bluuebunny/crossref_metadata_2025 huggingface dataset:
Inelastic Pipework Dynamics and Aseismic Design
Authors: Norville C. C.
Published: June 2008

This paper shows a simple correlation between elastic and inelastic dynamic pipework responses enabling realistic/pessimistic prediction of dynamic pipework responses beyond the elastic range using current elastic aseismic design procedures. In this paper, theoretical studies relating dynamic responses directly to nonlinear material stress/strain characteristics show how such a correlation arises, particularly for materials exhibiting a well-defined yield point inflection, and the evaluation of the correlative parameters (moduli and damping factors). The ABAQUS computer program was used to study and simulate the dynamic inelastic response characteristics of a pressurized tube in the form of simple beam and a pressurized cantilevered elbow (in-plane responses). Using comparative dynamic test results for these components, the foregoing design concepts were verified for representative cyclic material characteristics. So, given appropriate cyclic material characteristics, pessimistic incremental and reverse cyclic fatigue strains may be simply evaluated for loadings beyond the elastic range (for assessment against ASME fatigue criteria) using existing design techniques as shown in the paper.
Nondestructive Evaluation of Adhesively Bonded Joints in Graphite/Epoxy Composites Using Acousto-Ultrasonics
Authors: Tanary S. , Haddad Y. M. , Fahr A. , Lee S.
Published: June 2008

This paper is concerned with the use of the acousto-ultrasonic technique to evaluate nondestructively the mechanical performance of composite bonded joints. In this context, acousto-ultrasonic measurements followed by destructive shear tests were performed on single lap joint specimens made from graphite/epoxy adherends joined with FM 300 film adhesive. The results indicate a good correlation between acousto-ultransonic wave propagation characteristics and the shear strength of the bonded joints under different testing conditions. These correlations suggest that an estimation of the joint strength can be made by using acousto-ultrasonics provided that the measurement system is calibrated for variations of the material and geometry of the specimen.
RTP-1: A Standard for Reinforced Plastic Corrosion-Resistant Equipment
Authors: Marsh H. N.
Published: June 2008

The use of FRP (also known as RTP—reinforced thermoset plastic) in chemical process service has grown rapidly since introduction due to its unique corrosion-resistant properties and cost effectiveness. There have been some failures due to inadequate specifications, poor design or improper fabrication. An ASME Committee was formed to provide a standard and ASME/ANSI RTP-1 “Reinforced Thermoset Plastic Corrosion Resistant Equipment” was approved as an American National Standards Institute (ANSI) Standard in March 1989. The Standard applies to stationary vessels operating at pressures not exceeding 15 psig external and/or 15 psig internal above any hydrostatic head. This article describes the detailed specification process, the methods for design and fabrication, material requirements, procedures for qualification of a shop and its personnel, the fabricator’s Quality Control Program, and inspection and testing required by the Standard. It is recognized that there will be significant costs associated with fabrication of vessels to this standard. The careful preparation of the specifications, the conservative approach to design, the qualification of the Fabricator’s shop and personnel, the inspection of incoming raw materials, the inspection and testing of the finished vessel and the services of the mutually acceptable Inspector are all cost items. Balancing these costs will be the benefits of improved safety and reliability, long life, low maintenance, and hopefully less litigation and liability. It is believed that, on an overall long-term cost basis, these benefits will far outweigh the added costs.
Study of Unsteady Flow in a Heat Exchanger by the Method of Characteristics
Authors: Huang Yuan Mao
Published: June 2008

The one-dimensional, unsteady flow in an air-to-air heat exchanger is studied. The governing equations are derived and the method of characteristics with the uniform interval scheme is used in the analysis. The effect of the fin improvement factor on the air temperature in the heat exchanger and the heat transfer rate of the heat exchanger, and air properties in the heat exchanger are analyzed. The numerical results are compared and show good agreement with the available data.
Study on the Vibrational Characteristics of a Tube Array Caused by Two-Phase Flow—Part 2: Fluidelastic Vibration
Authors: Nakamura T. , Fujita K. , Kawanishi K. , Yamaguchi N. , Tsuge A.
Published: June 2008

Fluidelastic vibration of a tube array caused by two-phase flow has been reported in some papers. The critical flow velocity is usually estimated with a simple Connors-type criterion which is based on average flow velocity, average fluid mass density and damping in two-phase flow. However, there is no explanation why this simple criterion can be used or how the fluidelastic instability occurs by two-phase flow. This paper shows the experimental results on the fluidelastic vibration both by air-water two-phase flow and by steam-water flow in the condition of up to 7.0 MPa in pressure and to 284°C in temperature, and a new criterion based on an assumption of energy balance is here introduced using a “true” flow velocity. However, the comparison with the experimental data indicates that an intermittently rising slug speed, which has been introduced in Part 1, in slug or in froth flow region, should be used, and a modified new criteria for slug or froth flow region is derived. In addition, the new criteria is compared with the usual Connors-type criteria, which greatly depend on the estimation of the damping in two-phase flow. The agreement of both criteria is revealed to be in the vicinity of the variance of the unknown parameters in the usual criteria.
Design and Analysis of a Test Coupon for Fusion Welding
Authors: Jones B. K. , Emery A. F. , Marburger S. J.
Published: June 2008

