bluuebunny/crossref_metadata_2025 huggingface dataset:
Tensile Properties of Boiler Materials for FAD Based Failure Analysis
Authors: Ellis Fred V.
Published: August 2008

Failure assessment of components with crack-like flaws are performed using the Failure Assessment Diagram (FAD) approach. Both fracture toughness and tensile properties of the component material are required for the analysis. The temperature dependence for the tensile properties of yield strength, flow stress, and ratio of yield strength to ultimate tensile strength were studied. The yield/tensile ratio is used to estimate the strain hardening exponent. The materials include carbon steel, 1/2Cr to 9Cr-1Mo steels, 1CrMoV rotor material, and 422 stainless steel bolting material. The tensile data was from the NRIM data compilation. Least squares regression was performed for log of the tensile property as the dependent variable and a sixth order Chebyshev polynomials in temperature. In general, the fits were good based on comparisons of the observed and calculated, specifically the mean at each temperature, the standard deviation, and the R2 value. The distribution function was shown to be normal. Values for the regression coefficients and standard deviation in log Y are tabulated.
Fitness-for-Service and Remaining Useful Life Assessment of a Steam Drum
Authors: Yee Raymond K.
Published: August 2008

A steam drum in a typical power plant has experienced in-service cracking. Nondestructive examinations (NDE) were performed and a small sample was collected from the drum to evaluate the extent of the cracking that had occurred in the drum shell. Fitness-for-service and remaining useful life analyses of the drum were performed based on the NDE results and operating conditions. In this paper, the fitness-for-service analyses of the steam drum are described. The analysis procedure, material property determination, stress analysis, limiting flaw size evaluation, and remaining useful life evaluation for the drum are discussed. Recommendations for appropriate action are also presented.
Case Studies of Pulsed Eddy Current to Measure Wall Loss in Feedwater Heater Shells
Authors: Cohn Marvin J. , Norton Jordan W.
Published: August 2008

There have been several feedwater heater shell failures in nuclear power plants caused by flow-accelerated corrosion (FAC). This failure mechanism may be one of the most important types of damage to mitigate because FAC damage has occasionally resulted in catastrophic failures and human fatalities. Predicting, detecting, and eliminating significant FAC damage can significantly reduce future forced outages and increase personnel safety. This paper describes the implementation of recent developments to perform cost-effective examinations. These advances include the use of specialized pulsed eddy current (PEC) hardware and software to scan for wall thinning without removing insulation. APTECH has performed more than 50 nuclear power plant projects on hundreds of feedwater shells, as well as numerous pipe examination projects, using the PEC equipment as a cost-effective screening tool for the detection of areas with significant wall loss. Results of shell wall loss measurements using ultrasonic examination (UT), the PEC average wall thickness (AWT) estimate, and the PEC evaluated Defect Algorithm are compared in this study.
External Weld Overlays for Repair of Pressure Components
Authors: Findlan Shane J.
Published: August 2008

External weld metal deposit overlays have been successfully implemented in industry as both temporary and permanent repair for the restoration of thinning or degraded steel piping. Pressure components systems suffer from numerous degradation mechanisms, including microbiologically influenced corrosion (MIC), erosion-corrosion damage (EC), fatigue, and general corrosion. The magnitude of the damage induced in the component determines whether a weld overlay repair can be successfully applied to restore the component’s integrity. This paper addresses the use of weld overlays for repair of pressure components degraded by wall thinning due to corrosion, erosion-corrosion, MIC and other mechanisms.
Safety Assessment of the Junction Between a Thick Pressure Vessel Shell and a Thinner Hemispherical Head
Authors: Wang Xiaochun , Zheng Jinyang
Published: August 2008

A junction of shell to hemispherical head whose thickness is half of that of the shell has been developed and safely used in the People’s Republic of China in the past ten years. Great achievements of mesomechanics in ductile fracture have been made in P. R. China. The load when local shear band prongs the ligament in the front of crack tip is regarded as the limit load and the direction of the maximum plastic strain along a constant radius around the crack tip might be considered as the direction of shear fracture. Based on these concepts and small-deformation elastic-plastic analysis with finite element method, safety of the junction under operating pressure, 31.4MPa, is assessed and the possible failure modes of it are forecasted. The reasonability of the design of the junction is also considered.
Predictions of Residual Stresses in the Mechanical Roll Expansion of HX Tubes Into TEMA Grooves
Authors: Williams Dennis K.
Published: August 2008

