bluuebunny/crossref_metadata_2025 huggingface dataset:
Composite Overwrapped Pipe Burst Test
Authors: Littlefield Andrew , Smith Lucas , Macri Michael , Root Joshua , Bartolucci Stephen
Published: October 2020

With the emphasis on lightweighting, composites are being turned to for help to reduce weight while still maintaining strength and stiffness. However, composites tend to be linear elastic to failure so there is often no warning of failure unlike in metallic components. For this research, a pipe section was fabricated from an Inconel 718 liner with a carbon composite overwrap. The pipe was instrumented and then subjected to increasing internal pressure until failure. The carbon composite was composed of IM7 fibers in a geopolymer matrix. Since the exact properties of the composite were not initially known, a simple laminate model of the tube was done using carbon-epoxy data. This resulted in an over prediction of the failure load. The exact material used was tested and a new laminate model was created that better matched the experimental results. The results from the experiment and laminate model were used to assist in the creation and validation of a finite element model of the experiment. The model makes use of advanced numerical techniques to predict when failure will occur. The failed specimen was then analyzed to determine failure mechanism and quality of the composite wrap. This paper will present the fabrication, modeling, testing and failure analysis of this effort.
Venting Manhole Cover: A Nonlinear Spring-Mass System
Authors: Tijsseling Arris S. , Vasconcelos Jose G. , Hou Qingzhi , Bozkuş Zafer
Published: October 2020

Manholes are vertical shafts connecting underground sewers with street-level terminals. They are covered by heavy lids. During periods of heavy rainfall, the air column in the upper part of the manhole may be compressed to such high level that the lid moves up. Of course, this is a dangerous situation for pedestrians and road traffic. Bolting the lid may provide a solution to the problem, but it is known that air pressurization underneath can result in structural damage.

A simple model is proposed to describe the lifting of the lid (manhole cover). When the lid moves up, air is allowed to escape so that the lifting pressure decreases and the lid moves down, whereupon the air pressure increases again. This repetition might lead to the realistic phenomenon of the dancing manhole cover. Since the model is strongly nonlinear, interesting dynamic behavior is expected.
Strength Analysis and Influence Factors Research of Carbon-Fiber Wound Composite Gas Cylinder With Aluminum Liner
Authors: Wang Zunwu , Duan Chenghong , Luo Xiangpeng
Published: October 2020

The carbon-fiber wound composite gas cylinder with aluminum liner is a kind of the commonly used composite material wound gas cylinder, which has the advantages of light weight, high strength and high explosion resistance, and it has been widely used in aviation, chemical industry and other industries. As the application conditions of composite gas cylinder are more and more strict, the strength requirements of composite gas cylinder are higher, and the composite layer parameters in the manufacturing process are important factors that affect the strength of composite gas cylinder. In this paper, the finite element model of a carbon-fiber wound composite gas cylinder with aluminum liner is established by using APDL (ANSYS Parametric Design Language), and the stress distribution rules of aluminum liner and composite of gas cylinder under the conditions of autofrettage pressure, zero pressure, working pressure, hydrostatic test pressure and minimum bursting pressure is studied. The strength of the gas cylinder is evaluated according to the “DOT-CFFC” Code (basic requirements for fully wrapped carbon-fiber reinforced aluminum lined cylinders). In addition, influence rules of composite layer structure of winding mode and autofrettage on the strength and bearing capacity of gas cylinder is further explored. The work could provide reference for the practical application of carbon-fiber wound composite gas cylinder with aluminum liner.
The Effects of Material Properties on Crack Tip Constraint and CTOD Fracture Toughness for Commonly Used Pipelines Steels
Authors: Zhang Yinhui , Shuai Jian
Published: October 2020

As the main transportation carrier of oil and gas, pipelines play a very important role in the petroleum industry. When the crack-containing pipelines subjected to external loads, the cracks may propagate gradually, and result in serious failure eventually. Therefore, accurately obtaining the fracture toughness is very essential for the safety assessment of the crack-containing pipelines. However, the fracture toughness is not a material intrinsic parameter, but heavily depends on the constraint. To obtain the accurate relationship between the constraint and the fracture toughness for different materials, it is necessary to determine the effects of different material parameters on the change characteristics of the constraint and the fracture toughness.

In this work, the commonly used pipelines steels are selected as the research materials. The SENB specimens and the complete Gurson model are used to conduct the simulation with ABAQUS. The material parameters analyzed include strain hardening exponent, yield strength and initial void volume fraction. The results show that for the thinner specimen, the higher strain hardening capacity will result in lower constraint. The higher strain hardening capacity will result in higher constraint for the thicker specimen. For the thinner specimen, the constraint is approximately the same for the materials with different yield strength. The constraint will decrease with the increase of yield strength for the thicker specimen. In the middle range of the thickness of specimen, higher initial void volume fraction will result in higher constraint. For the thicker and thinner specimen, the effect of initial void volume is very weak. As the increase of strain hardening capacity and yield strength, the decreasing degree of the fracture toughness becomes higher in the increasing process of the constraint. A higher initial void volume will result in a lower decreasing degree of the fracture toughness. All of the results indicate that the strain hardening capacity is the main factor affecting the constraint and the fracture toughness. The initial void volume also has a significant effect on the fracture toughness. For the relationship between the constraint and the fracture toughness, the main affecting factor is the strain hardening capacity.
Comparative Study on the Nonlinear Calculation of Ratcheting Deformation Using Different Constitutive Model
Authors: Shao Xuejiao , Xie Hai , Xiong Furui , Fu Xiaolong , Shi Kaikai , Yu Xiaohuan
Published: October 2020