The objective of a weld coupon is to provide a simple test to determine the effects of different welding parameters and constraints on the final state of fusion welds. With such a test it will be possible to judge the performance of a particular weld under known states of temperature and external restraint. This paper describes the experiments and analyses performed on a thin coupon with a circular weld bead which was designed to simulate a typical manufacturing geometry. The temperatures and deformations measured in the experiments corresponded closely to those of the analyses. It was found that such a geometry provides a high degree of restraint regardless of the radius of the circular weld bead. Experimental and analytical stresses indicate that extensive yielding occurs throughout the coupon.
Pipeline Response to Directionally and Spatially Correlated Seismic Ground Motions
Authors: Zerva A.
Published: June 2008

This study analyzes the response of continuous, straight, large diameter pipelines subjected to spatially and directionally correlated seismic ground motions. The stochastic characteristics of the seismic motions of Event 5 recorded at the SMART-1 array in Lotung, Taiwan, are used as input motions in random vibration analyses of the structures. The results indicate that the pipeline response is sensitive to the structure’s axis orientation relative to the directions of the recorded seismic motions and to the degree of exponential decay of the spatial variability.
Design of Tubesheet for U-Tube Heat Exchangers
Authors: Paliwal D. N. , Saxena R. M.
Published: June 2008

Thorough analysis of two-side integral tubesheet of U-tube heat exchanger is carried out, using Panc’s component theory of plates. Effects of solid annular rim and interaction between tubesheet and shell/channel are considered. A design procedure based on foregoing analysis is proposed. Fictive elastic constants due to Osweiller, as well as effective elastic constants due to Slot and O’Donnell, are employed. Deformations, internal forces and primary stress intensities are evaluated in both pitch and diagonal directions. Stress category concept of ASME Sect. VIII Div. 2 is used. Design thickness obtained by this method is compared with the thicknesses calculated, using ASME Sect. VIII Div. 1, TEMA and BS-5500. This method enables us to calculate stresses in shell and channel in the junction region as well. Present analysis and design procedure thoroughly investigates the tubesheet behavior and leads to a thinner tubesheet. It is concluded that though all the codes based on Gardner’s work provide safe and efficient design rules, and lie on firm footing, still there is further scope for reducing the design thickness of tubesheet by about ten percent.
Impact Simulation of Liquid-Filled Containers Including Fluid-Structure Interaction—Part 1: Theory
Authors: Sauve´ R. G. , Morandin G. D. , Nadeau E.
Published: June 2008

In a number of applications, the hydrodynamic effect of a fluid must be included in the structural evaluation of liquid-filled vessels undergoing transient loading. Prime examples are liquid radioactive waste transportation packages. These packages must demonstrate the ability to withstand severe accidental impact scenarios. A hydrodynamic model of the fluid is developed using a finite element discretization of the momentum equations for a three-dimensional continuum. An inviscid fluid model with an isotropic stress state is considered. A barotropic equation of state, relating volumetric strain to pressure, is used to characterize the fluid behavior. The formulation considers the continuum as a compressible medium only, so that no tension fields are permitted. The numerical technique is incorporated into the existing general-purpose three-dimensional structural computer code H3DMAP. Part 1 of the paper describes the theory and implementation along with comparisons with classical theory. Part 2 describes the experimental validation of the theoretical approach. Excellent correlation between predicted and experimental results is obtained.
Impact Simulation of Liquid-Filled Containers Including Fluid-Structure Interaction—Part 2: Experimental Verification
Authors: Sauve´ R. G. , Morandin G. D. , Nadeau E.
Published: June 2008

In a number of applications, the hydrodynamic effect of a fluid must be included in the structural evaluation of liquid-filled vessels undergoing transient loading. Prime examples are liquid radioactive waste transportation packages. These packages must demonstrate the ability to withstand severe accidental impact scenarios. A hydrodynamic model of the fluid is developed using a finite element discretization of the momentum equations for a three-dimensional continuum. An inviscid fluid model with an isotropic stress state is considered. A barotropic equation of state, relating volumetric strain to pressure, is used to characterize the fluid behavior. The formulation considers the continuum as a compressible medium only, so that no tension fields are permitted. The numerical technique is incorporated into the existing general-purpose three-dimensional structural computer code H3DMAP. Part 1 of the paper describes the theory and implementation along with comparisons with classical theory. Part 2 describes the experimental validation of the theoretical approach. Excellent correlation between predicted and experimental results is obtained.
Extensive Modeling of High-Temperature Deformation Based on Unified Approach
Authors: Nakamura T. , Asada Y.
Published: June 2008

A unified inelastic constitutive equation is proposed to describe the cyclic inelastic deformation of 2 1/4Cr-1Mo steel at 550°C. In the present study, an evolution of the overstress is discussed which leads the time-independent term into the inelastic strain rate. A mathematical model is developed and some examples of the numerical simulation are presented.
Predictability of Long-Term Creep and Rupture in a Nozzle-to-Sphere Vessel Model
Authors: Corum J. M. , Battiste R. L.
Published: June 2008