The mechanical roll expansion of heat exchanger tubes into tubesheets containing TEMA grooves, which are thought to aid in the mechanical integrity of the tube-to-tubesheet (TTT)joint, has for many years provided an acceptable means of completing a TTT joint. Inherent with the intentional roll expansion of the tube is the creation of a tensile residual stress field within the tube that is greatest in the transition region between the expanded and unexpanded zones of the tube. An additional complicating factor in the tube-to-tubesheet joint design is the choice of utilizing a seal weld or a “full strength” weld at the tube end in conjunction with a level of roll expansion quantified by the degree of tube wall reduction. This paper presents the results of an initial study of the mechanical roll expansion of 1 inch diameter tubes into a typical TEMA-R designed tubesheet, utilizing two grooves in the tubesheet hole. Two combinations of tube and tubesheet materials are studied that include duplex stainless steel tubes and tubesheet, while the second combination includes type 321 tubes roll expanded into a 2-1/4 Cr-1 Mo tubesheet, clad with 321 SS overlay. The predicted residual stress fields are calculated by the finite element method and employ a simplified two dimension nonlinear axisymmetric model.
Evaluation of Short Term Creep-Rupture Strength of High Temperature P122 Boiler Material
Authors: Pumwa John
Published: August 2008

The complex thermal-mechanical loading of power-generating plant components usually comprises of creep, high-cycle and low-cycle fatigue which are thermally induced by start-ups, load changes and shut-downs, producing instationary temperature gradients and hence creating strain as well as stress fields. In order to select the correct materials for these hostile environmental conditions, it is vitally important to understand the behaviour of mechanical properties such as creep rupture properties of these materials. This paper reports the results of standard creep rupture tests of P122 (HCM12A or 12Cr-1.8W-1.5Cu) high temperature boiler material. P122 is one of the latest developed materials for high temperature environments, which has the potential to be successful in hostile environments. The tests were conducted at temperatures ranging from 550°C to 700°C at 50°C intervals with stress levels ranging from 80–400 MPa using a locally made creep rupture testing machine. The results are found to have stable creep-rupture strength at short term creep stage for over 800-hours at elevated temperatures. Creep life prediction from Larson-Miller relationship was also carried out and the accuracy of life prediction is demonstrated. Moreover, the fracture mode assessments strongly revealed a typical ductile transgranular fracture mode with dimples and voids.
Coupled Fluid-Solid Problems: Survey on Numerical Approaches and Applications
Authors: Scha¨fer Michael
Published: August 2008

The paper gives a survey on relevant topics related to the numerical simulation of coupled fluid-solid problems. Firstly, the corresponding problems are classified according to different possible coupling mechanisms. The modelling of the problems within a continuum mechanical framework are discussed and numerical aspects related to discretization and solution procedures are addressed. Exemplary approaches for these issues are indicated. A variety of numerical examples involving various coupling mechanisms are presented, including a discussion of questions of numerical accuracy and computational efficiency of numerical solution procedures.
Improved Wall Law Methods for Industrial Applications of CFD
Authors: Eggleton Stephen Iain , Holdo̸ Arne Erik , de With Govert
Published: August 2008

As geometries become more complex due to industry demands, the more inherent problems will occur with the current wall law methods. This paper investigates one commonly used wall function (log-law) and another which is well developed, however it is not currently widely used (Coles law). The Coles model was developed to overcome some of the major errors educed by the assumptions made to obtaining the log-law function, no separation modelling. The implemented functions are preliminary and are used to evaluate the overall performance of the algorithm. However, it is still possible to observe the short comings involved in using a wall function, and the associated problems with the implementation. Dynamic Grid Adaptation (DGA) is present as one method of the solving the major problems which wall functions incur.
Computational Fluid Dynamic Modelling of High Aspect Ratio Cross-Sectional Jets II: The Flow Within the Pipe and Flange
Authors: Wakes Sarah J.
Published: August 2008

Increasingly computational methods are being used for industrial problems in place of expensive or very difficult physical experiments. Attention needs to be given to all aspects of the input into these complex flow problems such as the inlet conditions as these may have a significant effect on the subsequent solution. High aspect ratio cross-sectional orifice (HAR) jets is one such field as such jets occur in many industrial situations. These can include gas dispersion within an enclosed space, within machinery and manufacturing processes. These will often be part of a more complex problem and previous work [1] has shown that it is crucial to model these jets numerically in as accurate and consistent way as possible given the limitations of turbulence models and computing power. The aim of this paper is to extend previous work [1] and to further analyse initial numerical results from simulations of the flow described in the experimental work of Meares [2]. The work here undertakes to do an initial assessment of the effect turbulence modelling has on the internal flow within the pipe and through the flange and gap in the gasket. The standard two-equation k-ε and the variant RNG and realisable models will be used with a standard wall law. Future work will look at time dependent simulations and also the use of Large Eddy Simulation. The effect of the length of pipe modeled and pipe pressure are also explored, consistent with the experimental work done by Meares [2] on HAR orifice jets for one gasket shape.
Comparison of Fracture Response of Preflawed Tubes Under Internal Static and Detonation Loading
Authors: Chao Tong Wa , Shepherd Joseph E.
Published: August 2008