In the fatigue assessment of nuclear components following the RCC-M B3200, if the results using the simplified elastic-plastic method cannot meet the Code’s requirements, it is necessary to conduct a detailed elastic-plastic fatigue analysis of the component. In this paper, the A-F and Chaboche nonlinear kinematic hardening constitutive models are used to conduct an elasto-plastic fatigue analysis for a typical nozzle component, aiming to calculate the secondary cumulative cyclic plastic strain of the structure induced by the rapid temperature change transient.

The calculation method of nonlinear ratcheting behavior under cyclic loading is studied. The method of determining the parameters of constitutive model based on cyclic stable stress-strain curve is also studied. A sensitive study of the parameters for the same constitutive law is presented, including the results of cumulative plastic strain. The ratcheting behavior simulation calculated by different constitutive models are compared. The results show that the A-F model has a conservative prediction of ratcheting behavior as the dynamic recovery term is too strong. It was found that the Chaboche constitutive model is the better methodology for ratcheting analysis.

In order to evaluate the bearing ability of the section, the membrane strain and bending strain is obtained by linearizing the node strain along the cross section. The ratios of membrane strain and membrane plus bending strain to total strain are calculated, which is helpful to determining the limit criteria for the cumulative strain of structures.
FEM Stress Analysis and Leakage Behavior of Pipe-Socket Threaded Joints Subjected to Bending Moment and Internal Pressure
Authors: Nagata Satoshi , Fujita Shinichi , Sawa Toshiyuki
Published: October 2020

This paper is a report of the studies on the mechanical behaviors and leakage characteristics of pipe-socket threaded joints subjected to bending moment as well as internal pressure by means of experimental tests and finite element simulations. The paper dealt with the 3/4″ and 3″ joints, and the joints for both sizes have two different combinations of thread types in the pipe and socket, i.e. taper-taper thread combination or taper-parallel one, respectively. Experimental bending leak tests showed that the taper-taper joints could retain internal pressure under bending load up to nearly plastic collapse. The taper-parallel joints, however, could hardly keep internal pressure against bending moment even the sealing tape was applied to enhance the sealing performance. Finite element analysis was carried out to simulate those bending tests, especially to clarify the deformation and the stress distribution in the engaged threads in detail. The analysis demonstrated that the sealing performance of the joints highly depend on the contact conditions not only at the thread crest to thread root but also in between flank surfaces. A complicated leak path across the engaged threads under bending moment was identified by the simulation.
Effect of Hydrogen Content in Natural Gas Blend on the Mechanical Properties of a L485-MB Low-Alloyed Steel
Authors: Ez-Zaki Hamza , Christien Frederic , Bosch Cédric , Briottet Laurent , Bertin Maxime , Levasseur Olivier , Leriverain Alain
Published: October 2020

The purpose of the present work is to study the effect of the hydrogen content in a H2-NG (Natural Gas) blend on the mechanical behavior of a C-Mn low alloy steel L485-MB (NF EN ISO 3183) under monotonic loading. Different testing conditions were explored for the blend: 2% H2-NG, 25% H2-NG, 100% H2 and 100% NG at a total pressure of 8.5 MPa using two slow strain rates: 10−4 s−1 and 10−6 s−1. Tests in the blend were compared to those under pure hydrogen at the same partial pressures. Furthermore, two surface roughnesses have been explored, one corresponding to a mirror polish, the other as lathed. The embrittlement has been assessed by necking measurements and fracture analysis for the whole testing conditions. The results show a drop of ductility with the increase of partial pressure of hydrogen in NG. Besides, no significant effect of hydrogen were observed on flow stress. In addition, the L485-MB pipeline steel presents a shear type fracture mode in high partial pressure of hydrogen, whereas a cup and cone type fracture were observed in air, NG and low partial pressure of hydrogen in NG (0.2 MPa H2).
A New Proposal to Obtain the CTOD Fracture Parameter for Offshore Pipeline Steels by Using Only One Clip Gage
Authors: Silvestre Marcus Nathan , Sarzosa Diego F. B. , Hertelé Stjin
Published: October 2020

