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Accepted Manuscripts

BASIC VIEW  |  EXPANDED VIEW
research-article  
Masoud Mohammadi, Mohammad Arefi and Sara Amirahmadi
J. Pressure Vessel Technol   doi: 10.1115/1.4043842
The purpose of this paper is showing the electro-elastic static behavior of a cylindrical sandwich pressure integrated with piezoelectric layers. The core is made from functionally graded carbon nanotubes reinforced composite (FG-CNTRC) materials while is integrated with piezoelectric layers made from PZT-4. The effective material properties of reinforced core with carbon nanotubes(CNTs) are calculated based on rule of mixture. The constitutive relations are developed in cylindrical coordinate system based on a higher-order shear deformation theory for both core and piezoelectric layers. The employed higher-order theory is based on third-order variation of deformations along the thickness direction to improve the accuracy of numerical results. The method of eigenvalue-eigenvector is used for solution of system of governing equations along the longitudinal direction. The numerical results are provided along the longitudinal and radial directions in terms of significant parameters such as various patterns of CNTs, Various volume fractions of CNTs, various elastic foundation coefficients and various applied electrical potentials.
TOPICS: Pressure vessels, Shear deformation, Carbon nanotubes, Eigenvalues, Materials properties, Constitutive equations, Pressure, Deformation, Composite materials
Review Article  
Jian-Guo Gong, Cheng Gong, Fu-Zhen Xuan and Haofeng Chen
J. Pressure Vessel Technol   doi: 10.1115/1.4043843
Structural discontinuities (e.g. nozzle, hole, groove, etc) widely occur in many high temperature components of nuclear and fossil power plants. In general, the notched component is used for simplified tests and analyses due to the complexity of the introduction of a practical component. In previous work, the effects of the notch on failure life of the components have been reported experimentally, including the strengthening and weakening effects, however, the internal mechanisms have not been clearly demonstrated. This work reviews the notch effects on the structural strength of the notched components at elevated temperatures under creep, fatigue and creep-fatigue loading conditions. Experimental phenomena (i.e. strengthening or weakening effects) for typical notched specimens subjected to the above three loading conditions are summarized, and related factors for notch effects on creep rupture life or cycle to failure of the components are discussed. The mechanisms for the strengthening or weakening effects induced by a notch are described. Evaluation procedures for notch effect analysis under complex loading conditions are also included, and the primary challenges concerning the notch effect are provided for further investigations.
TOPICS: Creep, Fatigue, Temperature, Failure, Fossil fuels, Rupture, High temperature, Nozzles, Cycles
research-article  
Imad Barsoum, Zuheir Barsoum and Didarul Islam
J. Pressure Vessel Technol   doi: 10.1115/1.4043844
In the current study the integrity of a manhole structure made of a 78" HDPE stub-end, steel ring and blind flange, sealed with a compressed non-asbestos fiber (CNAF) gasket is investigated by means of a parametric FEA. A coupled thermo-mechanical non-linear model is built, which allows modelling the complex thermal and mechanical loads and their interactions present during operation of the manhole. The temperature-dependent elastic-plastic HDPE material behavior and the temperature-dependent non-linear response of the CNAF gasket are accounted for in the model. Factors influencing the performance and integrity of the manhole such as stud-bolt pre-torque level (Tb), internal pressure (Pi) and outer temperature (To) are considered. Based on the results, the integrity and performance of the structure is assessed in view of a leakage through-gasket criterion and a yielding of the HDPE stub-end criterion. The FEA results reveal that both Tb, Pi and To significantly influence the performance (i.e. leakage) of the gasket and the integrity (i.e. yielding) of the HDPE stub-end. At 40 C it is possible to find a safe operational window for a range of Tb and Pi values where no leakage through the gasket or yielding of the stub-end occur. However, as temperature is increased this safe operational window decreases considerably, and at 80 C safe operation cannot be guaranteed and leakage, yielding or both simultaneously, will lead to loss in performance and integrity of the manhole structure.
