bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Scale Simulation of Fluid-Structure Interaction Induced Erosion on the Pipe Surface
Authors: Tang Ping , Yang Jian , Zheng Jinyang , Ou Guofu , He Shizheng , Wu Rongren , Lam Chikong , Ma Yanbao
Published: July 2009

Erosion results from interactions between the pipe surface and fluids traveling along the surface. Fluid-structure interactions have a profound influence on the erosion that takes place. The location, rate and extent of thinning or loss of a protective surface film depend strongly on the nature of the flow regime and interactions. Erosion-corrosion involves the modification, thinning and removal of protective films composed of corrosion product or scale deposits from a susceptible metal surface by fluid shear stress under high turbulence conditions. In the paper, multi-scale simulation of fluid-structure interactions between the flow and the protective films on the pipe surface is presented. The fluid shear stress and pressure of the flow in a pipe with a step is obtained by macro-fluid dynamic analysis. Viscous forces and the system’s pressure impose forces to the surface of the pipe. Using micro-simulation method, the fluid-structure interactions between the flow and the protective films is modeled. The deformation of the protective films is shown and changed with the different velocity and flow regime. Using the multi-scale simulation of fluid-structure interactions, the location, rate and extent of the erosion on the pipe surface can be predicted. The results are proved by the actual instances.
Fracture Assessment Procedures for Steel Pipelines Using a Modified Reference Stress Solution
Authors: Tkaczyk Tomasz , O’Dowd Noel P. , Nikbin Kamran
Published: July 2009

An accurate defect assessment procedure is needed to ensure integrity of girth welded steel pipelines while avoiding unnecessary repairs. An integral part of such a procedure is an estimation scheme for the crack driving force. In this work, a modified reference stress solution was developed for the assessment of elastic-plastic pipes with surface breaking defects. For the particular case of interest (reeled offshore pipelines) the loading is phrased in terms of applied strain. The stress-based approach has therefore been extended to the case of strain/displacement control. The results obtained using the modified reference stress solution have been compared with a three-dimensional finite-element analysis. Very good agreement has been obtained. The predictions are also significantly better than those obtained from existing approaches. A comparison between the proposed method and full scale testing will be presented in a separate paper.
A Revised Approach to Damage Measurement Based on Stiffness Loss Technique
Authors: Bonora Nicola , Ruggiero Andrew , De Meo Stefania , Gentile Domenico , Esposito Luca
Published: July 2009

In the last decades damage mechanics has received a lot of attention and has proved to be a powerful approach to describe the occurrence of failure in materials. In order to became an effective tool of practical application in the industrial design world, clear, reliable, and — when possible — simple procedures and practices, aimed to perform damage measures and to identified damage model parameters, are needed. In the literature, only a limited number of papers addresses the issue of the damage measurements. Among the possible different techniques, the measure of the progressive loss of stiffness as a function of the increasing inelastic strain level, is the most commonly used and referred. Even though this technique is conceptually simple, it can be affected by a number of error that can invalidated the measures. In this paper a clear and effective procedure based on the use of finite element simulation and experiments is presented. The proposed procedure allows one to correctly account for the geometry changes occurring in the sample even in the post necking regime where stresses and strain are no longer uniform along the section and the gauge length. The proposed methodology has been used to measure damage in 99.99% pure copper.
Effect of Welding Conditions on TIG Welded AISI 304 Stainless Steels Using FEM and Experimental Methods
Authors: Kocherlakota Pavan , Savarimuthu Jerome
Published: July 2009

Classical approaches to the modeling of welding, whilst accurate, are not readily usable in the industry. The time and cost associated with running such models appear to be the main reasons contributing to the situation. The use of computer simulative techniques has the potential to significantly reduce the cost of welded fabrications by allowing for predictions to be made long before a single weld bead is put down on the workshop floor. In this paper, a computational procedure is presented to analyze temperature fields during TIG welding process using a non linear transient thermal analysis in ANSYS [1]. Various phenomena associated with welding like temperature dependent material properties, effects of latent heat of fusion are accounted for in the model. The heat loss through radiation and effect of shielding gas are neglected here. This work has considered only a 2D analysis considering axis symmetric model. The analysis was done on AISI 304 stainless steels. The effect of welding conditions on the weld microstructure is studied over a range of heat input values and welding speed and the columnar to equiaxed transition (CET) is investigated. The influence of the welding conditions is related to changes in temperature gradient G, and local solidification velocity R, at the solid-liquid interface along the weld pool edge. It was observed that increase in the welding speed increases the equiaxed fraction. The effect of alloy composition on CET was neglected during this study. The results of finite element analysis were compared with experimental results and were found in good agreement. Based on these studies, a simplified modelling procedure of reasonable accuracy was proposed.
Buckling of Local Thin Areas Under External Pressure
Authors: Nadarajah Chithranjan , Schachinger Tom
Published: July 2009