The results of a long-term (approximately 2-1/2 yr), high-temperature failure test of a pressurized nozzle-to-spherical-shell model made of a well-characterized heat of type 304 stainless steel are presented and compared with inelastic deformation and failure predictions. The model, which was tested at 593°C (1100°F), was instrumented with capacitive strain gages in key locations. In addition to recording strains, the surface of the model in the junction region was periodically examined throughout the test for the formation and progression of the creep cracking that ultimately led to a leakage failure. The inelastic analysis predictions were based on guidelines developed and used for design of elevated-temperature nuclear components. Similarly, the failure model used was that upon which the ASME elevated-temperature Code Case N-47 for nuclear components is based. Thus, the reasonable agreement observed between experimental results and predictions adds confidence in the overall design methodology for elevated-temperature components. The results also demonstrated the leak-before-break nature of failure and the fact that pressure-induced stresses do not necessarily relax with time.
Behavior of Pipe Flange Connection in Transient Temperature Field
Authors: Sawa T. , Hirose T. , Kumano H.
Published: June 2008

The behavior of a bolted connection, using several aluminum alloy pipe flanges with steel bolts and nuts, was examined under the condition of thermal conduction. Using the finite difference method, temperature distributions in the connection subjected to transient thermal conduction were analyzed. A method for obtaining an increment in axial bolt force and the maximum stress produced in the bolts was demonstrated. In the experiments, the temperature distribution in the connection was measured by use of thermocouples. In addition, both the increment and the maximum stress due to the difference in coefficients of linear expansion as well as the stress produced in the hub were measured by strain gages when the inner circumference of the pipe flanges was subjected to thermal conduction and the outer circumference was kept at room temperature. The analytical results were fairly consistent with the experimental ones.
FE Analysis Strategies for Structural Materials With Small Tensile Strength
Authors: Borri A. , Sorace S.
Published: June 2008

A review of the “smeared crack” approach to the finite element analysis of small tensile strength (STS) materials is presented. The most widely applied strategies for crack modeling, shear transfer mechanism, and the definition of the mechanical constitutive laws and failure criteria are critically discussed. The models and special options in the ANSYS, ADINA, and ABAQUS programs are considered in detail, and applied to the analysis of a square panel under boundary pressures. The three solutions were compared in terms of the final broadening of the panel cracked zones. The results of the analysis of an hemispherical dome over a cylindrical drum are also presented. The Romulus Temple in the Roman Forum was the reference structure for this FE model. The problem was analyzed by a special procedure using the ANSYS “concrete” element. The results were compared with those of a “discrete crack” solution which reproduced the real cracked configuration of the building, and then with an experimental survey carried out by the flat jack technique.
Axisymmetric Free Vibration of Shallow Spherical Shells With a Circular Rigid Insert
Authors: Hwang D. Y. , Foster W. A.
Published: June 2008

A general solution for the third-order partial differential equations for the axisymmetric free vibration of thin isotropic shallow spherical shells with a rigid insert is presented in this paper. The frequency equation in terms of Bessel functions as well as modified Bessel functions is solved for the fundamental vibrational frequency and mode shape. Both linear and non-linear boundary conditions are applied and the results are compared. The relationship between the vibrational frequency, mode shape and the size of the rigid insert is discussed.
Creative Design-by-Analysis Solutions Applied to High-Temperature Components
Authors: Dhalla A. K.
Published: June 2008

Elevated temperature design has evolved over the last two decades from design-by-formula philosophy of the ASME Boiler and Pressure Vessel Code, Sections I and VIII (Division 1), to the design-by-analysis philosophy of Section III, Code Case N-47. The benefits of design-by-analysis procedures, which were developed under a US-DOE-sponsored high-temperature structural design (HTSD) program, are illustrated in the paper through five design examples taken from two U.S. liquid metal reactor (LMR) plants. Emphasis in the paper is placed upon the use of a detailed, nonlinear finite element analysis method to understand the structural response and to suggest design optimization so as to comply with Code Case N-47 criteria. A detailed analysis is cost-effective, if selectively used, to qualify an LMR component for service when long-lead-time structural forgings, procured based upon simplified preliminary analysis, do not meet the design criteria, or the operational loads are increased after the components have been fabricated. In the future, the overall costs of a detailed analysis will be reduced even further with the availability of finite element software used on workstations or PCs.
Assessment of Fully Plastic J and C*-Integral Solutions for Application to Elastic-Plastic Fracture and Creep Crack Growth
Authors: Lee D. R. , Bloom J. M.
Published: June 2008

