bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of Fracture Toughness With Charpy Impact Energy for Low Alloy, Structural Steel Welds
Authors: Bianchi Kleber E. , Barbosa Vitor Scarabeli , Savioli Rafael , Fernandes Paulo Eduardo Alves , Ruggieri Claudio
Published: October 2017

Correlations between Charpy impact energy and fracture toughness values have continuously been developed because of their applicability in structural integrity assessment methodologies. This also applies to the integrity analysis of welded joints, which represent material discontinuities and potential failure locus in structures. Therefore, in effective FFS methodology applications, the fracture toughness of welded joints located in critical regions should be accurately estimated. This work addresses an estimation procedure of fracture toughness values based on Charpy impact energy for low alloy, steel welds made from an ASTM A572 Gr 50 base plate material. To produce the welded joints, two processes were used: SMAW and FCAW. To ensure valid toughness test values corresponding to high constraint conditions, a strength overmatched, deeply-cracked SE(B) configuration having a weld centerline notch was adopted. The ductile-to-brittle transition curve was established by means of Charpy tests. Direct CVN correlations with fracture toughness, as well as reference temperature based correlations derived from the Master Curve approach, were evaluated. The obtained results indicate that both correlation procedures are suitable for weld metal toughness estimations based on Charpy data. However, slightly different values of correlation constants than those indicated for the base metal should be employed in the case of the reference temperature method.
Fibre Reinforced Composite Pressure Vessel Heads Subject to External Pressure
Authors: Muscat Martin , Camilleri Duncan , Ellul Brian
Published: October 2017

The increase in stiffness to weight ratio and relative ease of manufacturing fibre reinforced composite pressure vessels, have put such vessels at the forefront of technology. However only limited research and specific codes pertaining exclusively to composite pressure vessel design can be found in literature. The ASME Boiler and Pressure Vessel (BPVC) Section X Code and the European design codes EN 13121-3:2016 (GRP tanks and vessels for use above ground) together with EN 13923:2005 (Filament wound FRP pressure vessels — materials, design, manufacturing and testing) are some of the few known design codes applicable to composite pressure vessels. These codes utilise both design by rule (DBR) and design by analysis (DBA) methods. The authors believe that more studies along the DBA route would benefit the composite pressure vessel design community and make it more accessible to designers and engineers. A similar scenario has already been seen in the last 10 to 15 years for steel pressure vessel design codes when DBA based on inelastic analysis was introduced. In line with these thoughts, this study compares the different design methods to prevent buckling and applies finite element analysis (FEA) to analyse a hemispherical GFRP pressure vessel head subjected to external pressure. The effect of material damage and geometrical imperfections on the final collapse failure is examined and discussed.
Composite Fibre Reinforced Pipe Elbows Subject to Combined Loading
Authors: Camilleri Duncan , Ellul Brian
Published: October 2017

Composite pipes are currently being used in a multitude of applications varying from civil to oil and gas applications. Pipes are generally connected together by means of pipe elbows that in turn are subjected to bending moment and pressure loading. This study looks into the effect of combined loading on the first ply and ultimate failure load of pipe elbows. The influence of pressure loading followed by a bending moment versus firstly applying bending moment followed by subsequent pressure loading, on the ultimate catastrophic failure, is investigated through numerical methods. The combined bending moment and pressure load ramping is also studied. Design by analysis finite element damage mechanics numerical methods are applied to investigate post first ply failure and stress redistribution. The study shows that different loading combinations can give rise to different damage mechanisms and ultimately failure loads. A safe design load envelope for a typical fibre-reinforced pipe elbow and following first ply failure and ultimate catastrophic is established and discussed.
ASME B16.20 Spiral Wound Gaskets Performance Testing
Authors: Hamilton Scott , Baulch Joel , Veiga José
Published: October 2017

Spiral Wound Gaskets have widespread use in the Process Industry, with adequate results in both piping and equipment applications. The current revision of ASME B16.20-2012 provides several details of gasket construction and dimensions. Paragraph 3.2.6 of the referenced standard has been the object of many discussions, and some question its effectiveness since it does not assure a suitable sealing performance. This paper proposes to address this issue showing results of sealability tests with many different sizes of gaskets. It also proposes a test protocol that could eventually rewrite Paragraph 3.2.6 with a protocol for sealability in addition to the compression evaluation.
Stress Intensity Factor Solutions for Crack-Like Anomalies in ERW Seam Welded Pipe
Authors: O’Brian Jennifer , Olson Richard , Young Bruce
Published: October 2017

In response to the National Transportation Safety Board (NTSB) Recommendation P-09-1, the Department of Transportation (DOT) Pipeline and Hazardous Material Safety Administration (PHMSA) initiated a comprehensive study to identify actions that could be implemented by pipeline operators to significantly reduce longitudinal seam failures in electric resistance weld (ERW) pipe. As part of the project, Task 3 in Phase II was designed to determine more appropriate stress intensity factor solutions for non-standard, axial, crack-like anomalies in ERW seam-welded pipe.

