bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave Motions in a Flat Bearing
Authors: Yu Chau-Cho , Lee Wen-Hae , Liao Wen-I
Published: August 2008

Perpendicular vibrations induced by friction on a flat bearing pad is a common problem in mechanical industries. Such a coupled vibration appears as one of the characteristics for sliding squeals that might affect the bearing efficiency. The presented numerical work shows that the cyclic out-of-plane motion within a bearing pad is possible, if the vertical motion is triggered and the contact pressure, the friction, the relative sliding velocity, and material property are appropriate. The magnitude of the squeal is sensitive to the contact pressure, the friction, the damping and material property. Its initiation time may also differ due to the changes in these parameters. In the present analysis, a simplified analytical model is also proposed to explain why the horizontal free vibration can become forced vibration and to further study this phenomenon. More over, under a certain condition, a surface-freeze is observed on the contact interface. It is a potential direction heading toward the complete elimination of the squeal.
Experimental and Analytical Evaluation of Buckling Forces of a Spiral Wound Flexible Gasket
Authors: Larson Reid A. , Bibel George
Published: August 2008

Inward buckling forces of spiral wound flexible gaskets is studied experimentally and analytically using the finite element method. A series of experiments was conducted utilizing an NPS 16 Class 300 weld-neck pipe and flange conforming to specification ASME B16.5. Strain gauges were mounted on the inner and outer metallic rings of the spiral wound sealing gasket and strain data was recorded during initial bolt pre-loading. Using this particular experiment as a pattern, a finite element model was developed to simulate the flange, bolt, and nonlinear gasket response under identical loading conditions. The computer-generated solid model consists of a quarter-symmetry, three-dimensional assembly constructed to the specifications of the pipe, flange, bolts, and gaskets used in the hardware trials. The finite element model was loaded to simulate the initial bolt pre-loading through the same range as in the original experiment. Solutions obtained from the finite element model are compared with the experimental results, and conclusions are drawn.
Recent Process Improvements in Department of Energy Headquarters Packaging Certification
Authors: Primeau Stephen J. , Shuler James M.
Published: August 2008

The U.S. Department of Energy, Office of Licensing (EM-24), certifies the regulatory safety compliance of shipping containers for radioactive materials through a program of technical reviews and confirmatory analyses of Safety Analysis Reports for Packagings (SARPs). Recent initiatives undertaken to improve the speed and efficiency of the certification process include the following: 1) an Improved Packaging Certification Process flowchart that emphasizes early and systematic communication between the applicant and regulator; 2) a SARP Completeness Checklist; 3) guidelines for qualifications, education, and training of SARP Writing Team members; and 4) a training course for certification applicants on Management of SARP Preparation. A primary goal of these initiatives is to improve the quality of the SARP that is submitted with the initial application.
Meaning of Ke in Design-by-Analysis Fatigue Evaluation
Authors: Slagis Gerry C.
Published: August 2008

The ASME Section III Design-by-Analysis rules for pressure-retaining components include a detailed fatigue evaluation based on elastically-predicted primary, secondary, and peak stresses. A pre-requisite for the fatigue analysis is that the primary-plus-secondary stress range does not exceed 3Sm. If this limit is exceeded, the code provides “Simplified Elastic-Plastic Analysis” rules for the fatigue evaluation. A Ke penalty factor is applied to the elastically-predicting alternating stress. The maximum value of Ke (3.3 or 5) is a severe design limitation. Test data indicate that the code specified value of Ke is very conservative. The simplified elastic-plastic rules were originally developed for piping and published in B31.7. When the piping rules were incorporated into Section III in 1971, the B31.7 procedure was replaced by a less complex procedure. The development of the simplified elastic-plastic analysis approach is reviewed to establish the technical basis for the present code rules. The concepts of fatigue, shakedown to elastic action, thermal bending, elastic follow-up, notch factor, and strain redistribution are discussed. Recommendations for changes to the plastic strain correction factor are provided.
Fluctuating Forces in U-Tubes Subjected to Internal Two-Phase Flow
Authors: Riverin Jean-Luc , Pettigrew Michel J.
Published: August 2008

Severe in-plane vibrations were observed in a series of 20-mm dia. PVC vertical U-tubes of different elbow geometries subjected to air-water internal flow. An experimental study was undertaken to investigate the excitation mechanism. Vibration response, excitation forces and fluctuating properties of two-phase flow were measured over a wide range of flow conditions. The experimental results show that the observed vibrations are due to a resonance phenomenon between periodic momentum flux fluctuations of two-phase flow and the first modes of U-tubes. The excitation forces consist of a combination of narrow-band and periodic components, with a predominant frequency that increases proportionally to flow velocity. For a given void fraction, the force spectra for various flow velocities and elbow geometries coincide generally well on a plot of the normalized power spectral density as a function of a dimensionless frequency. The predominant frequencies of excitation agree with recent results on the characteristics of periodic structures in two-phase flow.
Axi-Symmetric Stress Analysis and Determination of Bolt Preload in Bolted Flange Connections With Cover of Pressure Vessel Subjected to Internal Pressure
Authors: Sawa Toshiyuki , Nagata Satoshi , Akita Yosuke
Published: August 2008