A critical part of the assessment of defects in power plant components, both fossil and nuclear, is the knowledge of the crack driving force (K1, J, or C*). While the determination of the crack driving force is possible using finite element analyses, crack growth analyses using finite element methods can be expensive. Based on work by Il’yushin, it has been shown that for a power law hardening material, the fully plastic portion of the J-integral (or the C*-integral) is directly related to an h1 calibration function. The value of h1 is a function of the geometry and hardening exponent. The finite element program ABAQUS was used to evaluate the fully plastic J-integral and determine the h1 functions for various geometries. The Ramberg-Osgood deformation theory plasticity model, which may be used with the J-integral evaluation capability, allows the evaluation of fully plastic J solutions. Once it was established that the grid used to generate the h1 functions was adequate (based on the more recent work of Shih and Goan), additional runs were made of other configurations given in the EPRI Elastic-Plastic Fracture Handbook. Differences as great as 55 percent were found when compared to results given in the Handbook (single-edge crack plate under tension and plane stress with a/b = 0.5). Effects of errors in h1 on predicted failure load and creep crack growth are discussed.
Creep-Fatigue Properties of Mod.9Cr-1Mo Steel Under Variable Straining
Authors: Miyahara M. , Tokimasa K.
Published: June 2008

Two-step variable straining tests, which included CP- (slow-fast) type and PC- (fast-slow) type tests, were conducted at 600°C in air for Mod.9Cr-1Mo steel. In the tests, CP and PC-type strain range level varied from high to low for the high-low test and from low to high for the low-high test. The deviations of the experimental data from the linear damage rule prediction were observed. These experimental results and the effect of the strain waveform on the creep-fatigue properties under variable straining were well explained by the life prediction model previously proposed by the authors in which the strain range partitioned crack growth rate equations were applied.
Numerical Stress Analysis of Intersecting Cylindrical Shells
Authors: Skopinsky V. N.
Published: June 2008

This paper presents the numerical approach for the stress analysis of the intersecting shells. For a systematic study of this problem, the classification of the model joints is introduced. Stress analysis has been made with the application of the finite element method based on the modified mixed formulation. The developed special-purpose computer program SAIS is used for elastic stress analysis of the model joints of the intersecting shells. Comparison of the calculated and experimental results for ORNL-1 model are presented for internal pressure and moment loadings. The parametric study of the model joints of the intersecting cylindrical shells under internal pressure loading was performed. The presented results show the effects of changing various geometric and angular parameters on the maximum effective stresses in the shells.
Wave Motion of a Compressible Viscous Fluid Contained in a Cylindrical Shell
Authors: Terhune J. H. , Karim-Panahi K.
Published: June 2008

The free vibration of cylindrical shells filled with a compressible viscous fluid has been studied by numerous workers using the linearized Navier-Stokes equations, the fluid continuity equation, and Flu¨gge ’s equations of motion for thin shells. It happens that solutions can be obtained for which the interface conditions at the shell surface are satisfied. Formally, a characteristic equation for the system eigenvalues can be written down, and solutions are usually obtained numerically providing some insight into the physical mechanisms. In this paper, we modify the usual approach to this problem, use a more rigorous mathematical solution and limit the discussion to a single thin shell of infinite length and finite radius, totally filled with a viscous, compressible fluid. It is shown that separable solutions are obtained only in a particular gage, defined by the divergence of the fluid velocity vector potential, and the solutions are unique to that gage. The complex frequency dependence for the transverse component of the fluid velocity field is shown to be a result of surface interaction between the compressional and vortex motions in the fluid and that this motion is confined to the boundary layer near the surface. Numerical results are obtained for the first few wave modes of a large shell, which illustrate the general approach to the solution. The axial wave number is complex for wave propagation, the imaginary part being the spatial attenuation coefficient. The frequency is also complex, the imaginary part of which is the temporal damping coefficient. The wave phase velocity is related to the real part of the axial wave number and turns out to be independent of frequency, with numerical value lying between the sonic velocities in the fluid and the shell. The frequency dependencies of these parameters and fluid velocity field mode shapes are computed for a typical case and displayed in non-dimensional graphs.
Defect Assessment of Tubular T-Joints Using the R6 Failure Analysis Diagram
Authors: Kristiansen N. O̸. , Turner C. E.
Published: June 2008

The present work centers on studying the application of the R6-type failure assessment diagram to the nodal joints of offshore platforms. The work concentrates on finite element models of tubular shells and T-joints with a part-through crack subjected to tension and out-of-plane bending loading of the brace. The overall conclusion is that the R6 procedure provided a satisfactory assessment procedure provided that, for tubular joints considered, the measure of fracture was expressed on the ordinate in terms of Gmid/Jmax and an appropriate definition of global collapse was used to normalize the applied load.
Mechanical Behavior of Bolted Joints Under Steady Heat Conduction
Authors: Kumano H. , Sawa T. , Hirose T.
Published: June 2008