A parametric study of square local thin areas on cylindrical shells under external pressure was conducted using finite element method. The study concentrated on both elastic and as well as plastic buckling of the local thin areas. From the study, conservative screening curves were developed to address the structural integrity of the local thin area under external pressure.
A New Rationale for Scatter in Fracture Toughness Measurements
Authors: Noronha Silvester J.
Published: July 2009

The observed scatter in fracture toughness is investigated based on a dislocation simulation model that has been proposed to predict the brittle ductile transition in ferritic steels. We carried out a series of Monte-Carlo simulations using uniform distribution of microcracks on the crack plane of macrocrack. Detailed statistical analysis of the simulation results showed that the fracture is always initiated at one of the largest microcracks, whose size correspond to the tail of the size distribution function, and the inherent scatter arises from the distribution in the size of the critical microcrack that initiates the fracture and not from the variation of the location of the critical microcrack. Utilizing the weakest-link theory, Weibull analysis shows good agreement with the Weibull modulus values obtained from fracture toughness measurements.
A Dislocation Simulation Approach to Physical Basis of Master Curve
Authors: Noronha Silvester J. , Gunawardane Heshan P.
Published: July 2009

Discrete dislocation simulations of crack-tip plasticity are used to study the sharp increase in fracture toughness around ductile-brittle transition temperature of ferritic steels. The model used composed of a macrocrack with a microcrack ahead of it in its crack plane. The microcrack represents potential fracture sites at internal inhomogenities, such as brittle precipitates. The simulation has two stages: at first the fracture stress of microcrack, σF is calculated from dislocation simulation of microcrack-tip plasticity. In the next stage the fracture toughness is estimated by the macrocrack tip plasticity simulation; the fracture toughness is applied stress intensity at the macrorack when the tensile stress at the microcrack position attains σF. The brittle-ductile transition curve is obtained by determining the fracture toughness at various temperatures. Factors that contribute to the sharp upturn in fracture toughness with increasing temperature are found to be the increase in dislocation mobility, the decrease in tensile stress ahead of the macrocrack tip due to blunting and increase in mircocrack fracture stress due to increase in plasticity at the microcrack tips. The shape of the curve obtained is similar to the Master Curve.
The Toughness Index of X80 Mother Linepipe Steel and Its Optimum Microstructure
Authors: Zhang Xiaoli , Feng Yaorong , Liu Yinglai , Zhuang Chuanjing
Published: July 2009

Large amount of experimental data indicated, that the index of CVN toughness and shearing area of mother pipe of X80 are (200J, 90%). And the results showed that when charpy toughness was closing to 200J, the shearing area would reach to 90%; when the charpy toughness increased continuously, the shearing area would not increase further more. So the selection of charpy toughness value as 200J for pipeline steels is reasonable, and also its corresponding shearing area. To gain thus component index, the optimum microstructure of X80 steel should be strip-like ferrite mastered, small amount of granular bainite contained-acicular ferrite type steel, and, in which the size of MA island should be less than 1μm. This kinds of optimum microstructure of X80 pipeline steel will exert its softening role in improving toughness and simultaneity not decrease its strength.
Test Programs for Degraded Core Shroud and PLR System Piping: Seismic Test Results and Discussion on JSME Rules Application
Authors: Suzuki Kenichi , Kawauchi Hidefumi
Published: July 2009

Since the age-related degradation of structures and components in NPPs has been a key issue regarding assessments of seismic safety, JNES initiated seismic test programs in fiscal 2004 for the degraded core shroud and PLR system piping used in old BWR plants. The objectives were to: i) obtain a better understanding of the vibration characteristics and seismic strength of degraded structures and components having cracks due to aging; ii) ensure a margin of seismic design safety by considering age-related cracking; and iii) verify the JSME Rules on Fitness-for-Service for NPPs in Japan. The quasi-static displacement or load control testing of the components of the core shroud and PLR system piping were conducted. The dynamic load testing of combined components were also performed on a shaking table by using an approximately 1/3 scale PLR system piping specimen and a 1/2.5 scale core shroud specimen. All test specimens were designed to contain simulated cracking due to aging, involving cracks assumed to have the maximum allowable size according to the JSME Rules. These test results were discussed by focusing on the effects of cracking on vibration characteristics and seismic strength, and the margin of seismic safety under the JSME Rules.
Shaking Table Tests of Static Dynamics Interchangeable-Ball Pendulum System for Motion Sensitive Equipment
Authors: Tsai C. S. , Chen Wen-Shin , Tsou Ching-Pei , Yang Chen-Tsung
Published: July 2009

