Accepted Manuscripts

Bouko Vogelaar and Michael Golombok
J. Pressure Vessel Technol   doi: 10.1115/1.4037120
Axial pipeline defects are detectable from torsional guided wave reflections through 90o elbows. We demonstrate that damage localization in carbon steel pipes with a so-called standard long and very long radius elbow is possible using a single permanently installed source-receiver pair. We use dispersion imaging to determine why this is not possible in a short radius elbow pipe. Although the remote damage is detected in a standard short radius bend pipe, there is not enough signal for damage localization. Since pipeline bends are normally of at least standard long radius, the acoustical behavior is similar to that previously determined in straight pipes. The reflective method can thus be applied fruitfully to monitor structural health beyond industrial pipeline bends.
TOPICS: Pipe bends, Damage, Pipes, Pipelines, Signals, Imaging, Acoustics, Reflection, Carbon steel, Waves
Mordechai Perl and Joseph Perry
J. Pressure Vessel Technol   doi: 10.1115/1.4037121
The design of a gun barrel aims at maximizing its firing power, determined by its SMP- the maximal allowed firing pressure - which is considerably enhanced by inducing a favorable residual stress field through the barrel's wall commonly by the autofrettage process. Presently, there are two distinct processes: hydrostatic and swage autofrettage. In both processes the barrel's material is fully or partially plastically deformed. A new 3-D code, enabling a realistic simulation of both swage and hydraulic autofrettage processes, using experimentally measured stress-strain curves and incorporating the Bauschinger effect is used. This code enables the analysis of all the factors relating to the final SMP of a barrel, and can be used to optimize the barrel's design. A major outcome of this analysis was the fact that the SMP of an autofrettaged barrel is dictated by the detailed plastic characteristics on the barrel's material. The main five plastic parameters of the material that have been identified are: the exact (zero offset) value of the yield stress, the universal plastic curve in both tension and compression, the Bauschinger Effect Factor (BEF) curve, and the Elastic-Plastic Transition Range (EPTR). A detailed analysis of these three materials points to the fact that the major parameter determining the barrel's SMP is the yield stress of the material and that the best way to determine it is by the newly developed "zero offset" method.
TOPICS: Materials properties, Firing, Autofrettage, Yield stress, Design, Performance, Compression, Pressure, Hydrostatics, Simulation, Stress, Stress-strain curves, Gun barrels, Tension
N Rino Nelson, Siva Prasad N and A. Seshadri Sekhar
J. Pressure Vessel Technol   doi: 10.1115/1.4037070
Gasketed flange joints are widely used in pressure vessels and piping systems. They are subjected to bending load due to differential thermal expansion, wind load, self-weight etc., in addition to assembly and internal fluid load. Most of the flange designs are based on equivalent pressure method to include the effect of external bending loads. The behaviour of gasketed flange joint is complex due to the nonlinear hysteretic behaviour of gasket material and contact interfaces between joint members. It becomes more complex when the joint is subjected to bending load at elevated temperatures. In the present work, performance of a flange joint has been studied under internal pressure and external bending load at elevated temperatures. A 3D finite element model is developed, considering the nonlinearities in the joint due to gasket material and contact between its members along with their temperature dependent material properties. The performance of joint under different bolt preloads, internal fluid pressures and temperatures is studied. Flange joint with two gaskets (twin gasket) placed concentric, is also analyzed. The results from finite element analysis are validated using 4-point bending test on gasketed flange joint. The sealing and strength criteria are considered to determine the maximum allowable bending moment at different internal fluid temperatures, for both single and twin gasketed flange joints with spiral wound gasket. Twin gasket is able to withstand higher bending moment without leakage compared to single gasket. Results show that the allowable load on flange joint depends on operating temperature and gasket configuration.
TOPICS: Stress, Gaskets, Flanges, Temperature, Fluids, Pressure, Thermal expansion, Fluid pressure, Weight (Mass), Manufacturing, Pressure vessels, Sealing (Process), Materials properties, Finite element analysis, Finite element model, Piping systems, Wind, Leakage, Operating temperature
Majid Khayat, Davood Poorveis and Shapour Moradi
J. Pressure Vessel Technol   doi: 10.1115/1.4037042
Linearized buckling analysis of functionally graded shells of revolution subjected to displacement dependent pressure which remain normal to the shell middle surface throughout the deformation process is described in this work. Material properties are assumed to be temperature dependent, and varied continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of a ceramic and metal. The governing equations are derived based on first-order shear deformation theory which accounts for through thickness shear flexibility with Sanders-type of kinematic nonlinearity. Displacements and rotations in the shell middle surface are approximated by combining polynomial functions in the meridional direction and truncated Fourier series with an appropriate number of harmonic terms in the circumferential direction. The load stiffness matrix which accounts for variation of load direction derived for each strip and after assembling global load stiffness matrix of the shell which may be un-symmetric is formed. The un-symmetric parts which are due to load non-uniformity and unconstrained boundaries have been separated. The results indicate that considering pressure stiffness causes buckling pressure reduction. A detailed numerical study is carried out to bring out the effects of power-law index of functional graded material and geometry of the shell on the effect of follower action of lateral pressure on buckling load diminishes.