The stresses of a bolted flange connection with a cover of pressure vessel (CPV) in which a spiral wound gasket is inserted, under internal pressure are analyzed taking account a hysteresis of the gasket using the axi-symmetrical theory of elasticity as a three-body contact problem. In addition, for the verification of the analyses, finite-element calculations were also done. The Leakage tests were conducted for an actual bolted flange connection with a CPV and a spiral wound gasket. Using the calculated contact gasket stress distribution of the bolted flange connection with the CPV under internal pressure and the tightness parameter, the values of the new gasket constants were obtained by taking into account the changes in the contact gasket stress. A difference in the new gasket constants between the estimated values obtained from the actual bolted flange connection with the CPV and the values obtained by the PVRC procedure was small. In addition, a method to determine the bolt preload for a given tightness parameter was demonstrated. The obtained results of the bolt preload for the bolted flange connection with the CPV were in a fairly good agreement with those obtained by the PVRC procedure under a lower pressure application. However, a difference in the bolt preload was about 7% when the given tightness parameter was increased.
Evaluation of Energy Absorption in Nonlinear Vibration System With Gaps
Authors: Shintani Masanori , Ikuta Hiroyuki , Takada Hajime
Published: August 2008

This paper deals with nonlinear vibration characteristics of a continuum system with collision phenomena under random waves with gaps. In order to investigate such a nonlinear vibration characteristic, an experimental apparatus consisting of a nonlinear vibration system was made. Moreover, we propose an analytical model based on the restoring force characteristics of the experiments. In this report, the size of the gap between a mass and a plate is set to 0.5mm or 1.0mm. For this experimental model we also propose an analytical model. We use plates of 1.6mm thickness in the collisions both in the experiment and the analysis. The analytical model is based on an elasto-plasticity solid model. When considering the coefficients of restitution or energy absorption, the experimental results nearly agree with the analytical results [10]. We found that the rate of a collision changes with the size of the gap at each input acceleration level. As the gap size widens, energy absorption decreases for each input acceleration level. Consequently, in order to increase the energy absorption, it becomes necessary to increase the rate of the collision.
Further Results on the Analysis of Penetrator Stability in Sand and Soil Targets — I
Authors: Graham Courtney H. , Jones S. E. , Hughes Mary L. , Lee Kathryn G.
Published: August 2008

In an earlier paper [1], a fundamental analysis of penetrator stability was presented that resulted in a simple criterion for penetrator design. This criterion was based on some features of long rod penetrator design that could be anticipated: namely, length, cross-sectional area of the shank, area moment of inertia of the cross-section, and the elastic properties of the body material. A number of approximations were made in this early work to reduce the complexity of the modeling effort. Of course, this led to some uncertainties in the results. The purpose of this paper is to explore some of the more prominent sources of uncertainty and to refine the stability estimate. Of specific concern is the effect of a crude approximation on the lowest Eigen function in the problem. In this paper, a small parameter is identified and used to find a regular perturbation solution. The results are found to be in good agreement with those presented earlier.
Exfoliation of Marine Organisms Technology by Using Underwater Shock Wave
Authors: Watanabe Toshiaki , Iyama Hirofumi , Takemoto Ayumi , Itoh Shigeru
Published: August 2008

Adhesion problem of marine organisms often becomes a problem, in the case of ship, marine floating construction and sluice gate of power plant. These make fluid resistance of a hull increase, cause a buoyancy fall, or cause reducing coolant etc. Although these are chiefly removed by manual operation now, immense expense and immense labors, such as personnel expenses and time and effort, are needed. We tried application of an underwater shock wave, in order to solve these problems. Interference of a shock wave and the mechanism of marine organisms exfoliation were explored using the explosive and PMMA plate, which imitated a marine organisms adhesion. The process of exfoliation of organisms from PMMA plate was observed by using of the high-speed camera.
The Sloshing Simulation of Floating Roof Tank
Authors: Miura Masahiro , Kikuchi Tsutomu
Published: August 2008

It is well known when the natural period of tank is same to speed response value by an earthquake that the sloshing height of the floating roof is remarkably amplified. Although it is important to clarify the behavior of the floating roof induced the sloshing for preventing tank damage, the mechanism of behavior of the floating roof has not been fully analyzed at present. Therefore a finite element method (FEM) is carried out based on the useful information such as actual seismic wave, sloshing wave height, damage situation of tank, etc. Then the cause of the failure is well understood by comparing the simulation result and actual failure situation.
Parametric FEM Evaluation of Residual Stress by Circumferential Welding for Austenitic Stainless Steel
Authors: Katsuyama Jinya , Mochizuki Masahito , Higuchi Ryota , Toyoda Masao
Published: August 2008