Recently, the high-tech industry has become a key industry for economic development in many countries. However, motion sensitive equipments located in these industrial buildings are vulnerable during earthquakes, which may cause huge economic loss. In this study, an isolator for safeguarding the motion sensitive equipment, namely, the static dynamics interchangeable–ball pendulum system (SDI-BPS) is proposed and investigated to examine its protective capability for the motion sensitive equipment during earthquakes through a series of shaking table tests. The experimental results illustrate that the SDI-BPS isolator can provide significant damping to reduce the large bearing displacement and size, and avoid the stress concentration, which can cause damage or scratches on the sliding surface of the isolator, to prolong its life span of service. The SDI-BPS isolator also provides excellent capability in protecting the motion sensitive equipment and exhibits a stable behavior under long terms of service loadings and earthquakes.
An Evaluation System of Tube Wall Thickness of Feed Water Heater Base on the Advanced NDE Technique
Authors: Hamada Seiichi , Uchikura Takahisa , Morisaki Kouichi
Published: July 2009

The inspection of the tubes of feed water heaters on the wall thickness is generally conducted using the ultrasonic pulse technique. According to the past method, the wall thickness at each measured point is evaluated in comparison with the minimum required wall thickness of the tube, namely it is based on the general metal loss evaluation criteria. However, these tubes often show the local metal loss due to erosion and corrosion. Evaluation techniques and acceptance criteria regarding the locally thinned tubes require many wall thickness data around the local metal loss locations. However, it is inefficient to perform this evaluation work with human power because of the required huge measured data. With recent improvement of the inspection technique, technology enabled faster, larger amount, and more accurate electronic digital data acquisition of tube wall thickness. The authors have developed the systematized evaluation methodology that can transact data acquisition and evaluation simultaneously. This paper describes the logic of evaluation methods and examined algorithms to make them systematized.
Recent Developments in Japanese Flaw Assessment Methods of WES 2805
Authors: Hagihara Yukito , Kurihara Masayoshi , Yoshinari Hitoshi , Miyata Takashi
Published: July 2009

The standard for the method of assessment for flaws in the welded joints of WES 2805 was first published in 1976 and was revised in 1980 and 1997. A further revision has been carried out by the technical committee of FTS in the Japan Welding Engineering Society and the revision was completed in 2007. The standard of WES 2805 is based on a CTOD (crack tip opening displacement) design curve approach for brittle fracture, and is used for the assessment of the significance of flaws in a stress concentrated region, where large scale yielding takes place. Main topics for the recent developments for flaw assessment methods are described in this paper. These are the interaction criterion of multiple flaws, fatigue crack growth laws, determination of equivalent crack length and strain due to stress concentration, estimation method of the critical CTOD from Charpy energy and proposal of partial safety factors. In order to examine the effectiveness of the standard, extensive 2-D and 3-D FE analyses are performed for various welded joints such as a load-carrying fillet welded joint, a non-load-carrying fillet welded joint and a box welded joint. Some of them are introduced in this paper. Their analytical results indicate that the present CTOD design curve method gives a reasonable evaluation.
Application of Design by Analysis to Casing of Centrifugal Pump
Authors: Naruse Tomohiro , Nabesaka Shusaku , Sakurai Shinsuke , Takahara Kyoji
Published: July 2009

The ASME Design by Analysis (DBA) procedures, namely the stress categorization and limit load approaches were applied to the spiral casing of a centrifugal pump. The spiral casing, which has stay vanes inside the spiral duct, has a more complicated structure than other pressure vessels, and therefore, the stress categorization procedure cannot be directly applied to it. We simplified the spiral casing into a finite element shell model. The membrane and bending stresses were determined by measuring the shell stresses, and then those stresses were classified into primary and secondary stresses. The limit load approach is simpler to apply, but requires an inelastic analysis. The allowable loads of the limit analysis are calculated using the solid and shell models of the spiral casing. In addition, the calculated allowable loads were assessed and compared for the different methods.
Probabilistic Fracture Mechanics Using Fractal Finite Element Method
Authors: Reddy R. M. , Rao B. N.
Published: July 2009

This paper presents probabilistic fracture-mechanics analysis of linear-elastic cracked structures subjected to mixed-mode (modes I and II) loading conditions using fractal finite element method (FFEM). The method involves FFEM for calculating fracture response characteristics; statistical models of uncertainties in load, material properties, and crack geometry; and the first-order reliability method for predicting probabilistic fracture response and reliability of cracked structures. The sensitivity of fracture parameters with respect to crack size, required for probabilistic analysis, is calculated using continuum shape sensitivity analysis. Numerical examples based on mode-I and mixed-mode problems are presented to illustrate the proposed method. The results show that the predicted failure probability based on the proposed formulation of the sensitivity of fracture parameter is accurate in comparison with the Monte Carlo simulation results. Since all gradients are calculated analytically, reliability analysis of cracks can be performed efficiently using FFEM.
Strength Design Requirements in Chinese Pressure Piping Code
Authors: Qin Shujing
Published: July 2009

