon].sub.v.ps]) were noted to generally increase with the maximum cyclic excess pore-water pressure ([DELTA][u.sub.max]) and maximum cyclic shear strain experienced by the specimens during cyclic loading. The values of [[epsilon].sub.v-ps] and maximum cyclic excess pore-water pressure ratio ([r.sub.u-max]) were observed to form a coherent relationship regardless of overconsolidation effects, particle fabric, and initial (precyclic) void ratio of the soil. The specimens with high [r.sub.u-max] suffered significantly higher postcyclic reconsolidation strains; [[epsilon].sub.v-ps] ranging between 1.5 and 5% were noted when [r.sub.u-max] > 0.8. The observed [[epsilon].sub.v-ps] versus [r.sub.u-max] relationship, when used in combination with the observed dependence of cyclic excess pore-water pressure on CSR and number of load cycles, seems to provide a reasonable approach to estimate postcyclic reconsolidation strains of low-plastic silt. DOI: 10.1061/(ASCE)GT.1943-5606.0000349 CE Database subject headings: Shear tests; Soil liquefaction; Earthquakes; Silts; Cyclic loads; Soil consolidation; Pore water; Water pressure; Canada. Author keywords: Direct simple shear testing; Liquefaction; Earthquake response of silts; Cyclic loading; Postcyclic reconsolidation strains.

An experimental and analytical program was designed and conducted to evaluate the magnitude and distribution of seismically induced lateral earth pressures on cantilever retaining structures with dry medium dense sand backfill. Results from two sets of dynamic centrifuge experiments and two-dimensional nonlinear finite-element analyses show that maximum dynamic earth pressures monotonically increase with depth and can be reasonably approximated by a triangular distribution. Moreover, dynamic earth pressures and inertia forces do not act simultaneously on the cantilever retaining walls. As a result, designing cantilever retaining walls for maximum dynamic earth pressure increment and maximum wall inertia, as is the current practice, is overly conservative and does not reflect the true seismic response of the wall-backfill system. The relationship between the seismic earth pressure increment coefficient ([DELTA][K.sub.AE]) at the time of maximum overall wall moment and peak ground acceleration obtained from our experiments suggests that seismic earth pressures on cantilever retaining walls can be neglected at accelerations below 0.4 g. This finding is consistent with the observed good seismic performance of conventionally designed cantilever retaining structures. DOI: 10.1061/(ASCE)GT.1943-5606.0000351 CE Database subject headings: Retaining walls; Earth pressure; Seismic effects; Earthquakes; Centrifuge models; Numerical models; Simulation; Seismic design; Backfills. Author keywords: Retaining walls; Earth pressures; Earthquakes; Centrifuge models; Numerical models; Simulation; Seismic design; Backfills.

A simple semi-empirical model for predicting the peak overpressure field that results when a shock emerges from a circular shock tube is presented and validated. By assuming that the shape of the expanding shock remains geometrically similar after an initial development period, an equation that describes the peak overpressure field in the horizontal plane containing the shock tube's centerline was developed. The accuracy of this equation was evaluated experimentally by collecting peak overpressure field measurements along radials from the shock tube exit at 0 deg, 45 deg, and 90 deg over a range of shock Mach numbers from 1.15 to 1.45. It was found that the equation became more accurate at higher Mach numbers with percent differences between experimental measurements and theoretical predictions ranging from 1.1% to 3.6% over the range of Mach numbers considered. (1) Shocks do propagate in a geometrically similar manner after some initial development length over the range of Mach numbers considered here. (2) The model developed here gives reasonable predictions for the overpressure field from a shock emerging from a circular shock tube. (3) Shocks are expected to be completely symmetric with respect to the shock tube's centerline, and hence, a three dimensional overpressure field may be predicted by the model developed here. (4) While there is a range of polar angle at which the shock shape may be described as being spherical with respect to the shock tube's exit, this range does not encompass the entirety of the half space in front of the shock tube, and the model developed here is needed to accurately describe the entire peak overpressure field. [DOI: 10.1115/1.4002183] Keywords: shock tube, pressure field, semi-empirical

An improved method based on pseudostatic and limit-equilibrium analysis is proposed for evaluating seismic (static plus dynamic) active earth pressures induced by backfill behind movable rigid retaining walls. The proposed method can take into account the effects of strain localization and postpeak shear resistance reduction in the dense backfill soil during a strong earthquake, and the main improvement over the existing method is that a simple analytical solution is provided. DOI: 10.1061/(ASCE)GT.1943-5606.0000291 CE Database subject headings: Seismic effects; Earth pressure; Strain; Localization; Limit equilibrium. Author keywords: Seismic active earth pressure; Strain localization; Pseudostatic; Limit equilibrium; Postpeak reduction.