Bolted joints in heat exchangers, cylinder heads in combustion engines, and so on are subjected to heat fluxes. It is necessary to examine the mechanical behavior of such bolted joints under thermal changes in order to establish an optimal design. This paper deals with mechanical behavior of bolted joints, in which two hollow cylinders and two rectangular thick plates made of aluminum are fastened at room temperature by a bolt and nut made of steel, and are subjected to thermal changes or steady heat conduction. Temperature distributions of the joints are analyzed using the finite difference method. Then, methods for estimating an increment in axial bolt force and a maximum stress produced in the bolts are proposed. In the experiments, the aforementioned bolted joints are put in a furnace. Furthermore, the rectangular thick plates fastened by a bolt and nut are heated by an electric heater. Then, the temperatures on the surfaces of the clamped parts and the bolts are measured with thermocouples. The increase in axial bolt force and the maximum stress produced in the bolts under steady heat conduction or thermal changes are measured. The analytical results are in fairly good agreement with the experimental ones.
Avoiding Steam Bubble Collapse-Induced Water Hammer in the Auxiliary Piping of Steam Power Plants
Authors: Lobo C. A. O. C. , Griffith P.
Published: June 2008

The mechanisms of steam bubble collapse-induced water hammer are identified for nominally horizontal or inclined pipes. On the basis of these observations, two methods of preventing steam bubble collapse-induced water hammer in nominally horizontal pipes are proposed. They are inclining them and injecting the water at a controlled rate at either the lowest point or injecting the water at several locations. The success of these methods is demonstrated for horizontal pipes and for pipes of other orientations. These ways of preventing steam bubble collapse-induced water hammer are then used to test filling strategies for “L”-shaped pipes oriented in practically every way. Both methods are found to work though the application of multiple injection ports and has complications when applied to a complex piping system. The use of the recommended design guidelines for avoiding steam bubble collapse-induced water hammer is demonstrated in an example problem.
Dynamics and Stability of Pipes Conveying Fluid
Authors: Chang C. O. , Chen K. C.
Published: June 2008

This paper deals with the dynamics and stability of simply supported pipes conveying fluid, where the fluid has a small harmonic component of flow velocity superposed on a constant mean value. The perturbation techniques and the method of averaging are used to convert the nonautonomous system into an autonomous one and determine the stability boundaries. Post-bifurcation analysis is performed for the parametric points in the resonant regions where the axial force, which is induced by the transverse motion of the pipe due to the fixed-span ends and contributes nonlinearities to the equations of motion, is included. For the undamped system, linear analysis is inconclusive about stability and there does not exist nontrivial solution in the resonant regions. For the damped system, it is found that the original stable system remains stable when the pulsating frequency increases cross the stability boundary and becomes unstable when the pulsating frequency decreases cross the stability boundary.
Estimation of Elastic Follow-Up Behavior on 18Cr-8Ni Steel Using Simplified Inelastic Analysis
Authors: Kobayashi K. I. , Saitoh Y. , Udoguchi T.
Published: June 2008

Elastic follow-up behavior was estimated using simplified inelastic methods newly developed, where only a constitutive equation of creep and a triangle of elastic follow-up were employed in the analysis. Then, uniaxial cyclic elastic follow-up tests were performed on an austenitic stainless steel SUS 304 at 700°C, and test results were compared with analyses. Since most of the starting points of elastic follow-up tests in the present experiments were beyond the elastic limit of the test material, the triangle of elastic follow-up had to be modified in the analyses. As a consequence, experimental results of elastic follow-up behavior for the first cycle agreed well with those analytically determined. Moreover, the test results obtained in subsequent cycles were found conservative compared with an extension of analyses that used the data obtained in the first cycle of cyclic test.
Hydraulic Effects on a Large Piping System During Strong Earthquakes
Authors: Ogawa N. , Mikoshiba T. , Minowa C.
Published: June 2008

Liquid in a large piping system could become a resonance column under axial excitations. A 1000-m long closed-boundaries pipeline with pressure wave propagation velocity of 1000 m/s would have the fundamental liquid resonance frequency of 0.5 Hz. Then, some hydraulic transients might occur during strong earthquakes. If dynamic pressure amplitude exceeds the value of system stationary pressure, then vaporizing at negative pressure, and after that, cavity or liquid column separation and reconnection can be produced. One of the effects of these behaviors would be equivalent damping of dynamic response, and the other an impact force on pipe structural system. The latter effect is considered as one of potential damage factors of a large liquid piping system. In this paper, an analytical method of earthquake-induced hydraulic transients of piping system is applied to a real underground large piping system subjected to a strong earthquake motion which has occurred in Japan. The results of the analysis have shown that the occurrence of earthquake-induced negative pressure in liquid column is possible. Further, the analysis has explained the difference between two long straight pipelines buried in the same route, one failed by axial cracking and the other had no damages.
Prediction of Fluid Temperatures From Measurements of Outside Wall Temperatures in Pipes
Authors: Guyette M.
Published: June 2008

