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Showing papers in "Journal of Pressure Vessel Technology-transactions of The Asme in 2005"


Journal ArticleDOI
TL;DR: In this article, the dispersion curves for toroidal structures have been calculated using a finite element method, as there is no available analytical solution, and the factors affecting the transmission and reflection behavior have been identified by studying a straight-curved-straight structure both numerically and experimentally.
Abstract: The practical testing of pipes in a pipe network has shown that there are issues concerning the propagation of ultrasonic guided waves through bends. It is therefore desirable to improve the understanding of the reflection and transmission characteristics of the bend. First, the dispersion curves for toroidal structures have been calculated using a finite element method, as there is no available analytical solution. Then the factors affecting the transmission and reflection behavior have been identified by studying a straight-curved-straight structure both numerically and experimentally. The frequency dependent transmission behavior obtained is explained in terms of the modes propagating in the straight and curved sections of the pipe.

74 citations


Journal ArticleDOI
TL;DR: Theoretical work on flexural torsional guided waves in pipe is presented along with angular profile experimental justification in this paper, which forms a framework of nonuxisymmetric guided wave mechanics in pipe.
Abstract: Theoretical work on flexural torsional guided waves in pipe is presented along with angular profile experimental justification. Combined with previous work on flexural longitudinal modes and axisymmetric longitudinal and torsional modes, this work now forms a framework of nonuxisymmetric guided wave mechanics in pipe. Pipe inspection experiments are also carried out by flexural torsional. wave focusing to demonstrate the advantages of the focusing technique.

62 citations


Journal ArticleDOI
TL;DR: In this paper, a small notch cut in an ASTM-A53-F steel pipe at depths ranging from 1% to 17% of the pipe cross-sectional area was investigated.
Abstract: This paper casts pipe inspection by ultrasonic guided waves in a feature extraction and automatic classification framework. The specific defect under investigation is a small notch cut in an ASTM-A53-F steel pipe at depths ranging from 1% to 17% of the pipe cross-sectional area. A semi-analytical finite element method is first used to model wave propagation in the pipe. In the experiment, reflection measurements are taken and six features are extracted from the discrete wavelet decomposition of the raw signals and from the Hilbert and Fourier transforms of the reconstructed signals. A six-dimensional damage index is then constructed, and it is fed to an artificial neural network that classifies the size and the location of the notch. Overall, the wavelet-based multifeature analysis demonstrates good classification performance and robustness against noise and changes in some of the operating parameters.

59 citations


Journal ArticleDOI
TL;DR: In this article, a master S-N curve approach has been developed using a mesh-insensitive structural stress procedure for fatigue evaluation of welded components and a series of recent test data (small weld details and a full-scale vessel) published by De Jesus et al. (2004, Fatigue and Fracture of Engineering Materials and Structures, 27, pp. 799-810) were analyzed.
Abstract: In support of the ASME Div 2 Rewrite, a master S-N curve approach has been developed using a mesh-insensitive structural stress procedure for fatigue evaluation of welded components. The effectiveness of the master S-N curve approach has been demonstrated in a number of earlier publications for many joint types and loading conditions for pipe and vessel components as well as plate joints. To further validate the structural stress method, a series of recent test data (small weld details and a full-scale vessel) published by De Jesus et al. (2004, Fatigue and Fracture of Engineering Materials and Structures, 27, pp. 799-810) were analyzed in this paper. A comparative assessment of various existing procedures and their effectiveness in correlating the fatigue test data by De Jesus is also presented. These assessment procedures include current ASME Sec. VIII Div 2, weld classification approach in PD 5500, and the surface extrapolation-based hot spot stress approach in recently approved European EN 13445 Standards.

