bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Residual Stress in Multi-Pass Butt-Welded Stainless Steel Pipe
Authors: Kasa S. , Mouri M. , Tsunori M. , Takakura D.
Published: July 2010

It is necessary to obtain an accurate welding residual stress distribution for the evaluation of stress corrosion cracking (SCC) behavior. However, a welding residual stress simulation for pipes is often performed by a two dimensional axisymmetric model because this type of simulation requires significant time to analyze the complicated inelastic behavior. This approximation deteriorates the modeling accuracy since the welding heat input and the structural response are approximated by axisymmetric responses although they are originally three dimensional. The authors propose “a virtual additional stiffness method” in order to improve the accuracy of the axisymmetric model. With this method, the difference between the axisymmetric model and a three dimensional behavior was greatly reduced. The virtual additional stiffness method was used to reproduce three dimensional constraints that were not taken into account in the axisymmetric model. In the case of the axisymmetric model, an unrealistic large thermal expansion was observed because of simultaneous heating along a hoop direction of the whole pipe. In order to compensate this unrealistic deformation, a virtual additional stiffness was added in axial and radial directions on the axisymmetric model. This stiffness was added by using spring elements whose positions and spring constants were determined by comparing the two and three dimensional models. Results obtained by this new method in the multi-pass butt-welded stainless steel pipe were in very good agreement with measurements of the mock-up specimens.
Fracture Assessment of Austenitic Stainless Steel Piping With Twin Flaws in TIG Weld
Authors: Itatani Masao , Narazaki Chihiro , Hayashi Takahiro , Saito Toshiyuki , Ogawa Takuya
Published: July 2010

Fracture behavior of austenitic stainless steel piping for boiling water reactor (BWR) internals with circumferential through wall twin flaws at the weld was investigated. A 150A Sch.40 piping of type 316L stainless steel which has an outer diameter of 165.2 mm and a thickness of 7.1 mm was butt welded by tungsten inert gas (TIG) weld and single or twin through wall slits were introduced by an electro discharge machining (EDM) on the weld bead. Four point bending tests were conducted and failure stress was evaluated by currently proposed limit load equation for a piping with multiple flaws. The fracture loads obtained by the test were higher than the limit load based on the recently proposed equation for pipe with multiple flaws using 2.7Sm. It was concluded that the limit load criterion is able to be applied to the fracture assessment of austenitic stainless steel piping with twin flaws in the TIG weld. Through the pipe fracture test, it was found that the crack tends to grow in base metal rather than weld metal.
Numerical Analyses of Ductile Fracture Behavior in 2D Plane Strain and Axisymmetric Models Using the Complete Gurson Model
Authors: Xu Jie , Zhang Zhiliang , O̸stby Erling , Nyhus Ba˚rd , Sun Dongbai
Published: July 2010

Ductile crack growth plays an important role in the analyses of fracture behavior of structures. A strong geometry dependence of ductile crack growth resistance emerges under large scale yielding conditions. This geometry dependence is associated with different levels of crack tip constraint. However, an independent relationship between the fracture resistance and crack tip constraint has also been observed in experimental studies for selected specimen geometries. To verify these results, crack growth resistance curves for plane strain, mode I crack growth under large scale yielding have been computed using the complete Gurson model. Single edge notched bending (SENB) and tension (SENT) specimens with three different crack geometries have been selected for the numerical analyses. Specimen size effect on ductile crack growth behavior has also been studied. In addition, the SENT specimen appears as an alternative to conventional fracture specimens to characterize fracture toughness of circumferentially cracked pipes due to its similar geometry constraint ahead of the crack tip with that of cracks in pipes. 2D axisymmetric models have been carried out to investigate the effect of biaxial loading (axial tension combined with internal pressure) on the resistance curves for pipes with long internal circumferential cracks under large scale yielding conditions.
Prestrain Influence on Fatigue Crack Propagation in a 304L Stainless Steel
Authors: Vor Kokleang , Gardin Catherine , Sarrazin-Baudoux Christine , Petit Jean , Amzallag Claude
Published: July 2010

The scope of this study is to investigate the effect of tensile prestrain on crack growth behavior in a 304L stainless steel. Fatigue crack propagation tests were performed on single-edge notched tension (SENT) raw specimens (0% of prestrain) and on prestrained specimens (2% and 10%). On one hand, it is found that the different levels of prestrain exhibit no significant influence on crack propagation in the high range of Stress Intensity Factor (SIF), where there is no detectable crack closure. On the other hand, a clear effect of prestrain on crack growth rate can be observed in the near threshold region where closure is detected. Thus, it can be concluded that the prestrain mainly affects the crack growth rate through its influence on the crack closure.
Application of Plastic Region Bolt Tightening to Flange Joint Assembly: Behavior of Large Diameter Flange
Authors: Kaneda Shinobu , Tsuji Hirokazu
Published: July 2010