TOPICS: Bolted flanges, Thermomechanics, Gaskets, Manholes, Temperature, Leakage, Finite element analysis, Modeling, Steel, Fibers, Asbestos substitutes, Stress, Flanges, Torque, Pressure
Technical Brief  
Chidambaram Subramanian
J. Pressure Vessel Technol   doi: 10.1115/1.4043812
This paper highlights about the high temperature creep failures affecting refinery materials, structures and components for which good operational practices, proper maintenance and inspection are required to avoid major failures and to maintain safety of personnel, integrity of static equipment and to avoid unplanned shut down.
TOPICS: High temperature creep, Failure, Risk, Inspection, Maintenance, Safety
research-article  
Seikh Mustafa Kamal, Mordechai Perl and Debasish Bharali
J. Pressure Vessel Technol   doi: 10.1115/1.4043591
In recent years, a few new methods of achieving autofrettage in thick-walled hollow cylinders have been developed. Rotational autofrettage is one of the new methods proposed recently for pre-stressing thick-walled cylinders. The principle of rotational autofrettage is based on inducing plastic deformation in the cylinder at the inner side and at its neighborhood by rotating the cylinder about its own axis at a certain angular velocity and subsequently bringing down it to zero angular velocity. However, the analysis of the process is still in its nascent stage. In order to establish the rotational autofrettage as a potential design procedure for pre-stressing thick-walled cylinders, accurate modelling of the process is necessary. In this paper, the rotational autofrettage for thick-walled cylinders is analyzed theoretically based on the generalized plane strain assumption. The closed form analytical solutions of the elasto-plastic stresses and strains and the residual stresses after unloading during the rotational autofrettage of a thick-walled cylinder are obtained. In Part II of the paper, the numerical evaluation of the theoretical model will be presented in order to assess its feasibility.
TOPICS: Cylinders, Plane strain, Theoretical analysis, Autofrettage, Deformation, Residual stresses, Stress, Design, Modeling
research-article  
Ramgopal Thodla, Colum M. Holtam and Rajil Saraswat
J. Pressure Vessel Technol   doi: 10.1115/1.4043512
High pressure high temperature (HPHT) design is a significant new challenge facing the subsea sector, particularly in the Gulf of Mexico. API 17TR8 provides HPHT Design Guidelines, specifically for subsea applications. Fatigue endurance (i.e. S-N) and fracture mechanics design are both permitted, depending on the criticality of the component. Both design approaches require material properties generated in corrosive environments, such as seawater with cathodic protection and/or sour production fluids. In particular, it is necessary to understand sensitivity to cyclic loading frequency (for both design approaches), crack growth rates (for fracture mechanics approach) as well as fracture toughness performance. For many subsea components, the primary source of fatigue loading is associated with the start-up and subsequent shutdown operation of the well, with long hold periods in-between, during which static crack growth could occur. These are the two damage modes of most interest when performing a fracture mechanics based analysis. This paper presents the preliminary results of a novel single specimen test method that was developed to provide fatigue crack growth rate and fracture toughness data in corrosive environments, in a timeframe that is compatible with subsea HPHT development projects. Test data generated on alloy 625+ in seawater with cathodic protection is presented along with a description of how the test method was developed. A crack tip strain rate based formulation was applied to the data to rationalize the effect of frequency, stress intensity factor range (?K) and maximum stress intensity factor (Kmax).