In order to improve the design, fabrication and inspection of pressure piping and to enhance the safety level of pressure piping in operation, a new pressure piping code has been issued in 2007 by Standardization Administration of The People’s Republic of China. In this paper, the structure of this new code and, especially, the requirements of strength design stipulated in the code were introduced. In this code, except for the structure, many provisions have the same meanings with that in ASME piping code B31.3. But, there are some other provisions, in view of the fact that the pressure piping code needs to be conformed with corresponding Chinese codes and standards, are different from that in B31.3, such as the classified categories of piping, the treatment of pressure fluctuation, the application of stress intensification factor, and so on. The contents on pressure design of fittings and piping stress analysis in the code were emphatically described herein. However, at the same times, other requirements on material and inspection to fulfill the safety of pressure piping were also briefly introduced.
Advances in Dynamic Analysis for Hypercompressor Cylinder Valves
Authors: Bianchini Michele , Campo Nicola , Francini Stefano , Vidyasagar R.
Published: July 2009

The life of valves is extremely important for the availability of hypercompressors in LDPE plants. Different factors such as high gas temperatures, early wear, the presence of polymers or loud noise, can give an indication of poor valve performance that could shorten their life. 3D computational fluid dynamics (CFD) has been extensively used to obtain an accurate evaluation of pressure losses, drag forces and flow coefficients at various operating conditions. CFD dimensionless flow field coefficients have been fed into 1D valve dynamics model simulations, resulting in a more accurate calculation, able to better predict the poppet position during valve opening and closing. The poppet motion can be correlated to critical performance factors and can be used to estimate valve life. Experimental validation will allow a fine tuning of this modified model for valve performance prediction, which can be used to design optimized valve geometries with improved reliability.
Comparison Between API 579-1/ASME FFS-1 and ASME VIII Division 3 Stress Intensity Factor Solutions Used for Fracture Mechanics and Fatigue Analysis of Thick Walled Cylinders
Authors: Keltjens Jan G. M.
Published: July 2009

The paper discusses the differences between API 579-1/ASME FFS-1-1/ASME FFS-1 [1] and ASME Section VIII Division 3 [2] stress intensity factor solutions. In addition to this, the use of the Failure Assessment Diagram (FAD) in leak before burst analysis is compared to the present Division 3 approach. The paper contains the background of both approaches and a worked example demonstrating the effect of both methods. Finally, a simplified fatigue crack growth based life time study is presented.
Finite Element Mesh Considerations for Reduced Integration Elements
Authors: Bjorkman Gordon S. , Piotter Jason M.
Published: July 2009

Finite element models of spent fuel casks and canisters that are typically used in impact and impulse analyses may contain tens of thousands of nonlinear elements. These models use explicit time integration methods with small time steps. To achieve reasonable run times, fully integrated elements are replaced with under-integrated elements that use reduced integration procedures. When fully integrated these elements produce a linear strain distribution. Reduced integration, however, results in a constant strain distribution, which requires more elements through the thickness of the canister shell to achieve the same accuracy as fully integrated elements. This paper studies the effect of the number of reduced integration elements through the thickness of the canister shell and the ratio of element height to shell thickness on the accuracy of the strains in regions of high through-thickness bending, such as the junction between the shell and base plate. It is concluded that mesh refinement has a significant effect on the maximum plastic strain response in such regions and that a converged solution may not be attainable within practical limits of mesh refinement, if the results are based solely on the maximum plastic strain on a cross section at a structural discontinuity. The objective is not to chase the stress concentration with ever finer meshes, but rather the objective is to establish a mesh density within the discontinuity region that results in the stresses and strains that are associated with the bending moment that restores compatibility at the structural discontinuity. In this case a converged solution is obtained by investigating the response of other elements on the same cross section that are not located on the surface of the stress concentration at the structural discontinuity. Based on the results, a “rule of thumb” is proposed for mesh refinement in a region of severe structural discontinuity wherein reasonably proportioned reduced integration solid elements are used and plastic strains are evaluated.
Welding Residual Stress Analysis Using Axisymmetric Modeling for Shroud Support Structure
Authors: Ogawa Kazuo , Okuda Yukihiko , Saito Toshiyuki , Hayashi Takahiro , Sumiya Rie
Published: July 2009

Recently, several cracks caused by stress corrosion cracking (SCC) have been found on welds of shroud supports in Boiling Water Reactor (BWR) plants. The major cause of SCC in a weld joint is considered due to welding residual stress generated in the fabrication processes of the components. For continuous safety operations, it is necessary to estimate the structural integrity of such shroud supports with cracks based on the distribution of residual stresses induced by welding. In order to know and to validate the numerical method of residual stresses induced by welding of large scale and complex shaped components, a BWR shroud support mock-up with a hemispherical base of reactor pressure vessel (RPV) was fabricated by Japan Nuclear Energy Safety Organization (JNES) as a national project. The mock-up has a 32° section of actual BWR shroud supports with approximately the same configurations, materials and welding conditions of an actual component. During welding in the fabrication process of the mock-up, temperature was measured and after completion of the mock-up fabrication, surface residual stress distributions for each weld were also measured by the sectioning method. In addition, through-thickness residual stress distributions were investigated. Residual stress for each weld was calculated by using axisymmetric models considering temperature dependent elastic-plastic material properties. Though the actual structure of shroud supports is essentially complex, we simplified axisymmetric models in the center of the cross section. The analysis results show a similar profile and good agreement with the measured results on the surface of all the welds and through the welds at the upper and lower joints of the shroud support leg.
Simulation of a Three-Stage Process for Forming a Closed Cone From a Plate
Authors: Feng Zhengkun , Champliaud Henri , Dao Thien-My
Published: July 2009