Fracture experiments were performed on thin-walled and preflawed aluminum 6061-T6 tubes. Flaws were machined as external axial surface notches. The tubes were 1) statically loaded with oil, 2) statically loaded with nitrogen, and 3) dynamically loaded with gaseous detonations traveling at 2.4 km/s. The experiments were controlled so that comparisons could be made on sets of specimens with the same material, tube and flaw geometry, nominal loading amplitude, and flange supports, with the only difference being the dynamics of the loading. It was found that there is a significant difference in crack propagation behavior for the three types of loading. In this paper, fracture behavior will be discussed along with the fluid dynamics involved. The tubes were also instrumented with pressure transducers, crack detection gages, and strain gages so that data on loading, crack propagating speeds, and strain history can be compared.
Basic Study for Destruction of Cryogenic Pressure Vessel By Shock Wave
Authors: Watanabe Toshiaki , Itoh Shigeru , Hamada Toru , Hokamoto Kazuyuki
Published: August 2008

In recent years, a use for cryogenic fluids as a coolant has been increasing because of the industrial development of low temperature technology. Therefore, the use of the cryogenic pressure vessel becomes general. LNG-tank, LN2, O2-tank at food factory and medical facilities are given for example. The shock tolerance of the various material under cryogenic temperature region that consist cryogenic pressure vessel is necessary with considering about them safety. The fact that material becomes fragile when it becomes a low temperature has already been known. Property of material in the temperature area of −200°C and under aren’t known very much. Therefore, we carried out experiments, which test piece are exposed to shock wave under cryogenic temperature region, and investigated destruction of test piece. The breaking surface of test piece was observed by using of the SEM. Structure of material was observed by an optical microscope.
Damping Effect in Fluid-Structure Interaction: Application to Slamming Problem
Authors: Aquelet N. , Souli M.
Published: August 2008

During a high velocity impact of a structure on an incompressible fluid, impulse loads with high pressure peaks occur. This physical phenomenon called ‘slamming’ is a concern in the shipbuilding industry because of the possibility of hull damage. Shipbuilding companies are carrying out several studies on the slamming modeling using FEM software. This paper presents the prediction of the local high pressure load on a wedge striking a free surface. The fluid-structure interaction is simulated by a fluid-structure coupling algorithm. This method of coupling, which makes it possible to transmit the efforts in pressure from the Eulerian grid to the Lagrangian grid and vice versa, is a relatively recent algorithmic development. It was successfully used in many scientific and industrial applications: the modeling of the bird strike on the fuselage of a Jet for the Boeing Corporation, underwater explosion shaking the oil platforms, and airbag simulation in automotive industry... Predicting the local pressure peak on the structure requires an accurate fluid-structure interaction algorithm. Thus, some penalty coupling enhancements make the slamming modeling possible. The main improvement is a numerical damping factor which permits to smoothing of the pressure signal.
Simulation of the Ultrasonic Diffraction in Viscous Fluids
Authors: Bouaoua N. , Alia A. , Djelouah H.
Published: August 2008

In this paper, Impulse Response Method (IRM) and Finite Difference (FD) are used to model the acoustic radiation in a viscous fluid where the attenuation is obeying a squared frequency law. Some results are presented to illustrate the attenuation effect on the diffraction. A good agreement between the IRM results and those numerically predicted by FDM is observed.
Shock Sterilization of Dry Powder Foods
Authors: Fujiwara Kazuhito , Hiroe Tetsuyuki , Asakawa Makio
Published: August 2008

The sterilization for fungi and bacteria in some kinds of dry powder foods is limited to keep their grade. Especially in spices the heat sterilization is restricted to minimum use, because the heat reduces the hot-taste that is a principal component in spices. The operation for the sterilization has to act only on fungi and bacteria, not to degrade the volatile components contained in flavor elements. In this paper, the instance of shock sterilization is shown, and the development of the idea to the sterilization equipment and its performance are presented. Experimental results showed the potential of the shock for the sterilization and the feasibility for the industrial use.
The Design of Supercritical Liquid Pipe for Organic Material Treatment
Authors: Iyama Hirofumi , Raghukandan K. , Itoh Shigeru
Published: August 2008

The supercritical liquid discovered in 1821, the specific character was known for many years. However, it began to be used industrially in Japan after the oil shock of the second half of the 1970s. Development of the process which extracts the high ingredient of added value focusing on fields, such as food and medical supplies, using the super-criticality CO2 was furthered at first in Germany. The supercritical water attracts attention with a rise of the concern of the latest resources problem or an environmental problem. Moreover, the process development such as recycling, decomposition of dioxin and PCB and oilizing and monomerizing of a waste plastic have been active. In recent years, use of the woody biomass is briskly performed on Europe. Since there is the woody biomass abundantly, it tends to go into a hand. In this paper, the supercritical liquid is described briefly. Next, the experiment of supercritical treatment of wood is described. And finally, we proposed using the explosive welding technique for the development of pressure vessel and performed the numerical simulation.
Recent Advances for J Simplified Assessment in RSE-M Code
Authors: Michel Bruno , Sermage Jean-Philippe , Gilles Philippe , Barthelet Bruno , Le Delliou Patrick
Published: August 2008