TOPICS: Pressure, Buckling, Displacement, Functionally graded materials, Shells, Stress, Stiffness, Strips, Kinematics, Geometry, Polynomials, Shear deformation, Shear (Mechanics), Materials properties, Fourier series, Deformation, Temperature, Metals, Ceramics
Jan Blachut and Olawale Ifayefunmi
J. Pressure Vessel Technol   doi: 10.1115/1.4037043
The paper describes burst pressures of eight mild steel toriconical shells and proposes a criterion for their ultimate loss of structural integrity based on true stress-strain material relationship. All test models were initially loaded by quasi-static external pressure until they buckled/collapsed. They were subsequently internally pressurised until burst. The details about the numerical process which simulates the two-stage loading process, i.e., starting with buckling by external pressure being followed by reloading using internal pressure for up to the burst, are given. The paper concentrates on numerical procedure which allows computation of the burst pressure using extensive plastic straining. It is shown that burst pressures based on the excessive plastic straining are closer to reality (and experiments) than those based on plastic instability.
TOPICS: Shells, External pressure, Pressure, Steel, Stress, Buckling, Computation
Zhanfeng Chen, Hao Ye, Sunting Yan, Xiaoli Shen and Zhijiang Jin
J. Pressure Vessel Technol   doi: 10.1115/1.4037045
Accurate prediction of the burst pressure is indispensible for the engineering design and integrity assessment of the oil and gas pipelines. A plenty of analytical and empirical equations have been proposed to predict the burst pressures of the pipelines, however, it is difficult to accurately predict the burst pressures and evaluate the accuracy of these equations. In this paper, a failure window method was presented to predict the burst pressure of the pipes. Firstly, the security of the steel pipelines under the internal pressure can be assessed. And then the accuracy of the previous analytical and empirical equations can also be generally evaluated. Finally, the effect of the wall thinning of the pipes on the failure window was systemically investigated. The results indicate that it is extremely formidable to establish an equation to predict the burst pressure with a high accuracy and a broad application, while it is feasible to create a failure window to determine the range of the dangerous internal pressure. Calculations reveal that some predictions of the burst pressure equations like Faupel, Sderberg, Maximum stress and Nadai (1) are overestimated to some extent; some like ASME, maximum shear stress, Turner, Klever and Zhu-Leis and Baily-Nadai (2) basically reliable; the rest like API and Nadai (3) slightly conservative. With the wall thinning of the steel pipelines, the failure window is gradually lowered and narrowed.
TOPICS: Failure, Pipelines, Pressure, Steel, Pipes, Stress, Engineering design, American Petroleum Institute, Security, Shear stress
Yangyan Zheng, Chen Xiao, Zheng Yang and Xiang Ling
J. Pressure Vessel Technol   doi: 10.1115/1.4037046
In this paper line- and ring-notched SPT specimens were studied, a 3D model of a ring-notched SPT specimen was established using the contour integral method, and the validity of the model was verified using ring-notched specimens. The stress and strain fields were analyzed using numerical simulations of a ring-notched SPT specimen, and the change in the stress gradient during deformation was considered. To verify the finite element model, the results of the numerical simulations were compared with those of three-point bending tests and a Gurson-Tvergaard-Needleman (GTN) model. Compared with the line-notched specimen, the ring-notched specimen was more suitable for crack propagation analysis and fracture toughness evaluation. The results of the numerical simulations were in good agreement with those of the experiments, which showed that the numerical model used in this study was correct. For a crack that initiated when the load reached its maximum value, the value of the J integral was 335 kJ/m2, and at time 0.85Pmax, the value of the J integral was 201 kJ/m2, and the difference from the result of the three-point bending test was 14.4%. For a crack that initiated during the stretching deformation stage, the relevant fracture toughness was 225 kJ/m2, and the difference from the result of the three-point bending test was 3%.
