bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation B/W Stress, Nozzle Load and Total Length in a Process Piping Line
Authors: Ozmaian Javad , Farzaneh Amir H.
Published: January 2011

Nowadays, time saving in piping stress analysis is a major concern among consultant engineering companies in power and process plants. In this paper, we are going to have a quantity review between some important parameters such as sustained, occasional and expanding stresses with total length and nozzle load of a real case according to ASME B31.3. Most of the times, piping stress designers try different and more flexible piping routes completely arbitrary. Longer piping route means greater mass, and it means a big trouble in earthquake time especially for allowable nozzle loading, on the other hand shorter piping route increases thermal nozzle loading and operating stresses. We will try to find a relationship among mentioned parameters to have an optimal piping route in order to save time and material. Finally, different routes will be analyzed using Caesar II to plot related parameters and find optimum criterion.
Determination of Gimbal and Hinged Expansion Joints Reaction Moments
Authors: Veiga Jose´ Carlos , Kavanagh Nelson , Sousa Ana Maria F. , Medeiros Jorivaldo , Veiga Jordana Luiza
Published: January 2011

This paper proposes a method to estimate the actual reaction loads in gimbal and hinged metal bellows expansion joints. Friction and some media pressure forces, which are not considered in current EJMA Standard calculations, are added to bellows spring rate to estimate the expansion joint movement reaction moment. The proposed calculation method is based upon pressure and movement tests of large size expansion joints.
Plastic Instabilities in Statically and Dynamically Loaded Spherical Vessels
Authors: Duffey Thomas A. , Rodriguez Edward A.
Published: January 2011

Significant changes were made in design limits for pressurized vessels in the 2007 version of the ASME Code (Section VIII, Div. 3) and 2008 and 2009 Addenda. There is now a local damage-mechanics based strain-exhaustion limit, including the well-known global plastic collapse limit. Moreover, Code Case 2564 (Section VIII, Div. 3) has recently been approved to address impulsively loaded vessels. It is the purpose of this paper to investigate the plastic collapse limit as it applies to dynamically loaded spherical vessels. Plastic instabilities that could potentially develop in spherical shells under symmetric loading conditions are examined for a variety of plastic constitutive relations. First, a literature survey of both static and dynamic instabilities associated with spherical shells is presented. Then, a general plastic instability condition for spherical shells subjected to displacement controlled and short-duration dynamic pressure loading is given. This instability condition is evaluated for six plastic and visco-plastic constitutive relations. The role of strain-rate sensitivity on the instability point is investigated. Calculations for statically and dynamically loaded spherical shells are presented, illustrating the formation of instabilities. Conclusions of this work are that there are two fundamental types of instabilities associated with failure of spherical shells. In the case of impulsively loaded vessels, where the pulse duration is short compared to the fundamental period of the structure, one instability type is found not to occur in the absence of static internal pressure. Moreover, it is found that the specific role of strain-rate sensitivity on the instability strain depends on the form of the constitutive relation assumed.
A Non-Destructive Evaluation Method: Measuring the Fixed Strength of Spot Welded Joint Points by Surface Electric Resistivity
Authors: Shimamoto Akira , Yamashita Keitaro , Inoue Hirofumi , Yang Sung-mo , Iwata Masahiro , Kato Natsuko
Published: January 2011

Destructive tests are generally applied for evaluating fixed strength of spot welding nuggets on zinc plating steel, which is swidely used as the primary automobile structural material. Destructive tests, however, are expensive and time consuming. This paper discusses a non-destructive method for evaluating of welded joints fixed strength by utilizing surface electric resistance. A nugget tester has developed by authors for this purpose. The non-destructive method focuses on surface electric resistance decreasing rate; α, and effect of the corona bond. Nugget diameter is estimated by RQuota calculated from variation of resistance and constant representing the area of the corona bond. Since maximum tensile strength is correlated with the nugget diameter, it is inferred from the estimated nugget diameter.
Assessment of Fatigue Crack Growths for Transformed Surface Flaws Using FFS Codes
Authors: Hasegawa Kunio , Li Yinsheng
Published: January 2011

If embedded flaws are detected that are close to the component surfaces, proximity rules are used to determine whether the flaws should be treated as embedded flaws as is, or transformed surface flaws. This re-characterization concept is the same in all fitness-for-service codes in the world. However, the rules on transforming embedded flaws to surface flaws differ around the world. The sizes of the re-characterized surface flaws are significantly different. The objective of this paper is to introduce the proximity rules provided by the fitness-for-service codes, and it is shown that lives of components due to fatigue crack growths for the transformed surface flaws are significantly different among the fitness-for-service codes.
Applications of Code Case 2605 for Fatigue Evaluation of Vessels Made in 2.25Cr-1Mo-0.25V Steels Slightly Into Creep Range
Authors: Terada Susumu
Published: January 2011