55 citations


Journal ArticleDOI
TL;DR: In this paper, the waveform energy (indicative of attenuation) is presented and discussed in terms of corrosion damage in reinforced concrete, and the results indicate that the loss of bond strength between the reinforcing steel and the surrounding concrete can be detected and evaluated.
Abstract: Corrosion of reinforced concrete is a chronic infrastructure problem, particularly in areas with deicing salt and marine exposure. To maintain structural integrity, a testing method is needed to identify areas of corroding reinforcement. For purposes of rehabilitation, the method must also be able to evaluate the degree, rate, and location of damage. Toward the development of a wireless embedded sensor system to monitor and assess corrosion damage in reinforced concrete, reinforced mortar specimens were manufactured with seeded defects to simulate corrosion damage. Taking advantage of waveguide effects of the reinforcing bars, these specimens were then tested using an ultrasonic approach. Using the same ultrasonic approach, specimens without seeded defects were also monitored during accelerated corrosion tests. Both the ultrasonic sending and the receiving transducers were mounted on the steel rebar. Advantage was taken of the lower frequency (<250 kHz) fundamental flexural propagation mode because of its relatively large displacements at the interface between the reinforcing steel and the surrounding mortar. Waveform energy (indicative of attenuation) is presented and discussed in terms of corrosion damage. Current results indicate that the loss of bond strength between the reinforcing steel and the surrounding concrete can be detected and evaluated.

48 citations


Journal ArticleDOI
TL;DR: In this article, the US Army engineer research and development center developed an improved methodology to predict the effect of pressure relief from the free edges of the loaded wall, which can significantly reduce the magnitude of the late-time portion of the positive reflected pressure phase, resulting in a substantial decrease in the peak impulse load.
Abstract: The interaction of an airblast wave with a structure, and the blast wave propagation around and over the structure is of significant importance. In order to protect a structure from the airblast produced by such explosive threats as terrorist bombs, a facility designer must possess an adequate knowledge of the expected blast wave loading. Of greatest importance are pressures and impulses on the directly loaded face of the structure, since it is typically subjected to the highest (reflected) pressures. It has long been recognized that reflected pressure time histories can be strongly influenced by pressure relief from the free edges of the loaded wall. The relief wave can significantly reduce the magnitude of the late-time portion of the positive reflected pressure phase, resulting in a substantial decrease in the peak impulse load. Most current predictive methodologies attempt to account for the relief wave and its effect on impulse. Unfortunately, these methods tend to be rather inaccurate because the exact manner in which the relief wave is manifested is not accurately defined. The US Army Engineer Research and Development Center has developed an improved methodology to predict the effect of pressure relief. This paper presents the basis for the methodology and its practical application.

42 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed a constraint-corrected J-R curve for X80 pipeline steel with a set of single-edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks.
Abstract: Fracture properties of API X80 pipeline steel have been developed using a set of single edge notched bend (SENB) and single edge notched tension (SENT) specimens with shallow and deep cracks to generate different crack-tip constraint levels. The test data show that the J-R curves for X80 pipeline steel are strongly constraint dependent. To facilitate transfer of the experimental J-R curves to those for actual cracked components, like flawed pipeline, constraint corrected J-R curves are developed. The two-parameter J-A2 formulation is adopted to quantify constraint effect on the crack-tip fields and the J-R curves. The constraint parameter A2 is extracted by matching the J-A2 solution with finite element results for a specific crack configuration. A constraint corrected J-R curve is then formulated as a function of the constraint parameter A2 and crack extension Δa. A general method and procedure to transfer the experimental J-R curves from laboratory to actual cracked components are proposed. Using the test data of J-R curves for the SENB specimens, a mathematical expression representing a family of the J-R curves is constructed for X80. It is shown that the predicted J-R curves developed in this paper match well with experimental data for both SENB and SENT specimens. To demonstrate its application in assessing flaw instability, a pipeline with an axial surface crack is considered. For a crack depth of 50% of the wall thickness, the predicted J-R curve is found to be higher than that for the SENB specimen with the same crack length to width ratio. From this predicted J-R curve and crack driving force obtained by finite element analysis, the failure pressures of the pipeline at the crack initiation and instability are determined and discussed.Copyright © 2005 by ASME