The RSE-M Code [1] provides rules and requirements for in-service inspection of French Pressurized Water Reactor power plant components. Non mandatory guidance is given in the Code for analytical flaw evaluation in a wide range of situations. In Appendix 5.4 of the Code, influence coefficients are provided to calculate stress intensity factors in pipes and shells containing semi-elliptical surface defects. The J assessment method is based on the reference stress concept with two options for reference loads evaluation: “CEP elastic plastic stress” and “CLC modified limit load”. In this paper recent advances concerning J assessment under mechanical loading for a crack located in a pipe-elbow junction are presented. Reference stress evaluation with “CLC” option is developed and mechanical foundations of the equation of large scale yielding under complex loading (pressure, in-plane and out-of-plane bending) are presented.
Normalized Stress Intensity Factor Solution of an Inner-Surface Circumferential Crack in Thin- to Thick-Walled Cylinder Under Thermal Striping
Authors: Meshii Toshiyuki , Watanabe Katsuhiko
Published: August 2008

In this paper we considered the normalized stress intensity factor (SIF) of an inner-surface circumferential crack in a thin- to thick-walled finite-length cylinder under thermal striping. The edges of the cylinder were rotation-restrained and the outer surface was adiabatically insulated. Inner surface of the cylinder was heated by a fluid with sinusoidal temperature fluctuation. We combined an analytical temperature solution for the problem and our SIF evaluation method for the crack, and as a result, showed that the transient SIF solution can be expressed in a generalized form by dimensionless parameters such as mean radius to wall thickness ratio, Biot number, normalized striping frequency and Fourier number. Finally, normalized SIF ranges for the 1st cycle and steady state were given for these dimensionless parameters in tables for mean radius to wall thickness ratio of 10, 5 and 1.
Approximate Elastic-Plastic J Estimate of Cylinders With Off-Centered Circumferential Through-Wall Cracks
Authors: Shim Do-Jun , Huh Nam-Su , Kim Yun-Jae , Kim Young-Jin
Published: August 2008

This paper provides approximate J estimates for off-centred, circumferential through-wall cracks in cylinders under bending and under combined tension and bending. The proposed method is based on the reference stress approach, where the dependence of elastic and plastic influence functions of J on the cylinder/crack geometry, the off-centred angle and strain hardening is minimised through the use of a proper normalising load. Based on published limited FE results for off-centred, circumferential through-wall cracks under bending, such normalising load is found, based on which the reference stress based J estimates are proposed for more general cases, such as for a different cylinder geometry and for combined loading. Comparison of the estimated J with extensive FE J results shows overall good agreements for different crack/cylinder geometries and for combined tension and bending, which provides sufficient confidence in the use of the proposed method to fracture mechanics analyses of off-centred circumferential cracks. Furthermore, the proposed method is simple to use, giving significant merits in practice.
Frequency Transfer Function From Fluid Temperature Fluctuations to Stress Intensity Factors
Authors: Kasahara Naoto , Ando Masanori , Furuhashi Ihciro , Fuquan Chen , Takasho Hideki
Published: August 2008

Temperature fluctuation from incomplete fluid mixing can induce fatigue cracks on structures of nuclear components, which should be prevented. For rational analysis of this phenomenon, the authors have developed a frequency transfer function that translates fluid temperature fluctuation to stress intensity factors. This function is formulated by a product of the effective heat transfer and the stress intensity factor functions, and enables us to quickly calculate stresses intensity factors induced by fluid temperature fluctuations. Furthermore, it can evaluate sensitivities of stress intensity factors to frequencies of temperature fluctuation, Biot number and constraint conditions of structures. Applicability of this function was verified through comparison with stress intensity factors calculated by the finite element method.
Statistical and Constraint Loss Size Effects on Cleavage Fracture: Implications to Measuring Toughness in the Transition
Authors: Rathbun H. J. , Odette G. R. , Yamamoto T. , He M. Y. , Lucas G. E.
Published: August 2008

A systematic investigation of the effects of specimen size on the cleavage fracture toughness of a typical pressure vessel steel is reported. Size dependence arises both from: i) statistical effects, related to the volume of highly stressed material near the crack tip, that scales with the crack front length (B); and ii) constraint loss, primarily associated with the scale of plastic deformation compared to the uncracked ligament dimension (b). Previously, it has been difficult to quantify the individual contributions of statistical versus constraint loss to size effects. Thus, we developed a single variable database for a plate section from the Shoreham pressure vessel using a full matrix of bend specimens, with B from 8 to 254 mm and b from 3.2 to 25.4 mm, that were tested at a common set of conditions. The University of California Santa Barbara (UCSB) b-B database was analyzed using three-dimensional finite element simulations of the crack tip fields combined with a cleavage model calibrated to the local fracture properties of the Shoreham steel. This paper focuses on the possible significance of these results to the Master Curve Method Standard as formulated ASTM E 1921-97. The statistical scaling procedure used in E 1921-97 to treat variations in B was found to be reasonably consistent with the UCSB b-B database. However, constraint loss for bend specimens begins at a deformation level that is much lower than the censoring limit specified in E 1921-97. Unrecognized constraint loss leads to a non-conservative, negative bias in the evaluation of To, estimated to be typically on the order of a −10°C for pre-cracked Charpy specimens.
Constraint Quantification of Single Edge Notched Bend Specimens Under Large-Scale Yielding
Authors: Chao Yuh J. , Zhu Xian-Kui , Kim Yil , Pechersky M. J. , Morgan M. J. , Lam Poh-Sang
Published: August 2008