In the past study the plastic region tightening has been applied to the bolted flange joint with smaller nominal diameter and its advantages have been demonstrated, however, behavior of the bolted flange joint with larger diameter is not investigated. Flange rotation of the bolted flange joint with large diameter increases when the internal pressure is applied. Gasket stress is not uniform and it may cause leak accident. So, it is necessary to investigate the behavior of the larger diameter flange. The present paper describes the behavior of bolted flange joint with large diameter under plastic region tightening. Firstly, API 20-inch flange joint tightened to the plastic region by bolt with a smaller diameter and superiority in the uniformity of the axial bolt force is demonstrated. And then the internal pressure is applied to the bolted flange joint and the behavior of the additional axial bolt force is demonstrated. The axial bolt force decreases with increasing the internal pressure, and the load factor is negative due to increasing of the flange rotation. However, the load factor of the bolted flange joint tightened to the plastic region by using the bolt with the smaller diameter approached zero. Using the bolts with smaller diameter is advantageous to the flange joint with the larger diamter, whose load factor is negative, to prevent the leakage. Additionally, the leak rate from the bolted flange joint is measured and the sufficient sealing performance is obtained.
Investigation of Samples From the High-Velocity Water Jet Driven Micro/Nano Particle Collider
Authors: Hlava´cˇ Libor M. , Hlava´cˇova´ Irena M. , Vasˇek Jaroslav , Jandacˇka Petr , Zegzulka Jirˇi´ , Viliamsova´ Jana , Ma´dr Vile´m , Uhla´rˇ Radim
Published: July 2010

The power of the high-velocity waterjets has been utilized for intentional disintegration of material particles, namely minerals. Firstly, the garnet particles were tested and studied being used usually as the most common abrasive additives for waterjets improving their cutting abilities. Later on, other mineral particles have been investigated because there are some practical applications of them. Primarily, the product generated inside the mixing chamber and the focusing tube has been studied. Subsequently, the special colliding chamber has been designed and produced enabling the collision of the two opposite moving waterjets containing material particles. This device was named “Water Jet Driven Particle Collider”, shortly WJDPC. The product created in the collision of the opposite moving particle containing waterjets has particle sizes covering partially both the nano-scale and the micro-scale. The investigation of parameters influencing the amount of particles with sizes in respective dimension scales is the topic of the contribution. Some samples of special materials were studied and tested. The discussion of the results of the computational modeling of the suction process and its influence on the final product is included. All results are discussed regarding their application in practice and further development of special routings for material particle preparation.
Stability and Pressure Boundary Conditions in the Collapsible Channel Flows
Authors: Liu H. F. , Luo X. Y. , Cai Z. X.
Published: July 2010

In this study, we investigate dynamic behaviour and the linear stability of collapsible channel flows under various physical parameters and boundary conditions. Two approaches are adopted in the study: one is a fully coupled numerical solver for solving fluid-structure governing equations; the other is an eigenvalue solver which is used for linear stability analysis. We focus on the situation where the inlet pressure drop (relative to the outlet) is prescribed. Static divergence and mode-1 instabilities are found in addition to higher modes, which can co-exist in a structure which is quite different from the cascade structure identified with the flow rate inlet boundary condition. Mode transfer from lower to higher modes is also discovered as the stiffness of the elastic wall is reduced. Finally, our results are compared with the asymptotic prediction for high Reynolds number and tension region.
Water Hammer Likely Cause of Large Oil Spill in North Sea
Authors: Nennie Erik D. , Korst Harry J. C. , Lunde Knud , Myklebust Rune
Published: July 2010

On December 12, 2007, the second largest oil spill in the history of Norwegian oil exploration occurred on StatoilHydro’s Statfjord Alpha platform. The spill was caused by a snapped 20″ oil off-loading hose. Thorough investigations by StatoilHydro [1] and by the Norwegian authorities [2] revealed the chain of events that led to this incident. One of the links in this chain was the unintended fast closure of the shuttle tanker’s bow loading valve during off-loading. This closure initiated a pressure surge in the oil off-loading system. As part of the internal investigation by StatoilHydro, TNO carried out a water hammer analysis of the entire oil off-loading system, including the off-loading hoses to the seabed and further subsea piping up to the platform. These simulations revealed that high pressures could occur in the oil off-loading system due to fast closure of the bow loading valve followed by multiple reflections at diameter changes. The maximum pressures were more than 100 bar above the normal operating pressure of 10 bar. The diameter changes were introduced into the oil off-loading system to maximize the off-loading capacity. The results of the water hammer analysis provided the missing link between the fast closure of the valve and the damaged hose and also showed that this damage most likely occurred within 0.5 second after the closure of the valve. Based on the results of this analysis, also other oil off-loading systems are being reinvestigated to prevent a similar incident to occur in the future.
A Risk-Informed Methodology for ASME Section XI, Appendix G
Authors: Gamble Ronald , Server William , Bishop Bruce , Palm Nathan , Heinecke Carol
Published: July 2010