The current Section VIII Division 2 of ASME code does not permit method A of paragraph 5.5.2.3 to be used for the exemption from fatigue analysis when the design allowable stress is taken in the time dependent temperature range. Method B of paragraph 5.5.2.4 also cannot be used because it requires the use of the fatigue curve which is limited to 371 ° C and below the needed temperature. Code Case 2605 is a rule for fatigue evaluation of 2.25Cr-1Mo-0.25V steels at temperatures greater than 371 ° C and less than 454 ° C. An inelastic analysis including the effect of creep shall be performed for all pressure parts according to Code Case 2605. Especially, a full inelastic analysis shall be performed using the actual time-dependent thermal and mechanical loading histograms for the lateral nozzle based on preliminary study. It takes much time to perform this inelastic analysis for all full histograms and obtain the fatigue evaluation results when large number of cycles of full pressure is specified in user’s design specification. This paper provides sample analysis results for nozzles and clarifies issue of implementation of Code Case 2605. Then, the proposal of simplification and modification of Code Case 2605 from these results are proposed.
A Numerical Study of Cavitation Induced Vibration
Authors: Benaouicha M. , Astolfi J. A. , Ducoin A. , Frikha S. , Coutier-Delgosha O.
Published: January 2011

The present work deals with an original study of the dynamics of an elastic structure immerged in an unsteady partial cavitating flow. The latter corresponds to the case of a leading edge attached cavity that exhibits periodical oscillations. The elastic structure is a cantilevered rectangular hydrofoil made of polyacetal plastic material (E = 3GPa). The computational fluid dynamics is based on a 2D unsteady single fluid model of cavitation with a barotropic law and a k – ε – RNG modified turbulent model. The computational structure dynamics is carried out using a 3D finite element code. The fluid structure coupling is based on a chained weak coupling algorithm for which the 2D unsteady local fluid loading is computed on a rigid hydrofoil, then interpolated on the 3D deformable hydrofoil to compute the structural dynamics. The results are compared to the experiment ones carried out in the hydrodynamic tunnel of the research institute at the French Naval Academy for flow conditions close to the numerical ones. It is shown that in spite of a weak coupling algorithm, the forced vibration due to the periodical behaviour of the unsteady partial cavity is rather well predicted by the computation and compared favourably with the experiments. However, the experiments reveal that cavitation influences the natural modal response of the elastic structure in a more complex fluid structure interaction process.
Effect of Bending Load on the Failure Pressure of Wall-Thinned Pipe Bends
Authors: Kim Jin Weon , Jung Oon Young
Published: January 2011

Under normal operating conditions, piping systems in nuclear power plants (NPPs) are subject not only to internal pressure but also to bending loads induced by deadweight and thermal expansion [1]. Bending is thus considered to be an important factor in evaluating the integrity of defective piping components. Local wall-thinning due to flow-accelerated corrosion is a main degradation mechanism of carbon steel piping systems in NPPs [2], and the integrity evaluation of wall-thinned piping components has become an important issue [3]. This study investigated the effects of bending load on the failure pressure of wall-thinned pipe bends under internal pressure. Our previous study experimentally evaluated the bending load effects on the failure pressure of wall-thinned elbows under displacement controlled in-plane bending load [4], but the numbers of experimental data were insufficient to determine the effects of bending load on the failure pressure of wall-thinned pipe bends. Therefore, the present study systematically evaluates the effects of bending load on the failure pressure of wall-thinned pipe bends using parametric finite element analyses.
Effects of Prior Stress Relaxation on the Prediction of Creep Life Using Time and Strain Based Methods
Authors: Payten Warwick M. , Snowden Ken U. , Dean David W. , Humphries Samuel R. , Edwards Lyndon
Published: January 2011

A critical requirement for both next generation conventional and nuclear plants is the development of simplified inelastic design and fitness for purposes procedures that give a reasonably accurate prediction of the complex multi-axial time dependent stress strain behavior. The accumulation of this inelastic strain in the form of coupled creep-fatigue damage over time is one of the principal damage mechanisms which will eventually lead to crack initiation in critical high temperature equipment. Two main procedures that address creep-fatigue loading are generally used, either a time fraction or a ductility exhaustion approach. It is generally accepted that these methods enable conservative predictions within a factor of 2 to 3 and hence are reliable methods for code based design and fitness for purpose type assessments. However, for complex cycles, this may not be the case, for example prior relaxation cycles are found to accelerate the creep rupture of the material with the result that a significant reduction in creep life can be observed. An investigation was undertaken into the influence of prior relaxation on resultant failure using a typical low alloy ferritic power station steel. Both time based and strain based methods were used to predict the damage caused by the stress relaxation cycles followed by operation at steady state. The predictions found that while ductility exhaustion methodologies based on mean properties where adequate in predicting the failure life, time fraction methods were found to be extremely non-conservative for mean properties and only lower bound solutions provided an estimate of remaining creep life. The Monkman-Grant approach resulted in predictions that erred on the conservative side. The results have implications for both current and future conventional and nuclear power stations as it may be difficult for time based approaches to accurately account for complex cycling, shakedown conditions or stress relaxation at welds.
An Analysis of Thermo-Mechanical Behavior in a Multilayer Composite Pipe Under Temperature Variation
Authors: Yang Wei , Wang Jyhwen
Published: January 2011