The production and exploitation of oil and natural gas reserves environmentally challenging regions imposes many technological challenges related to new design requirements. Engineering Critical Assessment (ECA) is an umbrella term for complex methodologies used o assess the criticality of defects in welded structures. ECA is commonly used for oil and gas industry to derive tolerable defect sizes during installation and operation of risers. Current standardization efforts make extensive use of single edge notch tension (or SENT) specimen to reduce the level of conservatism during the assessment. A great effort has been made to evaluate CTOD as a mean to assess fracture toughness, especially for offshore structures. The double clip gage method (DCGM) is an alternative CTOD test method, which produces less conservative values comparing with J-integral conversion into CTOD. In this paper, a novel CTOD definition is developed according to the philosophy of the DCGM, but requiring a single clip gauge and providing values similar to the J-integral converted CTOD. Further details need to be validated and studied to increase the applicability of the previous proposal. So, motivated by the earlier explanation, the goal of this paper is to present a new methodology to estimate the CTOD using geometrical relationship on crack opening displacement over the crack flank.
Rapid Prediction of High-Temperature Properties of Furnace Tube Alloys Using Deep Learning Approaches
Authors: Xiang Shulin , Chen Tao , Fan Zhichao , Chen Xuedong , Wu Zhigang , Lian Xiaoming
Published: October 2020

With the development of Materials Genome Initiative (MGI) and data mining technology, machine learning (ML) has emerged as an important tool in the research of materials science. For the heat resistant alloys used in furnace tubes, the rapid prediction of the high-temperature properties is critical but difficult until now. In this work, the ML method based on the deep learning algorithm is developed to establish the direct correlation between microstructure inputs and output stress rupture properties of Fe-Cr-Ni based heat resistant alloys. Two simple convolutional neural networks (CNN) and the complex network with VGG16 architecture are implemented and evaluated. The simple CNN and VGG16 models are trained from scratch and pre-trained, respectively. Due to the relatively few training samples in the dataset, the data augmentation configuration and the improved architecture are effective to mitigate overfitting in simple CNN models. The result also shows that in the case of transfer learning, the features extracted from other datasets can be used directly to this new visual task. It is demonstrated that both the simple CNN and VGG16 models reach the high prediction accuracies (more than 90 %) of high-temperature properties with a wide range of microstructures. In addition, the good prediction performance achieved in the small dataset also reveals the deep learning approaches can be used to construct powerful vision models in engineering practice, where very limited data is the common situation.
Development of Stress Intensification Factors for Collared Type Piping Joints
Authors: Ewing Cameron
Published: October 2020

Stress Intensification Factors or SIFs allow piping to be analyzed using beam theory, with a SIF representing local effects of specific piping geometry. However, the current piping codes do not explicitly provide SIFs for collared type piping joints for use in pipe stress calculations.

The objective of this paper is to describe the methodology on how a finite element analysis (FEA) was to model the behavior of collared joints, and to ultimately develop appropriate SIFs that can be used in pipe stress analyses.

This paper describes a real-life analysis example on collared joints installed on a set of existing fuel transfer lines. The lines, which ranged in size from DN200 to DN350, were concrete lined carbon steel with the collars fillet welded to the carbon steel section of the piping.

Test coupons cut from existing pipe-collar sections were tested in a laboratory to determine the forces required to break the collar welds. Using FEA, the same test coupons were modelled to replicate the failure tests.

Multiple iterations were undertaken to determine an appropriate bi-linear stress-strain curve fit for the weld material. The curves of different weld electrode materials were considered. The curve which lead to results similar to those observed in physical testing was selected. From this, a failure stress across the weld could be determined. This stress, 435MPa was then used in subsequent models to determine the point at which the weld fails under bending loads. Multiple tests were analyzed to allow for possible effects of inclusions and voids.

Finite element models of the collar geometries were constructed and non-linear analyses were undertaken using the weld strengths determined from the coupon testing data. A simple cantilever type arrangement with a point load at one end was analyzed, inducing a bending moment across the collar.

The peak stress resulting from the bending moment across the collar weld at the center of the cantilevered pipe arrangement, was investigated across various pipe diameters, wall thicknesses, weld sizes and collar geometries.

Based on the results, a relationship between the pipe geometry and SIF was developed. Hence a pipe stress model of the transfer lines could ultimately be developed using these SIFs to predict the behavior of the piping.
GRP Composite Pipe Elbows Subject to an Internal Pressure and In-Plane Bending: An Experimental Study
Authors: Ellul Grech Brian , Dimech Michael A. , Camilleri Duncan , Muscat Martin
Published: October 2020

The use of polymer composite materials in the piping industry is increasingly gaining popularity. However, the design rules of these novel materials are relatively more complex and high safety factors are applied, requiring costly experimental validation. Experimental tests on e-glass reinforced polymer (GRP) pipe elbows is limited and in view of these challenges, this study presents a set of experimental results obtained from a series of pressurization and in-plane bending tests of polyester pipe elbows reinforced with e-glass chopped strand and woven roving mats. Details of the specimen manufacturing procedure, testing fixture and loading setup, are also given. A data acquisition system was setup to control, monitor and record the applied loads, the resulting meridional and hoop strains around the mid-plane of the elbows. A total of 3 specimens were tested where the first specimen was subject to an increasing positive pressure until global failure and was used to serve as a benchmark for the other two specimens. The latter were similarly subject to a positive pressure limited to the first-ply-failure load region established from the initial test. Both specimens were unpressurized and then subjected to a two cycle opening and unloading in-plane bending moment. Results show that the GRP pipe elbows were capable of sustaining loads beyond the identified failure initiation and successive bending cycles produced pipe elbow stiffening effect.
Fatigue Assessment of Installed Thermowells: Fatigue Stress Evaluation Based on In-Situ Vibration Measurements and Dedicated Models
Authors: van Beek Pieter
Published: October 2020