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code [1], Section XI, Appendix G provides a deterministic procedure for defining Service Level A and B pressure-temperature limits for ferritic components in the reactor coolant pressure boundary. An alternative risk-informed methodology has been developed for ASME Section XI, Appendix G. This alternative methodology provides easy to use procedures to define risk-informed pressure-temperature limits for Service Level A and B events, including leak testing and reactor start-up and shut-down. Risk-informed pressure-temperature limits provide more operational flexibility, particularly for reactor pressure vessels with relatively high irradiation levels and radiation sensitive materials. This work evaluated selected plants spanning the population of pressurized water reactors (PWRs) and boiling water reactors (BWRs). The evaluation included determining appropriate material properties, reviewing operating history and system operational constraints, and performing probabilistic fracture mechanics analyses. The analysis results were used to define risk-informed pressure-temperature relationships that comply with safety goals defined by the United States (U.S.) Nuclear Regulatory Commission (NRC). This alternative methodology will provide greater operational flexibility, especially for Service Level A and B events that may adversely affect efficient and safe plant operation, such as low-temperature-over-pressurization (LTOP) for PWRs and system leak testing for BWRs. Overall, application of this methodology can result in increased plant efficiency, and increased plant and personnel safety.
High-Density Polyethylene Piping Butt-Fusion Joint Examination Using Ultrasonic Phased Array
Authors: Frederick Caleb , Porter Allen , Zimmerman Dave
Published: July 2010

With the increasing use of High-Density Polyethylene (HDPE) piping for nuclear applications, nondestructive evaluation is an important tool for evaluation of the integrity in fused joints. This paper will discuss the method of using Ultrasonic Phased Array for inspecting Butt-Fusion (BF) joints in HDPE piping. The benefit of Phased Array is the ability to perform a volumetric inspection using multiple angles which greatly increases the probability of detection of defects, and allows the data to be analyzed using a representative 2-dimentional image of the joint [1]. It has been determined that successfully producing BF joints is highly dependent on environmental and mating-surface conditions. The primary defects of concern are lack-of-fusion (LOF), an area of the joint where there is no bond [2], cold fusion (CF), an area of partial bond, and inclusion. Phased Array has successfully demonstrated the ability of detecting and characterizing these defects using low frequency ultrasound. Factors addressed include joint location, wall thickness, material temperature, transducer wedge material, and manual vs. automated data acquisition.
Producing HP Pump Barrels Utilizing Powder Metallurgy and Hot Isostatic Pressing
Authors: Bjurstro¨m Martin , Hjorth Carl-Gustaf
Published: July 2010

The fabrication of near net shape powder metal (PM) components by hot isostatic pressing (HIP) has been an important manufacturing technology for steel and stainless steel alloys since about 1985. The manufacturing process involves inert gas atomization of powder, 3D CAD capsule design, sheet metal capsule fabrication and densification by HIP in very large pressure vessels. Since 1985, several thousand tonnes of parts have been produced. The major applications are found in the oil and gas industry especially in offshore applications, the industrial power generation industry, and traditional engineering industries. Typically, the components replace castings, forgings and fabricated parts and are produced in high alloy grades such as martensitic steels, austenitic stainless steels, duplex (ferritic/austenitic) stainless steels and nickel based superalloys. The application of PM/HIP near net shapes to pump barrels for medium to high pressure use has a number of advantages compared to the traditional forging and welding approach. First, the need for machining of the components is reduced to a minimum and welding during final assembly is reduced substantially. Mechanical properties of the PM/HIP parts are isotropic and equal to the best forged properties in the flow direction. This derives from the fine microstructure using powder powder and the uniform structure from the HIP process. Furthermore, when using the PM HIP process the parts are produced near net shape with supports, nozzles and flanges integrated. This significantly reduces manufacturing lead-time and gives greater design flexibility which improves cost for the final component. The PM HIP near net shape route has received approval from ASTM, NACE and API for specific steel, stainless steel and nickel base alloys. This paper reviews the manufacturing sequence for PM near net shapes and discusses the details of several successful applications. The application of the PM/HIP process to high pressure pump barrels is highlighted.
Severe Transportation Accidents: Impacts of Severe Fires on Radioactive Material Transportation
Authors: Bajwa Christopher S. , Easton Earl P. , Dunn Darrell S.
Published: July 2010

In 2007, a severe transportation accident occurred in Oakland, California in what is commonly known as the “MacArthur Maze” section of Interstate 580 (I-580). The accident involved a tractor trailer carrying gasoline that impacted an overpass support column and burst into flames. The subsequent fire burned for over 2 hours and led to the collapse of the overpass due to the loss of strength in the structural steel that supported the overpass. The US Nuclear Regulatory Commission (NRC) studied this accident to examine any potential regulatory implications related to the safe transport of radioactive materials, including spent nuclear fuel. This paper will discuss the details of the NRC’s MacArthur Maze fire investigation.
Technical Basis for Revisions to ASME Section XI Acceptance Standards for Surface Flaws in Piping in Stress Corrosion Cracking Susceptible Materials
Authors: Scarth Douglas A. , Miyazaki Katsumasa , Hasegawa Kunio , Bamford Warren H.
Published: July 2010