36 citations


Journal ArticleDOI
TL;DR: In this article, a literature search is conducted to review existing riser inspection methods and identify candidate nondestructive methods for riser inspections, which can be capable of detecting and monitoring general corrosion, localized corrosion pitting, and stress-corrosion cracking as external or internal corrosion damage.
Abstract: Offshore pipeline failure statistics have been collected for more than 30 years now and illustrate that the riser predominantly fails as a result of corrosion. The consistent wetting and drying in the splash zone combined with defects in the coatings are the usual contributors to the problem. Risers are inspected at some determined frequency and can be done by internal and external methods. Inspecting by either means brings into account caveats and limitations from the technology used as well as human factors. For example, external inspections can be inefficient and inaccurate with some tools missing defects in areas of coating disbondment. In addition, internal inspections sometimes create false positives and can miss defects. These inaccuracies in the technologies or the techniques used may miss defects that eventually lead to failure. On the other hand, using corrosion mapping and fitness-for-service (FFS) assessment from the data collected, along with the inherent conservatism of this data from limited measurement accuracy, may result in the premature replacement of risers. A literature search is being conducted to review existing riser inspection methods and identify candidate nondestructive methods for riser inspection. These methods should be capable of detecting and monitoring general corrosion, localized corrosion pitting, and stress-corrosion cracking (sulfide or hydrogen induced) as external or internal corrosion damage. Thus far, this search has found that assessing the remaining service life of aging risers is largely dependent on the accuracy of analyzing corrosion damage to the riser surface in the atmospheric, splash (tidal), submerged, and buried environmental zones. The accuracy of each technology was analyzed. The capabilities and limitations of each method/technique used for riser inspection are summarized. The investigation is focused on long- and short-range ultrasonic techniques used for initial screening and corrosion mapping. These techniques can be deployed to detect a significant reduction in wall thickness using guided and torsional waves or to map accurately a corrosion damage using single/multiple transducers and phased-array probes in manual or automated mode. A pulsed eddy-current technique that uses a stepped or pulsed input signal for the detection of corrosion areas under insulation (CUI) is also being evaluated. This allows the detection of wall-thinning areas in the riser without removing the outside coatings. In addition, it is found thatfilmless, real-time, and digital radiography can be used to find internal and external corrosion defects in an insulated splash zone while the riser remains in service.

32 citations


Journal ArticleDOI
TL;DR: Tungsten strengthened ferritic steels were developed and approved by the ASME Boiler and Pressure Vessels Code Committee for use in Section I construction, designated as T23 and T122, respectively as discussed by the authors.
Abstract: Tungsten strengthened ferritic steels, 2.25Cr-1.6W-V-Nb and 12Cr-0.4Mo-2W-V-Nb-Cu have been developed and approved by the ASME Boiler and Pressure Vessels Code Committee for use in Section I construction, designated as T23 and T122, respectively. A field exposure test installing both steel tubes in service along with comparative materials in the tertiary superheater and secondary reheater of a 156 MW utility power boiler has been conducted since April 1993. The tubes were removed to confirm their material properties and corrosion/steam oxidation behaviors after 1-year, 3-year, 6-year, and 10-year periods of service. The tensile and creep rupture strengths of both steels showed no remarkable change during service. Examination of steam oxidation scale on the inner surface of the tubes indicated that the scale growth rate of T122 was extremely small following 1-year service. The growth rate and morphology of steam oxidation scale is discussed, as compared with conventional materials.

31 citations


Journal ArticleDOI
TL;DR: The perturbation method, the Edgeworth series, the reliability-based optimization,The reliability sensitivity technique, and the robust design are employed to present a practical and effective approach for the robust reliability design of the Banjo flange with arbitrary distribution parameters on the condition of known first four moments of original random variables.
Abstract: The perturbation method, the Edgeworth series, the reliability-based optimization, the reliability sensitivity technique, and the robust design are employed to present a practical and effective approach for the robust reliability design of the Banjo flange with arbitrary distribution parameters on the condition of known first four moments of original random variables. The theoretical formulas of robust reliability design for the Banjo flange with arbitrary distribution parameters are obtained. The respective program can be used to obtain the robust reliability design parameters of the Banjo flange with arbitrary distribution parameters accurately and quickly.