A universal design method for pressurized cylindrical shells with attached nozzles subjected to external forces (moments) and internal pressure are presented, based on theoretical stress analysis. The applicable ranges of the presented design methods are extended to [[rho].sub.o] = d/ D [less than or equal to] 0.9 and [lambda] =d/ [(DT).sup.1/2] [less than or equal to]12. As a first step of design, the required reinforcement thicknesses, both of the main shell and nozzle due to internal pressure, can be determined by the presented theoretical solutions. When the junction is subjected to external nozzle loads, the next step is to determine the absolute values of dimensionless longitudinal and circumferential, normal and shear, membrane and bending stresses in the shell at the junction subjected to internal pressure, and six external nozzle load components by reading out from a number of sets of curves calculated by the present theoretical method. Then the stress components at eight examination points are calculated and superimposed for the combined loads. Finally, the membrane and primary plus secondary stress intensities can be calculated, respectively, to meet the design criteria. [DOI: 10.1115/1.4001200]

An improved version of the analytical solutions by Xue, Hwang and co-workers (1991, 'Some Results on Analytical Solution of Cylindrical Shells With Large Opening,' ASME J. Pressure Vessel Technol., 113, 297-307; 1991, 'The Stress Analysis of Cylindrical Shells With Rigid Inclusions Having a Large Ratio of Radii,' SMiRT 11 Transactions F, F05/2, 85-90; 1995, 'The Thin Theoretical Solution for Cylindrical Shells With Large Openings,' Acta Mech. Sin., 27(4), pp. 482-488; 1995, 'Stresses at the Intersection of Two Cylindrical Shells,' Nucl. Eng. Des., 154, 231-238; 1996, 'A Reinforcement Design Method Based on Analysis of Large Openings in Cylindrical Pressure Vessels,' ASME J. Pressure Vessel Technol., 118, 502-506; 1999, 'Analytical Solution for Cylindrical Thin Shells With Normally Intersecting Nozzles Due to External Moments on the Ends of Shells,' Sci. China, Ser. A: Math., Phys., Astron., 42(3), 293-304; 2000, 'Stress Analysis of Cylindrical Shells With Nozzles Due to External Run Pipe Moments,' J. Strain Anal. Eng. Des., 35, 159-170; 2004, 'Analytical Solution of Two Intersecting Cylindrical Shells Subjected to Transverse Moment on Nozzle,' Int. J. Solids Struct., 41(24-25), 6949-6962; 2005, 'A Thin Shell Theoretical Solution for Two Intersecting Cylindrical Shells Due to External Branch Pipe Moments,' ASME J. Pressure Vessel Technol., 127(4), 357-368; 2005, 'Theoretical Stress Analysis of Two Intersecting Cylindrical Shells Subjected to External Loads Transmitted Through Branch Pipes,' Int. J. Solids Struct., 42, 3299-3319)for two normally intersecting cylindrical shells is presented, and the applicable ranges of the theoretical solutions are successfully extended from d/ D [less than or equal to] 0.8 and [lamda] = d/ [(DT).sup.1/2] [less than or equal to] 8 to d/D [less than or equal to] 0.9 and [lambda] [less than or equal to] 12. The thin shell theoretical solution is obtained by solving a complex boundary value problem for a pair of fourth-order complex-valued partial differential equations (exact Morley equations (Morley, 1959, 'An Improvement on Donnell's Approximation for Thin Walled Circular Cylinders,' Q. J. Mech. Appl. Math. 12, 89-91; Simmonds, 1966, 'A Set of Simple, Accurate Equations for Circular Cylindrical Elastic Shells,' Int. J. Solids Struct., 2, 525-541))for the shell and the nozzle. The accuracy of results is improved by some additional terms to the expressions for resultant forces and moments in terms of complex-valued displacement-stress function. The theoretical stress concentration factors due to internal pressure obtained by the improved expressions are in agreement with previously published test results. The theoretical results discussed and presented herein are in sufficient agreement with those obtained from three dimensional finite element analyses for all the seven load cases, i.e., internal pressure and six external branch pipe load components involving three orthogohal forces and the respective three orthogonal moments. [DOI: 10.1115/1.4001199]

Simultaneous measurements of the fluctuating wall pressure along the cylinder span were used to examine the spanwise characteristics of the vortex-shedding for yaw angles varying from [alpha]=60 deg to [alpha] = 90 deg. The Reynolds number based on the diameter of the cylinder was 56,100. The results indicate that yawing the cylinder to the mean flow direction causes the vortex-shedding in the wake to become more disorderly. This disorder is initiated at the upstream end of the cylinder and results in a rapid decrease in correlation length, from 3.3D for [alpha] = 90 deg to 1.1D for [alpha] = 60 deg. The commonly used independence principle was shown to predict the vortex-shedding frequency reasonably well along the entire cylinder span for [alpha] > 70 deg, but did not work as well for a = 60 deg. [DOI: 10.1115/1.4000732]