Acceptance Standards for flaws in piping are provided in Section XI of the ASME B&PV Code to permit acceptance of relatively small flaws without the need to perform an analytical evaluation. The Acceptance Standards are based on maintaining large margins against failure, and are based on the assumption that flaw growth will be insignificant. The assumption of a small amount of flaw growth is justified when fatigue crack growth is the only crack growth mechanism. However, when stress corrosion cracking is operative, flaw growth could be significant. This conclusion was illustrated by comparison of the crack growth results due to fatigue and stress corrosion cracking in Pressurized Water Reactor (PWR), and Boiling Water Reactor (BWR), coolant environments. For this reason, IWB-3514 of Section XI prohibits use of the Acceptance Standards for planar surface-connected flaws that are detected in piping materials that are susceptible to stress corrosion cracking and are in reactor coolant environments. As part of a recent Code revision to include new Acceptance Standards tables for flaws in piping, restrictions on use of the Acceptance Standards of IWB-3514 have been refined and clarified. The recent Code revision now specifies different restrictions and requirements for use of the Acceptance Standards for such planar surface-connected flaws detected by preservice and inservice examination. In addition, similar restrictions have been imposed on use of the new Acceptance Standards for such planar surface-connected flaws in Class 2 piping in IWC-3514 of Section XI. The technical basis for the restrictions and requirements for use of the Acceptance Standards for planar surface-connected flaws in piping materials that are susceptible to stress corrosion cracking is provided in this paper.
Estimating ASME Section III and VIII Heat Exchanger Nozzle Loads
Authors: Ezekoye L. Ike , Arnold Colin
Published: July 2010

Heat Exchange Institute (HEI) Standards for Power Plant Heat Exchangers, 4th Edition provides guidance on how to estimate the nozzle loads of cylindrical shells. The procedure covered in one of the appendices of the document relies on WRC Bulletin 107 methodology which uses internal pressure, physical geometry and material properties to estimate external forces and moments. The forces and moments are the limiting loads when the heat exchanger material is taken to yield. The material yield defines the range of possible load combinations that will meet the design criteria. However, for operability, the design criteria sometimes may differ from the yield but usually is based on heat exchanger supplier experience. This paper provides a way to estimate heat exchanger nozzle loads that more closely reflect operating conditions that take into account supplier experience. In this paper, generalized load formulae are developed for the nozzles. The formulae are iteratively solved to meet the stress criteria based on supplier experience. The resultant loads are evaluated using WRC Bulletin 107 to ensure that the loads are bounded by the acceptance criteria. Unbounded loads are rejected and reiterated until the loads are acceptable.
Measurement of Residual Stresses in the Dissimilar Metal Weld Joint of a Safe-End Nozzle Component
Authors: Ogawa Kazuo , Chidwick Laurence O. , Kingston Edward J. , Muroya Itaru , Iwamoto Youichi , Smith David J.
Published: July 2010

This paper presents results from a programme of residual stress measurements and modelling carried out on a Pressurised Water Reactor Safe-end Nozzle component. The full-scale Safe-end Nozzle component was manufactured to the same specifications as those typically found on Japanese Pressurised Water Reactors. The basic component consisted of a ferritic steel nozzle with a tapered outer diameter (OD) ranging from 883mm to 1192mm, an inner diameter (ID) of 735mm and a length of roughly 1080mm. A stainless steel ring (i.e. the safe-end) of 883mm OD, 735mm ID and length 100mm was attached to the ferritic steel nozzle using a double-V nickel base alloy (i.e. alloy 132) weld with buttering. Later on in manufacturing a stainless steel, main coolant piping section (883mm OD, 735mm ID and 500mm length) was then attached to the safe-end using a single-V stainless steel weld. The residual stresses generated through the centre-line of the double-V weld connecting the stainless steel safe-end to the ferritic steel nozzle were measured using the Deep-Hole Drilling (DHD) and inherent strain techniques. The residual stresses generated by welding were modelled using ABAQUS. Presented here are the DHD measurements from six locations circumferentially around the weld made at three different stages during the manufacture and testing of the component. The DHD measurements are compared against those measured on a similar component using the totally destructive inherent strain technique and those modelled using finite element analysis. Details of the FE modelling carried out for this project are to be presented in another paper at this conference (PVP 2009-77269). The measured and modelled results are also compared against the UK based BS7910 and R6 standards. It is shown that there is excellent agreement between the DHD, inherent strain and modelling results in the as-welded state, showing peak tensile stresses at the inner and outer weld cap surfaces, reducing into compression in the centre at the meeting of the double-V grooves. It is also shown with the DHD measurements that after attaching the main coolant piping, the peak tensile residual stresses present at the inner surface in the hoop and axial directions changed to become compressive. Furthermore, following hydrostatic and operating condition tests, the DHD measured residual stresses at the inner surface were shown to move towards tension again, with the axial residual stresses remaining slightly compressive, but the hoop residual stresses becoming slightly tensile. The residual stresses generated at the outer surface were relatively unchanged by the manufacturing and operating processes carried out.
Evaluation of a Welded Joint Using the Structural Stress Method
Authors: George Shiju V. P.
Published: July 2010