31 citations


Journal ArticleDOI
TL;DR: In this paper, the dynamic response of U-tubes to two-phase cross-flow has been studied in tests involving a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to air-water crossflow over the mid-span region.
Abstract: The dynamic response of U-tubes to two-phase cross-flow has been studied in tests involving a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to air-water cross-flow over the mid-span region. Tube vibration and the interaction between tubes and supports were measured over a wide range of void fractions and flow rates, for three different tube-to-support clearances. The vibration properties and tube-to-support work-rates could be characterized in terms of the relative influence of fluidelastic instability and random-turbulence excitation. For the first time, in a U-bend tube bundle with liquid or two-phase flow, fluidelastic instability was observed both in the out-of-plane and in the in-plane direction. This raises the possibility of higher-than-expected tube-to-support work-rates for U-tubes restrained by flat bars, particularly if fluidelastic instability, random turbulence and loose supports combine adversely.

Journal ArticleDOI
TL;DR: In this article, the capabilities of advanced simulation to better understand and improve the manufacture of welded joints were discussed. And the best paper was presented at the American Society of Mechanical Engineers (ASME) conference in San Diego, USA.
Abstract: This paper has informed industry of the capabilities of advanced simulation to better understand and improve the manufacture of welded joints; in turn, to improve the lifetime and safety of high temperature structures used in the petrochemical and power generation industries. This paper was also presented at the American Society of Mechanical Engineers (ASME) conference in San Diego, USA, and was awarded the best paper prize.

Proceedings ArticleDOI
TL;DR: In this paper, the role of yield strength, microstructural orientation, and small concentrations of ferrite on hydrogen-assisted fracture in two austenitic stainless steels was investigated.
Abstract: Applications requiring the containment and transportation of hydrogen gas at pressures greater than 70 MPa are anticipated in the evolving hydrogen economy infrastructure. Since hydrogen is known to alter the mechanical properties of materials, data are needed to guide the selection of materials for structural components. The objective of this study is to characterize the role of yield strength, microstructural orientation, and small concentrations of ferrite on hydrogen-assisted fracture in two austenitic stainless steels: 21Cr-6Ni-9Mn (21-6-9) and 22Cr-13Ni-5Mn (22-13-5). The testing methodology involves exposure of tensile specimens to high-pressure hydrogen gas at elevated temperature in order to precharge the specimens with hydrogen, and subsequently testing the specimens in laboratory air to measure strength and ductility. In all cases, the alloys remain ductile despite precharging to hydrogen concentrations of ∼1 at. %, as demonstrated by reduction in area values between 30% and 60% and fracture modes dominated by microvoid processes. Low concentrations of ferrite and moderate increases in yield strength do not exacerbate hydrogen-assisted fracture in 21-6-9 and 22-13-5, respectively. Microstructural orientation has a pronounced effect on ductility in 22-13-5 due to the presence of aligned second-phase particles.

Journal ArticleDOI
TL;DR: In this paper, a magnetostrictive sensor for generating and detecting guided waves in ferromagnetic plate is described, which consists of a channel-shaped core and coils wound around the core along its length.
Abstract: The development of a magnetostrictive sensor for generating and detecting guided waves in ferromagnetic plate is described. The sensor consists of a channel-shaped core and coils wound around the core along its length. It is shown that the sensor is capable of generating and detecting both the symmetric and antisymmetric Lamb wave modes and the shear horizontal wave modes in plates. It is also found that the beam pattern produced by the sensor follows the pattern expected for a line source in a two-dimensional medium.