For measurement of the gas temperature inside process piping, temperature sensors are installed in a thermowell. In most cases these cylindrical thermowells are installed perpendicular to the flow direction. Declining pressures of many aging oil & gas assets results in higher gas velocities. This will increase the so-called Strouhal frequency and amplitude of the dynamic forcing at the thermowell. If the frequency of this force coincides with the installed resonance frequency of the thermowell, this can lead to fatigue failure.

The design of thermowells is comprehensively described in ASME PTC19.3 TW Code. In a recent version the excitation of the so-called in-line resonance condition was introduced, which already occurs at half the flow velocity of the original transverse resonance condition. As a result, many already installed thermowells do not pass the so-called ‘frequency criterion’ anymore. However, when all other criteria in the ASME Code are passed, the thermowell may operate at higher flow velocities, only if the fatigue stress remains acceptable.

When calculating the fatigue stress with the tools as provided in the Code, in many cases this will lead to prediction of unacceptable fatigue stresses. Therefore, here a more detailed fatigue assessment method has been developed. It consists of in-situ vibration measurements at the tip of the thermowell and a numerical evaluation with a detailed FE model of the installed thermowell. With this approach the fatigue stress is then calculated and judged against a fatigue limit.

In the meanwhile, this detailed assessment method has been successfully applied to numerous high pressure, gas filled installations. In most cases this led to acceptable fatigue stresses and preservation of the desired gas production profiles.
Research and Development of Three-Dimensional Isolation System for Sodium-Cooled Fast Reactor: Part 6 — Development of High Speed Oil Damper for Isolated Building
Authors: Fukasawa Tsuyoshi , Somaki Takahiro , Miyagawa Takayuki , Uchita Masato , Yamamoto Tomohiko , Miyazaki Masashi , Okamura Shigeki , Fujita Satoshi
Published: October 2020

The design of seismically isolated structures has been required not only for damping devices with large damping capacities but also for those with high allowable velocities. This is because the seismic response assessment has been conducted using various ground motions, with high acceleration levels, to increase the structural integrity of buildings and components. However, the research focused on increasing the allowable velocity remains to be largely limited because the research involves a testing machine problem as well as a technical problem to increase the allowable velocity.

To solve these problems, the authors have developed a new oil damper for seismic isolation buildings with an allowable velocity that is two times higher than commercially available oil dampers, which is the largest damping capacity class in Japan, using the test machine with one of the largest dynamic loading performance in the world. This paper demonstrates the availability of the proposed oil damper through the following items:

The first is to clarify the damping force characteristics on the basis of the test results up to the maximum input velocity of 2.7 m/s. The second is to present the analytical model for the oil damper to apply to the seismic response analysis including the method to identify its variables. The third is to demonstrate the isolation performance through the seismic response analysis using the analytical model identified the variables obtained from the test results.

These results imply that the proposed oil damper will be able to contribute to expanding the feasible design range for the isolation technology as well as increasing the seismic safety margin of the components for SFR.
Study on the Predictive Evaluation Method of Load Acting on the Roof and Internal Components of Cylindrical Tanks by Nonlinear Sloshing
Authors: Morita Hideyuki , Takata Tomoshige , Madokoro Hideki , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko
Published: October 2020

When cylindrical tanks installed in the ground, such as oil tanks and liquid storage tanks, receive strong seismic waves, including the long-period component, motion of the free liquid surface inside the tank called sloshing may occur. If high-amplitude sloshing occurs and the waves collide with the tank roof, it may lead to accidents such as damage of the tank roof or outflow of internal liquid of the Tank. Therefore, it is important to predict the wave height of sloshing generated by earthquake motions.

Sloshing is a type of vibration of free liquid surface, and if the sloshing wave height is small, it can be approximated with a linear vibration model. In this case, the velocity-response-spectrum method using velocity potential can estimate the sloshing wave height under earthquake motions. However, if the sloshing wave height increases, the sloshing becomes nonlinear, and necessary to evaluate the wave height using other methods such as numerical analysis. Design earthquake magnitude levels in Japan tend to increase in recent years, long-period components of earthquake wave which act on the sloshing wave height also increase instead of introducing seismic isolation mechanisms. To evaluate load acting on the internal components of cylindrical tanks by nonlinear sloshing, there are few applications which quantitatively evaluated the crest impact load of nonlinear sloshing.