The Structural Stress Method of determining the fatigue strength of welded joints was formally incorporated into the ASME Boiler and Pressure Vessel Code in the 2007 edition of ASME Section VIII Division 2 and is also included in API 579-1/ASME FFS-1 2007, “Fitness-For-Service”. This method presents a number of advantages over the commonly applied approach of determining a peak stress, various fatigue and stress factors, and polished bar S-N fatigue curves to determine the fatigue strength. In this paper, the author illustrates the use of the Structural Stress Method as a means of assessing the fatigue strength of a welded joint through evaluation of a weldment attaching a carbon steel stiffening ring to a stainless steel vessel undergoing thermal cycles. Some advantages of this method and particular points of interest are discussed.
New Russian National Standards on Pressure Vessel and Apparatus Design and Strength Calculation
Authors: Volfson Boris
Published: July 2010

A report is devoted to new Russian National standards GOST R 53630-2006 “Steel welded vessels and apparatus. General specifications” and GOST R 52857.1-2007÷GOST R 52857.12-2007 “Vessels and apparatus. Norms and methods of strength calculation”, which were published in 2007–2008. They changed 33 regulations, which were in force earlier. This report contains general description of recently developed standards, considers its structure, approaches and methods of calculation and design, main distinctions with previous normative documents. It is significant, that developed standards meet the requirement of the standard ISO 16528-1 “Boilers and pressure vessels. Part 1: Performance requirements”. The author compares new Russian standards with ASME Boiler and pressure vessel code. Section VIII, Division 1 and 2, EN 13445 “Unfired pressure vessel” and other well-known international standards. There is also a description of the software, designed in accordance with new Russian standards. Further development of normative methods of calculation and design, including those, that based on computational modeling of constructions, are discussed in the final part of the report.
Research on Defects Examination and Crack Assessment for Cast Iron Dryer
Authors: Han Shu-xin , Sheng Shui-ping , Yu Ping , Li Wei-zhong , Chen Hai-yun , Du Qing
Published: July 2010

The strength and hardness tests to the experiment dryer were carried on, from the relation of strength and hardness, the relative hardness RH is 0.8 according to ‘principle met using’. The velocity of sound should be measured first in the thickness measurement, the ‘false’ thickness phenomenon in dryer flange and the convex transition segment were discovered. The ultrasonic examination characteristics of the cast iron dryer was analyzed, the sensitivity of various sensors were carried on. The small angle double crystal longitudinal wave sensor can examine the Φ3 equivalent diameters of the volume defects, and the big angle double crystal longitudinal wave sensor can examine 2 mm deep surface crack of the body and the transition area. The safety assessment on 2 mm deep surface crack was carried on.
An Appraisal of Two Simplified Inelastic Methods of the ASME Code
Authors: Chattopadhyay Somnath
Published: July 2010

In this work, two simplified inelastic analysis rules existing in the ASME Boiler and Pressure Vessel Code have been appraised. The first rule is intended as a correction for plasticity due to Poisson’s ratio effects. Based on a number of analytical and experimental evaluations, it is shown that the variable Poisson’s ratio approach helps bring the simplified elastic analyses in line with inelastic analysis findings. This is carried out by multiplying the elastically calculated stresses (that are based on an assumed Poisson’s ratio of 0.3) by the factor Kν to reflect changes in the Poisson’s ratio associated with local plastic deformation. The second rule makes use of a fatigue enhancement factor, Ke which is employed when the linearized elastically calculated stress ranges exceed twice the material yield strength, thus necessitating inelastic evaluations. An analytical approach based on local strain method, as well as the expressions used in the Japanese MITI code has been used for comparison. A number of practical situations have been cited to illustrate the application of these rules.
Variational Method for Limit Load Analysis of Inhomogeneous Media
Authors: Adibi-Asl R. , Seshadri R.
Published: July 2010

The load carrying capacity of a body with varying material properties (inhomogeneous) is investigated using the various lower and upper bound limit load multipliers in the context of varational principles originally proposed by Mura and co-workers. In order to evaluate the different limit load multipliers, Elastic Modulus Adjustment Procedure (EMAP) is used to obtain statically admissible stress and kinemattically admissible strain fields at a limit load stage. The proposed upper and lower bound limit load solutions are compared with the results obtained from inelastic finite element analysis (FEA) for several examples with two-dimensional and three-dimensional geometries.
Effect of Constraint on Creep Crack Propagation of Mod. 9Cr-1Mo Steel Weld Joint
Authors: Yamamoto Masato , Miura Naoki , Ogata Takashi
Published: July 2010