Journal ArticleDOI
TL;DR: In this article, the authors used phase array technology with capability for beam steering, electronic scanning, focusing, and sweeping the ultrasonic beams for weld inspection, which can optimize angles and focusing to maximize defect detection.
Abstract: Major improvements in weld inspection are obtained using Phased Array technology with capability for beam steering, electronic scanning, focusing, and sweeping the ultrasonic beams. Electronic scanning is much faster than raster scanning, and can optimize angles and focusing to maximize defect detection. Pressure vessel (PV) inspections typically use “top, side, end” or “top, side, TOFD” views, though other imaging is possible. Special inspections can be performed, e.g., for specific defects, or increased coverage. Defects can be sized by pulse-echo as per code, by time-of-flight Diffraction or by back diffraction. New PV inspection codes, particularly ASME Code Case 2235, permit the use of advanced ultrasonic inspection techniques. Pipeline girth weld inspections use a unique inspection approach called “zone discrimination,” and have their own series of codes. While similar equipment is used in pipeline as in PV inspections, the pipeline philosophy is to tailor the inspection to the weld profile and predicted lack of fusion defects. Pipeline displays are specifically designed for near real-time data analysis. Both ASME CC 2235 and the pipeline codes permit the use of Fitness-For-Purpose, which reduces construction costs. Overall, phased array systems meet or exceed all PV and pipeline codes.

Journal ArticleDOI
TL;DR: In this paper, a robust ANN with the ability to determine flow stresses based on strain, strain rate, and temperature is developed and linked with finite element code, and compared with conventional means.
Abstract: The accuracy of a finite element model for design and analysis of a metal forging operation is limited by the incorporated material model’s ability to predict deformation behavior over a wide range of operating conditions. Current rheological models prove deficient in several respects due to the difficulty in establishing complicated relations between many parameters. More recently, artificial neural networks (ANN) have been suggested as an effective means to overcome these difficulties. To this end, a robust ANN with the ability to determine flow stresses based on strain, strain rate, and temperature is developed and linked with finite element code. Comparisons of this novel method with conventional means are carried out to demonstrate the advantages of this approach.

Journal ArticleDOI
TL;DR: A review of the current state of experimental and computer-modeling research on the violence of impact, thermal, and shock-induced reactions is briefly reviewed in this article, where the degree of violence depends on many variables, including the rate of energy delivery, physical and chemical properties of the explosive, and the strength of the confinement surrounding the explosive charge.
Abstract: High explosive reactions can be caused by three general energy deposition processes: impact ignition by frictional and/or shear heating; bulk thermal heating; and shock compression. The violence of the subsequent reaction varies from benign slow combustion to catastrophic detonation of the entire charge. The degree of violence depends on many variables, including the rate of energy delivery, the physical and chemical properties of the explosive, and the strength of the confinement surrounding the explosive charge. The current state of experimental and computer-modeling research on the violence of impact, thermal, and shock-induced reactions is briefly reviewed in this paper.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the denting response of tubular members and pipes subjected to lateral (transverse) quasi-static loading, in the presence of internal pressure.
Abstract: The paper examines the denting response of tubular members and pipes subjected to lateral (transverse) quasi-static loading, in the presence of internal pressure. Tubes are modeled with nonlinear shell finite elements, and the numerical results are in good agreement with available experimental data. Using the numerical tools, a parametric study is conducted to examine the effects of pressure level, as well as those of denting device size and pipe end conditions. It is mainly concluded that for a given denting displacement, the presence of internal pressure increases significantly the corresponding denting force. A simplified two-dimensional heuristic model is also adopted, which yields closed-form expressions for the denting force. The model equations are in fairly good agreement with the test results and illustrate pipe denting response in an elegant manner.© 2005 ASME