Recently, stress corrosion cracking (SCC) of core internals and/or recirculation pipes of austenite stainless steel has been observed. SCC is considered to occur and progress near the welding zone because of the weld tensile residual stress. In the present work, thermo-elastic-plastic analysis of the residual stress was performed in order to clarify the effect of several parameters (diameter, thickness, number of multilayer welding) in the circumferential welding zone. Butt welding joint of SUS316L-pipes was examined. The residual stress was calculated by three dimensional-model and axisymmetric model and the results were compared and discussed in detail.
Strain Rate of Pipe Elbow at Seismic Event and Its Effect on Dynamic Strain Aging
Authors: Kobayashi Hiroe , Urabe Yoshio , Asada Yasuhide
Published: August 2008

NRC expressed their refusal of revised seismic stress criteria for piping systems of the ASME Section III, 2001 Edition at their proposed rule making by 10CFR50.55a. One of technical bases of their refusal is “Dynamic strain aging of carbon steel at high strain rate caused by earthquake and at high temperature condition of nuclear power operation”. This paper presents that the effect of dynamic strain aging at the allowable stress limit is practically negligible small even if the seismic allowable stress for nuclear piping increases up to 150% at ASME Section III 2001 and 2003 Edition from 3.0Sm (ASME Section III 1995 Edition). This seismic stress limit revision was achieved by using the B′2 that is equal to 2/3 B2 instead of B2 stress index in Equation of ASME Section III NB-3656 at seismic stress evaluation. At first, maximum elastic-plastic strain of pipe elbow was calculated at various stress level up to revised allowable stress limits by using the elastic-plastic FEM which was verified by the comparison with experimental results. Obtained strain was converted to strain rate by introducing the dominant frequency of piping system at seismic events. Secondary, data of relationship of strain rate and yield to tensile stress ratio for various type of carbon steel was collected. The yield to tensile stress ratio at very low strain rate was compared with that at strain rate of seismic event. The value of yield to tensile stress ratio at strain rate of seismic event was also evaluated. Finally, effect of maximum strain rate at seismic event under revised stress limit condition was discussed by evaluating the change of the yield to tensile stress ratio at low and seismic event condition and the value of the yield to tensile stress ratio at seismic event. From this discussion, dynamic strain aging would not occur in carbon steel piping at seismic event and high temperature condition under revised stress limit condition.
Elastic-Plastic Modeling of the Hardening Materials Based on an Eulerian Strain Tensor and a Proper Corotational Rate
Authors: Naghdabadi Reza , Ghavam Kamyar
Published: August 2008

In this paper a model for analyzing elastic-plastic kinematic hardening materials is introduced, based on the additive decomposition of the corotational rate of an Eulerian strain tensor In this model, the elastic constitutive equation as well as the flow rule and the hardening equation is expressed in terms of the elastic and plastic parts of the corotational rate of the mentioned Eulerian stain tensor and its conjugate stress tensor. In the flow rule, the plastic part of the corotational rate of the Eulerian strain tensor is related to the difference of the deviatoric part of the conjugate stress and the back stress tensors. A proportionality factor is used in this flow rule which must be obtained from a consistency condition based on the von Mises yield criterion. A Prager type kinematic hardening model is used which relates the corotational rate of the back stress tensor to the plastic part of the corotational rate of the Eulerian strain tensor. Also in this paper a proper corotational rate corresponding to the Eulerian strain tensor is introduced. Finally the governing equations for the analysis of elastic-plastic kinematic hardening materials are obtained. As an application, these governing equations are solved numerically for the simple shear problem and the stress and back stress components are plotted versus the shear displacement. The results are compared with those, which are available in the literature.
Fatigue and Fracture Property of 0Cr18Ni10Ti Austenitic Stainless Steel at 350°C
Authors: Sun Weiming , Ren Xing , Zhang Kangda
Published: August 2008

0Cr18Ni10Ti austenitic stainless steel is one of steels used in nuclear plant and petrochemical works. There is no report about the steel’s strain fatigue behavior and fracture properties. This paper presents the steel’s strain fatigue behavior parameters at 350 °C that are tested by strain-control method in accordance with ASTM and state standards (GB). The 0Cr18Ni10Ti austenitic stainless steel fatigue cracks growth rates formula and J resistance curve is obtained in room temperature condition. The axial fatigue test results show it is suitable and safe to adopt ASME Sec. VII div.2 3XX steel fatigue design curve for homemade 0Cr18Ni10Ti austenitic stainless steel.
Some Advantages of the Elliptic Weight Function for the Element Free Galerkin Method
Authors: Naghdabadi Reza , Asghari Mohsen
Published: August 2008