The monitoring of the fatigue induced by thermal transients in thick-walled structures becomes more and more currently performed, mainly on equipment the failure of which could present severe implications on the environment. The easiest way of performing this monitoring is by use of Green’s functions in a convolution integral of the measured fluid temperatures to assess the stresses at the points of interest. Numerous cases, however, exist where the fluid temperatures are not available and only an outside wall temperature measurement is feasible. This paper describes the development and the industrial application of the so-called “inverse” transfer functions to predict the evolution of the fluid temperature from measurements of the metal temperature either at the outside or in the wall of the considered equipment. Some applications are shown for the particular case of the thermal stratification in piping systems.
A Displacement Measurement Method by Laser-Beam Scanning for Mapping the Interior Geometry of Pipes
Authors: Mizunuma M. , Ogawa S. , Nishimura C. , Kuwano H.
Published: June 2008

This paper proposes a displacement measuring technique for detailed noncontact mapping of the interior geometry of pipes. The technique, which is based on optical measurement using triangulation, employs a laser-beam scanner to measure radial displacement. To achieve high precision, three different algorithms for calculating the displacement from sensor output are compared in experiments. One of them, which calculates the displacement by using several direction-dependent characteristic curves, gives high accuracy. The accuracy of our experimental system is ±0.2 mm for radii between 33 and 42 mm. A mapping system using this technique with automated data-acquisition and 3D rendering of the interior is also described. Its effectiveness is illustrated by the experimental results.
Sloshing Impact Pressure in Roofed Liquid Tanks
Authors: Kurihara C. , Masuko Y. , Sakurai A.
Published: June 2008

A series of experiments were carried out in order to clarify the nonlinear sloshing phenomena in the reactor vessels of the pool-type LMFBRs, which may cause damages to the vessels or their inner structures. The test results for three types of models using a long-period large-amplitude shaking table provided us with the information on how the scales and the configurations of the models affect the sloshing wave crest impact pressures. Based on the test results and theoretical considerations, a formula was proposed to predict the impact pressures caused on the roofed liquid tanks due to sloshing. This formula is applicable to the same types of tanks, such as the oil storage tanks, as long as their sizes, liquid depths, and gaps between the roofs and the free surfaces are given.
On the Characteristics of Rectangular Bolted Flanged Connections With Gaskets Subjected to External Tensile Loads and Bending Moments
Authors: Morohoshi T. , Sawa T.
Published: June 2008

This paper deals with the characteristics of a rectangular bolted connection of “T” shape with a gasket (filler plate), in which the flanges and a gasket (filler plate) are fastened with two bolts and nuts, and are then subjected to an external tensile load or a bending moment. The contact stress distribution which governs the sealing performance (clamping effect), the load factor (the relationship between an increment of axial bolt force and an external load), and the maximum stress produced in the bolt were analyzed by using a two-dimensional theory of elasticity as a three-body contact problem. Experiments were performed concerning the load factor and the maximum stress produced in the bolt. The analytical results are fairly consistent with experimental ones. The effects on the load factor and the contact stress distribution were examined for variation in Young’s modulus of different gaskets and the different distances between the bolt holes.
Thermal Stresses in a Partially Filled Horizontal
Vessel
Authors: Russo E. P. , St. Cyr W. W. , Herrington P. D.
Published: June 2008

Stresses produced by a thermal gradient in the wall of a partially filled horizontal cylindrical vessel are presented. Three different thermal gradients are considered: 1) a discontinuous temperature change; 2) a hyperbolic temperature change; and 3) a linear temperature change at the liquid level. Thermal shock effects are also presented.
A Computational Procedure for Calculating Primary Stress for the ASME B&PV Code
Authors: Mackenzie D. , Boyle J. T.
Published: June 2008

A simple procedure for calculating primary stress consistent with the ASME B&PV Code is presented. The procedure is based on an iterative elastic analysis technique referred to as the elastic compensation method, which invokes the lower-bound limit load theorem to define maximum allowable static loads for the vessel. The method is simple to implement as an automatic computational procedure in a conventional elastic finite element program and requires minimal input from the designer.
Prediction of Fracture Toughness KIC Transition Curves of Pressure Vessel Steels From Charpy V-Notch Impact Test Results
Authors: Iwadate T. , Tanaka Y. , Takemata H.
Published: June 2008

A single and generalized prediction method of fracture toughness KIC transition curves of pressure vessel steels has been greatly desired by engineers in the petro-chemical and nuclear power industries, especially from the viewpoint of life extension of reactor pressure vessels. In this paper, the toughness degradation of Cr-Mo steels during long-term service was examined and the two prediction methods of fracture toughness KIC transition curves were studied using the data of 54 heats. 1) The toughness degradation of 2 1/4Cr-1Mo steels levels off within around 50,000 h service. 2) The FATT versus J-factor (=(Si+Mn)(P+Sn)×104) and/or X (=(10P+5Sb+4Sn+As)x10−2) relationships to estimate the maximum embrittlement of Cr-Mo steels were obtained. 3) A master curve method developed by authors et al.; that is, the method using a KIC/KIC−US versus excess temperature master curve of each material was presented for 2 1/4Cr-1Mo, 1 1/4Cr-1/2Mo, 1Cr and 1/2Mo chemical pressure vessel steels and ASTM A508 C1.1, A508 C1.2, A508 C1.3 and A533 Gr.B C1.1 nuclear pressure vessel steels, where KIC−US is the upper-shelf fracture toughness and excess temperature is test temperature minus FATT. 4) A generalized prediction method to predict the KIC transition curves of any low-alloy steels was developed. This method consists of KIC/KIC−US versus T–T0 master curve and temperature shift ΔT between fracture toughness and CVN impact transition curves versus yield strength relationship, where To is the temperature showing 50 percent KIC−US of the material. 5) The KIC transition curves predicted using both methods showed a good agreement with the lower bound of measured KJC values obtained from JC tests.
An Axisymmetric Stress Release Method for Measuring the Autofrettage Level in Thick-Walled Cylinders—Part I: Basic Concept and Numerical Simulation
Authors: Perl M. , Arone´ R.
Published: June 2008