The purpose of this paper is to provide an overview of the normalized stress intensity factor solutions for cold weld (CW), selected seam-weld corrosion (SSWC), and hook crack type anomalies. ERW seams with and without weld caps are also included. The limitations on design space are discussed in the context of presenting results and interpolation and extrapolation schemes beyond that space with infinitely long solutions used as a boundary value. Results are presented in the form of surface plots for various combinations of parameters.

The reports generated during the project are publicly available and are located on the following PHMSA website: http://primis.phmsa.dot.gov/matrix/PrjHome. rdm?prj=390.
Evaluation of the Reaction Moments of Metal Bellows Expansion Joints Subjected to Angular Movement
Authors: Veiga José Carlos , Kavanagh Nelson
Published: October 2017

The reaction moment calculations of Hinged and Gimbal expansion joints, designed according to the “Standards of Expansion Joint Manufacturers Association” (EJMA), consider the bellows spring rate and pin friction. The reaction moment due to the lateral pressure forces should also be considered. Metal bellows subjected to angular movement extends one side and contracts the opposite, generating a lateral force caused by the media pressure.

This paper evaluates the lateral force reaction moment in a hinged expansion joint with the hardware designed for angular movements. For this purpose prototypes were built and the moments evaluated, simulating actual field conditions.
Thermal Fatigue Crack Propagation in Large Scale Yielding (LSY) Conditions: Pacific Experiment on a 316L Quasi-Structure
Authors: Leopold Gaëlle , Curtit François , Courtin Stéphan
Published: October 2017

An experimental device was built to study fatigue crack propagation in Large Scale Yielding (LSY) conditions.

This paper deals with results obtained for the first experiment performed on a 316L quasi-structure containing four initial cracks. Crack lengths are measured and thermocouples and strain gauges enabled to follow the test.

A comparison of this experiment was then carried out with an operating transient and measured crack growth rates were compared to the RSE-M PWR codified laws [1].
Experimental and Numerical Investigations on Exfoliated Graphite Seals
Authors: Viéville Emilie , Laurent Hervé , Rio Gérard , Omnès Benoit , Lejeune Hubert
Published: October 2017

In order to improve the sealing performances of porous braided packing rings, an experimental study is currently performed on a dedicated device. This device has been specially designed to measure the stresses during cyclic loading tests with compressed exfoliated graphite valve packing. Indeed, different tests which reproduce the opening and closing cycles of the valves have been performed to enhance the understanding of the response of the packing mechanical behavior. To this respect, an Hyperelasto-Hysteretic model is now being developed to reproduce the mechanical behavior of the compressed exfoliated graphite. The material parameters of this model are then identified to describe the stress-strain response of the studied packed stuffing-box under these cyclic loading tests.
Natural Frequencies and Damping of a Full-Scale Pipe Loop in Air and Water
Authors: Goyder Hugh
Published: October 2017

A full scale pipework system, typical of oil and gas installations located on the sea floor, was subjected to vibration tests in both dry and submerged conditions. The frequency range examined covered 10 Hz to 500 Hz. The objective of the tests was to provide experimental data so that computer simulations could be developed and validated. The method used to determine the vibration properties was that of an experimental modal analysis using an impact hammer. The hammer was modified for underwater use. In dry conditions the damping was found to be very small (damping ratio less than 0.0002) despite the construction being typical. When submerged the effect of the surrounding water was significant. The changes in the natural frequencies from the dry case to the wet case occurred in such a complex manner that it was not possible to identify a simple shift between wet and dry vibration modes. It was necessary to include appropriate added mass coefficients in the computer simulation for both the pipe and the support system. The effect of the surrounding water on the damping was measured but found to be insignificant. It was concluded that immersion in water does not add significant damping to oil and gas pipework.
3D Micro-Macro Fluid-Structure Model of Pressure Relief Valve Leak Tightness
Authors: Anwar Ali A. , Dempster William , Gorash Yevgen
Published: October 2017

Controlling and assessing the leak tightness of a Pressure Relief Valve (PRV) has been a challenge since the original design of the product. With more stringent demands from the nuclear power industry for leakproof PRV’s, closer to the set point, there has been a drive by both industry and academia for a better design method for many known metal-to-metal contacting seal/surface problems. This paper outlines a numerical modelling strategy drawn from industry experience and metrology measurements and investigates the effects of lapping and surface finish on leakage rate. Key influencing parameters of surface form, waviness and roughness are incorporated in the analysis. The numerical approach requires efficient coupling of a non-linear structural Finite Element Analysis (FEA) with a Computational Fluid Dynamic (CFD) solver. This allows the examination of the relationship between deformation of the contacting surfaces, based on the applied spring force, and the resulting micro-flow of gas through any available gaps and the overall leakage to be found. The API527 Seat Tightness methodology is followed to allow leakage rates to be measured and the computational model to be preliminarily validated. Using this model, engineers can adjust and optimise the design of pressure relief valves to find the minimal leakage condition for a given configuration. In addition, the numerical approach can potentially be applied to other metal-to-metal contacting surface components, such as flanges with metal gaskets, and help eliminate leakage.
Flow-Induced Noise of Perforated Plates at Oblique Angles of Incidence
Authors: Vanoostveen Paul , Ziada Samir
Published: October 2017

This paper investigates experimentally the mechanism of tone generation from flow over a simplified model of a perforated plate. To simplify the geometry to two dimensions, a perforated plate is modeled by a series of rectangular slats with an adjustable gap width between them. This apparatus is tested at various angles of incidence and flow velocities, to identify the conditions favorable to the production of tonal noise.