TOPICS: Fracture toughness, Computer simulation, Stress, Fracture (Materials), Deformation, Three-dimensional models, Crack propagation, Finite element model
Albert E. Segall, Faruk A. Sohag, Faith R. Beck, Lokanath Mohanta, Dr. Fan-Bill Cheung, Timothy J. Eden and John Potter
J. Pressure Vessel Technol   doi: 10.1115/1.4037001
During a Reaction Initiated Accident (RIA) or Loss of Coolant Accident (LOCA), passive external-cooling of the reactor lower head is a viable approach for the in-vessel retention of Corium; while this concept can certainly be applied to new constructions, it may also be viable for operational systems with existing cavities below the reactor. However, a boiling crisis will inevitably develop on the reactor lower head owing to the occurrence of Critical Heat Flux or CHF that could reduce the decay heat removal capability as the vapor phase impedes continuous boiling. Fortunately, this effect can be minimized for both new and existing reactors through the use of a Cold-Spray delivered, micro-porous coating that facilitates the formation of vapor micro-jets from the reactor surface. The micro-porous coatings were created by first spraying a binary mixture with the sacrificial material then removed via etching. Subsequent quenching experiments on uncoated and coated hemispherical surfaces showed that local CHF values for the coated vessel were consistently higher relative to the bare surface. Moreover, it was observed for both coated and uncoated surfaces that the local rate of boiling and local CHF limit varied appreciably along the outer surface. Nevertheless, the results of this intriguing study clearly show that the use of Cold Spray coatings could enhance the local CHF limit for downward facing boiling by more than 88%. Moreover, the Cold-Spray process is amenable to coating the lower heads of operating reactors.
TOPICS: Coatings, Boiling, Nuclear reactor cooling, Critical heat flux, Emergencies, Sprays, Vessels, Vapors, Accidents, Heat, Cooling, Plasma spraying, Coolants, Spraying (Coating processes), Jets, Quenching (Metalworking), Cavities, Etching
Hiun Nagamori and Koji Takahashi
J. Pressure Vessel Technol   doi: 10.1115/1.4037002
The stress states of elbow and tee pipes are complex and different from those of straight pipes. The low-cycle fatigue lives of elbows and tees cannot be predicted by Manson’s universal slope method; however, a revised universal method proposed by Takahashi et al. was able to predict with high accuracy the low-cycle fatigue lives of elbows under combined cyclic bending and internal pressure. The objective of this study was to confirm the validity of the revised universal slope method for the prediction of low-cycle fatigue behaviors of elbows and tees of various shapes and dimensions under conditions of in-plane bending and internal pressure. Finite element analysis was carried out to simulate the low-cycle fatigue behaviors observed in previous experimental studies of elbows and tees. The low-cycle fatigue behaviors, such as the area of crack initiation, the direction of crack growth, and the fatigue lives, obtained by the analysis were compared with previously obtained experimental data. Based on this comparison, the revised universal slope method was found to accurately predict the low-cycle fatigue behaviors of elbows and tees under internal pressure conditions regardless of differences in shape and dimensions.
TOPICS: Pipes, Low cycle fatigue, Pressure, Dimensions, Shapes, Fracture (Materials), Finite element analysis, Stress, Fatigue
Maria Vathi, Spyros A. Karamanos, Ioannis A. Kapogiannis and Konstantinos V. Spiliopoulos
J. Pressure Vessel Technol   doi: 10.1115/1.4036916
In the present paper, performance criteria for the seismic design of industrial liquid storage tanks and piping systems are proposed, aimed at defining a performance-based design framework, to be used for reliable development of fragility curves and assessment of seismic risk. Considering “loss of containment” as the ultimate damage state, the proposed performance limits are quantified in terms of local quantities obtained from a simple and efficient earthquake analysis. Liquid storage tanks and the corresponding principal failure modes (elephant’s foot buckling, roof damage, base plate failure, anchorage failure and nozzle damage) are examined first. Subsequently, performance limits for piping systems are presented in terms of local strain at specific piping components (elbows, Tees and nozzles), against ultimate strain capacity (tensile and compressive) and low-cycle fatigue. Modeling issues for liquid storage tanks and piping systems are also discussed, for simple and efficient analysis that provides reliable estimates of local strain demand. These models are compared successfully with available experimental data. Using the above reliable numerical models, the proposed performance limits are applied in two case studies: (a) a liquid storage tank and (b) a piping system, both located in areas of high seismicity.