A generalized analytical solution of mechanical and thermal induced stresses in a multi-layer composite cylinder is presented. Based on the compatibility condition at the interfaces, an explicit solution of mechanical stress due to inner and outer surface pressures and thermal stress due to temperature change is derived. A finite element model is also developed to provide the comparison with the analytical solution. It was found that the analytical solutions are in good agreement with finite element analysis result. The analytical solution shows the non-linear dependency of thermal stress on the diameters, thicknesses and the material properties of the layers. It is also shown that the radial and circumferential thermal stresses depend linearly on the coefficients of thermal expansion of the materials and the temperature change. As demonstrated, this solution can also be applied to analyze the thermo-mechanical behavior of pipes coated with functionally graded materials.
Analysis of ASME Codes for Fatigue of Pressure Vessels
Authors: Farhangdoost Khalil , Hamrahan Payman
Published: January 2011

In industries, pressure vessels or in general thick-wall cylinders under internal pressure are important parts and analysis of their applications in various conditions is essential. Therefore, for design of pressure vessels usage of standard codes like ASME is necessary. Most of cracked or damaged pressure vessels are exposed to cyclic loading. This failure process is fatigue. ASME codes have some codes for analyzing this process. These codes show the conditions and formulas for fatigue analysis. In this paper, a thick wall pressure vessel is analyzed with three cyclic loading regimes. The maximum stress intensity, fatigue life and damage factor are calculated by ASME codes. Then by usage of finite element method, ASME results are compared for fatigue life analysis. Previous investigations show that nozzle connection area of pressure vessels have high stress concentration, and usually crack is propagated from this zone. Thus fatigue analysis is accomplished for nozzle connection of pressure vessel by ASME codes and finite element method. Then nine shape of crack with same crack front size are modeled on the maximum stress zone of the nozzle connection. Then stresses of crack fronts and stress intensity factors of cracks are computed by finite element method with ABAQUS software which is powerful for fracture mechanic analysis. The critical crack which is elliptical prismatic crack virtually is grown step by step and for each step, stress intensity factor is computed by ABAQUS software. With relation between stress intensity factor and crack size also using Paris formula, fatigue life is computed. This operation is done for two type of crack growth. In first type length and depth of crack are grown and in second type only crack length is grown. Finally, the fatigue life obtained from Paris formula and ASME codes are compared.
Ultrasound Imaging Using Multilayer Synthetic Aperture Focusing
Authors: Skjelvareid Martin H. , Birkelund Yngve
Published: January 2011

Synthetic aperture focusing techniques (SAFT) have already been studied within several fields of non-destructive testing, but so far only with a single, relatively homogenous medium. In this article, we modify the original time-domain SAFT in order to image the interior of a multilayer structure. Standard focusing techniques assume that the wave velocity is constant within the volume to be imaged. The concept of the root-mean-square (RMS) velocity is used here to modify the classical delay-and-sum algorithm to handle layers with differing wave velocities. A scheme for iteratively using this to estimate the interfaces between the layers is also presented. The proposed method is demonstrated on ultrasonic B-scans of two test objects immersed in water, and it is shown that the increased lateral resolution and signal-to-noise ratio of standard SAFT is extended to the multilayer case. The increased resolution also makes it possible to accurately estimate the interfaces between consecutive layers, as long as the preceding interfaces are relatively smooth.
NESC VII: A European Project for Application of WPS in RPV Assessment Including Biaxial Loading
Authors: Moinereau Dominique , Chapuliot Ste´phane , Marie Ste´phane , Gilles Philippe
Published: January 2011

The Reactor Pressure Vessel (RPV) is an essential component liable to limit the lifetime duration of PWR plants. The assessment of defects in RPV subjected to PTS transients made at a European level do not necessarily take into account the beneficial effect of load history (warm pre-stress WPS) on the resistance of RPV material regarding the risk of brittle failure. A 4-year European Research & Development program — SMILE — was successfully conducted between 2002 and 2005 as part of the 5th Framework of the European Atomic Energy Community (EURATOM). The objective of the SMILE project (‘Structural Margin Improvements in aged-embrittled RPV with Load history Effects’) was to provide sufficient evidence in order to demonstrate, to model and to validate the beneficial WPS effect in a RPV integrity assessment. Numerous experimental, analytical and numerical results have been obtained which confirm the beneficial effect of warm pre-stress on RPV steels, with an effective significant increase of the material resistance regarding the risk of brittle failure. In addition to SMILE, a new project dealing with WPS — NESC VII — has been launched in 2008 (linking with the European Network of Excellence NULIFE) with the participation of numerous international organizations (R&D, Utilities and Manufacturers). Based on experimental, analytical and numerical tasks, the project is focused on topics generally not covered by past experience on WPS: biaxiality of loading on large-scale specimens, effect of irradiation, applicability to intergranular fracture, modeling (including analytical and numerical models) … Among these tasks, some new novel WPS experiments are being conducted on large scale cruciform bend bar specimens in order to study the influence of biaxial loading on WPS effect, using a fully representative RPV steel (18MND5 steel similar to A533B steel). After a synthesis of main WPS results available from previous projects on representative RPV steels, a description of the NESC VII project is presented in this paper together with the corresponding organization, including the present status of the project.
Environmental Fatigue Evaluation for Primary Components of APR1400 Reactor Coolant System
Authors: Kim J. M. , Kim K. W. , Yoon K. S. , Park S. H. , Kim I. Y. , Kim Y. H.
Published: January 2011