In an earlier paper (2009, 'Burst Pressure of Pressurized Cylinders With the Hillside Nozzle,' ASME J. Pressure Vessel Technol., 131(4), p. 041204), an elastic-plastic large deflection analysis method was used to determine the burst pressure and fracture location of hillside cylindrical shell intersections by use of nonlinear finite element analysis. To verify the accuracy of the finite element results, experimental burst tests were carried out by pressurizing test vessels with nozzles to burst. Based on the agreement between the numerical simulations and experimental results of Wang et al. (2009, 'Burst Pressure of Pressurized Cylinders With the Hillside Nozzle,' ASME J. Pressure Vessel Technol., 131(4), p. 041204), a parametric study is now carried out. Its purpose is to develop a correlation equation by investigating the relationship between various geometric parameters (d/ D, D / T, and t/ T) and the burst pressure. Forty-seven configurations, which are deemed to cover most of the practical cases, are chosen to perform this study. In addition, four different materials are employed to verify that the proposed equation can be employed for different materials. The results show that the proposed equation resulting from the parametric analysis can be employed to predict the static burst pressure of cylindrical shell intersections for a wide range of geometric ratios. [DOI: 10.1115/1.4000731]

In capillary flow, integral momentum approach is used to derive the governing equation, which requires an expression for the pressure field at the inlet of the capillary. Generally, the pressure field for circular capillary is deduced with hemispherical control volume. This expression has been extended for other noncircular capillaries with an equivalent radius approximation. In case of high aspect ratio channels, the semicylindrical control volume needs to be considered. In the present study, the correct expression for the entrance pressure field for high aspect ratio capillaries is derived with such appropriate control volume. [DOI: 10.1115/1.4001641]

A total of seven versions of two-equation turbulence models (four versions of low Reynolds number k-ζ model, one k-ω model and two versions of k-ζ / k-ω blended models) are tested against the direct numerical simulation (DNS) data of a one-dimensional oscillatory boundary layer with flat crested free-stream velocity that results from a steep pressure gradient. A detailed comparison has been made for cross-stream velocity, turbulent kinetic energy (TKE), Reynolds stress, and ratio of Reynolds stress and turbulent kinetic energy. It is observed that the newer versions of k-ζ model perform very well in predicting the velocity, turbulent kinetic energy, and Reynolds stress. The k-ω model and blended models underestimate the peak value of turbulent kinetic energy that may be explained by the Reynolds stress to TKE ratio in the logarithmic zone. The maximum bottom shear stress is well predicted by the k-ζ model proposed by Sana et al. and the original k-ω model. Key words: turbulence model, oscillation, boundary layer, k-ζ model, k-ω model, shear stress. Un total de sept versions de modeles de turbulence a deux equations (quatre versions du modele k-ζ a faible nombre de Reynolds, un modele k-ω et deux versions de modeles mixtes k-ζ/k-ω) ont ete mis a I'epreuve avec des donnees DNS d'une couche limite oscillatoire unidimensionnelle avec une vitesse d'ecoulement libre a crete rectiligne. engendrant un gradient de pression abrupt. Une comparaison detaillee a ete faite de la vitesse transversale, de 1'energie cinetique turbulente, de la tension de Reynolds et du rapport tension de Reynolds et energie cinetique turbulente. II a ete remarque que les plus recentes versions du modele k-ζ predisent tres bien la vitesse, 1'energie turbulente cinetique et la tension de Reynolds. Le modele k-ω et les modeles mixtes sous-estiment la valeur de crete de 1'energie turbulente cinetique. ce qui peut etre explique par le rapport tension de Reynolds et energie cinetique turbulente dans la zone logarithmique. Le modele k-ζ propose par Sana et al. el le modele k-ω original predisent bien la contrainte de cisaillement maximale au fond. Mots-des : modele de turbulence, oscillation, couche limite, modele k-ζ, modele k-ω, contrainte de cisaillement., Introduction An accurate prediction of sediment transport in coastal environments depends on a reasonable estimation of bottom shear stress in addition to other factors. With a rapid development in the [...]