In this paper, an anisotropic weight function in the elliptic form is introduced for the Element Free Galerkin Method (EFGM). In the circular (isotropic) weight function, each node has one characteristic parameter that determines its domain of influence. In the elliptic weight function, each node has three characteristic parameters that are major influence radius, minor influence radius and the direction of the major influence. Using the elliptic weight function each point of the domain may be affected by a less number of nodes in certain conditions. Thus, the computational cost of the method is decreased. In addition, the dependency of the solution on the method that is used for the enforcement of the essential boundary conditions, decreases. As an application of the proposed elliptic weight function, some examples of elastostatic problems are solved and the results are compared with those available in the literature.
Structural Damage Detection by Using Modal Data and Wave Propagation
Authors: Ikeshita Toshiyuki , Nakane Toshihiro , Kitagawa Yoshikazu
Published: August 2008

Demand for monitoring systems applied to structures for quality assurance and for evaluating seismic risk is stronger than ever. Here, a monitoring systems to assess structural integrity was developed in which the damage-detection strategy uses two newly developed methods to first identify the damage sites globally (i.e., detect whether the damage occurred or not, and detect the story level) and to then evaluate the damage sites locally. One method identifies the sites and extent of damage globally by using an improved MDLAC (Multiple Damage Location Assurance Criterion) method by using modal data (i.e., frequency and mode shape), and the other identifies the damage sites locally by using wave propagation. Results showed that these two methods are practical and effective in assessing structural integrity of a structure for seismic safety.
The Effect of the Distance From the Center of a Weld to the Fixed End on the Residual Stress and Stress Intensity Factor of a Piping Weld
Authors: Miyazaki Katsumasa , Numata Masanori , Saito Koichi , Mochizuki Masahito
Published: August 2008

The fixed conditions of butt welds between straight pipe and valve or pump in the actual piping system are different from those of straight pipes. However, the effect of fixed condition on the residual stress and the stress intensity factor for evaluation of structural integrity of cracked piping is not clear. In this study, the finite element analyses were conducted by considering the differences in the distance from the center of weld to the fixed end L to clarify the effect of fixed condition on the residual stress and the stress intensity factor. For the 600A piping, the residual stress distribution was not affected by the distance L. Furthermore, the stress intensity factor of circumferential crack under the residual stress field could be estimated by using the existing simplified solution for piping.
Finite Element Analysis on Bolted Flange Connection Subjected to Bending Moment and Thermal Loads
Authors: Nagata Satoshi , Sawa Toshiyuki
Published: August 2008

Gasketed flange connections should be designed taking into consideration the actual behavior of the connections under their operating conditions. However, such actual behaviors as the bolt load change, the gasket load change and the flange rotation are not considered in the current design calculation method due to the difficulty to solve a statically indeterminate problem among three bodies, flanges, bolts and gasket. In this paper, the authors perform finite element analyses on a 4 inch bolted flange connection with a spiral wound gasket inserted subjected to the bending moment or the thermal load in addition to the internal pressure. It is taken into consideration the nonlinearity shown in the loading-unloading curve of the gasket. For the bending moments, the gasket contact stress distribution due to the bending moment after pressurizing is evaluated by using a 3-dimensional FE model. The calculated gasket contact stress is compared with the one obtained from the extended load factor method to calculate the behavior of the flange connection subjected to bending moments. The authors propose the extension of the load factor method incorporating with the concept of the conventional equivalent pressure representing the bending moment. For the thermal load, an axisymmetric FE model is utilized to evaluate the changes in the flexibility and the thermal expansions of the flange connection at the elevated temperature. The authors also extend the load factor method to incorporate with the change of the flexibility of the flange connection and the thermal expansion depending on the change of temperature. The results obtained from the extended load factor method are cross-checked with those from the finite element analysis.
Update on the Development of a Joint API/ASME Fitness-for-Service Standard for Pressurized Equipment
Authors: Osage David A.
Published: August 2008

An overview of the efforts to produce a Joint API/ASME fitness-for-service standard for application to pressurized equipment is presented in this paper. This new standard is based on API 579 Recommended Practice for Fitness-For-Service [1]; however, many modifications to API 579 are being made to address the special needs of other industries such as the fossil electric power industry, and the pulp and paper industry. API 579 was initially released in January of 2000, and since that time has become the de facto international fitness-for-service standard for the refining and petrochemical industry. Insights into the driving force to create the first edition of API 579, a detailed overview of the second edition of API 579, and plans for the establishment of the first edition of a new Joint API/ASME 579 Standard are provided in this paper.
Tightness Characteristics of Packings
Authors: Schaaf Manfred , Klenk Thomas , Vogel Ralf , Bartonicek Jaroslav
Published: August 2008