The results of this research are presented in two main parts. First, the acoustic response of the test plates is documented by means of microphone measurements. It is found that for an angle of incidence between 5 and 30 degrees and a flow velocity of 10 to 30 m/s, tonal noise is produced. Outside of this range of angles, the produced sound is broadband. In the second part, phase-locked particle image velocimetry (PIV) is used to study the flow field. It is found that vortices form in the free shear layer of the gaps between the slats. These vortices impinge on the side of the downstream slat and are then ejected through the gap to the backside of the plate. As these vortices leave the edge of the downstream slat, counter rotating vortices are shed in sympathy with the incident vortices. Vortex pairs are therefore periodically shed which are thought to be the cause of tone generation.
Fatigue Assessment of a Bulged Coke Drum
Authors: Vivas Gabriel A. , Moret Armando J. , Bello Roberto E. , Melian Luis M. , Carmona Jose R. , Araque Egler D.
Published: October 2017

Coke drums are subjected to batch cycles processing residue from refineries and upgrading the fuel streams back to the plant for further processing. As a result of operating conditions, these vessels are subjected to severe non-uniform thermal gradients that lead to localized hot and cold spots. The predominant failure mode in the coke drum shell is therefore the natural, but unwanted, progression of bulges and corrugations and eventual cracking. According to a coke drum survey coordinated by API in 1996 from 145 coke drums, 57% were found to have shell bulging problems. A common trend to increase profitability in coke drum units is reducing operational cycle length; which aggravates bulging and cracking mechanisms on these vessels.

As part of the bulging monitoring process, laser mapping and bulge severity factor (BSF) analysis were conducted in a total of six coke drums. The vessel that exhibited the most significant bulges was subsequently instrumented with strain gauges and thermocouples in three specific regions. Finite element analyses (FEA) of the instrumented regions were performed using the laser mapping and 2-dimensional temperature gradients as inputs, and compared with the strain gauge measurements. The assessment shows the level of damage produced during operation, as well as the changes in damage from one cycle to the next. The usage factor can be used as a decision criterion by operation personnel for potential changes, as well as aiding in decision making on when to repair, replace or reinforce the sections of interest.
Understanding the Multiple Purposes of Refractory Linings in Sulfur Recovery Units
Authors: Shargay Cathleen , Tajalli Tina , Wong Vincent
Published: October 2017

Within Sulfur Recovery Units (SRU), many equipment and piping items are built with internal refractory linings, but between the various process areas, the refractory is being used for completely different functions. Understanding the “purpose” of the refractory is important for both the initial selection of the optimum type of refractory, and also for repair decisions whenever refractory damage is found during turnarounds. This paper will describe each area where refractory is used, the operating and turnaround conditions, and the four unique purposes of the refractory to provide a mechanistic understanding of the function of refractory. It will also discuss the relationship between the purpose and repair philosophies for use as a general guideline.
Hot Tapping in Oil Refineries: Corrosion and Material Concerns
Authors: Shargay Cathleen , Daru Kuntak , Desai Jigneshkumar J.
Published: October 2017

The purpose of hot tapping is to add connections on piping or equipment without depressurization or disruption of normal process operations. Hence, hot taps involve welding on items while they are in service. Although not desirable, owners are faced with situations in which hot tapping is the best option. With due regards to safety, owners rely on published industry standards, such as API RP 2201 Safe Hot Tapping Practices in the Petroleum and Petrochemical Industries and ASME PCC-2, Repair of Pressure Equipment and Piping, Article 2.10, for guidance on hot tapping. These standards provide excellent guidelines on the safety reviews, design details, welding procedures, testing, etc., and cover some special restrictions for hot taps due to the specific service and/or base materials. However, there are numerous additional hot tapping cases which arise in the refining industry, and the purpose of this paper is to highlight considerations due to potential corrosion or environmental cracking risks and/or due to refinery materials with special welding requirements. Examples are hot taps in services containing sour water and on low alloy Cr-Mo steels. The considerations and suggested special requirements are explained.
Engineering and Simulations to Investigate and Predict the Failure of the Four Commonly Used Flat Head Designs in Heat Recovery Steam Generators
Authors: Asadi Mahyar , Henry Jeff , Torkildson Steve , Kashani Majid Tanbakuei , Smith Mathew
Published: October 2017

Failure has been observed to occur on grade P91 alloy flat head closures in Heat Recovery Steam Generators (HRSG), operating at high temperature (>538°C) and high pressure (>125 bar), after a relatively low in-service life. Since creep is expected to be the major failure mechanism, creep analysis and creep life prediction were conducted on four commonly used flat head designs. We have previously shown that failure of welded P91 material is highly dependent on the material properties in the Heat Affected Zone (HAZ). As such we modeled a common multilayer welding procedure to determine the local material properties of both the Coarse Grain and Fine Grain HAZ for each flat head design. Once the final material properties were obtained, we exposed each simulated flat head to typical operational conditions and calculated the total stress (pressure + thermal) and temperature at each node. With this we then used a Deformation Mechanism Map (DMM) for the P91 alloy to determine the creep rate at each node. This allowed us to identify areas that are accumulating creep strain from different creep mechanisms and therefore susceptible to creep and to approximate the creep life.