USNRC Regulatory Guide (RG) 1.207 provides a guideline for evaluating fatigue analyses due to the environmental effects on the new light water reactor (LWR). The environmental correction factor (Fen) is used to incorporate the LWR environmental effect into fatigue analyses of ASME Class 1 components. In this paper, the environmental fatigue evaluation is applied to some primary components with 60 year design life of Advanced Power Reactor (APR1400). The materials sampled from Class 1 components are the low alloy steel for the reactor vessel (RV) outlet nozzle and the carbon steel for the hot leg which are attached to the outlet nozzle. The simplified method, time-based integral method and strain-based integral method are used to compute the Fen values. The calculated fatigue usage factors including the environmental effects are compared with those obtained using the current ASME Code rules. As the calculated cumulative fatigue usage factor considering environmental effects (CUFen) is below 1.0, there is no concern for the RV outlet nozzle to implement design for environmental fatigue effects.
Fluid Structure Interactions for Tube Bundles: Physical Meaning of a Rayleigh Damping
Authors: Broc Daniel , Sigrist Jean Franc¸ois
Published: January 2011

It is well known that a fluid may strongly influence the dynamic behaviour of a structure. Many different physical phenomena may take place, depending on the conditions: fluid flow, fluid at rest, small or high displacements of the structure. Inertial effects can take place, with lower vibration frequencies, dissipative effects also, with damping, instabilities due to the fluid flow (Fluid Induced Vibration). In this last case the structure is excited by the fluid. The paper deals with the vibration of tube bundles under a seismic excitation or an impact. In this case the structure moves under an external excitation, and the movement is influenced by the fluid. The main point in such system is that the geometry is complex, and could lead to very huge sizes for a numerical analysis. Important developments have been made in the last years to develop homogenization methods for the dynamic behaviour of tube bundles. The numerical size of the problem is reduced, and it is possible to make numerical simulations on large tube bundles with reasonable computer times. These methods consider that the fluid movement is governed by the Euler equations for the fluid. They are based on an analysis on an elementary cell, corresponding to one tube, and on an expression of the forces applied by the fluid to the structure. This force only depends on the fluid’s and tube’s acceleration. Only “inertial effects” will theoretically take place, with globally lower frequencies. A research program is under progress to take into account dissipative effects also, with a homogenization of the Navier-Stokes equations in the tube bundle. It is common, in numerical simulations, to add a damping for the structures by using a global Rayleigh damping. The paper deals with the physical meaning of this Rayleigh damping in the Euler homogenized equations. It can be demonstrated that this damping corresponds to a force applied by the fluid to the structure depending not only on the acceleration, but on the fluid and structure velocity also. This Rayleigh damping is a first step to take into account the dissipative effects for FSI in tube bundles.
Detection of the Crack Initiation by Means of AE Method Under Low Cycle Fatigue of Elbow Pipe Having Local Wall Thinning
Authors: Kasai Naoya , Ando Kotoji , Nishio Maki , Urabe Yoshio , Takahashi Koji
Published: January 2011

This paper describes the detectability of the crack initiation by means of the AE method under low cycle fatigue of the elbow pipe having local wall thinning to clarify the crack growth behavior for the pipes. Elbow specimens having local wall thinning were prepared, and local wall thinning due to flow accelerated corrosion was simulated by machined pipe wall thinning. Low cycle fatigue tests for the specimens were then carried out. AE method during low cycle fatigue tests was conducted to evaluate the crack initiation and location. In AE measurement, wide band AE sensors of 5mm in diameter were used to attach to the convex surfaces of the specimens. The circumference and axial strain of the specimens and the cross head displacement were also stored to the digital AE system signal. As a result, it is clear that the AE signals indicated the crack initiation in small circumference strain.
Blast Load Significance on Pressure Testing Enclosure Designs
Authors: Edel Matthew , Ketchum Donald
Published: January 2011

Pressure vessels that operate at high pneumatic pressures (greater than 10,000 psi [69 MPa]) pose several potential hazards to nearby personnel, including projectile launch and blast loads that may occur as a result of a vessel failure. In order to provide personnel protection, pressure vessels are often placed inside test enclosures. However, sometimes these enclosures are built with the intent to create an exclusion zone but are not designed to contain these hazards. On some occasions, local shields are used to provide protection from potential projectiles that may be launched from a failed pressure vessel without regard to blast loads that will ensue from a pneumatically-charged vessel. The purpose of this experimental test is to demonstrate the importance of properly designing test enclosures to contain blast loads from a pneumatic pressure vessel failure. In this test, the walls and roof of the enclosure failed in response to blast loads emanating from a failed pneumatic pressure vessel test and were thrown as a secondary debris hazard. The vessel was designed to fail in a manner consistent with the most common failure modes as reported in industry. Blast loads inside the enclosure and the dynamic structural response were monitored during the experiment. Blast loads obtained from a computational fluid dynamics (CFD) model and the structural response from a finite element analysis (FEA) model are also discussed.
Oyster Creek Nuclear Generating Station Containment Drywell Buckling Analysis
Authors: Kok Soo Bee , Tang Shu S. , Ku Francis H. , Herrera Marcos L. , O’Rourke John F. , Ray Francis H.
Published: January 2011