Within the frame of industrial automation, the mechanical power related to pneumatic actuator systems involves air flows along with mechanical component, such as valves, connecting tubes, cylinder chambers and possible linkages in order to finally actuate a specific objective. Gas dynamic of the air flowing into connecting ducts plays a fundamental role in the description of the global dynamic phenomena of these systems. Several studies deal with the dynamics of such pneumatic systems but through streamlined analysis where the influence of pressure-waves propagating in ducts is neglected or poorly described. The related models are even more complex when finite volumes are placed at the ends of connecting lines. In this paper, two different mathematical models describing transient pressure-waves propagating through lines closed by finite volumes are presented. The investigation regards pressure and velocity ranges normally operating in industrial pneumatic systems. Besides the value of new system modeling of different complexity, these models are compared from an analytical and numerical point of view; advantages, disadvantages, weakness, abilities, and inabilities are highlighted and, finally, the relevant analysis is corroborated through experimental validations of wave propagating pressure at fixed positions of ducts. This study results both in the presentation of models of practical interest, as well as in an attempt to provide an elucidation on the need to resort to an accurate model rather than a streamlined one with respect to the geometric and/or operative characteristics of industrial pneumatic systems. [DOI: 10.1115/1.4000652] Keywords: industrial automation, ducts, wave propagation, pneumatic transmission line, fluid mechanics

Clear-water scour due to a short vertical (pressure flow) contraction was investigated in a laboratory channel. Two approach velocities were studied for a (nominally) single configuration of depth and degree of contraction, with experiments conducted lot various durations up to a maximum of 48 h, and the evolution of the scour hole over time monitored. The location of maximum scour in both cases was observed to occur downstream of the contraction, with maximum scour depths substantially in excess of values predicted by published models, even though equilibrium scour conditions were not reached. DOI: 10.1061/(ASCE)0733-9429(2010)136:2(137) CE Database subject headings: Contraction; Scour; Channels; Laboratory tests.

Strouhal number, pressure drag, and separation pressure are some of the intrinsic parameters for investigating the flow around a bluff-body. An attempt is made to formulate a relationship involving these quantities forflow around a two-dimensional bluff section of various shapes in a confined environment such as a wind tunnel. It includes (a) establishing a relation between the Strouhal number and a modified Strouhal number by a theoretical wake width and (b) incorporating this wake width into a momentum equation to determine the pressure drag. Comparisons have been made with the experimental data, a theoretical prediction (for unconfined flow), and an empirical proposal in literature to indicate that the present methodology is appropriate. Together with its extension to axisymmetric bodies, the current method is able to provide proper limits to the experimental data for a rectangular flat-plate of various width-to-span ratios. In addition, if the separation pressure is given, then the Strouhal number is inversely proportional to the drag coefficient, being comparable to a proposal based on statistical results. Finally, through an example, it is also demonstrated how one of these three parameters may be reasonably estimated from the measured values of the other two. [DOI: 10.1115/1.4000575]

In this paper, an adaptive controller is developed for the pressure tracking of the pressurized toolhead in order to maintain the constant contact stress for the polishing process. This is a new polishing control method, which combines the adaptive control theory and the constant stress theory of the contact model. By using an active pneumatic compliant toolhead, a recursive least-squares estimator is developed to estimate the pneumatic model and then a minimum-degree pole-placement method is applied to design a self-tuning controller. The simulation and experiment results of the proposed controller are presented and discussed. The main advantage of the constant contact stress control is high figuring accuracy. [DOI: 10.1115/1.4000959]

A procedure is presented for analyzing postconstruction deformation of seepage barriers due to changes in the pore pressure regime after seepage barrier construction. The procedure uses the changes in pore pressures calculated by finite-element seepage analyses to calculate changes in buoyancy and seepage forces that occur as a result of seepage barrier construction. When the buoyancy and seepage forces are applied to a finite-element soil-structure interaction model, the result is an effective-stress analysis that rigorously models seepage effects. This paper discusses application of the procedure to five dams to calculate postconstruction deformation and stresses in seepage barriers. The results of the analyses indicate that deformation due to pore pressure regime changes is a likely mechanism causing cracking in rigid seepage barriers. DOI: 10.1061/(ASCE)GT.1943-5606.0000241 CE Database subject headings: Seepage; Barriers; Deformation; Dams; Finite element method; Cracking; Pore pressure. Author keywords: Seepage barrier; Cutoff; Seepage; Deformation; Dam; Finite element.

The next generation nuclear power/advanced gas reactor (NGNP/AGR) fuel development and qualification program included the design, installation, and testing of a 6-in. diameter nuclear fuel particle coater to demonstrate quality tri-structural isotropic (TRISO) fuel production on a small industrial scale. Scale-up from the laboratory-scale coater faced challenges associated with an increase in the kernel charge mass, kernel diameter, and a redesign of the gas distributor to achieve adequate fluidization throughout the deposition of the four TRISO coating layers. TRISO coatings are applied at very high temperatures in atmospheres of dense particulate clouds, corrosive gases, and hydrogen concentrations over 45% by volume. The severe environment, stringent product and process requirements, and the fragility of partially-formed coatings limit the insertion of probes or instruments into the coater vessel during operation. Pressure instrumentation were installed on the gas inlet line and exhaust line of the 6-in. coater to monitor the bed differential pressure and internal pressure fluctuations emanating from the fuel bed as a result of bed and gas 'bubble' movements. These instruments are external to the particle bed and provide a glimpse into the dynamics of fuel particle bed during the coating process and data that could be used to help ascertain the adequacy of fluidization and, potentially, the dominant fluidization regimes. Pressure fluctuation and differential pressure data are not presently useful as process control instruments, but data suggest a link between the pressure signal structure and some measurable product attributes that could be exploited to get an early estimate of the attribute values. [DOI: 10.1115/1.3126772] Keywords: pressure fluctuations, Hurst exponent, spouted bed, particle properties