Finally, a comparison made between the four commonly used flat head designs by ASME to show which design is more desired with respect to welding process.
Investigation of Partial Safety Factor Approach for Flaw Assessment Procedure in Chinese FFS Code
Authors: Han Zhiyuan , Xie Guoshan , Shao Shanshan , Li Zhifeng
Published: October 2017

Partial safety factor (PSF) is a reliability approach for considering the variance of parameters in flaw assessment procedure in major fitness-for-service (FFS) codes, such as recent API579 and BS7910 codes, but is still not adopted in Chinese FFS code GB/T 19624-2005. This study investigated the derivation method for PSFs based on GB/T 19624 procedure. The limit state equations for PSFs calculation were proposed based on GB/T 19624 level 2 failure assessment diagram (FAD). The distribution of random variables was determined according to China’s domestic features. The first order reliability method (FORM) and second order reliability method (SORM) were employed as reliability analysis methods, and the calculated results were both compared with that simulated using Monte Carlo method. The PSFs at different target reliability levels were established and compared with that in API 579 and BS 7910. The method proposed in this study provides a basis for introducing PSF approach into Chinese FFS code.
The Fatigue Threshold Computation of Steel in Hydrogen Environment by Shakedown Analysis
Authors: Huang Song , Chen Zhiping , Su Wenqiang
Published: October 2017

In this paper, the fatigue threshold of steel servicing in hydrogen environment is studied by means of shakedown analysis. First of all, the application of shakedown analysis on the fatigue threshold prediction is reviewed briefly. Secondly, the classical static shakedown theorem for elasto-perfectly plastic structure is modified to take hydrogen’s effect into consideration. In the proposed method, the effect of hydrogen is described by a yield stress associated with hydrogen concentration and hydrogen content in metal is assumed to be composed of the hydrogen in lattice sites and in reversible trap sites. The effect of plastic flow on hydrogen trap density is involved in by considering the plastic strain as the function of residual stress, which is expected to result in a lower bound of the shakedown load. Finally, the fatigue threshold of a steel is computed as example. The performance of the proposed method is discussed and compared with the results from references. The results indicate that the proposed method is of validity.
Numerical Simulation of the Creep Failure of a Steam Reformer Outlet Manifold
Authors: van Zyl Gys , Keltjens Jan , Al-Shawaf Ali
Published: October 2017

After eleven years of service, a through-thickness crack developed at a circumferential welded joint in the outlet manifold of a steam reformer. The crack led to a minor fire and controlled shutdown of the reformer. The manifold was fabricated from cast 20Cr-30Ni-Nb material, with welds from Inconel 617 nickel base filler.

This paper will present the findings of the failure analysis that was performed to ascertain the cause of the incident. A metallurgical failure analysis was performed to determine the damage mechanism and found clear signs of creep damage, highly localized to the weld. Theoretical calculations and finite element analysis were performed to determine the estimated creep rupture life and found that failure occurred long before the minimum estimated end-of-life.

Further numerical simulations were performed to evaluate the effect of an unusually high number of startup/shutdown cycles. The analyses considered elastic-plastic and inelastic (creep) properties of the weld and base materials and simulated a number of operational cycles where thermal and pressure conditions were cycled between ambient and operational.

The simulations found clear evidence that operational cycles contributed to a dramatic reduction in life through the action of repeated cycles of plastic strain, due to a mismatch in the thermal expansion of the base and weld metals, and creep relaxation. The study concludes with recommendations that can be implemented at fabrication to mitigate this mode of damage.
Simplified Analysis of the Rocking Motion of a Cylindrical Tank Focusing on the Role of Dynamical Forces Involved in Rocking-Bulging Interaction
Authors: D’Amico Marta , Taniguchi Tomoyo , Nakashima Teruhiro
Published: October 2017

Evaluation of rocking motion of unanchored cylindrical tanks subjected to the ground acceleration is a main topic in the framework of the seismic vulnerability assessment of this particular kind of structures. Previous researchers basing on a mechanical model including rocking and bulging effects carried out non-linear seismic analyses of the tank-fluid system. However, in order to provide simple tools for the evaluation of the tank response, they neglected the influence of rocking on the tank bulging motion. In this paper, an interesting investigation on the role of inertial and centrifugal forces in the context of the interaction between rocking and translational motions has been conducted by solving the simultaneous dynamic equations of a 2DOF model through a numerical software and comparing results with those of experimental tests. Moreover, employing the dynamic properties governing the tank rocking-bulging motion into the simultaneous equations, a simplified method to determine the tank bulging response and the measure in which it is reduced by the rocking appearance is provided. Validation of the proposed analysis is conducted comparing its results with those computed through an Explicit Finite Element Analysis on a sample tank.
Design of Threaded Closures for High Pressure Screw Plug Heat Exchangers Designed to ASME Section VIII Div. 2
Authors: Sippy Haresh K. , Chandiramani Dipak K.
Published: October 2017

Threaded closures for pressure vessels have been in use for decades. Much work has been done to develop safe threaded closures. Threaded closures are very advantageous when there is a need for opening the vessel at intervals for maintenance purposes.