In order to evaluate the load acting on the internal components of cylindrical tanks, the range of applicability of the fluid flow analysis method which validated the analysis accuracy of impact load acting on the roof in a simple cylindrical tank in the past study (PVP2019-93442) is extended to cylindrical tanks with internal components.
Effect Ultrasonic Nanocrystal Surface Modification (UNSM) Treatment on Fatigue Strength of Additive Manufactured UNS S31603
Authors: Pyun Young Sik , Karimbaev Ruslan , Choi Seimi , Ro Jun Suek , Sanseong Choong Ho , Sembiring Jan , Kim Jong Seog , Amanov Auezhan , Kang Suk Hoon , Ahn Hee Sung
Published: October 2020

Additive Manufacturing (AM) which is also known as metal 3D printing technique is one of the promising manufacturing processes due to the capability to process a complex geometry component. This is implemented in wide range of applications in various industries such as automotive, aerospace, power plants, etc. The aging nuclear power plant components and the obsolescence of those components has become a concern in this industry, and AM has come as an alternative solution for this matter. The Board on Pressure and Technology Codes and Standards (BPTCS) and Board on Nuclear Codes and Standards (BNCS) Special Committees started to study the application of Powder Bed Fusion (PBF) technique for pressure retaining equipment made from UNS S31603. Also, later Korean International Working Group (KIWG) was also started a Task Group on Additive Manufacturing for Valves which focusing on Powder Bed Fusion (PBF) and Direct Energy Disposition (DED) process for pressure-retaining valve manufacturing especially for nuclear power plant application with the same material. However, the poor mechanical properties and performance, especially fatigue strength of AM materials become a concern due to the defects and flaws as the results of layering and multiple interfaces and welding related discontinuities. In this study, the fatigue strength of PBF and DED manufactured and Ultrasonic Nanocrystal Surface Modification (UNSM) treated UNS S31603 austenitic stainless steel was investigated.
Evaluation of Crack Growth Rate of Neutron Irradiated Austenitic Stainless Steels at High Stress Intensity Factor Levels
Authors: Seto Hitoshi , Koshiishi Masato , Tanaka Shigeaki , Obata Ryoji
Published: October 2020

Crack growth rates (CGRs) at high K levels (more than 30 MPa·m0.5) were obtained in simulated boiling water reactor normal water chemistry under constant K conditions for Type 316NG stainless steel irradiated up to 2.0 dpa. Valid CGRs were obtained even at high K conditions such as K ≈ 40 MPa·m0.5 although branching was observed on the fracture surface of the specimen after CGR testing. CGRs were compared with predictions by a theoretical model and a disposition curve and it was found that these predictions are applicable even to high K levels around K ≈ 40 MPa·m0.5.
Analysis of Seismic Experiment of Hexagonal Multi Bundle Model Using Core Assembly Mock-Up
Authors: Iwasaki Akihisa , Matsubara Shinichiro , Harada Hidenori , Yamamoto Tomohiko
Published: October 2020

The fast reactor core is composed of hundreds of core elements that stand independently on the core support plate, but does not have support to constrain vertical displacement in order to avoid effects such as thermal elongation. When the earthquake occurs, the group vibration behavior is shown, including the rising of core elements in vertical direction, the collision with adjacent core elements in horizontal direction, and the fluid structure interaction. The three dimensional core group vibration analysis code (REVIAN-3D) was constructed to evaluate them. In the case of fast reactor cores in Japan, the horizontal displacement of core elements at the outermost periphery is restricted by the core former (core barrel). However, since there is no core former in fast reactors other than Japan and the boundary conditions are different from those in Japan, the vibration behavior also differs.

In this study, to grasp and estimate the group vibration behavior with and without a core former under the earthquake motion, seismic experiment of hexagonal multi bundle model using core assembly mock-up was conducted [1]. These test results show that the horizontal displacements are larger and impact force between pads of core assembly mock-up is smaller without the core former. In this paper, the analysis was verified by group vibration tests with and without a core former.
Uplift Deformation of the Bottom Plate of the Cylindrical Shell Tanks Under Steady-State Response of Tank Rocking Motion
Authors: Yoshida Yuichi , Taniguchi Tomoyo , Nakashima Teruhiro
Published: October 2020

The uplift phenomenon of a flat-bottom cylindrical shell tank is a long-term unsolved problem. In this study, uplift deformation of a tank bottom plate calculated by an explicit finite element analysis (refer to PVP2016-63916) is observed, and a hand calculating model based on Euler–Bernoulli beam theory is examined by comparing with the results of the numerical analysis. First, this study analyzes the results of uplift displacement and uplift width calculated by the FE analysis. Then, the results of the relationship between the uplift displacement and the uplift width are observed. Moreover, comparing the results of the maximum uplift width of a thick bottom plate case and a thin bottom plate case, trends of the maximum uplift width that depends on the thickness of the tank bottom plate are obtained.