This article presents the overall methodology and the results of the three-dimensional (3D) finite element buckling analysis of the primary containment drywell shell at the Oyster Creek Nuclear Generating Station (Oyster Creek). The buckling stresses, eigenvalues, and eigenvectors are computed using ANSYS finite element analysis software [1], and the structural integrity of the drywell in terms of the buckling (stability) limits are based on the ASME B&PV Code Case N-284-1 [2].
Verification of the Prediction Methods of Strain Range in Notched Specimens Made of Mod.9Cr-1Mo
Authors: Ando Masanori , Hirose Yuichi , Date Shingo , Watanabe Sota , Enuma Yasuhiro , Kawasaki Nobuchika
Published: January 2011

Several innovative prediction methods of strain range have been developed in order to apply to the Generation IV plants. In a component design at elevated temperature, ‘strain range’ is used to calculate the fatigue and creep-fatigue damage. Therefore, prediction of ‘strain range’ is one of the most important issues to evaluate the components’ integrity during these lifetimes. To verify the strain prediction method of discontinues structures at evaluated temperature, low cycle fatigue tests were carried out with notched specimens. All the specimens were made of Mod.9Cr-1Mo, because it is a candidate material for a primary and secondary heat transports system components of JSFR (Japanese Sodium Fast Reactor). Deformation control fatigue tests and thermal fatigue tests were performed by ordinary uni-axial push-pull test machine and equipment generating the thermal gradient in the notched plate by induction heating. Stress concentration level was changed by varying the notch radius in the both kind of tests. Crack initiation and propagation process during the fatigue test were observed by the digital micro-scope and replica method. Elastic and inelastic FEAs were also carried out to estimate the ‘strain range’ for the prediction of fatigue life. Then the ranges of several strain predictions and estimations were compared with the test results. These predictions were based on the sophisticated technique to estimate the ‘strain range’ from elastic FEA. Stress reduction locus (SRL) method, simple elastic follow-up method, Neuber’s rule method and the methods supplied by elevated temperature design standards were applied. Through these results, the applicability and conservativeness of these strain prediction and estimation methods, which is the basis of the creep-fatigue life prediction, is discussed.
Research of Fatigue Crack Growth Behavior of X70 Pipeline Steel in Corrosive Environment and Evaluation of Defect
Authors: Wang Jing , Li Xiao-yang , Li Shu-rui
Published: January 2011

Long distance pipeline transmission is considered to be the most economic and safest method to transport natural gas nowadays and pipeline safety problem is a focus of concern in the academic and industrial circles. Pressure fluctuation and corrosive environment can make the typical working condition of long distance pipeline become a low frequency corrosion fatigue condition, which leads to high risk. In this paper, mathematic model of fatigue crack growth rate (FCGR) considering frequency and stress ratio has been developed and the expressions of every parameter were fitted. Critical stress intensity factor (KISCC) in H2S saturated environment (2300ppm) was measured. In view of the operating condition and applied stress of pipeline, low frequency, high stress ratio corrosion fatigue tests of X70 base metal were carried out in H2S saturated and air environments respectively. According to the ASME BPVC Section XI, by using inverse inferring method, considering critical crack sizes of H2S stress corrosion cracking, crack increments of corrosion fatigue and different service periods, allowable crack sizes of different service period were calculated and the curves between allowable crack depth and original crack length were obtained, which would supply more accurate data to determine the service period and to evaluate West-East natural gas transmission pipeline’s residual life.
On Mixed Mode Crack Propagation Analysis Based on VCCM (Virtual Crack Closure-Integral Method) for Tetrahedral Finite Element
Authors: Okada Hiroshi , Kawai Hiroshi , Tokuda Takashi , Fukui Yasuyoshi
Published: January 2011

The authors have been developing a crack propagation analysis system that can model arbitrary shaped cracks in three-dimensional solids. In the system, automatic mesh generation program, parallel/large finite element program (ADVENTURE_Solid) and virtual crack closure-integral method (VCCM) for the quadratic tetrahedral finite element are used as its key-components. In this paper, the components in the crack propagation system are briefly described and some demonstration problems are presented for an illustrative purposes.
Research About Pulverization of Rice Using Underwater Shock Wave by Electric Discharge
Authors: Ide Makoto , Irie Seiichi , Matsuo Nobuyuki , Oda Asuka , Tanaka Shigeru , Itoh Shigeru
Published: January 2011