The stability of blood vessels under the lumen blood pressure is essential to the maintenance of normal arterial function. Buckling equations have been established recently for linear and nonlinear elastic artery models with assumed sinusoidal mode shapes. However, the theoretical base for the assumption is not clear. This study established differential equations of artery buckling and then proved that straight arteries bifurcated into sinusoidal mode shapes when buckling occurs. These results set the buckling equation on a solid theoretical foundation. [DOI: 10.1115/1.4000080] Keywords: artery, vein, bent buckling, stability, tortuosity, differential equation, mode shapes, critical pressure

It is well established that the main mechanism for the occurrence of liquefaction under seismic loading conditions is the generation of excess pore water pressure. Most previous research efforts have focused on clean sands, yet sand deposits with fines are more commonly found in nature. Previous laboratory liquefaction studies on the effect of fines on liquefaction susceptibility have not yet reached a consensus. This research presents an investigation on the effect of fines content on excess pore water pressure generation in sands and silty sands. Multiple series of strain-controlled cyclic direct simple shear tests were performed to directly measure the excess pore water pressure generation of sands and silty sands at different strain levels. The soil specimens were tested under three different categories: (1) at a constant relative density: (2) at a constant sand skeleton void ratio: and (3) at a constant overall void ratio. The findings from this study were used to develop insight into the behavior of silty sands under undrained cyclic loading conditions. In general. beneficial effects of the fines were observed in the form of a decrease in excess pore water pressure and an increase in the threshold strain. However, pore water pressure appears to increase when enough fines are present to create a sand skeleton void ratio greater than the maximum void ratio of the clean sand. DOI: 10.1061/(ASCE)GT.1943-5606.0000147 CE Database subject headings: Pore pressure: Soil liquefaction: Silts; Sand. soil type: Shear tests: Strain: Cyclic tests.

The hydrodynamic pressure field is important for the design and safety of steeply sloping stepped spillways, which are typically designed for considerably lower maximum specific discharges than smooth spillways. The hydraulic performance of stepped spillways at high velocities may compromise its use due to major concern with safety against cavitation damage. Hydraulic model investigations were conducted in different large-size stepped chutes to characterize the nonaerated flow region which is potentially prone to cavitation damage and the pressure field acting on the step faces. The clear water depths and energy dissipation in the developing flow region are described in terms of integral measures of the turbulent boundary layer. Expressions for the location of and the flow depth at the inception point of air entrainment are derived. Pressure distributions on the horizontal and vertical faces of the step along the spillway are presented. Measurements indicated a different behavior of the pressure field in the aerated and nonaerated flow region. The mean and fluctuating pressure coefficients along the spillway are approximated by a regression function. The vertical face near the outer step edge close to the inception point of air entrainment is identified as a critical region for predicting cavitation inception in flow over stepped spillways. From the analysis of the pressure fluctuations in that region a maximum velocity of 15 m/s is proposed as a criterion to avoid extreme negative pressures in typical prototype steeply sloping stepped spillways, eventually leading to the occurrence of cavitation in the nonaerated flow. DOI: 10.1061/(ASCE)HY. 1943-7900.0000118 CE Database subject headings: Spillway; Dams; Air entrainment; Cavitation; Hydrodynamic pressure.

The geometrical development of unlined plunge pools downstream large dams depends on both local geology and type of plunging jet and its diffusion pattern. Experimental investigations in plunge pools with different lateral confinements are presented. They show that the pool geometry influences plunging jet diffusion, air entrainment in the pool, and, as a consequence, impact pressures at the water-rock interface and inside the fissured rock mass. Results include impact pressures definition for variable pool depths, jet velocities, and pool geometries, depending explicitly on the lateral confinement of the jet. The main pool flow features are described focusing on their contribution to energy dissipation. Should the lateral confinement limit the development of macroturbulent rollers around the plunging jet (instead of the pool depth), the mean pressures at impact are considerably reduced, as well as RMS pressures in transitional and deep pools. For shallow pools, RMS pressures increase as a result of enhanced jet development. DOI: 10.1061/(ASCE)HY.1943-7900.0000090 CE Database subject headings: Hydraulic structures; Dynamic pressure; Rocks; Air-water interactions; Scour; Velocity; Hydraulic jets.