TOPICS: Ocean engineering, Materials properties, Design, Fracture (Materials), Fracture mechanics, Fatigue, Cathodic protection, Stress, Fracture toughness, Seawater, Gulf of Mexico, High temperature, American Petroleum Institute, Damage, Fatigue cracks, High pressure (Physics), Fluids, Alloys
research-article  
Neeta Mandhare, Karunamurthy K and Saleel Ismail
J. Pressure Vessel Technol   doi: 10.1115/1.4043383
Centrifugal Pump is one of the significant consumers of electricity as it is most commonly encountered rotodynamic machinery in a domestic and Industrial application. Centrifugal Pump operating at off-design conditions subjects to different periodic flow randomness, which in turn hampers functionality and performance of a centrifugal pump. These limitations can be overcome by modification in the conventional design of different components of a centrifugal pump, which can assuage flow randomness and instabilities, reconstitute flow pattern and minimize hydraulic flow losses. In this article, flow vulnerabilities like pressure and flow inconsistency, recirculation, boundary layer separation, adverse rotor-stator interaction, its effects on operation and performance of a centrifugal pump are reviewed. This article also aims to retrospect design modification attempts made by different researchers like impeller trimming, rounding, geometry modification of different components, providing microgrooves on the impeller and many more. Based on the findings of this study, it is concluded that some design modifications in impeller, diffuser and casing results into improvement in functionality, efficiency and reduction in pressure fluctuations, flow recirculation and vibrations. Design modifications should improve the performance without hampering functionality and useful range of pump operation. In view of the present energy crisis, enhancement of performance of a centrifugal pump saves fluid power and in turn, contributes to energy and financial saving. This also reduces emissions of greenhouse gas and carbon credits. Considerable research is still necessary to understand and correlate flow physics and design modifications for impeller, diffuser, and casing.
TOPICS: Physics, Internal flow, Design, Flow instability, Centrifugal pumps, Flow (Dynamics), Impellers, Pressure, Diffusers, Chaos, Geometry, Stators, Emissions, Hydraulic flow, Boundary layers, Carbon, Pumps, Rotors, Vibration, Fluctuations (Physics), Separation (Technology), Fluids, Machinery
research-article  
Nak-Kyun Cho, Haofeng Chen, Donald Mackenzie and Dario Giugliano
J. Pressure Vessel Technol   doi: 10.1115/1.4043376
Pipe bends are generally employed for routing piping systems by connecting to straight pipes but back-to-back pipe bends are often necessary for confined space applications. In order to achieve safe operation under complex loading, it requires a thorough pipeline integrity assessment to be commenced. This paper investigates the effects of cyclic thermo-mechanical loading on cyclic plastic behaviour of a ninety-degree back-to-back pipe bend system, including temperature-dependent yield stress effects. Structural response interaction boundaries are determined for various different combinations of cyclic and steady loading. Constructed structural responses are verified by full cyclic incremental, step-by-step, Finite Element Analysis. The numerical studies provide a comprehensive description of the cyclic plastic behaviour of the pipe bends, and semi-empirical equations for predicting the elastic shakedown limit boundary are developed to aid pipeline designers in the effective assessment of the integrity of the pipe bends without a requirement for complex Finite Element Analysis.
TOPICS: Thermomechanics, Pipe bends, Finite element analysis, Pipelines, Pipes, Pipeline integrity, Piping systems, Yield stress, Temperature, Structural response analysis
Review Article  
Kamlesh Chikhaliya and Bhavesh Patel
J. Pressure Vessel Technol   doi: 10.1115/1.4043095
Differential longitudinal thermal expansion between the shell and the tube bundle is a well known problem in fixed tubesheet heat exchanger design. An expansion bellows provide flexibility for thermal expansion and also function as a pressure retaining part. In this paper, guidelines for design of flanged and flued type (thick wall) expansion bellows available in international codes and standards including ASME VIII-1 & 2, EN-13445, TEMA and EJMA codes are presented. These codes and standards are compared in terms of information available for thick wall expansion bellows design with regards to condition of applicability of design formula, spring rate determination, parameter to define the initial geometry, stress determination and fatigue evaluation. Inherent limitations of these codes with respect to expansion bellows design, research gape and recommendations for effective design are also presented in this paper. Brief history and information provided in various codes and standards related to unreinforced thin wall expansion bellows (bellows expansion joints) are also presented to understand evaluation of expansion bellows design.