Because crack-tip fields of single edge notched bend (SENB) specimens are significantly affected by the global bending moment under the conditions of large-scale yielding (LSY), the classical crack tip asymptotic solutions fail to describe the crack-tip fields within the crack tip region prone to ductile fracture. As a result, existing theories do not quantify correctly the crack-tip constraint in such specimens under LSY conditions. To solve this problem, the J-A2 three-term solution is modified in this paper by introducing an additional term derived from the global bending moment in the SENB specimens. The J-integral represents the intensity of applied loading, A2 describes the crack-tip constraint level, and the additional term characterizes the effect of the global bending moment on the crack-tip fields of the SENB specimens. The global bending stress is derived from the strength theory of materials, and proportional to the applied bending moment and the inverse of the ligament size. Results show that the global bending stress near the crack tip of SENB specimens is very small compared to the J-A2 three-term solution under small-scale yielding (SSY), but becomes significant under the conditions of LSY or fully plastic deformation. The modified J-A2 solutions match well with the finite element results for the SENB specimens at all deformation levels ranging from SSY to LSY, and therefore can effectively model the effect of the global bending stress on the crack-tip fields. Consequently, the crack-tip constraint of such bending specimens can now be quantified correctly.
A New Approach to Evaluate Fracture Toughness of Structural Materials
Authors: Wang J. A. , Liu K. C.
Published: August 2008

A new method, designated as Spiral Notch Torsion Test (SNTT), is developed recently to measure the intrinsic fracture toughness (KIC) of structural materials. The SNTT overcomes many of the limitations inherent in traditional techniques and makes it possible to standardize fracture toughness testing. It is uniquely suitable for testing a wide variety of materials used extensively in pressure vessel and piping structural components and weldments, including others such as ceramics, their composites, and concrete. The SNTT system operates by applying pure torsion to uniform cylindrical specimens with a notch line that spirals around the specimen at a 45° pitch. The KIC values are obtained with the aid of a three-dimensional finite-element computer code, TOR3D-KIC, developed at ORNL.
Case Study on LBB Application for Field Fabrication Weld Metal of Nuclear Primary Piping Systems
Authors: Kim K. C. , Kim J. T. , Suk J. I. , Kwon H. K. , Sung U. H. , Yang B. I.
Published: August 2008

In order to apply leak before break (LBB) design for nuclear primary piping systems, dynamic and static J-R tests of field fabrication weld metal were carried out to determine mechanical properties at 316°C. For the reactor coolant piping system made by SMAW (Shielded Metal Arc Welding) process of the SA508 Cl.1a, the variation of J-R fracture characteristics with the loading rate of 1mm/min and 1,000mm/min was examined to prevent the catastrophic break under seismic loading. In the J-R test results, the J-R curves at 1,000mm/min are about 60% higher than those at 1mm/min. It suggests that the welding joints of the reactor coolant piping may be susceptible to dynamic strain aging at 316°C. For the surge line piping made by GTAW (Gas Tungsten Arc Welding) process of the SA312 TP347, excellent static J-R properties are required because the nominal diameter of the pipe is relatively small size of 12 inch. In order to examine the effect of carbon content in the filler metal on the fracture toughness of its welded metal, weld metal specimens were made by using 3 kinds of filler metals whose carbon contents were 0.050, 0.030 and 0.025%, respectively. In the static J-R test results, weld metal made by one of three electrodes satisfied the LBB acceptance criteria. Much better J-R fracture characteristics with decreasing carbon content of filler metal can be shown.
Effects of Hydrided Region Overload on Delayed Hydride Cracking Initiation From Flaws in Zr-2.5 Nb Pressure Tubes
Authors: Shek Gordon K. , Cui Jun
Published: August 2008

The Zr-2.5 Nb pressure tubes of CANDU™ (CANada Deuterium Uranium) reactors are susceptible to a crack initiation and growth mechanism known as Delayed Hydride Cracking (DHC), which is a process that involves hydrogen diffusion, hydride precipitation, hydrided region formation and fracture at a flaw-tip. An overload occurs when the hydrided region at a flaw is loaded to a stress higher than that at which this region is formed. Flaw disposition requires justification that the hydrided region overload from normal reactor operating and transient loading conditions will not fracture the hydrided region, and will not initiate DHC. To evaluate the effects of hydrided region overload on DHC initiation, a series of monotonically increasing load experiments were performed on specimens prepared from unirradiated pressure tube materials with the hydrided region formed at flaws with root radii varying from 15 to 350 μm, and blunt notches with and without secondary flaws. Test results indicate that the resistance to overload fracture is dependent on a variety of parameters including flaw geometry, hydride formation stress, loading history, and overload test temperature.
Fitness-for-Service Assessment for Pressure Equipment in Japan
Authors: Tahara Takayasu
Published: August 2008