High geometrical quality of bent cones is required in assembling several cone segments into a crown of Francis turbines. Although closed cones were successfully obtained using pyramidal three-roll conical bending machines with cylindrical rolls which is more adaptive and less expensive, the zones close to the leading and trailing edges of the plate never pass under the inner roll and remain planar. For the purpose of obtaining high geometrical quality, a three-stage process is proposed to obtain a jointed cone with no planar zones. The planar zones resulted from the first stage of the conical bending is eliminated after the repassing of the bent cone in the bending machine with the leading and trailing edges jointed together by forces. Numerical simulations with commercial software ANSYS/LS-DYNA in explicit scheme and ANSYS in implicit scheme are performed and bent cones with improved qualities are obtained.
Numerical Modelling of Residual Stress and Distortion in Welded Thin Steel Plates
Authors: Tsunori M. , Davies C. M. , Dye D. , Nikbin K. M.
Published: July 2009

Current trends in ship design are to reduce panel thickness in order to minimise the vessels weight and hence maximise speed. These panels are manufactured through butt welding thin steel plates with the addition of fillet welded stiffeners. Excessive distortions are exhibited in these thin plates due to the welding process, resulting in major rectification or re-manufacturing costs. The aim of this study is to develop a tool to predict welding residual stresses and distortions in order to understand their governing factors, and thus enabling the optimum fabrication processes to be realized to minimise welding distortion. Finite element simulations are performed of the butt and fillet welding process in 4 mm thick plates of ferritic DH-36 steel and the residual stresses and distortions are predicted. Thermal and residual stress profiles are verified against experimental measurements. The effects of plate and stiffener dimensions are examined numerically. In addition, a sensitivity analysis has been carried out to quantify the effects of restraint on a small butt welded plate. It is concluded that final distortion may be severely reduced, in the plate size considered, if only an out-of-plane constraint is imposed on the plate’s surfaces. Further welding experiments are required to validate these findings.
ASME III Design Code Assessment of a Nuclear Power Station Fuelling Machine Cooling System Pipework
Authors: Shi Jinhua , Blythe David
Published: July 2009

An ASME III design code assessment of the fuelling machine cooling system pipework at a gas cooled nuclear power station has been carried out via the design analysis route of ASME III, Division 1, Section NB-3600 to support an update of its safety case. The objective of the work is to demonstrate that all components assessed are in compliance with the ASME III design code. More than 100 welds and components comprising plain pipe sections, elbows, tees and reducers have been selected and assessed against ASME III Service Levels A and D Stress Limits for a number of load cases. The loadings for the components assessed are internal pressures and piping system forces and moments obtained from the piping flexibility analyses. For all components assessed, the ASME III Service Level A requirements are met. For ASME III Level D assessments, the rules contained in ASME III NB-3656 and Appendix F are used. It is shown that the ASME III Level D requirements are also met. This paper details the assessment procedures on the selected components and also presents the assessment results.
SCF and Fatigue Analysis of Sphere-Nozzle Intersections With LTA
Authors: Qadir M. , Redekop D.
Published: July 2009

A linear elastic finite element analysis (FEA) is carried out to determine the stress concentration factor (SCF) of a pressurized sphere-nozzle intersection. Nine-noded axi-symmetric 2D (ring) elements are used, and vessels without and with inner-wall local thinned areas (LTA) are considered. The SCF values obtained for vessels with uniform wall thickness are compared with previously published experimental and analytical results, and also with results from standard formulas given in the literature. An evaluation is made of the effect on the SCF of three types of inner-wall LTA; thinning in the nozzle, in the sphere, and in both components. As well, an evaluation is made of the effect on the SCF of growth of the LTA away from the intersection. A detailed parametric study is then carried out to determine the SCF for vessels with different depths of LTA. An elastic-plastic fatigue analysis for simulated seismic action is next carried out for some sample intersections, without and with LTA. The results provided are intended to contribute to the information available on the stress and fatigue characteristics of sphere-nozzle intersections with LTA.
Reliability Analysis of Pressure Vessels in Lubricant Process Unit for Risk Based Inspection
Authors: Chien Chi-Hui , Chen Chun-Hung
Published: July 2009