In recent years, it is expected that the consumption of rice powder in Japan increases for food self-support rate improvement. The consumption of enormous energy during making rice powder and loss of starch in rice by frictional heat is occurred by using the existing manufacturing method. Application techniques using underwater shock wave which is generated by high voltage electric discharge are studied in our laboratory. When some food samples are treated by underwater shock wave, following advantages are obtained, a little heat treatment, decreasing consumption of the energy, and shortening of processing time. In food processing using underwater shock wave, the spalling destruction due to propagation characteristics of shock wave and mediums, which have difference density, is used. In this study, the pressure vessel for pulverization of rice was developed, and then, intensity of pressure in vessel is measured by way of experiment, and simulated numerical analysis.
Integrity Assessment of Defected Structure at High Temperature With a Material Database
Authors: Wang Zhengdong , Xuan Fu-Zhen , Tu Shan-Tung
Published: January 2011

The basic theory of Time Dependent Failure Assessment Diagram (TDFAD) is introduced in this paper to be modified for cracks in mismatched welds at high temperature. A time-dependent failure assessment curve is constructed using the method of R6 Option 2. This curve depends not only on the geometry and crack size but also on the mechanical properties of both weld and base materials. The application of such an approach is given to an internal circumferentially defected welded-cylinder under axial tension. An engineering tool of integrity assessment for defected structure at high temperature has been developed for a decade based on the Time Dependent Failure Assessment Diagram (TDFAD) technology for pressure vessels. The software is illustrated in this paper by framework and interfaces and some industrial cases are introduced to show the procedure of the assessment by using the software. A high temperature material database (HTMD) of main properties for typical high temperature steels and alloys is constructed to meet the needs of the safety assessment of the pressure vessels and other structures. The structure of the database is shown in the paper with some tables and charts.
Prevention of Stress Corrosion Cracking of SUS304 by Tensile Overload
Authors: Sano Hayato , Takahashi Koji , Ando Kotoji
Published: January 2011

The effects of overload on the threshold stress intensity factor (KISCC) for stress corrosion cracks (SCC) in stainless steel were studied. Tensile overload was applied to a wedge opening loaded specimen of SUS304, and SCC tests were carried out to determine the resultant KISCC. The value of KISCC was found to increase with increasing stress intensity caused by tensile overload. Comparison of the effects of tensile overload on KISCC of SUS304 and SUS316 revealed that the effect on KISCC of SUS304 was smaller than that of SUS316.
Annealing Models in Welding Simulation: Conservative and Non-Conservative Residual Stress Distributions
Authors: Keavey Mike , Mark Alison , Dai Hui , Withers Philip J.
Published: January 2011

The influence of residual stress on degradation mechanisms must be taken into account when performing structural integrity assessments. Conservative hypothetical distributions are often assumed, in which the maximum stress is equal to yield. Finite element simulation is now being used in an attempt to derive more realistic residual stress profiles for incorporation into assessment procedures. It is now possible to include self-annealing effects in finite element simulations of the welding process, whereby stresses in existing material in the immediate vicinity of a weld pass are relaxed locally on a very short time scale. Annealing models used in practice vary in sophistication from a simple erasure of strain hardening history at a particular temperature, through certain non-physical assumptions about temperature dependence, to phenomenological models based on the assumed kinetics of underlying microstructural processes. Even more sophisticated models based on thermodynamical principles have been proposed. The original incentive for developing such models was the hope that peak residual stress predictions within the weld and heat affected zone would be reduced, removing the need for over-conservative assumptions when performing structural integrity assessments. Preliminary 2-D results using a model developed by one of the authors, however, suggest that peak stresses predicted with annealing may actually be higher, the hypothesis being that it is compressive stresses that are relaxed during the welding cycle, and that the final tensile residual stresses are increased via the Bauschinger effect. This paper considers results from a further 3-D welding simulation and looks a little more closely at different annealing models. A number of different modelling approaches to annealing are described, together with the basic modelling parameters used to simulate a weld that has been the subject of various European round-robins, both theoretical and experimental. A brief overview of how a kinetics based model can be implemented in a finite element code is also presented. Predicted residual stress distributions are compared with each other and with neutron diffraction measurements and conclusions drawn.
Low Cycle Fatigue Behavior and Seismic Assessment for Elbow Pipe Having Local Wall Thinning
Authors: Urabe Yoshio , Takahashi Koji , Ando Kotoji
Published: January 2011