Seconds, this study tries to verify the hand calculating model based on Euler–Bernoulli beam theory. Compering the results of the deformation of the tank bottom plate calculated by the hand calculation and the FE analysis, accuracy of the hand calculating model is examined. The comparison implies that the hand calculating model may be able to estimate uplift deformation of the tank bottom plate until the uplift displacement of the juncture reaches some height even though the geometrical nonlinearity is not considered.
Estimation of Tightness of Bolted Flange Connections Subjected to Combined Loads of Axial Load and Bending Moment
Authors: Kobayashi Takashi , Nogi Ryosuke
Published: October 2020

This paper deals with the safety evaluation of bolted flange connections subjected to combined loads of axial load and external bending moment. Bolted flanged connections sometimes experience bending moments exerted by the wind load or earthquakes under working conditions. Under these circumstances, leakage accidents may occur. Therefore, it is important to understand the sealing capacity under the combined load of axial load and bending moment.

The purpose of this study is to examine the minimum gasket stress to maintain the tightness of bolted flange connections when subjected to combined loads of axial load and bending moment. Bolted flange connections with gaskets were prepared for this purpose. The bolted flange connection was pressurized and subjected to the combined load. The pressure decays were measured with a pressure transducer and the leak rates were also measured using a mass flow meter. The relationship between the measured results and the combined load were examined and the combined load when large leakage caused was determined. The effects of gasket type and flange type were also examined.

The finite element analysis of the contact stresses of the bolted flange connection was carried out using ANSYS. The gasket stress distribution when the tightness of flange connection is lost was clarified. Summarizing the experimental and analytical results, the initial tightening force to maintain the tightness under combined load of axial load and an external bending moment is discussed.
Estimation of Uniaxial Material Properties by Miniature Small Punch Testing to Support Post-Irradiation Examination of RPV Steels
Authors: Holmström Stefan , Martin Oliver , Bakker Theo , Kolluri Murthy , Bruchhausen Matthias
Published: October 2020

The small punch (SP) test technique is expected to become a more common tool for estimating tensile properties since the technique has been approved for standardization and will be published early 2020 as EN-10371. The testing technique is naturally of interest in the nuclear field due to the small amount of material needed for estimating the properties of both virgin and irradiation damaged materials. In the project STRUMAT-LTO, supported within the Sustainable Nuclear Energy Technology Platform (SNETP), there is intention to use both miniature uniaxial test specimen as well as miniature SP specimen to assess the influence of high fluence irradiation on mechanical properties of the samples of the joint NRG-JRC irradiation campaign LYRA-10. The alloys represented in the irradiation campaign are variations of VVER and PWR reactor pressure vessel steels with tailor made chemical compositions. Four of the PWR model steels are tested here with miniature uniaxial specimens using the SP technique at room temperature (RT) and 100°C in as-received material state and at RT for heat treated (450°C / 40 h) material. The SP samples were extracted from used KLST (miniature Charpy) specimens. The results of this test program are expected to provide the basis for the future development of material property determination of irradiated materials.
Allowable Stress Development of Diffusion Bonded Alloy 800H for Section III
Authors: Mahajan Heramb P. , Jentz Ian , Hassan Tasnim
Published: October 2020

There is increased interest in the application of compact heat exchangers (CHXs) for nuclear service given their high thermal efficiency and compactness. CHXs are fabricated by joining a stack of etched plates with dense microchannels through diffusion bonding. Diffusion bonding material has basic mechanical properties that differ from a base material, requiring appropriate mechanical properties and allowable stresses for design. Existing nuclear code ASME Section III, Division 5 does not address diffusion bonded materials . Hence, there is a need to develop material properties and allowable stresses of diffusion bonded materials and weldments. In this paper, one candidate material, Alloy 800H, was selected for diffusion bonding trials. Preliminary results obtained from a series of tensile and creep tests suggest that the diffusion bonded material is weaker than the base metal 800H. These experimental data are used in determining recommended allowable stresses of the diffusion bonded 800H material. In this paper, tables of the strength reduction factors for various allowable stresses which includes Smt, So, St, Sy and Su for diffusion bonded Alloy 800H are presented. These reduction factors are applicable to CHX design. The Larson Miller Parameter (LMP) is used to extrapolate short term creep tests to longer creep life and lower temperatures, and estimate the onset of tertiary creep strain.
Mechanical and Microstructural Characterization of Diffusion Bonded 800H
Authors: Mahajan Heramb P. , Elbakhshwan Mohamed , Beihoff Bruce C. , Hassan Tasnim
Published: October 2020

Compact heat exchangers have high compactness and efficiency, which is achieved by joining a stack of chemically etched channeled plates through diffusion bonding. In the diffusion bonding process, compressive stress is applied on plates at elevated temperatures for a specified period. These conditions lead to atomic diffusion, which results in the joining of all plates into a monolithic block. The diffusion bonding temperatures are above recrystallization temperatures, which changes the mechanical and microstructural properties of the bonded metal. Hence, diffusion bonded material needs mechanical and microstructural property evaluation. In this study, Alloy 800H is selected to study the influence of the diffusion bonding process on mechanical and microstructure properties of base metal. A series of tensile, fatigue, creep, and creep-fatigue experiments are conducted on base metal 800H (BM 800H) and diffusion bonded 800H (DB 800H) to explore the mechanical properties. Microstructure evolution during diffusion bonding is studied and presented in the paper. The mechanical and microstructural observations indicated ductile fracture at room temperature and brittle failure with bond delamination at elevated temperatures. The microstructure evolution during diffusion bonding is studied through tensile, fatigue, creep and creep-fatigue tests, and the implied root causes for the mechanical property changes are investigated. Efforts are made to correlate the microstructure change with mechanical property change in DB 800H.
Diffracted Blast Loads Behind Structures
Authors: Geng Jihui , Thomas J. Kelly
Published: October 2020