Journal ArticleDOI
TL;DR: In this article, the wave frequency and wall thickness to radius ratio were compared to find the origin of the similarity between pipe and plate models, and some criteria have been established for the plate model approximation.
Abstract: The plate approximation of a pipe is a topic discussed for decades. Rules have been established to make the comparisons. Presented here is a related topic, but one to answer the question of whether an easy-to-conduct plate experiment can be used to predict what happens in a pipe for ultrasonic guided wave. For longitudinal guided waves in a pipe, the approximation is valid clearly only over a very short distance or inordinate closeness to a defect for wave scattering analysis; but for circumferential guided waves, the validity is unclear and therefore it is worthwhile to study criteria on the approximation and simplification of a pipe experiment as a plate experiment by means of wave mechanics analysis and modeling computation. Circumferential shear horizontal (SH) waves in pipes and SH waves in plates were studied in this paper toward this goal and it was found that the wave frequency and wall thickness to radius ratio were the two key parameters with respect to the similarity. Dispersion curves and wave structures of the SH waves in plates and in pipes were compared to find the origin of the similarity. Experimental simulations and modeling with boundary element methods were also carried out for the reflection and transmission coefficients of the SH waves impinging into a defect, from which some criteria have been established for the plate model approximation. Although a pipe model is more accurate for pipe experiments, a plate model often gives a quick and reasonable solution especially when it is difficult to establish a pipe model.

Journal ArticleDOI
TL;DR: The use of creep strength enhanced ferritic alloys, such as Grade 91, in fossil power plants has become popular for high temperature applications as discussed by the authors, however, this alloy has had some incidents of premature failures.
Abstract: The use of creep strength enhanced ferritic alloys, such as Grade 91, in fossil power plants has become popular for high temperature applications. Since Grade 91 has higher stress allowables than Grade 22, a designer can specify thinner component wall thicknesses, resulting in lower throughwall thermal stresses during transient events and lower material and pipe support costs. During the past two decades, Grade 91 has been used successfully in fossil power plants. However, this alloy has had some incidents of premature failures. Case histories discuss such factors as excessively hard material, extremely soft material, overheating failures, and improper mill processing. This compilation also discusses likely root causes and solutions to avoid these potential Grade 91 problems.

Journal ArticleDOI
TL;DR: In this paper, the effect of the internal fluid operating temperature on the variation of the bolt load and consequently on the gasket stress in bolted flanged joints is addressed, and an analytical method based on the flexibility of the different joint components and their elastic interaction could serve as a powerful tool for elevated temperature flange designs.
Abstract: The tightness of bolted flanged joints subjected to elevated temperature is not properly addressed by flange design codes The development of an analytical method based on the flexibility of the different joint components and their elastic interaction could serve as a powerful tool for elevated temperature flange designs This paper addresses the effect of the internal fluid operating temperature on the variation of the bolt load and consequently on the gasket stress in bolted joints The theoretical analysis used to predict the gasket load variation as a result of unequal radial and axial thermal expansion of the joint elements is outlined It details the analytical basis of the elastic interaction model and the thermally induced deflections that are used to evaluate the load changes Two flange joint type configurations are treated: a joint with identical pair of flanges and a joint with a cover plate The analytical models are validated and verified by comparison to finite element results

Journal ArticleDOI
TL;DR: In this article, a simple mathematical model to predict the location of the condensation interface for four different shapes of steam plume at different heat transfer coefficients is presented which will be further developed into an advanced computational model for DCC.
Abstract: Various industrial devices exist where direct contact condensation (DCC) of steam in water takes place. Typical examples are the nuclear reactor coolant systems, steam driven jet pumps, and condensers. The modeling of steam condensation is crucial to obtain an appropriate design of such devices. Present models designed for DCC have shown limited agreement with experimental data. Computation of the flow regimes is performed with limited accuracy, due to initial model settings and empirical correlations, which form a main drawback in the computation of DCC related problems. This study, which is a part of a PhD study, presents an investigation of the steam-water interface for various conditions of steam and water, using the computation of balance equations and jump conditions. A simple mathematical model to predict the location of the condensation interface for four different shapes of steam plume at different heat transfer coefficients is presented which will be further developed into an advanced computational model for DCC.