As a safety concern to a pressurized system, to monitor the corrosion rate of each pressure vessel in order to make the repair decision at the right time based on the required thickness to withstand the maximum allowable working pressure (MAWP), is important to the plant owner. A plant inspector will normally assess the risk by evaluating the probability of failure of each pressure vessel during service hours with inspection and maintenance planning. Therefore, a scheme of reliability assessment to the pressure vessels should be established. The objective of this study is to discuss the failure probabilities of the pressure vessels in a lubricant unit in order to provide the input information for Risk Based Inspection (RBI) assessments. The reliability assessment of a pressure vessel involves the estimation of the failure pressure and evaluation of the limit state function. Based on the formula for calculating required thickness of a pressure vessel component, and due to the presence of non-linearity in the limit state function and the non-normal distributed variables, the first order second moment method (FOSM) was adopted for carrying out the reliability analysis. The uncertainties of the random variables in the limit state function were modeled by using normal and non-normal probabilistic distributions. As the heat exchanger is an important pressure vessel to a pressurized system, the failure probabilities together with the ranking categories of the heat exchangers in a lubricant unit are chosen as a case study to be discussed and presented in this paper.
Developing Methodology for Elevated Temperature Design of Section VIII, Division 1 Vessels Considering Load Durations
Authors: Becht Charles , Hollinger Greg L.
Published: July 2009

The rules of Section VIII, Division 1 provide an allowable stress for design of pressure vessels that is independent of load duration. In the time dependent regime, where failure by creep rupture is a consideration, the actual life of the vessel depends on a number of things, including the margins provided in the allowable stresses, the margin between design pressure and operating pressure, the margin between design temperature and operating temperature. While material properties for a time duration of 100,000 hours are included as part of the basis in establishing the allowable stress, this is neither an anticipated life nor a design life for the pressure vessel. There are short term conditions for which design based on an allowable stress set based on long term creep properties is unrealistically conservative. This paper provides recommendations for design rules for very short term loads for which creep should not be a design consideration, termed occasional loads herein, and rules for loads for which creep is a design consideration.
Counterfeit and Rogue Industrial Parts and Materials, and Their Impact on Safety and Reliability
Authors: Cheta Ayman
Published: July 2009

Counterfeit and rogue industrial parts and materials are a worldwide problem that can put workers and public safety at risk. Undetected counterfeit and rogue items may cause electrical or mechanical failure that may lead to death, personnel injury, or property damage. Although statistics are available for the fatalities caused by counterfeit alcoholic beverages, baby foods and medicine, there is no statistical data available for the impact of counterfeit and rogue parts and materials on the industry. This paper provides some examples of actual incidents in the industry in order to demonstrate the seriousness of the problem. The paper also provides some guidance on what the petrochemical industry can do to mitigate the risk.
CFD Analysis of Thermally Stratified Flow and Heat Transfer in a PWR Pressurizer Surge Line
Authors: Kang Dong Gu , Jo Jong Chull
Published: July 2009

Temperature gradients in the thermally stratified fluid flowing through a pipe may cause undesirable excessive thermal stresses at the pipe wall in the axial, circumferential, and radial directions, which can eventually lead to damages such as deformation, support failure, thermal fatigue, cracking, etc. to the piping systems. Several nuclear power plants have so far experienced such unwelcome mechanical damages to the pressurizer surge lines, feedwater nozzle, high pressure safety injection lines, or residual heat removal lines. In this regard, to determine the transient temperature distributions in the wall of a piping system subjected to internally thermal stratification with accuracy is the essential prerequisite for the assessment of the structural integrity of the piping system subjected to internally thermal stratification. In this study, to predict the transient temperature distributions in the wall of PWR pressurizer surge line with a complex geometry of 3-dimensionally bent piping realistically, 3-dimensional transient CFD calculations involving the conjugate heat transfer analysis are performed for the actual PWR pressurizer surge line subjected to stratified internal flows either during out-surge or in-surge operation using a commercial CFD code. In addition, the wall temperature distributions obtained by taking account of the existence of wall thickness as it is are compared with those by neglecting the existence of wall thickness to identify some requirements for a realistic and conservative thermal analysis.
Effect of Free Surface Shape at Edge of Interface on Bonding Strength of Ceramic to Metal Joint
Authors: Tateno Masayoshi , Hagiwara Yoshiaki , Kokubo Kunio
Published: July 2009

The focus of this study is to clarify the effect of the interface edge shape on the bonding strength of ceramic to metal joint. Each silicon nitride to copper joint plate with arc-shaped free surfaces edge was produced by Electric Discharge machining (EDM). The interface edge shape was characterized by defining the edge angle as a configuration angle between the interface plane and tangential line at the arc edge of the bonded interface. Each joint was bonded at high temperature using thin braze metal under vacuum and slowly cooled. Good fit was achieved at each bonded face in this process. The dependence of the bonding strength on the edge angle was experimentally clarified in Silicon nitride to Copper joint with arc-shaped free surfaces. The result shows that changing the edge angle from right angle improves bonding strength since it decreases residual stress near the interface edge. The highest bonding strength appears at the specific interface where the fracture pattern changes. It also shows that secondary machining, which cuts both edges into optimum geometrical conditions after bonding, can improve bonding strength.
Comparative Study of Stress Corrosion Cracking of 304L and 316L Stainless Steel in Low Concentration Sodium Hydroxide Solution With High Temperature
Authors: Gong Jianming , Liu Jianjie , Jiang Yong , Zhou Rongrong
Published: July 2009