Fractional scaling analysis (FSA) is demonstrated at the system level. The selected example is depressurization of nuclear reactor primary systems undergoing large- and small-break loss of coolant accidents (LOCA), specifically in two integral test facilities of different sizes and shapes, namely, LOFT and Semiscale. The paper demonstrates (1) the relation between pressure and volume displacement rates in analogy to generalized 'effort' and 'flow' in interdisciplinary analysis of complex systems and (2) using experimental data that a properly scaled depressurization history applies to both large- and small-break LOCA in two different facilities. FSA, when applied at the system, component, and process levels, serves to synthesize the worldwide wealth of results from analyses and experiments into compact form for efficient storage, transfer, and retrieval of information. The demonstration at the system level shows that during LOCAs the break flow dominates for break sizes between 0.1% and 200% of cold-leg flow cross-sectional area, and that FSA ranks processes quantitatively and thereby objectively in the order of their importance. FSA supersedes the hereunto subjectively implemented phenomena identification and ranking table. FSA readily quantifies scale distortions. FSA reduces significantly the need for and current cost of experiments and analyses. [DOI: 10.1115/1.3155994] Keywords: fractional scaling, fractional rate of change, fractional change metric, hierarchy of complex system processes, scale distortion, information synthesis, holistic scaling approach

An efficient quasi-2D numerical waterhammer model for turbulent waterhammer flows has been previously developed for a single pipe system (reservoir-pipe-valve system). Basic boundary conditions, such as valves, reservoirs, and external flows, were also implemented. This paper extends this previously developed efficient scheme to a general model for a multipipe system. More specifically, an approach for matching the family of characteristic equations in each pipe at a junction of two or more pipes is proposed. In addition, the numerical stability conditions of the efficient scheme are investigated using the Von Neumann method. The resulting model is verified against experimental data and then applied to different complex systems involving pipes in series, branching, and network. Using this model, the effects of unsteady friction in complex pipe systems are examined and analyzed in this paper. From the case studies, it is found that the quasi-2D model is highly efficient, robust, and suitable for application to waterhammer problems in real complex pipe system. [DOI: 10.1115/1.3176978] Keywords: complex pipe system, quasi-2D model, waterhammer, efficiency

The complex three-dimensional unsteady flow developing in the draft tube of a Francis turbine is responsible for pressure fluctuations, which could prevent the whole hydropower plant from operating safely. Indeed, the Francis draft tube is subjected to inlet swirling flow, divergent cross section, and the change of flow direction. As a result, in low discharge off-design operating conditions, a cavitation helical vortex, so-called the vortex rope develops in the draft tube and induces pressure fluctuations in the range of 0.2-0.4 times the runner frequency. This paper presents the extensive unsteady wall pressure measurements performed in the elbow draft tube of a high specific speed Francis turbine scale model at low discharge and at usual plant value of the Thoma cavitation number. The investigation is undertaken for operating conditions corresponding to low discharge, i.e., 0.65-0.85 times the design discharge, which exhibits pressure fluctuations at surprisingly high frequency value, between 2 and 4 times the runner rotation frequency. The pressure fluctuation measurements performed with 104 pressure transducers distributed on the draft tube wall, make apparent in the whole draft tube a fundamental frequency value at 2.5 times the runner frequency. Moreover, the modulations between this frequency with the vortex rope precession frequency are pointed out. The phase shift analysis performed for 2.5 times the runner frequency enables the identification of a pressure wave propagation phenomenon and indicates the location of the corresponding pressure fluctuation excitation source in the elbow; hydroacoustic waves propagate from this source both upstream and downstream the draft tube. [DOI: 10. 1115/1.3155944]

The fracture behavior of pipes with penetrating cracks was experimentally investigated with the results of the load-deflection curves and crack length. J-R curves were obtained from the testing results for different temperatures. With the decrement in temperature, the critical J integral decreases and the tearing modulus increases. An updated continuum damage model was proposed, in which the fracture energy density as a function of the stress triaxiality, temperature and strain rate in the transition region was taken as the critical damage factor. The uni-axial tension experiments at different temperatures were carried out to obtain the basic material properties and the critical fracture energy density, to verify the validity of the damage model. Based on detailed finite element analyses with the proposed updated continuum damage model, the loading level of pipes with penetrating cracks was estimated and compared with the experimental results, meanwhile the fracture processes of the pipeline structure in the ductile-brittle-transition-temperature region were reproduced. It has been shown that the fracture process in the transition region strongly depends on both the stress and strain state, and can be effectively predicted using the continuum damage models incorporating with the stress state effect. [DOI: 10.1115/1.3110015] Keywords: continuum damage model, transition temperature region, fracture energy density, stress triaxiality