Heat Exchangers are a typical application where there is a need for opening the vessel to get good access to the inside and outside of the tubes for mechanical cleaning, thus maintaining heat transfer efficiency. These are known as Screw Plug Heat Exchangers and are basically U-tube heat exchangers. The tube side normally operates at high pressure and temperature and is closed by a threaded end closure.

Two problems are often encountered in screw plug heat exchangers. These are:

1. Leakage through the gasket at the tubesheet causing intermixing of shell side and tube side fluids, which is unacceptable

2. Jamming of the threaded plug due to deformation of channel barrel

In an earlier paper (PVP2016-63137) these problems were studied for a vessel designed to ASME Section VIII Div. 1. It was found that leakage through the tubesheet gasket could be eliminated by changing the gasket to a grooved metal gasket with covering layers as defined in ASME B16.20.

Preventing leakage from the tubesheet gasket is extremely necessary to get the ultra-low sulphur requirements for clean fuel.

In the work reported in this paper, a procedure for obtaining leak-free performance on a vessel designed to ASME Section VIII Div. 2 was developed and verified using a prototype.

Code formulae for calculation of thickness of various parts normally consider only the need to limit the component stress to be within allowable limits defined in the Code. Allowable stresses for Section VIII Div. 2 construction may be about 18 % higher than the allowable stress for Section VIII Div. 1 construction at design temperature, thereby allowing thinner sections for the same design conditions.

As the thinner sections would deform more, the likelihood of jamming of the end cover could be more severe in ASME Section VIII Div. 2 constructions. Hence this study was additionally undertaken to verify the adequacy of the earlier proposed design methodology, i.e., use of an additional steel ring shrunk fit to the end of the channel to prevent flaring of the channel and jamming of screw threads, for Section VIII Div. 2 constructions.
Development of Weld Residual Stress Measurement Method for Primed Steels
Authors: Yang Y. P. , Dull R. , Huang T. D. , Rucker H. , Harbison M. , Scholler S. , Zhang W. , Semple J.
Published: October 2017

Welding, as a major manufacturing process in shipbuilding, induces residual stress and distortion that affects buckling strength, fatigue performance, corrosion resistance, and dimensional stability of ship structures. Understanding residual stress in ship structures is required in engineering design to ensure structural strength and safety and is essential in dimensional accuracy for distortion control during fabrication. However, measuring residual stress in ship structures presents unique challenges, such as structure complexity, surface primer, and a non-friendly measurement environment. Fortunately, portable X-ray diffraction equipment has been successfully developed and proven accurate in other industries to measure residual stress. This study is to evaluate the feasibility of measuring residual stress in a shipyard environment in terms of accuracy and adaptability. Typical welded joints (butt joint and T-joint) were selected for evaluation instead of evaluating complicated ship structures. The welded joints were fabricated using common shipyard welding procedures. This makes the evaluation easier since weld residual stress distributions and magnitudes on these joints are well understood. In addition, the hole-drilling method was also used to validate the X-ray diffraction results. Measured results show that X-ray diffraction can penetrate the pre-construction surface primer used in shipbuilding to directly measure residual stress of the metal surface, without the need to remove the surface primer. The residual stress data measured by X-ray diffraction agreed with the data obtained by the hole-drilling method. In addition, the residual stress trend measured by X-ray diffraction agreed with the theoretical residual-stress distributions. This study concluded that a portable X-ray diffraction is a potential technology for residual stress measurement in a shipyard.
Estimation of Q345R Fracture Toughness Based on Master Curve
Authors: Gui Lele , Xu Tong , Shou Binan , Yu Haiyang
Published: October 2017

1T CT specimens are used to evaluate the fracture toughness of Chinese Q345R steel in the ductile-brittle transition regime by Master Curve method. Tensile tests, Charpy impact tests and drop-weight tests of Q345R steel are also carried out to get the ductile-brittleness transition temperature and nil-ductility transition temperature. Master Curves are compared with the empirical formulas adopted in ASME, API and BS codes. Results show that the reference temperature T0 values derived from single-temperature and multi-temperature method by 1T specimen are basically consistent. Master Curve can well envelop the fracture toughness and temperature curves derived from the empirical formulas, and is more economic and flexible than the K1C curve with sufficient conservation.
Short-Term Mechanical Analysis of Polyethylene Pipe Reinforced by Winding Steel Wires Using Steel Wire Spiral Structural Finite Element Model
Authors: Shi Jun , Shi Jianfeng , Chen Hanxin , He Yibin , Wang Qingjun , Zhang Yue , Li Guangzhong
Published: October 2017