TOPICS: Engineering standards, Design, Bellows (Equipment), Thermal expansion, Fatigue, Stress, Heat exchangers, Geometry, Shells, Springs, Thin wall structures, Bellows expansion joints, Pressure
research-article  
Bingjun Chen, P.-Y. Ben Jar, Pierre Mertiny and Robert Prybysh
J. Pressure Vessel Technol   doi: 10.1115/1.4042593
This paper investigates the influence of primer on mechanical properties and fracture behavior for ring specimens, prepared from commercial chlorinated polyvinyl chloride (CPVC) pipe. After immersing the specimens in primer for 30 minutes, the specimens were dried for eight different periods, ranging from half day to 113 days, and then fractured in tension along the hoop direction. Results suggest that the longer the drying time, the higher the recovered strength, with the specimens after the longest drying time showing up to 63% of the strength for the virgin pipe. However, such a level of recovery cannot be achieved for ductility. Examination of specimens indicated that the exposure to primer created a core-shell structure on the cross section, of which the area ratio was independent of the drying time. It is believed that exposure to primer caused swelling and formed the shell region. Presence of the shell region has two roles in the ductility reduction. One is to provide multiple sites along the border between the shell and the core regions for crack initiation, and the other to enhance stress concentration at the crack tip. The paper concludes that exposure to primer in the solvent welding process may reduce ductility of CPVC pipe, thus affecting its resistance to slow crack growth in long-term applications.
TOPICS: Ductility, Pipes, Shells, Fracture (Materials), Drying, Welding, Stress concentration, Mechanical properties, Tension
research-article  
A. Ravi Kiran, Reddy G. R. and M.K. Agrawal
J. Pressure Vessel Technol   doi: 10.1115/1.4042596
A procedure is described for risk-based seismic performance assessment of pressurized piping systems considering ratcheting. The procedure is demonstrated on a carbon steel piping system considered for OECD-NEA benchmark exercise on quantification of seismic margins. Initially, fragility analysis of the piping system is carried out by considering variability in damping and frequency. Variation in damping is obtained from the statistical analysis of damping values observed in earlier experiments on piping systems and components. The variation in ground motion is considered by using twenty strong motion records of intra-plate region. Floor motion of a typical reactor building of a nuclear power plant under these actual earthquake records is evaluated and applied to the piping system. The performance evaluation of the piping system in terms of ratcheting is carried out using a numerical approach, which was earlier validated with shake table ratcheting tests on piping components and systems. Three limit states representing performance levels of the piping system under seismic load are considered for fragility evaluation. For each limit state, probability of exceedance at different levels of floor motion is evaluated to generate fragility curve. Subsequently, the fragility curves of the piping systems are convoluted with hazard curves for a typical site to obtain the risk in terms of annual probability of occurrence of the performance limits.
TOPICS: Piping systems, Risk, Damping, Probability, Statistical analysis, Carbon steel, Stress, Pipes, Earthquakes, Nuclear power stations, Performance evaluation, Hazards
Technology Review  
Kyle Gough and Daniel Peters
J. Pressure Vessel Technol   doi: 10.1115/1.4037197
Layered vessels have been in-service for many years which use layered construction. This construction technique has been employed since the 1930's. This generally involved either concentric plates or spirally wrapped plates to manufacture vessels with thick walls that otherwise would require very thick and heavy forgings. Long term asset management of these vessels, including non-destructive evaluation of the vessels welds and life assessment of the vessels due to operational cycling the vessels experience can be challenging. This paper is meant to address some of the challenges in managing these critical assets and provide a discussion on the application of state of the art techniques which are being applied today.
TOPICS: Design, Vessels, Fitness-for-service, Plates (structures), Construction, Nondestructive evaluation, Forgings (Products), Welded joints

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