Assessment of multiple volumetric flaws is one of the most common problems relating to pressure vessels and piping components. Under the current fitness for service rules, such as ASME, BS, and so on, multiple volumetric flaws are usually recharacterized as an enveloping volumetric flaw (defined as a single larger volumetric flaw) as well as multiple cracklike flaws, following their assessment rules. However, the rules proposed in their codes will not often agree and their justification is unknown. Furthermore, they can provide unrealistic assessment in some cases. In this paper, the interaction between two differently sized nonaligned volumetric flaws such as local thin areas is clarified by applying the body force method. Unlike multiple cracklike flaws, the effect of biaxial stresses on the interaction is evident. Based on the interaction that indicates the magnification and shielding effects and reference stress solutions, a new procedure for multiple volumetric flaws is proposed for assessing the flaws in the p-M (pressure-moment) diagram, which is a simple assessment procedure for vessels with volumetric flaws. [DOI: 10.1115/1.3110036] Keywords: fitness for service (FFS) rule, plastic collapse, volumetric flaws, alignment rule, p-M (pressure-moment) diagram

During normal operating conditions, piping systems in nuclear power plants are subject to internal pressure and bending loads induced by deadweight, thermal expansion, and internal pressure. Thus, understanding the effect of bending load on the failure of wall-thinned elbows is important to understand failure behavior and to evaluate the failure pressure reliably. This study includes a series of burst tests using full-scale 4-in. schedule 80 elbow specimens with local wall-thinning under combined internal pressure and in-plane bending load. The results are compared with those tested under simple internal pressure only. In the tests, various circumferential thinning angles ([theta]/[pi]=0.125, 0.25, 0.5, 1.0) and thinning locations (intrados, extrados, and full-circumference) were considered. Each specimen was initially subjected to a displacement controlled in-plane bending load, closing mode for extrados wall-thinned elbows, and opening mode for intrados wall-thinned elbows, and then internal pressure was applied up to the point of final failure. The results showed that the effect of in-plane bending on the failure pressure and failure mode was minor under all wall-thinning conditions. In addition, the dependence of failure pressure on the circumferential thinning angle and thinning locations was identical to that observed under simple internal pressure. [DOI: 10.1115/1.3122032] Keywords: wall-thinned elbow, full-scale pipe test, failure pressure, in-plane bending load, flow-accelerated corrosion (FAC), nuclear power plants (NPPs)

Performance of a bolted flange joint is characterized mainly due to its 'strength' and 'sealing capability.' A number of analytical and experimental studies have been conducted to study these characteristics only under internal pressure loading. A very limited work is found in the literature under combined internal pressure and bending loading. Due to the ignorance of this external loading, i.e., bending and axial in addition to the internal pressure loading, the optimized performance of the bolted flange joint cannot be achieved. The present design codes do not address the effects of combined loading on the structural integrity and sealing ability. To investigate joint strength and sealing capability under combined loading, an extensive experimental study of a nongasketed flange joint with two different assemblies and with different load combinations is carried out, and overall joint performance and behavior is discussed. Actual joint load capacity is determined under both the design and proof test pressure with maximum additional external loading (axial and bending) that can be applied for safe joint performance. In addition, application of combined load is also discussed in the light of equivalent pressure approach. [DOI: 10.1115/1.3110039] Keywords: nongasketed, joint, combined, operating, axial bending, sealing, strength

Pressure driven liquid flow through rectangular cross-section microchannels is investigated experimentally. Polydimethylsiloxane microchannels are fabricated using soft lithography. Pressure drop data are used to characterize the friction factor over a range of aspect ratios from 0.13 to 0.76 and Reynolds number from I to 35 with distilled water as working fluid. Results are compared with the general model developed to predict the fully developed pressure drop in arbitrary cross-section microchannels. Using available theories, effects of different losses, such as developing region, minor flow contraction and expansion, and streaming potential on the measured pressure drop, are investigated. Experimental results compare well with the theory based on the presure drop in channels of arbitrary cross section. [DOI: 10.111511.3077143]

Increasing the pressure of abrasive waterjet, while fixing the jet power, increases the jet's power density and thus the cutting speed may increase. This was observed for steel aluminum, and stone cutting. It was also observed that the kerf taper is less for higher pressure jets. Increasing the pressure while keeping the jet diameter fixed will increase both the power and the power density. This will result in increased cutting speed and less taper. The operating cost of the abrasive waterjets process consists mainly of the costs of abrasives, nozzle wear, utility, and maintenance of equipment. The cost per unit length of material (specific cost) is determined based on the cutting speed. It was found that the main advantage of increasing pressure is increasing the cutting speed or reducing the abrasive consumption per unit time or unit length of cut. The highest savings are obtained when the speed is maximized by increasing the pressure and the abrasive flow rate. Several study cases were addressed in this paper using assumptions and simple models to generalize the analysis. The analysis indicates that increasing the pressure from 400 MPa to 600 MPa may result in cost per unit length saving of over 30%. [DOI: 10.1115/1.3008033]