Pressure equipment in refinery and petrochemical industries in Japan has been getting old, mostly more than 30 years in operation. Currently, the Japanese regulations for pressure equipment in service are the same as those in existence during the fabrication of the pressure equipment. Accordingly, there is an immediate need for an up to date more advanced “Fitness For Service” (FFS) evaluation requirements for pressure equipment. In order to introduce the latest FFS methodologies to Japanese industries, the High Pressure Institute of Japan (HPI) has organized two task groups. One is a working group for development of a maintenance standard for non-nuclear industries. Its prescribed code “Assessment procedure for crack-like flaws in pressure equipment” is for conducting quantitative safety evaluations of flaws detected in common pressure equipment such as pressure vessels, piping, storage tanks. The other is a special task group to study of API RP579 from its drafting stage as a member of TG579. The FFS Handbook, especially for refinery and petrochemical industries, has been developed based on API RP579 with several modifications to meet Japanese pressure vessel regulations on April 2001. [1] It is expected that both the Standard and FFS handbook will be used as an exemplified standard with Japanese regulations for practical maintenance. This paper presents concepts of “Assessment procedure for crack-like flaws in pressure equipment” HPIS Z101, 2001 [2].
Assessment of Creep and Creep-Fatigue Crack Growth Following the R5 Procedures
Authors: Ainsworth R. A. , Budden P. J. , Dean D. W. , Fox M. J. H. , O’Donnell M. P. , Dean J. M. H. , Goodall I. W. , Hooton D. G.
Published: August 2008

Parts of the R5 high temperature assessment procedures address creep and creep-fatigue crack growth. The procedures were developed some years ago as separate approaches for creep crack growth (R5 Volume 4) and creep-fatigue crack growth (R5 Volume 5). A major revision to these procedures has recently been completed. This unifies the separate approaches into a single procedure for creep-fatigue crack growth (R5 Volume 4/5). The revision restructures the procedure for easier application and includes a number of technical developments, including criteria for deciding when creep-fatigue interactions are important. This paper describes in outline the new R5 creep-fatigue crack growth procedure.
Effects of Weld Repairs on Calculated Failure Probabilities for Reactor Pressure Vessels and Piping
Authors: Simonen F. A. , Schuster G. J. , Doctor S. R.
Published: August 2008

Section III of the ASME Boiler and Pressure Vessel Code for nuclear power plant components requires radiographic examinations (RT) of welds and repairs for RT indications that exceed code acceptable sizes. This paper describes research that generated data on welding flaws, which indicated that the largest flaws occur in repaired welds. Evidence suggests that repairs are often for small and benign RT indications at locations buried within the vessel or pipe wall. Probabilistic fracture mechanics calculations are described in this paper to predict the increases in vessel and piping failure probabilities caused by the repair-induced flaws. Calculations address failures of embrittled vessel welds for pressurized thermal shock (PTS) transients. In this case small flaws, which are relatively common, can cause brittle fracture such that the rarely encountered repair flaws of large sizes gave only modestly increased failure probabilities. The piping calculations simulated fatigue crack growth of fabrication flaws. These calculations showed that only relatively large fabrication flaws can fail piping because of the ductile nature of the piping material. The large repair flaws significantly increased the failure probabilities. The paper recommends the use of more discriminating UT examinations in place of RT examinations along with repair criteria based on a fitness-for-purpose approach that minimizes the number of unjustified repairs.
Investigation of Residual Stresses Caused by Welding, Cladding and Tempering of Reactor Pressure Vessels
Authors: Kostylev V. I. , Margolin B. Z. , Varovin A. Y. , Keim E.
Published: August 2008

Calculations of residual stress fields, which arise after welding, cladding and tempering, were performed as applied to reactor pressure vessels (RPVs) of WWER types. These calculations are based on a procedure, which takes into account Feα↔Feγ transformation happening in base and weld metal under welding and cladding, and also creep during tempering. The procedure is based on solutions of the temperature and non-isothermal elasto-plastic problem with and without creep by the finite element method. On the basis of the performed investigation it is shown that Feα↔Feγ transformation may affect the residual stress distribution. An analysis of cases has been performed for which the above effect is strong and for which this effect may be ignored. On the basis of the calculation performed, an engineering procedure is proposed that allows to determine the residual stress fields in welds of the WWER-440 and WWER-1000 for various durations of post-weld tempering.
Dynamic Analysis of a Radioactive Material Package Primary Containment Vessel in a High Pressure Event
Authors: Wu Tsu-te , Abramczyk G. A. , Blanton P. S.
Published: August 2008