The demands on industry to reduce fugitive emissions are increasing, steadily /1/, /2/. On this background it is necessary to improve function and tightness of tightening joints like flanged joints and stuffing box packings. Function and tightness can only be guaranteed if the entire chain of parameters involved is taken in to account (design criteria, gasket factors, calculation, mounting procedure). On the field of flanged joints there are standardization projects on the way that address the topics of the new regulatory demands. Only few work is done regarding stuffing box packings, however. Similar to flanged joints a reliable function and tightness of stuffing box packings can only be achieved if the behaviour of the parts (bolts, gland, stuffing box) is known and their interaction is understood. Regarding the behaviour of stuffing box packing materials it is necessary to determine characteristics like deformation capability, relaxation, friction and leak rate. These characteristics have to be used to prove function and tightness. Some attempts to define these characteristic values have already been made; test procedures and test rigs to determine these values have been developed. Parallel to that, gasket manufacturers are developing new packing materials and entire packing sets in order to meet the more stringent requirements on tightness. One of these newly developed products are nonwoven packing sets which should be applicable up to temperatures of 280 °C in the processing and chemical industry. In the paper the most relevant packing material characteristics and the necessary tests to determine these characteristics are reviewed, first. Then the results of extensive tests with new nonwoven packing sets regarding tightness characteristics, friction, wear and gap extrusion are presented.
Surveillance Specimen Programs for WWER Type Reactors
Authors: Brumovsky Milan
Published: August 2008

Reactor pressure vessels (RPV) are components with the highest importance for the reactor safety and operation as they contain practically whole inventory of fission material but they are damaged/aged during their operation by an intensive reactor radiation. Surveillance specimen programs are the best method for monitoring changes in mechanical properties of reactor pressure vessel materials if they are designed and operated in such a way that they are located in conditions close to those of the vessels. Reactor Codes and standards usually included requirements and conditions for such programs to assure proper vessel monitoring. WWER (Water-Water-Energetic Reactors) reactor pressure vessels are designed according to former Russian Codes and rules with somewhat different requirements using different materials comparing e.g. with ASME Code. Two principal types of WWER reactors were designed, manufactured and are operated in several European countries (and also in China, Iran): WWER-440 and WWER-1000. Their surveillance programs were designed in quite different way, with some modifications due to the time, country of manufacturing and experience gained from their operation. The paper gives a critical comparison of these programs in both types of reactors with requirements of both Russian and ASME/ASTM Codes and Standards. Finally, information about creation of the Integral Surveillance Program for WWER-1000 type reactor pressure vessels covering vessels from several countries is described.
Fatigue Crack Growth Properties of 16MnR and 316L Steels at High Temperature
Authors: Gao Zengliang , Sun Weiming , Jin Weiya , Wang Ying , Zhang Fang
Published: August 2008

Fatigue failures often take place in high temperature pressure vessels and equipment because of fluctuation of pressure and temperature. Fatigue crack growth properties of materials at high temperatures are very important for safety assessment of high temperature equipment. A series of fatigue crack growth tests were carried out, and fatigue crack growth rates were determined at 25∼500°C for typical steels 316L and 16MnR. The laws of fatigue crack growth of two materials at different temperatures and the effect of temperature on fatigue crack growth rates were studied. The results show that the crack growth rates increase with temperature for 316L steel. Both the exponent n and constant C for Paris law change with temperature. The fatigue cracks of 16MnR propagate at 150 °C and 300 °C more slowly than at room temperature and 425 °C. The fatigue crack growth rate at 425 °C is the highest for temperature range of 25–425 °C.
A Continuum Shape Sensitivity Method for Fracture Analysis of Orthotropic Functionally Graded Materials
Authors: Rao B. N. , Rahman Sharif
Published: August 2008

This paper presents a new continuum shape sensitivity method for calculating the mixed-mode stress-intensity factors of a stationary crack in two-dimensional, linear-elastic, orthotropic functionally graded materials with arbitrary geometry. The method involves the material derivative concept taken from continuum mechanics, the mutual potential energy release rate, and direct differentiation. Since the governing variational equation is differentiated prior to discretization, resulting sensitivity equations are independent of approximate numerical techniques, such as the finite element method, boundary element method, mesh-free method, or others. The discrete form of the mutual potential energy release rate is simple and easy to calculate, as it only requires multiplication of displacement vectors and stiffness sensitivity matrices. By judiciously selecting the velocity field, the method only requires displacement response in a subdomain close to the, crack tip, thus making the method computationally efficient. A finite-element based mixed-mode numerical example is presented to evaluate the accuracy of the fracture parameters calculated by the proposed method. Comparisons have been made between stress-intensity factors predicted by the proposed method and available reference solutions in the literature, generated either analytically or numerically using various other fracture integrals or analyses. Excellent agreement is obtained between the results of the proposed method and previously obtained solutions. Therefore, shape sensitivity analysis provides an attractive alternative to fracture analysis of cracks in homogeneous and non-homogeneous orthotropic materials.
Evaluation of Environmental Fatigue in PWR PLM Activities
Authors: Iwasaki Masanobu , Takada Yasukazu , Nakamura Takao
Published: August 2008