This paper is based on work done to establish the validity of a simple engineering approach to assess plastic collapse for a vessel with a local thin area (LTA). The approach is based on a recently developed p-M (internal pressure ratio and external bending moment ratio) diagram, which is an easy way to visualize the status of a vessel with a LTA simultaneously subjected to internal pressure, p and external bending moment, M due to earthquake, etc. If the assessment point ([M.sub.r], [P.sub.r]) lies inside the p-M line, the vessel with the LTA is judged to be safe. Numerous experiments and finite element analyses for a cylinder with an external flaw were conducted under (1) pure internal pressure, (2) pure external bending moment, and (3) subjected simultaneously to both internal pressure and external bending moment, in order to determine the plastic initiation load and plastic collapse load by applying the twice-elastic slope (TES) as recommended by ASME. It has been clarified that the collapse (TES) loads are similar to those calculated under the proposed p-M line based on the measured yield stress. The p-M line adopted in the Ibaraki fitness for service (FFS) rule based on the specified minimum yield stress with a safety factor of 1.5 indicates that the safety margin for the plastic initiation loads at LTA is about 1.0-3.0, about 1.5-4.0 for the TES loads at LTA, and 2.5-5.5 for the plastic instability (break) loads. [DOI: 10.1115/1.3027472] Keywords: fitness for service (FFS), collapse limit, p-M diagram, local thin area, internal pressure, external bending moment, buckling stress, plastic initiation load, twice elastic slope (TES) load, plastic instability load

In the present study, a compact analytical model is developed to determine the pressure drop of fully-developed, incompressible, and constant properties slip-flow through arbitrary cross section microchannels. An averaged first-order Maxwell slip boundary condition is considered. Introducing a relative velocity, the difference between the bulk flow and the boundary velocities, the axial momentum reduces to Poisson's equation with homogeneous boundary condition. Square root of area is selected as the characteristic length scale. The model of Bahrami et al. (2006, 'Pressure Drop of Laminar, Fully Developed Flow in Microchannels of Arbitrary Cross Section,' ASME J. Fluids Eng., 128, pp. 1036-1044), which was developed for no-slip boundary condition, is extended to cover the slip-flow regime in this study. The proposed model for pressure drop is a function of geometrical parameters of the channel: cross sectional area, perimeter, polar moment of inertia, and the Knudsen number. The model is successfully validated against existing numerical and experimental data collected from different sources in literature for several shapes, including circular, rectangular, trapezoidal, and double-trapezoidal cross sections and a variety of gases such as nitrogen, argon, and helium. [DOI: 10.1115/1.3059699] Keywords: slip-flow, microchannels, general cross section, pressure distribution

Studying heat transfer problems of supercritical water, the pressure dependency of thermophysical parameters (density, specific heat, viscosity, and thermal conductivity) and the work done by pressure are often neglected. Here we show that the variations of some physical parameters as functions of pressure have the same order of magnitude than their variations as functions of temperature in supercritical water. Therefore, pressure dependency of physical parameters should be taken into account in heat transfer calculations of supercritical water It is also pointed out that the work done by pressure should not be neglected in supercritical water since the pressure work term has the same order of magnitude than the convective term near the pseudocritical temperature. [DOI: 10.1115/1.2983135]

Comprehensive modeling of gas foil bearings (GFBs) anchored to reliable test data will enable the widespread usage of these bearings into novel high speed turbomachinery applications. GFBs often need a forced cooling gas flow, axially fed through one end of the bearing, for adequate thermal management. This paper presents rotordynamic response measurements on a rigid rotor supported on GFBs during rotor speed run-up and coastdown tests with the GFBs supplied with increasing feed gas pressures to 2.8 bars. Rotor speed run-up tests to 35 krpm show that the bearing end side feed gas pressurization delays the onset speed of rotor subsynchronous whirl motions. The test data validate closely the predictions of the threshold speed of instability and the whirl frequency ratio derived from a GFB model that implements the axial evolution of gas circumferential flow velocity as a function of the imposed side feed pressure. Rotor speed coastdown tests from 25 krpm with a low feed pressure of 0.35 bar evidence a nearly linear synchronous rotor response for small and moderately large imbalance mass distributions. A structural finite element rotordynamics model integrates linearized synchronous speed GFB force coefficients and predicts synchronous responses, amplitude, and phase angles, agreeing with the test data. The analysis and measurements demonstrate the profound effect of the end side feed gas pressurization on the rotordynamic performance of GFBs. [DOI: 10.1115/1.2966421] Keywords: gas foil bearing, external pressurization, rotordynamic stability, imbalance response