Polyethylene pipe reinforced by winding steel wires (PSP) is new type of polymer-matrix composite pipe, which is widely used in petroleum, chemical engineering, and water supply, etc. PSP is composed of a thermoplastic core pipe (HDPE), an outer cover layer (HDPE), and steel wire skeleton sandwiched in the middle. The steel wire skeleton is formed by crossly winding steel wires integrated with HDPE matrix by cohesive resin. In traditional analysis models of PSP, components of PSP were considered linear elastic, and steel wire skeleton was assumed to be orthotropic composite layer based on the classical laminated plate theory. Although achieving good results in engineering applications, traditional models neglected the material nonlinearity of steel wires and HDPE matrix, which was significant to failure analysis. In the present paper, a new finite element model was constructed using commercial software ABAQUS[1], based on the actual steel wire spiral structure of PSP. Steel wires and HDPE matrix were modeled separately, which were both represented by solid elements, and the interaction between steel wires and HDPE was characterized by tie interaction. Experimental result of short-term burst pressure of PSP was used to validate the nonlinear model. Compared with the experimental result, the calculation results of the nonlinear model agreed well. Furthermore, the effect of the nonlinear material property of components on the calculation results were investigated, and the short-term mechanical responses of PSP were determined and analyzed through the nonlinear model.
Evaluation of the Internal Hydrogen-Induced Threshold Stress Intensity Factor in 2.25Cr-1Mo Steels Determined by the Offset Potential Drop Method
Authors: Konosu Shinji , Inoue Takehiro , Murakami Yoshiaki
Published: October 2017

The single specimen offset potential drop method has been applied to obtain the internal hydrogen-induced threshold stress intensity factor KIH in Cr-Mo steels by using small-sized 12.7-mm-thick ASTM CT-specimens (1/2T-CT).The subcommittee on Hydrogen Embrittlement in the Material Division of the Japan Pressure Vessel Research Council (JPVRC) had been investigating internal hydrogen embrittlement by using 25.4mm thick compact tension specimens (1T-CT(1/2): B = 25.4mm, W = 25.4mm, 2H = 30.5mm), to enable an adequate supply of hydrogen from the uncracked region of the specimen near a crack tip to the crack tip zone during the experiment under normal atmospheric conditions.

In the present study, tests were performed on 1/2T-CT specimens under a mixed load control and grip-displacement control aimed at achieving a reduction in the test execution time. It was found that the threshold stress intensity factors for the 1/2T-CT specimens exhibited virtually the same behavior as those obtained in the previous studies using the 1T-CT (1/2) specimens.
Factors Influencing Nut Factor Test Results
Authors: Brown Warren , Long Stewart
Published: October 2017

Nut Factor is used to establish a bolt load for a given applied torque in bolted joint assembly. In previous papers the effects of different factors influencing Nut Factor results were examined, which included the type of anti-seize, bolt and nut material, bolt diameter and amount of anti-seize applied. This paper examines those factors further and then includes additional factors which have been shown to have significant effect on the measured Nut Factor.

The knowledge of these factors has been used to adjust the proposed ASTM specification for determining Nut Factor. It is also relevant to application in the field and to ensure that any testing conducted in a laboratory will be applicable in the field.
Consideration of Yield Discontinuity in the Elastic-Plastic Fracture Analysis of Circumferentially Flawed Pipes
Authors: Wang Longjie , Eren Elvin , Wang Bin , Wu Guiyi
Published: October 2017

This study examined the fracture behaviour of pipes containing surface flaws oriented circumferentially and made from a material that exhibits yield discontinuity (known as Lüders plateau) with the view of making recommendations for the assessment of pipes subject to high level of plasticity.

Starting with the fundamental and first principles, uniaxial tensile tests were carried out with the use of digital image correlation (DIC) to observe the formation and propagation of Lüders bands quantitatively. Finite element (FE) analyses were then carried out to simulate the Lüders banding phenomenon in uniaxial tensile specimens and consequently cracked pipes. Different material models were adopted in FE analyses, including the stress-strain curve with a flat stress plateau neglecting upper yield stress, and the so-called ‘up-down-up’ (UPU) stress-strain curve for refining crack driving force predictions.

The numerical analysis of tensile tests demonstrated that UPU stress-strain model satisfactorily simulated the main macroscopic features of Lüders band observed in the experiment. FE analysis of flawed pipes using both flat and UPU stress-strain curves produced a similar trend in the crack tip opening displacement (CTOD)-strain trajectory as that obtained from large-scale testing. It was seen that the shape of the UPU stress-strain curve, particularly the magnitude of softening, considerably affects the magnitude of crack driving force in the flawed pipe. However, the strain localisation associated with Lüders banding was not observed in the circumferentially flawed pipe in the case of using the flat stress-strain curve. The CTOD crack driving force obtained from simulations was lower than the CTOD obtained from experiments in the Lüders plateau regime, even with the consideration of ductile tearing.