It is important to evaluate environmental fatigue for establishing long-term maintenance plans as part of Plant Life Management (PLM) activities for nuclear power plants. In Japan, the former MITI requested the utilities in 2000 to use “The Guidelines for Evaluating Fatigue Initiation Life Reduction in LWR Environment (MITI guidelines)” for PLM evaluation. In 2002, Thermal and Nuclear Power Engineering Society (TENPES) issued the guidelines for applying the evaluation formulas of MITI guidelines to actual plants. At present, fatigue evaluations taking into account environmental effects as part of PLM activities are conducted in accordance with these guidelines. This paper describes how a typical PWR plant conducts such an evaluation. The Japan Society of Mechanical Engineers (JSME) is now drawing up a code for environmental fatigue evaluation, incorporating the latest data on fatigue experiments and know-how on fatigue evaluation. After being issued, this code will be used to evaluate environmental fatigue in PLM activities.
Prediction Method of Tensile Properties and Fracture Toughness of Thermal Aged Cast Duplex Stainless Steel Piping
Authors: Kawaguchi Seiichi , Nagasaki Takeharu , Koyama Koji
Published: August 2008

Cast duplex stainless steels of CF8M and CF8 are used in major components because of their superior characteristics, such as corrosion resistance, weldability, and so on. However, these stainless steels are known to have tendency of thermal aging embrittlement after long term service. Therefore, the mechanical properties have been investigated using tensile test specimens and fracture toughness specimens aged at 300 to 450°C for up to 40,000 hours. From the results, the effects of thermal aging on the mechanical properties of these cast duplex stainless steels were identified. The true stress-true strain curve prediction method (TSS model) and fracture toughness prediction method (H3T model) after long term service were established. These prediction methods are used for the evaluation on the plant life management of nuclear power plants in Japan.
Correlation Between Dynamic Strain-Stress and Vibration Based on Field Data
Authors: Motriuk Roman W.
Published: August 2008

High pressure stages of rotating machinery often produce high-frequency vibrations that cause failures in machinery components, pipes and their connections. Such failures happen even when the machinery operates well within design parameters. Predominant pressure patterns generated by rotating machinery are higher-order three-dimensional acoustic oscillations. In most cases, the piping/component failures result from high cycle events. In these events, a pipe shell is forced into unsteady sine wave deflections, producing deformation forces that initiate cracks, directly or indirectly, in the stress concentration areas. These are most dangerous in pipe welds, particularly in small bore attachment welds. For this reason, rapid detection and estimation of high cycle stresses associated with vibrations is highly desirable. For many years, researchers have studied and developed relationships for estimating maximum stress levels and predicting the service life of piping and machinery components. These studies have been carried out mainly in laboratory set-ups with components of limited size and, limited excitation strengths. In addition, the components were tested in a classical manner, i.e. their vibratory responses were related to their natural frequencies and non-resonant excitations were rarely considered. This work attempts to offer a simplified approach to correlate measured dynamic strain-stress with pipe wall vibrations for large diameter piping (NPS 36, wt = 19.7 mm) excited by a 27 MW centrifugal compressor. Diffused bending wave field and multimode excitation of the pipe shell constricted by factual boundary conditions are used. Particular attention is paid to the value distribution of the ratio (stress/strain to pipe wall velocity) in the straight pipe and in the areas of threadolet connections.
Stress and Sealing Performance Analysis of Containment Vessel
Authors: Wu Tsu-Te
Published: August 2008

This paper presents a numerical technique for analyzing the containment vessel subjected to the combined loading of closure-bolt torque and internal pressure. The detailed stress distributions in the O-rings generated by both the torque load and the internal pressure can be evaluated by using this method. Consequently, the sealing performance of the O-rings can be determined. The material of the O-rings can be represented by any available constitutive equation for hyperelastic material. In the numerical calculation of this paper, the form of the Mooney-Rivlin strain energy potential is used. The technique treats both the preloading process of bolt tightening and the application of internal pressure as slow dynamic loads. Consequently, the problem can be evaluated using explicit numerical integration scheme.
The M-Beta Multiplier Method for Limit Load Determination of Components With Local Plastic Collapse
Authors: Indermohan H. , Seshadri R.
Published: August 2008

The mβ-multiplier method based on Mura’s extended variational principles in plasticity relies on a reference stress that is obtained from an entire stress distribution in a structure. The method is relatively insensitive to components that undergo localized plastic action and generates limit load bounds that are better than the classical and mα-multiplier methods. The multiplier mβ is determined by evaluating a reference parameter βR, which may be difficult to determine if the stress distribution obtained using elastic modulus adjustment procedures does not converge to a limit type of distribution. In this paper, physical insights relating to the reference parameter βR are provided by linking the concept of reference volume to the local collapse of the structure. As well, a systematic procedure to identify the converged limit state is presented. The mβ-multiplier method, developed in conjunction with the reference volume concept, is applied to a number of cracked component configurations. The results are compared with the corresponding inelastic finite element analysis.
Reference Stress Approach for Failure Strength Estimates of a Pipe With Local Wall Thinning
Authors: Kim Yun-Jae , Kim Young-Jin
Published: August 2008