An incident blast wave interacting with a building will diffract around the side walls and roof, resulting in reduced blast loads on the back wall. There is also a region behind the back wall where the blast loads will be attenuated (i.e., lower than the incident blast loads). This paper focuses on defining the attenuated blast load region as a function of the blast wave strength and building dimensions. Characteristic parameters are utilized to present the analysis results, including wave length, wave length normalized by a characteristic building dimension, and normalized standoff distance from the building back wall. Blast load adjustment factors (i.e., ratio of the diffracted to incident blast load) are used to define the blast load attenuation as a function of these characteristic parameters. The purpose of this work was to generate a database of the shock attenuation behind a structure for engineering modeling applications.
Structural Design and Stress Analysis of a Fully-Wrapped Composite CNG Gas Cylinder With Nominal Working Pressure of 30 MPa
Authors: Qin Xiaoqiang , Liang Lin , Zhang Xiaobing , Deng Guide , Liang Haifeng
Published: October 2020

China is the world’s largest user of compressed natural gas vehicles, with a total of nearly 6 million compressed natural gas (CNG) vehicles. The nominal working pressure of the cylinders used in the CNG vehicles in China is 20 MPa, as a result, CNG vehicles have a short range. In order to improve the range of CNG vehicles, the development of CNG vehicles with higher pressure is promoted by the CNG vehicle industry in China nowadays. In this paper, structural design of a fully-wrapped composite CNG gas cylinder with nominal working pressure of 30 MPa are carried out. The steel liner is made of 4130X seamless steel with design wall thickness of 5.9 mm, and the outer surface of steel liner is wrapped with resin based glass fiber composite material. The fully-wrapped composite adopts mixed fiber winding mode: low-angle helical winding, high-angle helical winding and hoop winding. Stress analysis and autofrettage pressure optimization of the designed composite gas cylinder are carried out with finite element method. The results show that the designed composite gas cylinder meets the requirements of ISO 11439-2013, and the best autofrettage pressure of the gas cylinder is 52 MPa after optimizing the autofrettage pressure.
Comparison of Fracture Toughness Curves Obtained by Single and Multi-Specimen Methodologies for a Pipe Having an Undermatched Girth Weld
Authors: Sarzosa Diego F. B. , Savioli R. , Ruggieri C. , Garmbis Alexandre Galiani
Published: October 2020

Preventing catastrophic failure of engineering components is critical during the exploration and production of oil and gas resources from the offshore deep-water fields in Brazil. Pre-salt reserves are associated with high concentration of aggregated elements to hydrocarbons, particularly carbon dioxide (CO2) and hydrogen sulfide (H2S) which, in the presence of water can produce highly corrosive elements. One solution to this problem is to apply a metal liner made of corrosion-resistant alloy (CRA) internally to the carbon steel pipe. Such a bi-metallic configuration, commonly referred to as a lined pipe or clad pipe, consists essentially of a relatively thin CRA material pipe physically or metallurgically joined to the main carbon steel outer pipe. This experimental study presents an investigation of the ductile tearing properties for the girth weld of a typical C-Mn pipe internally clad with Inconel 625 CRA alloy using experimentally measured crack growth resistance curves. Here, the material of the external pipe is an API 5L Grade X65 pipeline steel and the inner clad layer is made of Inconel nickel-chromium alloy 625 (UNS N06625). The higher mechanical strength and superior resistance to a wide range of corrosive environments of unusual severity for this material derived from the combination of the nickel-chromium matrix with other microalloying elements. Testing of the pipeline girth welds employed clamped SE(T) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen method and the multi-specimen technique. The SE(T) specimens were extracted from a clad pipe having an external diameter of 220 mm and thickness of 23 mm. Further, the current experimental characterization provides toughness data that serve to evaluate the effectiveness of current procedures in determining accurate experimentally measured R-curves for this class of material.
Isothermal Low-Cycle Fatigue Evaluation of External Weld Repair Using Alloy 182 Filler Metal With Backing Plate Design
Authors: Zhang Shutong , Romo Sebastian A. , Penso Jorge , Guo Haixia , Ely Lisa , Ramirez Antonio J.
Published: October 2020