One of the concerned technical issues in the nuclear piping under operation is pipe wall thinning caused by flow accelerated corrosion. Recently it has been reported that the elbow section is more suspicious on pipe wall thinning by erosion-corrosion. Some researchers including authors have been studied static and fatigue strength of elbows with local wall thinning. However, still more experiment and analysis data are needed to clarify the technical issues. Accordingly, further experiments and their evaluations were carried out by the authors. This paper presents the influences of size and location on fatigue life. Also as one of the application of the test results, safety margin of elbows with wall thinning against seismic loading is discussed. Low cycle fatigue tests were conducted using elbow specimens made of STPT410 steel with local wall thinning. The local wall thinning was machined on the inside of elbow specimens in order to simulate erosion/corrosion metal loss. The local wall thinning areas were located at three different areas, called extrados, crown and intrados. Eroded ratio (eroded depth/wall thickness) is 0.5 and 0.8 and eroded angle is 90deg. and 180deg..The elbow specimens were subjected to cyclic in-plane bending under displacement control (±20mm) without and with internal pressure of 3MPa. Obtained main conclusions are shown bellow. (1) Existence of local wall thinning in extrados does not have an important effect on fatigue life. Especially, fatigue crack does not initiate at the extrados where the extreme local wall thinning exists (eroded ratio = 0.8 and eroded angle = 180 deg.). (2) Regardless of existence of internal pressure, fatigue crack initiates at the crown where local wall thinning does not exist. (3) Even if the eroded ratio and the eroded angle reached up to 0.8 and 180 deg., the elbows with local wall thinning have high safety margin against seismic loading, comparing to ASME Boiler and Pressure Vessel Code Sec. III allowable seismic stress criteria.
Integrity Assessment of a German PWR RPV Considering Loss of Constraint
Authors: Siegele Dieter , Varfolomeev Igor , Hohe Jo¨rg , Hardenacke Volker , Nagel Gerhard
Published: January 2011

The brittle failure assessment for five pressurized water reactor pressure vessels (RPV) of German nuclear power plants (NPP) has been revisited according to an advanced state of the art. Besides of recent innovation in fracture toughness curves and reference temperatures being already in the codes, also the effect of loss of constraint had to be considered when fracture toughness values determined from deep cracks in fracture toughness specimen with high multi-axial state of stress were transferred to crack configurations in the component. Thus, the available concepts were compared for their fitness for purpose, i.e. for their ability to give a fracture toughness representative to the crack configuration or flaw postulate in the component. The results of the investigation reveal a significant lower constraint in the component resulting in increased fracture toughness and showing that the brittle failure assessment based on the high constraint fracture toughness from the standard specimens can be very conservative. For consideration of the constraint conditions in the component besides the deterministic T-stress parameter also probabilistic local approach concepts based on the Weibull model were used which have the advantage of considering both the local stress strain field and the material volume under high loading. The loss of constraint was determined for several flaw postulates in the leading situations on the RPV being the coolant inlet nozzle corner and the flange joint. A considerable loss of constraint was demonstrated for flaw postulates with broken clad in the ferritic nozzle corner. Also in the flange joint the loss of constraint is evident for small flaws. In addition, for flaw postulates under the intact cladding the loss of constraint is remarkably higher than with broken postulated cladding. In summary, with the measured material toughness and the significant loss of constraint a considerable inherent margin against brittle failure can be demonstrated for the investigated load cases.
VERLIFE: Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs During Operation—Updating and Further Development
Authors: Brumovsky Milan
Published: January 2011

VERLIFE – “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs during Operation” was developed within the 5th Framework Programme of the European Union in 2003 and later upgraded within the 6th Framework Programme “COVERS – Safety of WWER NPPs” of the European Union in 2008. This Procedure has to fill the gap in original Soviet/Russian Codes and Rules for WWER type NPPs, as these codes were developed only for design and manufacture and were not changed since their second edition in 1989. VERLIFE Procedure is based on these Russian codes but incorporates also new developments in research, mainly in fracture mechanics, and also some principal approaches used in PWR codes. To assure that VERLIFE Procedure will remain a living document, new 3-year IAEA project (in close cooperation with the another project 6th Framework Programme of the European Union “NULIFE – Plant Life Management of NPPs”) has started in 2009. Within this project, upgrading/updating of the VERLIFE procedure is prepared together with the extension by (at least) following procedures: - Leak-before-break concept for WWER NPPs; - No-Break-Area Assessment Procedure for WWER Piping; - Lifetime of reactor pressure vessel internals; - Probabilistic approach for failure and lifetime assessment of WWER reactor pressure vessels and primary piping (including Risk-informed ISI); - Qualification of NDT procedures; - Supports of components and piping; - Monitoring and evaluation of erosion-corrosion damage in piping. Final document, after its approval by expert groups of the IAEA and NULIFE, will be issued as “IAEA/NULIFE Guidelines for Integrity and Lifetime Assessment of Components and Piping in WWER NPPs”. The paper will describe these main principles and also future plans.
Fracture Assessment for Butt Welded Plate of Ni-Based Alloy
Authors: Itatani Masao , Ogawa Takuya , Saito Toshiyuki , Narazaki Chihiro , Ogawa Kazuo
Published: January 2011

The objective of this study is to establish the fracture assessment method for nuclear power components made of Ni-based alloy weld metal. Fracture tests of butt welded plates of alloys 182 and 82 with a surface flaw were conducted in tension at 300°C. The dimensions and shapes of weld groove of the test plates were intended to simulate the weld joint of BWR shroud support. Semi-elliptical surface flaws were introduced by EDM. Fatigue pre-crack was introduced from an EDM notch for one test plate of alloy 182 to investigate the effect of crack tip shape on the fracture. It was found that the fracture load is conservatively estimated by using plastic collapse load with 2.7Sm for flow stress. It was also understood that the plastic collapse load using flow stress of actual data of tested materials gives good estimation for the experimental fracture load. The net section stresses at the maximum load of both fatigue pre-cracked and EDM notched alloy 182 test plates were almost the same. Consequently, the fracture mode of butt welded joint of alloys 182 and 82 at 300°C is characterized to be plastic collapse.
High Pressure Dynamic Seal for Plunger Pumps With Pressures Above 35 KPSI
Authors: Notzon Stephan
Published: January 2011