This paper proposes a method based on the reference stress a approach to estimate residual strength of a pipe with local wall thinning. The method is based on the equivalent stress averaged over the minimum ligament in the locally wall thinned region. Inspired by the reference stress method for approximate creep stress analysis, approximate estimation equations for the equivalent stress in the minimum ligament are proposed, which are then calibrated using detailed elastic-plastic 3-D FE analysis. The resulting estimation equations are found to be insensitive not only to pipe and defect geometries but also to material. Comparison of failure loads, predicted according to the proposed method, with published test data for corroded pipes shows excellent agreement.
Predicting Speed of Crack Running in Functionally Graded Material
Authors: Nakagaki Michihiko , Matsumoto Ryosuke
Published: August 2008

A theoretical and computational methodology for the analysis of the functionally graded material (FGM) is introduced, and its application is made to the problem of a dynamically propagating crack running transversely in the FGM, where the intensity of the estimated crack-tip severity is managed to keep in valance with the graded material toughness in the FGM during the propagation. To detect the crack-tip severity, an integral fracture parameter, T*, is used. The crack is propagated so that the value of T* is equated to the prescribed varying critical values of T* for the graded material. Emphasis is placed on the use of a fuzzy inference technique in order to control the crack speed, which is deduced from a few T* values immediately preceding the current crack position. As to describing the constitutive law for the FGM, micro-spherical particles of arbitrary size in mesoscale are considered to be randomly dispersed in the matrix medium. By assuming that the volume fraction of the inclusion is continuously varied from 0 to 100 percent in the material, the grading is modeled. For modeling the constitutive law for the FGM composite media of thermo-elastoplasticity, a closed form SCC-LRM constitutive model describing the nonlinear material mechanics of the particle-dispersed medium is used. The model is based on the self-consistent scheme and uses Eshelby’s equivalent inclusion method. Unprecedented analytical results of predicting the crack speed of a crack running transversely in the FGM plate are obtained. In some cases of material grading, apparent crack arresting is observed as the crack runs into the metal rich area of the FGM.
Mechanical Properties of Fiberboard Overpack Materials in the 9975 Shipping Package
Authors: Daugherty W. L. , Vormelker P. R.
Published: August 2008

Many radioactive material (RAM) shipping packages incorporate cane fiberboard overpacks for thermal insulation and impact resistance. Mechanical strength (tensile and compressive) has been measured on cane fiberboard and a similar wood-based product following short-term conditioning in several temperature/humidity environments. Both products show similar trends and vary in behavior with fiber orientation, temperature and humidity. A memory effect also exists where original strength values are only partially recovered following exposure to a degrading environment and return to ambient conditions.
Influence of Nitrogen Gas of Three Different Procedures of GTAW Welding on Final Metallurgical and Mechanical Properties of a 2% W SDSS Piping
Authors: Ju´nior Petroˆnio Z. , Alcaˆntara Paulo H. , Fedele Ricardo A. , Paiva Geraldo J. M. , Chaves Ney R. W.
Published: August 2008

Duplex stainless steels (DSS) are finding increased application on offshore process plants in Brazil. Welding them is always a challenge. Pure argon and argon/low-nitrogen gas mixtures are available for welding them with GTAW process. The use of the same kind of gases on shielding and backing is usual. If no nitrogen is present in the gas mixtures there may be loss of nitrogen from the weld metal or HAZ. Three different welding procedures were tested for a 2% tungsten superduplex parent metal to verify the loss of nitrogen from weld metal and HAZ. First procedure used a 2%N-88%Ar-10%He as the shielding mixture and pure Ar as the backing gas while the second one used pure Ar as shielding and pure nitrogen as backing gas. A third procedure with no nitrogen for shielding or backing was also carried out for comparisons. Chemical analyses, corrosion test and determination of austenite/ferrite content were done to check metallurgical and chemical properties. Mechanical tests were performed to compare mechanical properties of the weld metal and HAZ. ASME Code, section IX, plus Norsok standard M-601 were referenced. Results indicate good mechanical behavior, corrosion resistance and austenite/ferrite phases balance in both procedures that used nitrogen as one of the gases. The procedure using only pure argon showed a decrease of austenite content in weld metal and heat affected zone. However, it fulfilled all the requirements. They didn’t present secondary phases or very significant variances on austenite presence even on weld metal and HAZ.
Residual Stress Measurements Revealing Weld Bead Start and Stop Effects in Single and Multi-Pass Weld-Runs
Authors: Bouchard Peter J. , Santisteban Javier R. , Edwards Lyndon , Turski Mark , James Jon , Pratihar Sumit , Withers Philip J.
Published: August 2008