A new experimental method for measuring the level of autofrettage in thick-walled cylinders is suggested. The method is based on measuring the hoop-strain while axisymmetrically releasing the residual stress field prevailing in the cylinder’s wall. A parametric study of the proposed experimental procedure conducted by a finite element simulation yields a simple empirical relation, which readily enables determining the actual autofrettage level from the strain measurements. This relation is found to be practically unique for all relevant cases, i.e., cylinders with radii ratios of b/a=1.6÷2.2 and autofrettage percents of φ=50–100 percent. A pilot test conducted on a 105-mm autofrettaged gun barrel, which experimentally validates the proposed procedure, is presented in Part II (Perl and Arone, 1994) of this paper.
Fatigue-Seismic Ratcheting Interactions in Pressurized Elbows
Authors: Boussaa Dj. , Van K. Dang , Labbe´ P. , Tang H. T.
Published: June 2008

Three dynamic tests on pressurized elbows involving fatigue-ratcheting as the major failure mode are investigated. The fatigue analysis is carried out with two approaches: the first is global and consists of Markl’s equation; the second is local and is based on local fatigue criteria combined with a suggestion by Coffin to take ratcheting into account. The implementation of these approaches required some elementary signal processing to separate the cyclic part of the strain from ratcheting. Results on narrow-band processes were used to assess cumulative damage. Finite element computations extended the data into uninstrumented locations. The great sensitivity of the implemented criteria to their arguments is discussed and exemplified. Despite the complexities of the issue, computed results match well with the experimental data.
Response and Failure of Internal Structural Subsystems Under Blast and Shock Loading
Authors: Tennant D. W. , Levine H. S.
Published: June 2008

The objective of this paper is to evaluate the ability to accurately predict the motions, structural response, and failure modes of internal structural components subjected to high-intensity airblast and ground shock loading. The cases of interest involve a surface flush, buried reinforced concrete cylinder that is expected to experience negligible damage, within which are contained aluminum and steel structures that may or may not be shock-isolated at the internal attachment points. The structures and subsystems are modeled in detail using the FLEX three-dimensional nonlinear transient analysis code. The analyses were carried out using the soil island approach to represent the local airblast-induced, direct-induced, and crater-related ground shock from a simulated nuclear explosion. A test involving only local airblast effects with hard-mounted internal substructures was conducted. Comparisons of data from this test with calculations will be presented. Calculations will also be included that show potential failure mechanisms for the internal subsystems and their causes.
Valve Closure: Method for Controlling Transients
Authors: Elansary A. S. , Contractor D. N.
Published: June 2008

One of the objectives of this study was to reduce the undesirable dynamic pressure oscillation that occurs in a simple pipeline due to valve closure and to prevent the occurrence of column separation. This is accomplished by maximizing the minimum pressure in the pipeline. The second objective was to minimize the maximum dynamic pressure, and the third objective was to estimate the best (minimum) time of closure, T*c, that results in a pipe stress equal to the maximum allowable stress. The method of characteristics with the time-line interpolation technique was used to solve the transient stresses and pressures in a liquid-filled piping system. Frequency-dependent friction was used in the equation of motion for the fluid and the pipe wall. A nonlinear optimization technique was utilized to generate the optimum valve closure policy. Maximum and minimum pressure heads resulting from the optimal policy were calculated and compared with those resulting from a uniform valve closure. Plots of pressure variation at the valve for these two valve closure policies were also generated. Examples are presented to demonstrate the advantage of the optimum valve closure policy over the uniform valve closure policy. The reduction in the maximum dynamic pressure and stress at the valve for different Tc is also presented.
Damage Ratio Prediction for Buried Pipelines Based on the Deformability of Pipelines and the Nonuniformity of Ground
Authors: Nishio N.
Published: June 2008

Damage susceptibility of pipelines during an earthquake bears close correlation with both the degree of “deformability” and the degree of “nonuniformity” of subsurface ground in which the pipelines are laid. A ground-block model is used to define the “deformability index” and the “nonuniformity index” in this paper; the latter is defined as a standard deviation of expected seismic displacement in a ground which is expressed as a set of ground blocks. Then the possibility of damage to a pipeline system is expressed in terms of a probability that a relative displacement between two adjoining ground blocks, which depends on the value of nonuniformity index, exceeds the value of deformability index of the pipeline. In this paper, values of nonuniformity index for various types of grounds are evaluated using damage statistics obtained during past earthquakes, and a practical method of damage ratio prediction is proposed.
Evaluation of Weldment Creep and Fatigue Strength-Reduction Factors for Elevated-Temperature Design
Authors: Corum J. M.
Published: June 2008