The sealing of moving parts under high pressure is one of the most demanding tasks in high pressure technology. For the design of the sealing elements all influencing factors such as mechanical deflections, motion speeds and fluid properties under high pressure must be fully understood and considered. Developments in both materials and manufacturing methods provide new possibilities for the design of sealing systems. This technical paper describes typical sealing issues of dynamic seals at pressures in excess of 35 kpsi with emphasis on plunger seals of high pressure reciprocating pumps. Different plunger sealing concepts are compared and their technical characteristics are analyzed. A new friction-free metallic sealing system is presented and the performance of the sealing system is illustrated by means of numerical simulations considering the fluid-structure interaction and operational experience. The paper further summarizes investigations carried out on changes of fluid properties due to high pressure and shows how this influences the sealing system and the performance of high pressure pumps. Based on this data recommendations are given to prevent problems due to crystallization or polymerization which typically arises in high pressure co-monomer feed systems. The progress in sealing technology reveals new perspectives for high pressure applications in LDPE production plants.
Fatigue Life Improvement of Threaded Pipe Couplings
Authors: Van Wittenberghe Jeroen , De Baets Patrick , De Waele Wim , De Pauw Jan
Published: January 2011

In this study it is demonstrated experimentally that the fatigue life of threaded pipe couplings can be improved by providing a more uniform load distribution over the threads of the coupling. The load distribution was changed by applying both global and local stiffness reductions to the coupling. The obtained results were evaluated using finite element simulations of 2D axisymmetric models. To study the validity of these models a critical comparison was made with a full 3D model that accounts for non-linearities in material and contact properties.
Design Rules for Pipe Systems Subject to Internal Explosions: Part 1
Authors: Smeulers Jan P. M. , Pape Gersom
Published: January 2011

Pipe systems that are used in the process industry may occasionally be subjected to internal deflagration and detonation waves. In those cases the design of the pipe system should be explosion resistant or explosion proof. Special rules have been developed to design such pipe systems. On request of and in corporation with BASF in Ludwigshafen, Germany, the design rules for piping subjected to internal detonations have been reviewed, focusing on two main subjects: the generation and propagation of detonation waves and secondly the response of the piping to the loads imposed by detonation waves. This paper will focus mainly on the last subject, i.e. the response of the piping on the dynamic loads.
Influence of Chemical Compositions on Lower Ferrite-Austenite Transformation Temperatures in 9Cr Steels
Authors: Santella Michael
Published: January 2011

Computational thermodynamics approach was used to predict the ranges of the lower ferrite-austenite transformation temperatures, A1’s, in three 9% Cr steels. The predicted A1 ranges were: 766–856°C for SA387 Grade 91, 775–863°C for SA213 Grade T92, and 676–862°C for the weld metal SFA-5.23 B9 (2004). For Grade 91 and Grade T92 using the highest tempering temperature permitted by ASME Code, 800°C, would permit certain alloys conforming to the chemical composition specification to be tempered above their A1, thereby risking the formation of untempered martensite. Similar circumstances exist for weld metal conforming to the SFA-5.23 B9 specification. Linear regression analyses were performed to develop simplified expressions capable of representing the thermodynamically predicted relationships between chemical compositions and A1’s. These are, Grade 91/SFA-5.23 B9 (2004): 805°C + 2.5(%Cr) + 18.1(%Mo) + 19.1(%Si) + 37.1(%V) + 19.2(%Nb) − 63.7(%C) − 130.6(%N) − 60.5(%Mn) − 72.3(%Ni); Grade T92: 778°C + 4.9(%Cr) + 22.6(%Mo) + 10.8(%W) + 22.9(%Si) + 43.6(%V) + 20.2(%Nb) − 80.6(%C) − 150.7(%N) − 55.1(%Mn) − 68.0(%Ni).
Background on the New ASME PCC-1:2010 Appendix F “Alternatives to Legacy Tightening Sequence/Pattern”
Authors: Brown Warren , Waterland Jerry , Lay David
Published: January 2011

A revised ASME PCC-1 “Guidelines for Pressure Boundary Bolted Joint Assembly” has recently been published and includes several new appendices. Among those is a new Appendix F “Alternatives to Legacy Tightening Sequence/Pattern”, which outlines several alternative bolt tightening patterns that may save joint assembly time and result in a more uniform preload when compared with the traditional tightening pattern for certain applications. This paper outlines the background laboratory research that went into the justification or development of many of these procedures and provides insight through referenced publications and descriptions of where these methods have been successfully applied in industry. The cautions noted in the appendix are also examined in more detail to explain the basis and consequence.