Stress corrosion cracking (SCC) of austenitic stainless steel serviced in aggressive environment often occurs in power, petrochemical industry, and leads to premature equipment failure and great economic loss. This paper focuses on the problem of the SCC on the nozzle of hydrogenation reactor which is caused due to alkali cleaning. Susceptibility for SCC was evaluated by Slow Strain Rate Test (SSRT) for as-rolled 304L and 316L stainless steel (SS) in low concentration sodium hydroxide solution with high temperature. The effects of different concentration of sodium hydroxide and different solution temperatures on SCC were investigated at the strain rate of 1 × 10−6s−1. After SSRT was performed, fractograph of the fractured specimens was analyzed by using scanning electron microscopy (SEM). On the basis of this, fracture characteristic and susceptibility of SCC of 304L and 316L stainless steel were compared in low concentration sodium hydroxide solution with high temperature.
Brittle Fracture Criteria Transferability Evaluation by Testing on Different Specimen Geometries
Authors: Chapuliot S. , Marie S.
Published: July 2009

This paper describes an experimental and numerical study to assess the transposability of brittle fracture criteria from specimens of one type of geometry to another. The overall “master curve” approach, the Beremin model and a proposed model using the concept of critical stress were accordingly analysed. The experimental work supporting the analysis was made on 16MND5 reactor vessel steel. This was in the form of CT25 specimens, taken as the reference type, SENT specimens, ring specimens and CTpor specimens, which are CT specimens with a semi-elliptical surface defect. The analysis itself was made in two stages: the models were first calibrated on the basis of CT25 test results, then they were applied to specimens of other geometries. We then demonstrate that, in all cases, the models correctly replicated the variation of toughness (as measured on a CT25 specimen) with temperature. However, they all failed when applied to SENT and ring specimens, where calculation underestimates the probability of fracture. For CTpor specimens, the results are better, the master curve approach and the critical stress criterion give satisfactory results (but it has not yet been possible to apply the Beremin method). This paper concludes with a detailed analysis of the crack tip stress and strain fields, followed by an attempt to explain the differences between the different types of behaviour observed.
Hydrogen Assisted Fracture of Type 316 Stainless Steel at Sub-Ambient Temperature
Authors: San Marchi C. , Somerday B. P. , Tang X. , Schiroky G. H.
Published: July 2009

Applications requiring the containment and transport of hydrogen gas at pressures greater than 70 MPa are anticipated in the evolving hydrogen economy infrastructure. Since hydrogen is known to alter the mechanical properties of materials, data are needed to guide the selection of materials for structural components. Type 316 austenitic stainless steels are often considered one of the best choices for resistance to hydrogen-assisted fracture; however, at sub-ambient temperatures some alloy compositions of type 316 stainless steel can become more susceptible to hydrogen-assisted fracture than others. In this study, we report the tensile properties of two heats of type 316 stainless steel, emphasizing the effects of temperature and high concentrations of internal hydrogen on these properties.
A Quantitative Approach to a Risk-Based Inspection Methodology of Main Steam and Hot Reheat Piping Systems
Authors: Cohn Marvin J. , Fong Jeffrey T. , Besuner Philip M.
Published: July 2009

This paper presents an evaluation of the failure probability and cost of high energy piping (HEP) failures. Using a conventional definition of risk as the product of failure probability and failure consequence, we propose in this paper a dollar value of consequence in order to develop a quantitative approach to risk-based inspection (RBI) methodology. A 16-year historical database of probability and consequence was evaluated as an RBI methodology for devising a life management strategy for welds in main steam and hot reheat piping systems. This evaluation provides us the raw data necessary for producing a concrete example of this new Richter-scale-like approach. Uncertainty in consequence and probability estimates is also provided in plotting (a) a static consequence vs. likelihood diagram at a specific time for comparing the relative severity of a variety of potential failures, and (b) a dynamic risk vs. time diagram for a specific hardware under continuous monitoring where the effect of life management decisions over a period of time is quantitatively displayed. Significance of this new approach to risk-based inspection strategy for advancing the state-of-the-art of managing aging structures is discussed.
Fracture Mechanics and NDE: The Keys to Failure Prevention
Authors: Egan Geoffrey R. , Woodman Brian W.
Published: July 2009