Journal ArticleDOI
TL;DR: In this paper, the effects of stress intensity factor (K) profiles on the SCC growth rates of stainless steel and nickel alloys in high temperature water were studied in high-temperature water.
Abstract: Effects of rising and falling stress intensity factor (K) profiles on the SCC growth rates of stainless steel and nickel alloys has been studied in high temperature water. Sophisticated test control software was used that changes loading (P) based on crack length (a) to achieve a specific K trajectory by controlling dK/da, not simply dP/dt. The majority of SCC problems develop adjacent to welds, which have a complex residual stress profile vs. wall thickness. This, coupled with the dependence of K on crack length, causes K to change as the crack grows, not per se with time (t). The effect of “K-dot” on crack tip strain rate and the associated crack growth rate is discussed, along with the repercussions to understanding and dispositioning SCC response.Copyright © 2005 by ASME

Journal ArticleDOI
TL;DR: In this paper, a rotation-triangular array of cylinders were subjected to air/water flow to simulate two-phase mixtures over a broad range of void fraction and mass fluxes.
Abstract: Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting-wear or fatigue. Detailed vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air/water flow to simulate two-phase mixtures over a broad range of void fraction and mass fluxes. Both the dynamic lift and drag forces were measured with strain gage instrumented cylinders. The experiments revealed somewhat unexpected but significant quasi-periodic forces in both the drag and lift directions. The periodic forces appeared well correlated along the cylinder with the drag force somewhat better correlated than the lift forces. The periodic forces are also dependent on the position of the cylinder within the bundle.Copyright © 2005 by ASME

Journal ArticleDOI
TL;DR: In this paper, a 12-in. diameter standard seamless steel pipe was created by hydraulically pressing steel balls of various sizes into the pipe wall, and a cone-ferential guided ultrasonic Shear Horizontal (SH) wave Electromagnetic Acoustic Transducer (EMAT) pairs mounted on a mobile fixture in a through-transmission mode were used for detection and characterization of mechanical dents on the outer surface of a pipe wall from inside the pipe.
Abstract: Circumferential guided ultrasonic Shear Horizontal (SH) wave Electromagnetic Acoustic Transducer (EMAT) pairs mounted on a mobile fixture in a through-transmission mode were used for detection and characterization of mechanical dents on the outer surface of a pipe wall from inside the pipe. The dents were created on a 12 in. diameter standard seamless steel pipe by hydraulically pressing steel balls of various sizes into the pipe wall. n1 mode SH wave was directed through and along the wall of the pipe. Multiple measurements were obtained both from the dents and from the no-flaw region of the pipe using the EMAT pair. Dent features were extracted with a Principal Component Analysis (PCA) technique and classified into “cup” and “saucer” types using Discriminant Analysis (DA). The overall approach is able to detect and classify dents of depth 25% through wall or deeper, which should meet the needs of the pipeline safety inspection community (U.S. Department of Transportation, Research and Special Program Administration). Preliminary dent depth estimation potential is also shown via an amplitude correlation approach.

Journal ArticleDOI
TL;DR: In this article, the possibility of inspection under insulation, coatings, or with water filled pipes or around elbows is presented. But, the possibility is limited for nonaxisymmetric input to the elbow region, however, via partial loading around the circumference.
Abstract: Long range ultrasonic guided wave inspection is advancing rapidly and is quite commonplace today. Benefits of using longitudinal or torsional modes are being established in special circumstances of improved sensitivity, resolution, or penetration power. The possibility of inspection under insulation, coatings, or with water filled pipes or around elbows is possible. Detection of defects beyond a pipe elbow is difficult for axisymmetric wave impingement onto the elbow. For nonaxisymmetric input to the elbow region, however, via partial loading around the circumference, natural focusing occurs because of angular profile variation around the circumference of the pipe. Sample computations of possible angular profiles are illustrated. An experiment is also reported here to demonstrate this inspection process.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a graphical approach to determine the allowable plastic load in pressure vessel design by applying a graphical construction to a characteristic load-deformation plot of the collapse behavior of the vessel.
Abstract: The allowable plastic load in pressure vessel design by analysis is determined by applying a graphical construction to a characteristic load-deformation plot of the collapse behavior of the vessel. This paper presents an alternative approach to the problem. The plastic response is characterized by considering the curvature of a plot of plastic work dissipated in the vessel against the applied load. It is proposed that salient points of curvature correspond to critical stages in the evolution of the gross plastic deformation mechanism. In the proposed plastic work curvature (PWC) criterion of plastic collapse, the plastic load is defined as the load corresponding to zero or minimal plastic work curvature after yielding and the formation of plastic mechanisms have occurred. Application of the proposed criterion is illustrated by considering the elastic-plastic response of a simple cantilever beam in bending and a complex three-dimensional finite element analysis of a nozzle intersection. The results show that the proposed approach gives higher values of plastic load than alternative criteria when the material exhibits strain hardening. It is proposed that this is because the PWC criterion more fully represents the constraining effect of material strain hardening on the spread of plastic deformation.