In order to clarify the effect of constraint on creep crack propagation of modified 9Cr-1Mo steel, 1) 25.4mm thickness C(T) specimen with side grooves (thick specimen) and 2) 10mm thickness C(T) specimen without side grooves (thin specimen) were machined from base metal (BM) and weld joint (WJ), and subjected to creep crack propagation experiments under 650 °C. The crack in WJ propagated along the fine grain heat affected zone (HAZ), where the multi-axial constraint was high due to the difference in deformation properties among HAZ, WJ, and BM. While the thick specimens hardly allow deforming to the thickness direction and showed less crack tunneling, the thin BM specimen showed remarkable reduction of thickness and crack tunneling. The thin WJ specimen showed some thickness reduction and crack tunneling, but also showed larger crack extension than that of BM. In terms of the relationship between the crack propagation rate (da/dt) and the creep J integral (C* parameter), the data shows a wide scatter band. The specimens with higher geometrical constraint (thick specimen, WJ) locate above the lower constraint (thin specimen, BM) ones. All the specimen showed the reduction in thickness and suggests the change in constraint condition during the experiments. By picking up the data without significant thickness reduction, the C*- da/dt relationship has been gathered in a narrow and straight band regardless of the specimen geometry or difference in material. The picked up data locates at the upper bound of the current and literature data.
Sound Source Location Error Analysis of Acoustic Emission Technique for Thick-Wall Pressure Vessel Inspection
Authors: Liu Fujun , Ding Shoubao , Hu Dongming , Wang Qiang , Xu Yanting , Kong Shuai , Zheng Mulin
Published: July 2010

Acoustic emission (AE) technique has been widely applied to pressure vessel and piping inspection, such as local abrasion or corrosion, growing fatigue cracks. Sound source location analysis plays an important role in the whole AE inspection and evaluation process, how to improve the location precision to an extent is the research focus all over the world. For AE sound source location of pressure vessels, the arrival-time difference location method is mainly used, i.e. compute arrival-time difference which sound source signals arrive at different sensors to determine the sound source location. If an active sound source is on the internal surface or in the wall not on the external surface of thick-wall pressure vessels, the location error obviously exists because of the wall thickness influence. In this paper the sound source error for thick-wall pressure vessels is deduced in detail, the sound source location error formulas are founded and the change law of location error with the wall thickness is analyzed and discussed too. Furthermore, it is proposed that about 200 mm radius area around the source location should be rechecked by normal nondestructive testing methods to determine the actual source location when inspecting thick-wall pressure vessels by AE technique.
Ductile Failure Simulation of Tensile Plates With Multiple Through-Wall Cracks
Authors: Kim Nak-Hyun , Kim Yun-Jae , Oh Chang-Sik
Published: July 2010

This paper proposes a simple numerical method to simulate plastic behaviours of tensile plates with twin through-wall cracks. The method is based on finite element analysis with a simple damage theory. To validate the proposed method, simulated results are compared with experimental data performed by Japanese researchers. Despite its simplicity, the proposed method well predicts plastic behaviours of tensile plates with twin cracks, including crack coalescence. Predicted maximum loads are overall lower than experimentally-measured ones.
Towards Modelling Intergranular Stress-Corrosion Cracks Using Experimentally Obtained Grain Topologies
Authors: Simonovski I. , Cizelj L. , Marrow T. J. , Quinta da Fonseca J. , King A.
Published: July 2010

Predicting the effects of material aging in view of development of intergranular damage is of particular importance in a number of nuclear installations and especially in structural integrity assessments of critical components in energy generating power plants. Since the damage is initialized on small length scales, detailed multiscale models should be employed to tackle the problem. However, the complexity of such models is high due to the need of incorporating microstructural features. In line of this the research group from Jozˇef Stefan Institute and The University of Manchester joined forces and knowledge in development of such detailed multiscale models. The basic idea was to pair the knowledge of advanced experimental techniques of The University of Manchester group with the knowledge of advanced microstructure modelling techniques of the group at Jozˇef Stefan Institute. The presented paper proposes a novel approach for intergranular crack modelling whereby a state-of-the-art X-ray diffraction contrast tomography technique is used to obtain 3D topologies and crystallographic orientations of individual grains in a stainless steel wire and intergranular stress corrosion cracks. As measured topologies and orientations of individual grains are then reconstructed within a finite element model and coupled with advanced constitutive material behaviour: anisotropic elasticity and crystal plasticity. Due to the extreme complexity of grain topologies, transferring this information into the finite element model presents a challenging task. The feasibility of the proposed approach is presented. Difficulties in building a finite element model are discussed. Preliminary results of the analyses are also given.
Performance of a Gasketed Bolted Flange Joint Under Combined Structural and Thermal Transient Loading (Taking Bolt Scatter Into Consideration): FEA Approach
Authors: Abid Muhammad , Khan Kamran Ahmed , Chattha Javed Ahmad
Published: July 2010

Performance of a bolted flange joint is characterized mainly by its ‘strength’ and ‘sealing capability’. The weakest part of a high temperature and pressure envelope is the gasket in bolted flange joints, as these are prone to leakage. It causes loss of productivity and in severe cases, loss of lives. There is a need to evaluate the sealing performance of a gasketed bolted flange joint (GBFJ) under combined structural and thermal transient loadings as these occur in industrial applications. In this paper using complete 3D Finite Element Model, the joint’s performance is studied during bolt up and operating (combined structural and thermal transient loading) condition. During bolt up, bolts are tightened as per ASME bolt up strategy and any bolt scatter and its effect during applied operating conditions is discussed.
SCC Test Verification of Effect of Moving Heat Source on FEM Evaluation for Weld Residual Stress of Butt-Weld Pipe
Authors: Iwamatsu Fuminori , Aoike Satoru , Fukuda Yuka , Saitou Osamu
Published: July 2010