This paper describes transverse residual stress and strain measurements aimed at quantifying end effects in single and multi-pass weld-runs. Two test specimens are examined: a 60 mm long weld bead deposited on the surface of a 180 mm × 120 mm × 17 mm thick stainless steel plate, and a 62° arc-length multi-pass repair weld in a 432 mm outer diameter, 19.6 mm thick stainless steel pipe girth weld. The residual stress measurements were made by employing the relatively new Contour method and by neutron diffraction using ENGIN-X, the engineering spectrometer at the ISIS facility of the Rutherford Appleton Laboratory (UK). The measured underlying transverse residual stress levels are observed to be essentially uniform directly beneath the weld bead in the plate specimen and in the heat affected zone beneath the capping passes moving from mid-length towards the stop-end of the pipe repair. However, results from both test components demonstrate the existence of short-range concentrations of transverse residual stress along the welding direction owing to individual weld capping bead start and stop effects. Such short length-scale stress variations must be allowed for when interpreting residual stress measurements from line-scans. The experimental work also demonstrates the importance of knowing the expected stress or strain distribution prior to choosing measurement lines for detailed study. The Contour measurement method and neutron strain scanning are powerful tools for mapping residual stress and strain fields.
Ultrasonic Control of Fastener Tightening Using Varying Wave Speed
Authors: Nassar Sayed A. , Veeram Aditya B.
Published: August 2008

A high precision ultrasonic technique and a test apparatus are developed for the real-time control of the fastener elongation during the tightening process of bolted joints. This is accomplished by monitoring the propagation of longitudinal ultrasonic waves through the fastener material and the reflection of these waves at the end of the fastener. The round trip time of the longitudinal waves is continuously measured and monitored in real-time. Using the wave speed in the fastener material, the change in the round trip time determines the fastener elongation, which creates fastener tension and joint clamp load. The wave speed through the bolt material is stress dependent; hence, it continuously changes as the fastener is being elongated during the tightening process. A varying wave speed algorithm is developed and utilized in order to compensate for wave speed variations. Because the torque-tension relationship in threaded fasteners is highly sensitive to friction variations, the scatter in such relationship is often unacceptable, especially in critical applications. By contrast, the automatic control of the fastener elongation during the tightening process would eliminate the dependence on the torque value as a predictor for the bolt tension. Hence, the new ultrasonic technique for the real-control of the fastener tension, by monitoring its elongation, would significantly enhance the reliability of bolted assemblies.
A Finite Element Study on Contact Pressure Distribution in Draw-Bend Friction Test and Its Effect on Friction Measurement
Authors: Kim Young Suk , Metzger Don R. , Jain Mukesh K.
Published: August 2008

Various experimental and numerical works have shown the existence of pressure peaks at the contact interface of draw-bend tests. From this observation, a need has been raised for the re-examination of the methodology to calculate the friction coefficient from the draw-bend friction test. In this paper, the draw-bend friction tests have been simulated by the explicit finite element method. By using 3D finite element models and local axis system, the existence of pressure peaks was confirmed. A non-constant friction model (Stribeck friction model), which is more realistic for sheet metal forming than a constant friction model (Coulomb friction model), was implemented into the finite element code. Simulations were performed with constant and non-constant friction models. From the comparisons, the effect of existence of pressure peaks on the friction measurement was evaluated.
Experiment Study on Shrink Strain Monitoring of Concrete in the Cure Period With FBG Sensors
Authors: Sun Li , Li Hong-Nan , Ren Liang
Published: August 2008

Concrete is the material widely used in civil engineering. Cracks of concrete are mainly caused by the ununiform shrink in the cure period. The basic principle and merits of FBG are introduced. In order to monitor the shrink strain and temperature of concrete during the cure period, this paper presents a novelty strain sensor and temperature sensor based on FBG technology. The theoretical and experimental analyses of FBG sensor were implemented. The thermal drift experiment of sensor has also been carried out. Shrink strain and temperature of concrete have been successfully tested. The experiment results indicated that this monitor method is an ideal method in monitoring the concrete at the very early age. However, the thermal drift of FBG strain sensor should be considered during the strain measurement. This method could be used in monitoring the shrink strain and temperature of any volume concrete.
Evaluation of Thermal Fluctuations and Stresses in Piping Mixing Zones
Authors: Stephan J. M. , Peniguel C. , Genette P. , Curtit F. , Sakiz M. , Pasutto T. , Szaleniec S.
Published: August 2008

Following the incident (through-wall crack and crazing zones) of May 1998 on the principal mixing zone of the residual heat removal system at CIVAUX nuclear plant, EDF has initiated a R&D program to understand the incident and assess the risks of damage on other nuclear plants mixing zones. The program includes different sectors of developments: assessment of temperature fluctuations in mixing zones, study of high-cycle thermal fatigue behavior of austenitic steel and development of mechanical methodologies for damage assessment and propagation of crazing zones (thermal striping). The paper develops an attempt to calculate the spatial and temporal variations of fluid thermal fluctuations in a mixing zone, using a Large Eddy Simulation method (LES). Distribution of temperature in the wall is evaluated in the same calculation. This temperature distribution is then used to estimate the stress variations and fatigue damage of the pipe by using finite elements calculation or simplified methods.