This paper discusses the evaluation of the structural integrity of the Primary Containment Vessel (PCV) of a 9975 Shipping Package for radioactive materials subjected to an instantaneously applied pressure load. The instantaneous pressure increase is based on the postulated structural failure of a plutonium oxide container caused by either over pressurization due to detonation or gradual gas buildup. A nonlinear dynamic analysis was performed for a partial 9975 shipping package to evaluate the structural response of the PCV excited by the instantaneous pressurization. The structural integrity of the PCV is justified based on the analytical results in comparison with the stress criteria specified in the ASME Code, Section III, Appendix F for Level D service loads.
Prediction of the Cutting Forces on Stainless Steels When Using a Turning Process
Authors: Cassier Zulay , Mun˜oz-Escalona Patricia , Moreno Jannelly
Published: August 2008

Stainless steels have a great application in the manufacturing process especially due to their characteristic high corrosion resistance. The machining of these materials, the study of the cutting forces, and the power required for the cutting are important parameters to be evaluated. Their relationship with other cutting variables process is crucial for the optimization of the machining process. The results of this research are empirical expressions relating cutting parameters (cutting speed, feed rate and depth of cut) to cutting forces for each stainless steel studied, AISI 304, AISI 420 and AISI 420HT (HT: Heat treated). A general expression was also developed which includes the mechanical properties of these stainless steels. These results enable the user to predict cutting forces when using a turning process.
Die Design and Blanking Analysis
Authors: Hall Mary E. , Long Mike , Rhattigan Sean D. , Shields Elvin B.
Published: August 2008

The modified fine blanking technique is the subject of this research, along with a comparison of conventional blanking and shaving. The modified process does not require the use of a triple-action press and the press can be run at the same rate as conventional blanking. A counter-pressure punch and assembly are used to prevent the fracturing of the cut, which is similar to standard fine blanking. The difference between the two fine blanking techniques is that the modified method does not hold the material from lateral movement during the perforating operation. Furthermore, to achieve an optimum comparison of all three methods (conventional blanking, shaving, and modified fine blanking), a die set was designed that could produce parts for each of these processes. The evaluation of each method was done by cutting similar samples of each method and placing them in plastic, which allowed microscopic comparisons to be made of the three methods. A trade-off analysis of the various methods demonstrated that the modified fine blanking technique is superior to the other techniques.
Innovative Flash Control in Inertia Welding
Authors: Korinko P. S. , Peacock H. B.
Published: August 2008

Inertia welding is widely used to join cylindrically shaped objects such as disks and shafts in turbine engines, turbochargers, etc. Flash control in many of these applications is not critical because the excess material is on external surfaces and can readily be removed by machining. Internal flash on hollow vessels, however, may be difficult or impossible to remove and may be either controlled by the use of flash traps or the part can be used as welded. Both internal flash and flash traps reduce internal volume and the conditions are not always acceptable. To address this short-coming, several innovative methods have been tested to determine their effect on flash control in inertia welding of hollow vessels. The methods include introduction of high pressure inert gas and incorporation of an expendable mandrel to divert the flash. Both gas and internal mandrels appear promising methods for diverting flash.
Assessment of the Possibility of Operating Pipelines With Defects
Authors: Chernyavsky Alexander O. , Timashev Sviatoslav A. , Zaitsev Nicolay L.
Published: August 2008

The paper describes latest results of the non-linear FEM-analysis of the influence on pipeline integrity of dents, corrosion loss of the metal on the outer surface of the pipe and laminations of the pipeline web.
Application of the Linear Matching Method to Cracked Bodies
Authors: Habibullah M. Salahuddin , Ponter A. R. S.
Published: August 2008

The purpose of this paper is to demonstrate the application of the Linear Matching Method (LMM) to cracked bodies subjected to cyclic histories of loads and temperatures. The method [1,2,3], related to the methods of Elastic Compensation and Gloss r-node, used in design calculations for a number of years, involves matching the behaviour of a non-linear material to that of a linear material. The significance of the developed programming methods, in engineering design, is then discussed for two applications. The first is in the identification of ratchet limits for cracked structures subjected to variable loads and temperatures. Solutions are presented for both perfect plasticity and complete cyclic hardening conditions, for differing values of crack lengths, for the classical axisymmetric Bree problem. The other is in the investigation of the relationship between the near crack-tip fields and the cyclic loading histories. The analysis reveals the strong influence of the elastic stresses, immediately outside the stress singularities, allowing an understanding of the behaviour of mechanically and thermally induced crack-tip fields to be developed.
Estimation of Plastic Collapse Load of Steam Generator Tube With Two Parallel Axial Through-Wall Cracks
Authors: Moon S. I. , Kim Y. J. , Lee J. H.
Published: August 2008