TOPICS: Piping systems, Storage tanks, Damage, Failure, Nozzles, Pipes, Buckling, Earthquakes, Computer simulation, Earthquake resistant design, Anchorage, Design, Failure mechanisms, Modeling, Low cycle fatigue, Roofs, Containment, Earthquake risk
Daniele Barbera, Haofeng Chen, Yinghua Liu and Fuzhen Xuan
J. Pressure Vessel Technol   doi: 10.1115/1.4036919
The Linear Matching Method Framework (LMMF) consists of a number of simplified direct methods for generating approximate inelastic solutions and answering specific design related issues in pressure vessel design and assessment codes using standard finite element codes. This paper presents a detailed review and case study of the latest state-of-the art LMM direct methods applied to the structural integrity assessment. Different structural integrity aspects are covered including the calculation of shakedown, ratchet, creep rupture limits, low cycle fatigue and creep fatigue damages. Finally an overview of the in house developed LMM plug-in is given, presenting the intuitive Graphical User Interface developed. The efficiency and robustness of these direct methods in calculating the aforementioned quantities are confirmed through a numerical case study, which is a semi-circular notched (Bridgman notch) bar. A 2D axisymmetric finite element model is adopted, and the notched bar is subjected to both cyclic and constant axial mechanical loads. For the crack initiation assessment, different cyclic loading conditions are evaluated to demonstrate the impact of the different load types on the structural response. The impact of creep dwell is also investigated to show how this parameter is capable of causing in some cases a dangerous phenomenon known as creep ratcheting. All the results in the case study demonstrate the level of simplicity of the LMMs but at the same time accuracy, efficiency and robustness over the more complicated and inefficient incremental finite element analyses.
TOPICS: Creep, Pressure vessels, Stress, Fracture (Materials), Design, Finite element analysis, Fatigue damage, Finite element model, Low cycle fatigue, Robustness, Rupture, Graphical user interfaces
DEEPESH V, Krishnan Balasubramaniam and Prabhu Rajagopal
J. Pressure Vessel Technol   doi: 10.1115/1.4036852
Interaction of fundamental torsional ultrasonic pipe guided mode T (0, 1) from defects caused by Induction Pressure Welding (IPW) process is studied using 3-D Finite Element (FE) analysis validated by experiments. Defects are assumed as cross-sectional notches along the weld bond-line, and both surface-breaking and embedded features are considered. Results show that T (0, 1) mode reflection from weld defects is strongly influenced by features of the weld itself. However, with supplementary results such as the mode-converted flexural F (1, 3) and F (1, 2) modes and circumferential variation of T (0, 1) reflection, there is potential for an effective screening solution.
TOPICS: Pressure, Electromagnetic induction, Welding, Bonding, Reflection, Waves, Finite element analysis, Pipes
Review Article  
Omesh K. Chopra, Gary L. Stevens, Robert Tregoning and A. S. Rao
J. Pressure Vessel Technol   doi: 10.1115/1.4035885
The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) provides rules for the design of Class 1 components of nuclear power plants. However, the Code design curves do not address the effects of light water reactor (LWR) water environments. Existing fatigue strain-vs.-life (e-N) data illustrate significant effects of LWR water environments on the fatigue resistance of pressure vessel and piping steels. Extensive studies have been conducted at Argonne National Laboratory and elsewhere to investigate the effects of LWR environments on the fatigue life. This article summarizes the results of these studies. Existing fatigue e-N data were evaluated to identify the various material, environmental, and loading conditions that influence fatigue crack initiation; a methodology for estimating fatigue lives as a function of these parameters was developed. The effects were incorporated into the ASME Code Section III fatigue evaluations in terms of an environmental correction factor, Fen, which is the ratio of fatigue life in air at room temperature to the life in the LWR water environment at reactor operating temperatures. Available fatigue data were used to develop fatigue design curves for carbon and low-alloy steels, austenitic stainless steels, and nickel-chromium-iron (Ni-Cr-Fe) alloys and their weld metals. A review of the Code Section III fatigue adjustment factors of 2 and 20 is also presented and the possible conservatism inherent in the choice is evaluated. A brief description of potential effects of neutron irradiation on fatigue crack initiation is presented.
TOPICS: Fatigue life, Water, Light water reactors, Fatigue, Alloys, Steel, Design, Fatigue cracks, Fatigue design, Pipes, ASME Boiler and Pressure Vessel Code, Iron, Nuclear power stations, Stainless steel, Pressure vessels, Irradiation (Radiation exposure), ASME, Carbon, Temperature, Neutrons, Metals, Nickel, ASME Standards, Operating temperature

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