Finally, as a result of this study, recommendations on the optimum choice of material parameters were made for more accurate predictions of crack driving force in the presence of yield discontinuity.
Effects of Secondary Creep Formulation on API 579-1 Residual Life Evaluation
Authors: Scano Lorenzo , Esposito Luca
Published: October 2017

Although several ad hoc procedures are codified into main international standards, the creep life prediction remains a critical phase of each Fitness-For-Service assessment. Commonly, either a time-fraction or a ductility exhaustion approach can be used. In both cases, conservative predictions within a factor of 2 or 3 are expected [1]. However, since the procedures to determine the creep damage are based upon the results of a stress analysis, the residual life evaluation can be affected by the adopted creep formulation. The choice to use a simple modeling, only accounting for the dislocational creep range, could lead to overestimate the component creep life at low stresses, and this is also subtly true even at concentration points if triaxiality or deformation-controlled loading lead to marked stress relaxation over time. In this paper, the tube to header and the header to hemispherical end joints of a HRSG assembly were assessed by the API 579-1/ASME FFS-1 [2] Level 3 procedure, via inelastic FEA, changing the creep formulation to compare the results. The classical Nortons law was replaced by more sophisticated secondary creep models to account for the complex time-dependent stress-field. In particular, the primary and secondary stress re-distribution/relaxation in the creep range were investigated in order to evaluate the impact of the steady-state creep constitutive equation on the residual life prediction.
A Comparative Fatigue Analysis Study Based on RCC-M Code and EN13-445 Standard Through Actual Test Cases
Authors: Billon François , Halleguen Julien
Published: October 2017

This document is aimed at comparing the fatigue analysis methods based on the RCC-M code and on the harmonized standard EN 13445-3 with a view to quantifying the associated deviations and uncertainties, at each step of the calculation, by taking into account every aspect of each code such as calculation thickness of the FE model, physical properties, combination method and fatigue curve.

This comparison study consists in analyzing the 4 Test Cases (TC) described below:

• TC1: Study of the cylindrical-edge transition cone with its upper shell/shell type full-penetration butt weld.

• TC2: Study of the feedwater nozzle (FWN) with its full-penetration weld on the nozzle support ring.

• TC3: Study of the misalignment effect of neutral axes at shell/shell type full-penetration butt weld level.

• TC4: Study of the out-of-roundness effect at shell/shell type full-penetration butt weld level.

The welds considered in this study are full-penetration butt welds whose RCC-M quality is Level 1, whose welding procedure has been qualified, which are dressed, made flush with base metal by grinding and which have been fully (100%) inspected by NDE.
Optimum Design of Pressure Vessels Using Hybrid HGP and Genetic Algorithm
Authors: Abd El-Aziz Khalid M. , Metwalli Sayed M.
Published: October 2017

This paper presents research work about the design and optimization of pressure vessels using Hybrid Heuristic Gradient Projection (HGP), Sequential Quadratic Programming (SQP) and Genetic Algorithms (GA). The design is concerned with the pressure loading conditions, intended internal utility volume, geometrical dimensions and the induced stresses. Cylindrical pressure vessels with hemispherical ends are considered. They are required to hold a definite volume under a specific pressure. The thicknesses of each hemispherical part and the cylindrical part satisfy the recommended ASME code. The design also satisfies allowable stress constraints. The design multi-objectives are to generate the optimum geometry to satisfy required specifications, performance and cost requirements. A developed HGP, SQP and GA algorithms are utilized to perform the optimization. The efficiency of the procedure is indicated and the optimum results in the form of optimum design charts are presented.
Control of Retained Delta Ferrite in Type 410 Stainless Steel
Authors: Stone David J. , Alexandrov Boian T. , Penso Jorge A.
Published: October 2017

Type 410 stainless steel is used in petro-chemical refineries for its high resistance to halide stress corrosion cracking, sulfide corrosion cracking, and sulfur attack at elevated temperatures. Along with its adequate corrosion resistance 410SS also exhibits low cost and hardenability making it an ideal material for hydro-processing applications. Problems related to meeting toughness and hardness code requirements within the weld metal and heat effected zone (HAZ) have been experienced during fabrication of 410SS welded components. The loss of toughness has been related to excessive amounts of delta ferrite in the weld metal and HAZ. The objective of this study was to quantify the effect of cooling rate and alloying compositions within ASTM and AWS specifications for 410SS on delta ferrite formation. C, Cr, Ni, and Mo, were used as factors in a model-based design of experiment (DOE) within CALPHAD based software DICTRA™ to simulate the effects of composition and cooling rate on delta ferrite formation. Based on the DOE results, a predictive model for quantification of retained delta ferrite in 410SS welds was developed along with evidence for cooling rate effect on retained delta ferrite. Optical metallography was also used to demonstrate possible ferrite content within the 410 composition range.
Quantifying Bolt Relaxation During High Temperature Operation
Authors: Brown Warren , Lim Tze-Yew
Published: October 2017

This paper presents a summary of recent testing into bolt relaxation, which occurs at temperatures above 230°C (450°F). Bolt relaxation is problematic for pressure boundary bolted joints as it can lead to joint leakage in the longer term. In addition, it should be a major consideration at the design phase, with selection of the appropriate bolt material limited not by the creep or yield limit of the material, but by the point where bolt relaxation becomes significant.