Weld residual stress of a small bore pipe was evaluated using three-dimensional thermal elasto-plastic analysis, which was based on the finite element method (FEM), taking into consideration the effect of a moving heat source during the butt-weld process. A moving heat source during the weld process complicates analysis process due to the necessity of considering the set welding conditions at each time step and this increases computation time. Therefore, there are remarkably few studies on the effect of a moving heat source during the weld process on the analytical results of weld residual stress for small bore pipes. We used this analysis to find the effect of the welding start/end on weld residual stress. Weld residual stress is not a circumferentially uniform state. Increased tensile and compressive residual stress occurred near the end position of the final welding pass. In addition, an accelerated stress corrosion cracking (SCC) test was carried out using a boiling 42% magnesium chloride (MgCl2) solution. In particular, butt-weld joints of low-carbon austenitic stainless steel (Type 316L) pipe, which is often used in boiling water reactors (BWRs), were examined. Comparison between three-dimensional thermal elasto-plastic analysis and accelerated SCC testing showed the tensile stress zone indicated by analysis agreed well with SCC occurrence indicated by examination.
Development of Stress Reduction Method in the Pipe Welded Zone
Authors: Fukuda Yuka , Saito Osamu , Aoike Satoru , Iwamatsu Fuminori
Published: July 2010

Stress Corrosion Cracking (SCC) failures have occurred in the vicinity of austenitic stainless steel pipe welds used in boiling water reactors, since the late 70s. One of the initial countermeasures against SCC has been to use low-carbon stainless steel. However, in older plants, SCC failures in low-carbon stainless steel pipe were still observed in recent years. It is well understood that residual tensile stress due to welding largely affects occurrence and growth of SCC in low-carbon stainless steel. Because of this, it is important to reduce the residual tensile stress in the welded zone in addition to utilizing less susceptible material. However, a countermeasure to reduce residual tensile stress in small-bore pipe has not been established. In this study, a new stress reduction method is developed in order to reduce residual tensile stress in the welded zone, even for small-bore pipe. This method is applied to the butt-welded zone while the pipe is filled with water. First, the pipe is frozen at two points centering around the welded zone by cooling the outer surface of the pipe to transform the water to plugs of ice. The volume inside the pipe between the ice plugs becomes watertight and pressurized by the expansion of the plugs up-on freezing. The pipe expands near the zone of the weld groove, because the wall thickness of the butt-welded zone is thinner locally because of the weld counter bore. In this process, tensile strain occurs near the welded zone due to the pipe expansion beyond its plastic range, and then hoop tensile plastic strain of inner surface is larger than that of outer surface. Once the pressure load is removed, the difference in these tensile strains induces the hoop residual tensile stress on the inner surface to reverse to a compressive stress. On the other hand, the local bending deformation that occurs in the welded zone results in an axial residual compressive stress on inner surface. Both experimental studies and finite element analysis confirmed that the hoop and axial residual tensile stress at the inner surface of the welded zone are reversed to compressive stress by the pipe expansion.
Detected Flaw Evaluation on VVER Reactor Components Using ASME Code
Authors: Pa´lfi Tama´s , Ra´tkai Sa´ndor
Published: July 2010

There is an increasing attention on considering detected flaw evaluation according to the ASME code on the Hungarian VVER reactor components, as most time-limited aging analyses (TLAA) related analyses being done due to the American standard. Although — because of the evident differences between the Russian and American reactors — not all of the ASME articles might be applied to Russian designed components directly. A possible way of resolving this difference was developed at VEIKI and practical examples are given on the following fields: Material properties; Flaw characterization; Allowable end of life flaw size; determination; Crack growth analysis; Allowable detected flaw size determination. Allowable flaw size determination is based on tables in IWB/IWC 3500, which validity is partly verified during the work for VVER 440 components. This is done by analyzing defects in the welds of the components, which are iteratively postulated to have the flaw shape - critical size function. The article shows the analysis method, the finite element and the fracture mechanical models used in the calculations and the main results.
Stress and Fatigue Analysis Considering Thermal Stratification With the THERMAXS Code
Authors: Diaby Adama , De Smet Michel
Published: July 2010