Coke drums are pressure vessels used in the delayed coking process at oil refineries, which transform heavy residual oil into light-weight hydrocarbon molecules and solid coke through thermal cracking. Due to the severe thermal and mechanical loadings during operation, these vessels experienced low-cycle fatigue failure, which led to shell and skirt damage such as bulging and cracking. External weld repairs using the temper bead technique have been widely applied to repair damaged regions caused by bulging and cracking for preventing the leaks of the residual oil contents. However, a substantial proportion of the external repairs have been reported to experience post-repair cracking issues. In this study, an external weld repair mockup with a backing plate was evaluated through metallurgical characterizations and isothermal low-cycle fatigue tests. The micro-hardness mapping identified the mismatching interfaces from base metal to weld metal (WM) and from root passes to internal clad. Four types of dog-bone samples were extracted from the weld: weld metal, heat affected zone, internal clad and backing plate. These samples were used to evaluate the fatigue resistance of weld metal and transition zone under low-cycle fatigue tests. Failure analysis showed that weld metal samples were susceptible to multiple-crack initiations, while other transition samples failed at mismatching interfaces or stress concentration points at weld toes.
Fatigue Behavior of Metallic Pipes With Through-Wall Corrosion Damage Repaired With Bonded Metallic Patches
Authors: de Luca Camila , Sathler Julia , Souza João Fellipe , Mattos Heraldo
Published: October 2020

Composite repair systems have been gaining each time more space in industry, especially when it comes to repairing through-wall defects in pipes. They are simpler to apply, have no costly downtime and provide lower risks to the environment when compared to metallic repairs. ASME PCC-2 and ISO 24817 standards are responsible for defining the parameters necessary to a successful repair, however neither of them addresses a very common practice in such repairs, which is the addition of a bonded metallic patch over the defect. Several companies are adepts of such practice and it has already been proven that is actually the metallic patch and not the composite sleeve itself that sustains most of the load applied on the repair, and for that reason it becomes necessary to conduct further studies regarding the behavior of the patch alone. One important issue is to understand why the strength of similar repairs due to operation errors with very similar amplitude of pressure transients seems to vary randomly, with unexplained early failures. The present paper is concerned with an experimental study about how pressure variations can generate cyclic inelastic strains in the pipe, which can weaken the adhesion between pipe and patch, leading the repair to fail prematurely.
A Case Study for Using Engineering Judgement When Analyzing Finite Element Results
Authors: McGuffie Sean , Barkley Nathan
Published: October 2020

The authors were tasked with designing and fabricating a thick walled (t > 4.5″) ASME Division 2 – Class 2 separator vessel. Due to its service requirements, the vessel is to be regularly hydrotested at 18.87 MPa (2,737 psig). Linear-elastic finite element (FE) evaluations of the vessel indicated that it passed all required Code checks, including the hydrotest check specified in Section VIII, Division 2, Paragraph 4.1.6.2.

To develop a greater understanding of the advantages and disadvantages of each method, the FE analyst on the project routinely reanalyzes vessels that have been evaluated per the linear-elastic procedures of Part 5 of the ASME Section VIII, Division 2 Code with the nonlinear procedures also specified in Part 5. This practice allows for direct comparisons of the linear and nonlinear results and for identification of situations where nonlinear analyses could provide benefit. Such an analysis was performed on this vessel under the hydro-static test condition. However, this analysis failed due to solver failure / gross instability (plastic collapse) before the full hydro-static load was applied. The solver failure was confirmed and repeated in multiple FE packages. This presented a conundrum for the authors: should the linear-elastic results be accepted since the vessel passed the linear evaluations, or should they be invalidated since the nonlinear evaluations indicated that failure could occur during a hydrotest, which given the vessel’s operations, will occur frequently?

This paper discusses the additional evaluations that were required to establish confidence that the vessel could be successfully hydrotested when fabricated. These included both the Code specified evaluations, and evaluations that allowed engineering judgement to be applied to the design.
Design and Testing of an Explosively Loaded Pressure Vessel System for Proton Radiography
Authors: Spernjak Dusan , Fehlmann Kevin , Cardon Devin , Yost Nathan , Hill Dallas , Llobet Anna
Published: October 2020

A containment system is being developed to expand the capability of proton radiography of small-scale shock physics experiments at Los Alamos National Laboratory (LANL). The detonation of high explosives (HE) drives materials to extreme loading conditions, which are imaged using a proton beam and an imaging system. A qualified confinement and containment boundary needs to exist between a high-explosive experiment and the environment, and is comprised of the Inner Pressure Confinement Vessel (IPCV) and the Outer Pressure Containment Vessel (OPCV). The Inner Vessel is designed to the criteria of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 3, Code Case 2564. The vessel contains an Experimental Physics Package, fragment mitigation structure, and radiographic windows. The windows need to minimize radiographic blur contribution (thin, radiographically transparent material such as Beryllium) over the field of view for imaging, but also need to maintain the pressure boundary during and after the dynamic event. Further, the vessel covers need to seal before, during, and after the experiment . In addition, the covers have miscellaneous feedthroughs, to enable high-voltage signal (for HE detonator), instrumentation and control signals (e.g. valves, pressure and vacuum gauge, optical fibers). We present the preliminary design, analyses, and testing of the Inner Vessel components.