New explicit weldment strength criteria in the form of creep and fatigue strength-reduction factors were recently introduced into the American Society of Mechanical Engineers Code Case N-47, which governs the design of elevated-temperature nuclear plant components in the United States. This paper provides some of the background and logic for these factors and their use, and it describes the results of a series of confirmatory creep-rupture and fatigue tests of simple welded structures. The structures (welded plates and tubes) were made of 316 stainless steel base metal and 16-8-2 weld filler metal. Overall, the results provide further substantiation of the validity of the strength-reduction factor approach for ensuring adequate life in elevated-temperature nuclear component weldments.
Uniform Arrays of Unequal-Depth Cracks in Thick-Walled Cylindrical Pressure Vessels—Part I: Stress Intensity Factors Evaluation
Authors: Perl M. , Wu K. H. , Arone´ R.
Published: June 2008

The influence of the unevenness of crack lengths on the mode I stress intensity factors (SIF) for large uniform arrays of radial cracks of unequal depth in thick-walled pressurized cylinders is investigated applying the previously proposed “two-crack-length level model.” Using the finite element method, SIFs are evaluated for numerous configurations of crack arrays bearing a wide range of crack lengths. The interaction range for various combinations of crack arrays and crack lengths is then determined. The numerical results anticipate that any statistical unevenness of the initial crack lengths, prevailing in the pressurized cylinder, will be amplified during the process of fatigue crack growth. Thus, while the fatigue life of the vessel is determined by a large number of cracks, its final failure, which is governed by a small number of the largest cracks, is likely to be caused by one major crack, as is usually the case. This sequence of events results from the particular nature of the inter-crack stress field, which is analyzed and discussed in detail in Part II of the paper.
Uniform Arrays of Unequal-Depth Cracks in Thick-Walled Cylindrical Pressure Vessels—Part II: The Inter-Crack Stress Field
Authors: Wu K. H. , Perl M. , Arone´ R.
Published: June 2008

In Part I of this paper [1], it was suggested that the variation of the SIF at the tip of the varying cracks reflects, in fact, the characteristics of the stress field prevailing in the inter-crack region, prior to the introduction of these cracks. Therefore, using the FE method, the inter-crack stress field is investigated for various geometrical configurations, and the dependence of its characteristic parameters on the inter-crack region aspect ratio is determined. Under service conditions, it may sometimes occur that the penetration of the internal pressure into the crack cavity is only partial. Therefore, the effect of the actual fraction of the internal pressure, acting on the cracks’ faces is also analyzed. Once the inter-crack stress field is characterized, its effect on the initial values of the stress intensity factor of the varying cracks is determined. Finally, based on all the results obtained in both parts of this paper, a possible scenario of the time sequence of the cracking process of the vessel is suggested and discussed.
Stress Analysis and Weight Savings of Internally Pressurized Composite-Jacketed Isotropic Cylinders
Authors: Witherell M. D. , Scavullo M. A.
Published: June 2008

An isotropic cylinder designed to have a specific bore displacement per unit of internal pressure can be made lighter by removing material from the outer diameter and replacing it with the correct amount of a stiff lightweight composite material. A stress solution is presented for an internally pressurized compound cylinder constructed from an isotropic liner jacketed with a cylindrically orthotropic composite material. The solution is used to determine the set of compound cylinder geometries which have equivalent bore hoop strain to that of an isotropic monoblock cylinder. An equation for predicting the equivalent compound cylinder geometry which provides the maximum possible weight savings over the isotropic design is also presented. To verify the theory, an experimental study was conducted involving the measurement of bore strain for internally pressurized steel liners jacketed with a graphite bismaleimide composite.
An Improved Method for Stability and Damped Critical Speeds of Rotor-Bearing Systems
Authors: Kim D. , David J. W.
Published: June 2008

Many computer programs are available for stability and critical speed analysis of rotor-bearing systems. The iterative search-transfer matrix method is widely used for such programs. However, this method sometimes fails to converge or may miss some critical speeds. The polynomial method, which derives the characteristic polynomial and solves for the critical speeds, can partly overcome these shortcomings. However, the advantage of the polynomial method disappears as the number of elements in the system increases. This is because the computational time required to find a characteristic polynomial increases exponentially with the number of elements. This paper describes an improved technique based on the transfer matrix-polynomial method, which reduces the computational time significantly and completely eliminates the possibility of missing some critical speeds. A new technique is developed for the derivation of the characteristic polynomial. The characteristic polynomial equation is then converted into an eigenvalue problem of its companion matrix, whose eigenvalues are identical with the roots of the polynomial equation. The process, which can find only some dominant eigenvalues, eliminates the possibility of missing some eigenvalues without any penalties in the computational time and accuracy. The results from the method presented here are compared with those from some other methods.