Proceedings ArticleDOI
TL;DR: In this article, the authors evaluate the SIF of interacting cracks for various conditions and show that the change in the averaged SIF along the crack front caused by coalescence of two cracks can be estimated from the change of the area size.
Abstract: The interaction between multiple surface cracks is an important consideration in the cracking behavior due to thermal fatigue and stress corrosion cracking. However, it is difficult to evaluate the intensity of the interaction quantitatively because there are many factors, such as the relative position, size, and geometry of the cracks. Furthermore, the influence of the interaction differs with the crack tip position along the front. In this study, to investigate the intensity of interaction, the stress intensity factor (SIF) of interacting semielliptical surface cracks was evaluated by the finite element method and finite element alternating method. These methods enable us to evaluate the SIF of interacting cracks for various conditions. The analysis results reveal that the change in the averaged SIF along the crack front caused by coalescence of two cracks can be estimated from the change in the area size. The maximum interaction can be estimated by a simple addition of the area size of two cracks regardless of the loading condition and relative crack size. To exclude the conservativeness caused by the current combination rule, new criteria are shown.

Journal ArticleDOI
TL;DR: Remote field eddy current (RFEC) inspection is an excellent candidate for inspecting a pipeline with multiple diameters, valve and bore restrictions and tight or miter bends as discussed by the authors.
Abstract: In-line inspection tools cannot inspect most of the natural gas transmission pipelines and distribution mains due to restrictions in the pipelines that will not allow a tool equipped with current inspection technologies to pass. Remote field eddy current (RFEC) inspection is an excellent candidate for inspecting a pipeline with multiple diameters, valve and bore restrictions and tight or miter bends. The results of this paper show that the RFEC technique can inspect pipeline materials, and that all of the components needed for RFEC inspection can be made much smaller that the pipe diameter. RFEC inspection is commercially available for inspecting small diameter piping without restrictions, several hundred feet at a time. The prototype design described in this paper shows this technology will work in a free-swimming tool that can inspect miles of pipeline at time and bypass restrictions.

Proceedings ArticleDOI
TL;DR: In this paper, it was shown that pipes with wall thinning less than 50% of wall thickness have sufficient margins against a seismic event of the safety shutdown earthquake, compared with the design fatigue curve of the ASME Code Sec. III.
Abstract: It is important to assess the failure strengths for pipes with wall thinning to maintain the integrity of the piping systems and to make codification of allowable wall thinning. Full-scale fracture experiments on cyclic loading under constant internal pressure were performed for 4in. diameter straight pipes and 8in. diameter elbow pipes at ambient temperature. The experiments were low cycle fatigue under displacement controlled conditions. It is shown that a dominant failure mode under cyclic loading for straight pipes and elbows is crack initiation∕growth accompanying swelling by ratchet or buckling with crack initiation. When the thinning depth is deep, the failure mode is burst and crack growth with ratchet swelling. In addition, failure strengths were compared with the design fatigue curve of the ASME Code Sec. III. It is shown that pipes with wall thinning less than 50% of wall thickness have sufficient margins against a seismic event of the safety shutdown earthquake.