The 40% of wall criterion, which is generally used for the plugging of steam generator tubes, is applied only to a single crack. In the previous study, a total number of 9 failure models were introduced to estimate the local failure of the ligament between cracks and the optimum coalescence model of multiple collinear cracks was determined among these models. It is, however, known that parallel axial cracks are more frequently detected during an in-service inspection than collinear axial cracks. The objective of this study is to determine the plastic collapse model which can be appfied to the steam generator tube containing two parallel axial through-wall cracks. Three previously proposed local failure models were selected as the candidates. Subsequently interaction effects between two adjacent cracks were evaluated to screen them. Plastic collapse tests for the plate with two parallel through-wall cracks and finite element analyses were performed for the determination of the optimum plastic collapse model. By comparing the test results with the prediction results obtained from the candidate models, a COD base model was selected as an optimum model.
Fluidelastic Instability in a Tube Array Subjected to Uniform Flow and Jet Flow
Authors: Feenstra Paul , Weaver David S. , Abdullah Zia
Published: August 2008

A wind tunnel study was carried out to investigate the fluidelastic stability of a model heat exchanger tube array subjected to a uniform cross-flow of air and a concentrated jet flow of air down a tube lane. The latter experiments were intended to simulate the effects of a soot blower on the dynamic response of the tubes which had apparently been the cause of catastrophic tube failure in a heat exchanger. The experimental results showed that the model tube array experienced fluidelastic instability when subjected to a uniform cross-flow beyond a dimensionless pitch flow velocity of 24.4. For a mass damping parameter of 14.5, the Connors’ constant for this array is K = 6.4 which is over 2-1/2 times that of the conservative guideline of K = 2.4 recommended by the ASME boiler and pressure vessel code. These experiments established that the normal operating conditions of the heat exchanger should not lead to excessive tube vibration. It was shown that a continuously translating nozzle dispensing a jet of air at the tubes caused some static deflection of the tubes but no serious vibrations were observed that would be of concern from the standpoint of tube damage. However, when the nozzle was fixed at one location whereby the jet of air issued directly down a tube lane, fluidelastic instability occurred in the tubes in the first few rows, but some time was required for large amplitude vibrations to develop. It can be inferred that, for heat exchangers equipped with steam soot blowers, normal soot blower operation should not cause fluidelastic instability but that a parked soot blower can be expected to cause fatigue failure of the tube adjacent to the impinging jet in a relatively short period of time.
New Experimental Data and Analysis for Two-Phase Flow-Induced Vibration of Tube Bundles: Preliminary Results
Authors: Mitra Deepanjan , Dhir Vijay K. , Catton Ivan
Published: August 2008

In the past, fluid-elastic instability in two-phase flow has been largely investigated with air-water flow. In this work, new experiments are conducted in air-water cross-flow with a fully flexible 5 × 3 normal square array having pitch-to-diameter ratio of 1.4. The tubes have a diameter of 0.016 m and a length of 0.21 m. The vibrations are measured using strain gages installed on piano wires used to suspend the tubes. Experiments are carried out for void fractions from 0%–30%. A comparison of the results of the current tests with previous experiments conducted in air-water cross-flow shows that instability occurs earlier in a fully flexible array as compared to a flexible tube surrounded by rigid tubes in an array. An attempt is made to separate out the effects of structural parameters of three different experimental datasets by replotting the instability criterion by incorporating the instability constant K, in the reduced velocity parameter.
Thermalhydraulic Analysis of Steam Generators: Application of the Thirst Code to Vibration Analyses
Authors: Yetisir M. , Pietralik J. , Mirzai M.
Published: August 2008

Flow-induced vibration concerns may be avoided by analysis, which requires the knowledge of flow patterns and the flow distribution in steam generators (SG). Typically, the distributions of flow velocity, fluid density, and, in the case of two-phase flow, distributions of steam quality and two-phase flow regime are needed. Generating this data is not straightforward because of the 3-dimensional nature of flow, complex steam generator geometry, and uncertainties associated with two-phase flow modelling. In this paper, the main features of THIRST, a thermalhydraulic code for recirculating SGs, are described. In addition, the effects of thermalhydraulic modelling and design features on velocity distributions and gap flow velocity needed for flow-induced vibration and fretting-wear calculations are discussed. These include an anisotropic resistance model in the U-bend region, design modifications in the U-bend region to reduce tube vibration, and the prediction of two-phase flow regimes.
Severed Tubes in Operating Nuclear Steam Generators: Case Analysis — II
Authors: Au-Yang M. K.
Published: August 2008

During an eddy current inspection in April 2002, it was found that three tubes downstream of an out-of-service tube in a once-through nuclear steam generator (OTSG) had significant wear indications. Wear indications of these tubes has been recorded as early as 1995 and apparently has been progressing with time. A shell-side video inspection revealed that this tube was completely severed at the bottom tubesheet. This severed tube was discovered immediately after a tube in another OTSG of similar design was found to have severed at the top tubesheet. In the root-cause analysis of the other severed tube, the possibility of a similar tube failure due to flow-induced vibration at the bottom tubesheet was explicitly ruled out and corrective action was implemented based on this conclusion. This discovery cast doubt on the earlier analysis and raised concern on both steam generators. The purpose of this study is to carry out a root cause analysis of the failure of the second severed tube and show that even though the two failures appeared to be similar, the causes and failure mechanisms were different. The study also showed that what appeared to be an obvious fix turned out to be invalid upon more in-depth flow-induced vibration analysis.