Preliminary test results for different bolt materials at different temperatures are presented in this paper. The test results allow for some very high level observations regarding the acceptable design limits for different bolt and nut material combinations.
Development for Manufacture of Refining Reactors Made of 9Cr-1Mo-V Steel
Authors: Nakanishi Tomoaki , Terada Susumu , Yamada Masato , Ikeuchi Tadashi , Maeda Ikuo , Ikeda Tetsunao , Yamashita Ken , Miyamura Takeo , Nanba Shigenobu
Published: October 2017

9Cr-1Mo-V steel, which was developed for application as a steam generator for fast breed reactors in the 1970s, has a higher strength at high temperatures and has been used for equipment and piping systems in the fossil power industries. ASME, Section VIII, Division 2 [1] gives 9Cr-1Mo-V steel a maximum design temperature of 649°C and an operating temperature of 500°C. And it has higher allowable stresses at 450°C or over, compared to 2¼Cr-1Mo-V steel. Therefore, if this material can be used, more economical pressure vessels operating at 454–500°C can be designed and manufactured.

In our previous study for base metal, a large forged shell ring of 9Cr-1Mo-V steel was manufactured and for base metal welding, cracking susceptibilities and weldability were investigated. For overlay, welding consumables with high resistance to sigma phase embrittlement were developed [2]. In this study, highly efficient welding consumables for tandem SAW designed for circumferential welding of heavy wall shells were developed and welding using the full-scaled shell ring was demonstrated, and then the mechanical properties of the weld metal were evaluated. Results indicated that, regardless of the weld thickness, a minimum of 8 hours postweld heat treatment (PWHT) at 745°C was required to meet hardness and toughness requirements for conventional reactors. The strength of the materials can comply with the Code requirements after 3 cycles of PWHT considering the PWHT in fabrication and after weld repair.

Furthermore, the following new Code Cases and Code revision were proposed and approved in order that pressure vessels can be designed in accordance with ASME, Section VIII, Division 2.

• New Code Case for Fatigue Evaluation

• New Code Case to apply SA-336-F91 in ASME Section VIII, Division 2

• Revision of Table 5A to add SA-336-F91

As a result, it has become possible to design and manufacture refining reactors to operate at 454–500°C.
Study on the Relation Between Side Ratios of Rectangular Cross Sections and Secondary Vortices at Trailing Edge in Motion-Induced Vortex Excitation
Authors: Matsuda Kazutoshi , Kato Kusuo , Arise Kouki , Ishii Hajime
Published: October 2017

According to the results of conventional wind tunnel tests on rectangular cross sections with side ratios of B/D = 2–8 (B: along-wind length (m), D: cross-wind length (m)), motion-induced vortex excitation was confirmed. The generation of motion-induced vortex excitation is considered to be caused by the unification of separated vortices from the leading edge and secondary vortices at the trailing edge [1]. Spring-supported test for B/D = 1.18 was conducted in a closed circuit wind tunnel (cross section: 1.8 m high×0.9 m wide) at Kyushu Institute of Technology. Vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex excitation is calculated as Vr = 1.67×B/D = 1.67×1.18 = 2.0 [1], vibrations around Vr = 2 were considered to be motion-induced vortex excitation. According to the smoke flow visualization result for B/D = 1.18 which was carried out by the authors, no secondary vortices at the trailing edge were formed, although separated vortices from the leading edge were formed at the time of oscillation at the onset wind speed of motion-induced vortex excitation, where aerodynamic vibrations considered to be motion-induced vortex excitation were confirmed. It was suggested that motion-induced vortex excitation might possibly occur in the range of low wind speeds, even in the case of side ratios where secondary vortices at trailing edge were not confirmed.

In this study, smoke flow visualizations were performed for ratios of B/D = 0.5–2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re = VD/v = 1.6×103. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D = 0.02–0.15. Spring-supported tests were also carried out in order to obtain the response characteristics of the models.
Fracture Toughness Evaluation of Neutron-Irradiated Reactor Pressure Vessel Steel Using Miniature-C(T) Specimens
Authors: Ha Yoosung , Tobita Tohru , Takamizawa Hisashi , Nishiyama Yutaka
Published: October 2017

The applicability of miniature-C(T) (Mini-C(T)) specimens to fracture toughness evaluation was investigated for neutron-irradiated reactor pressure vessel (RPV) steel. By carefully selecting the test temperature, valid fracture toughness and reference temperature (To) were determined successfully with a relatively small number of specimens. The value of To determined using irradiated Mini-C(T) specimens was in good agreement with that determined using irradiated pre-cracked Charpy-type (PCCv) specimens. In addition, the scatter of the 1T-equivalent fracture toughness values obtained using the irradiated Mini-C(T) specimens was not significantly different from that obtained using the irradiated PCCv and other larger unirradiated specimens. The To values determined using Mini-C(T) specimens agree very well with the correlation between the Charpy 41J transition temperature and the To of commercially manufactured RPV steels reported in the past.