This paper focuses on the evolutionary steps in both fracture mechanics and NDE that have led to a better understanding of how failure prevention programs may be constructed to achieve the best balance of effectiveness and cost. Workmanship standards for weld imperfections that are embodied in most construction codes are contrasted with fitness for service methods for flaw acceptance that require more knowledge about the uncertainty in flaw characterization. The role of fracture mechanics in providing a yard stick for inspection programs is discussed and the concept of Tolerable Flaw Diagrams (TFD) is outlined. The use of fracture mechanics as a tool to define NDE limits for high asset value pressure vessels and piping is described in relation to several examples including: the evaluation of fitness for service of cracked chemical plant pressure vessels and water wall boiler tubes. Probabilistic methods to prioritize the emphasis that should be placed on the quality of inputs to a failure prevention program for nuclear plant steam generator tubes degraded by corrosion are also discussed.
Challenges and Status of Development of Inspection Rules in Japanese Fitness-for-Service (FFS) Code
Authors: Dozaki Koji
Published: July 2009

Inspection rules in JSME Fitness-for-service (FFS) Code have been developed as a combination of conventional In-Service Inspection (ISI), that had been established for every class of components, and specific inspection that has been recently added, considering realistically occurring and propagating phenomena based on the damage modes such as Stress Corrosion Cracking (SCC) and the positions where the damage mode appears. It is considered that some inspection rules of Japanese FFS Code could be modified as more rational ones, reflecting some experimental studies, accumulation of field inspection data, development of inspection techniques, and so on. In this paper, a proposal of the author, who is taking part in development and maintenance of the inspection rules of JSME FFS Code, is described on how to revise the inspection rules in order to realize more appropriate inspection in the future. In addition, modification of examination volume of weld joint at pressure boundaries, and the other items studied are described as the examples of the revision policy of inspection rules mentioned above.
A Numerical and Experimental Study of the Cleavage Fracture Behaviour of Non-Sharp Defects
Authors: Horn Anthony J. , Sherry Andrew H.
Published: July 2009

Structures containing non-sharp defects exhibit a higher apparent resistance to cleavage fracture than sharp cracks. This paper presents a numerical and experimental study of the cleavage fracture behaviour of single edge notch bend SE(B) specimens with cracks and notches with varying notch root radii. The experimental study demonstrates the increasing resistance to fracture that occurs with increasing notch root radius. This is complemented by a numerical study that quantifies the elastic-plastic stress field ahead of the crack or notch tip. The results of the numerical and experimental studies are used together to show that the cleavage initiation sites, identified using scanning electron microscopy, are located close to the peak tensile stress field occurring ahead of the notch. This implies that a tensile stress criterion is the main controlling factor for cleavage fracture in the notched specimens analysed.
Effect of Chemistry Variations of Wrought N06022 Plates on the Repassivation Potential in 1 M NaCl at 90°C
Authors: Mon Kevin G. , Rebak Raul B.
Published: July 2009

ASTM standard B 575 provides the requirements for the chemical composition of Nickel-Chromium-Molybdenum (Ni-Cr-Mo) alloys such as Alloy 22 (N06022). The composition of each element is given in a range (e.g., the lowest content of Mo is specified as 12.5 weight percent and the highest as 14.5 weight percent. It is important to determine the dependence of Alloy 22 electrochemical behavior on the composition of the alloying elements as they vary from the lowest to the highest end of the ranges specified in ASTM B 575 standard. Seven heats of Alloy 22 plate were melted and processed. The plates were tested in the mill annealed (MA) and solution heat treated (SHT) condition. Cyclic potentiodynamic polarization tests were performed in 1 M NaCl solution at 90°C. Results show no influence of Alloy 22 chemistry variations or heat treating on the measured repassivation potential.
Initial Investigation Into Optimizing Design of a Pressure Vessel Saddle
Authors: Khan Shafique M. A.
Published: July 2009

The ASME Boiler and Pressure Vessel Code does not provide details of the pressure vessel saddle supports. The existing design guidelines are based on classical stress analysis with several assumptions to simplify the problem. With the advances in the computational technology and numerical methods, it is now possible to obtain more detailed information about stress distribution and hence provide optimal saddle design guidelines. This study will present an initial investigation into a 3D computational modeling and analysis of the saddle design. Results are presented for maximum von Mises stress occurring in various parts of the saddle with the increase in load.
Micromechanical Modeling of Fiber Reinforced Metal Laminates Under Biaxial Deformation
Authors: Sepiani H. A. , Afaghi-Khatibi A. , Mosavi-Mashhadi M.
Published: July 2009

This presentation examines theoretically the elastic behavior of fiber reinforced metal laminates composed of layers of two types. Woven flexible fabric and metal, in which woven flexible fabric layer includes of sinusoidal shaped fibers. The composite is subjected under biaxial/uniaxial deformation. The theoretical analysis is based upon the Lagrangian description of deformation and the strain-energy density which is assumed to be a function of the Lagrangian strain components referring to the principle material coordinates. The micromechanical model has been obtained using strain energy of components. Finally, the model was solved numerically and then results were compared with published literatures.