This paper describes the stress and fatigue analysis of the feed water nozzles of the replacement steam generators of the Doel 2 NPP in Belgium. In the framework of the steam generators replacement, thermal stratification transients were considered in the stress and fatigue analyses of the feed water system components such as the feed water lines, their reactor building penetrations and the steam generator feed water nozzles. To do so, long term external wall temperature measurement have been performed on one feed water line of Doel 2 between the steam generator replacement in 2004 and December 2007. From those measurements a number of typical stratification phenomena were identified. For each phenomenon, a design stratification transient and its number of occurrences were derived from the measurements. A fatigue analysis and primary+secondary stress intensity analysis of the feed water nozzles of the Doel 2 NPP was performed taking into account the presence of the design thermal stratification transients in the feed water lines and feed water nozzles. The fatigue analysis was performed according to the rules of the ASME Boiler & Pressure Vessel Code, Section III, Division 1 – Subsection NB-3200 using the in-house developed computer code THERMAXS that is capable of dealing with measured stratification transients. For the analysis, one may finally conclude that the fatigue, P+Q stress intensity range and thermal ratcheting criteria are respected throughout the 40 years of plant life.
Cooling of a Massive Casting of Ductile Cast-Iron and Its Numerical Optimization
Authors: Kavicka Frantisek , Stransky Karel , Sekanina Bohumil , Dobrovska Jana , Stetina Josef
Published: July 2010

The numerical models of the temperature field of solidifying castings often observe two main goals: directed solidification and optimization of the technology. These goals can be achieved only if the deciding factors which either characterize the process or accompany it are analysed and their influence controlled. An original application of ANSYS, based on the numerical finite-element method, is applied. The numerical model simulated the forming of the temperature field of a two-ton 500×500×1000 mm casting from ductile cast-iron during the application of various methods of its cooling using steel chills. This model managed to optimize more than one method of cooling but, in addition to that, provided results for the successive model of structural and chemical heterogeneity, and so it also contributes to influencing the pouring structure. The file containing the acquired results from both models, as well as from their organic unification, brings new and, simultaneously, remarkable findings of causal relationships between the structural and chemical heterogeneity and the local solidification time in any point of the casting. This has established a tool for the optimization of the structure with an even distribution of the spheroids of graphite in such a way so as to minimize the occurrence of degenerated shapes of graphite, which is one of the conditions for achieving good mechanical properties of castings of ductile cast-iron.
History of A.M.E. Standard Creation
Authors: Vejvoda Stanislav
Published: July 2010

Czechoslovak specialists participated in creation of the Interatomenergo standards for design of WWER type nuclear power plant components from 1980 to 1989. The Interatomenergo standards had not been accepted as official standards in the Czech Republic. Temelin power plant was built in the ninetieth years of last century, but any public requirement followed the existing creation of the national nuclear standards of that time. The Standard Technical Documentation (STD) was asked for assessment of strength and lifetime analyses of components manufactured for the Temelin nuclear power plant. The Association of Mechanical Engineers (A.M.E) issued six Sections and one Section of Special Cases of the Standard Technical Documentation. Revisions of these Sections are made every three years with last revision being published in 2007.
Behavioral Study of IN-718 Due to High Pressure Shock Wave Loading in Contact Geometry
Authors: Sharma Ashok K.
Published: July 2010

Shock waves when propagate through materials produce sudden changes of pressure and temperature which result in the production of new phases/transformations. This paper describes the experimental work for the shock synthesis of IN 718 with unique properties and characterization of its pre and post shock compacts by spectroscopic methods. Super alloy powders of IN 718 of various chemical compositions and unique physical properties have been shock compressed to develop a new technology. From the spectroscopic records, intensity of reflected beam at a particular angle, the spacing between parallel planes, the lattice constant, the radius of an atom, FWHM value for each peak, etc. have been analyzed to investigate the unique properties of shock compacts. No porosity has been observed in the shock compacted specimens. On retrieval of samples from the compaction systems, the specimens are subjected to chemical composition, stress analysis and various other spectroscopic studies. The dendritic structure has been clearly observed in the centre with dendrites oriented in the radial direction which also happens to be the direction of heat flow. SEM analysis has indicated that the crystalline structure is intact in the shock compressed specimens.
Determination of Critical Crack Size Utilizing a Fracture Mechanics Test in Equipment Under Fatigue
Authors: Garcia Garcia Irene , Stefanovic Radoslav
Published: July 2010

Equipment that is exposed to severe operational pressure and thermal cycling, like coke drums, usually suffer fatigue. As a result, equipment of this sort develop defects such as cracking in the circumferential welds. Operating companies are faced with the challenges of deciding what is the best way to prevent these defects, as well as determining how long they could operate if a defect is discovered. This paper discusses a methodology for fracture mechanics testing of coke drum welds, and calculations of the critical crack size. Representative samples are taken from production materials, and are welded employing production welding procedures. The material of construction is 1.25Cr-0.5Mo low alloy steel conforming to ASME SA-387 Gr 11 Class 2 in the normalized and tempered condition (N&T). Samples from three welding procedures (WPS) are tested: one for production, one for a repair with heat treatment, and one for repair without heat treatment. The position and orientation of test specimen are chosen based on previous surveys and operational experience on similar vessels that exhibited cracks during service. Fracture mechanics toughness testing is performed. Crack finite element analysis (FEA) model is used to determine the path-independed JI-integral driving force. Methodology for the determination of critical crack size is developed.