Showing papers in "Journal of Pressure Vessel Technology-transactions of The Asme in 1991"

The Generalized Local Stress Strain (GLOSS) Analysis—Theory and Applications

Abstract: The underlying theory relates redistribution of inelastic stresses at a given location under consideration to the uniaxial stress relaxation process. GLOSS analysis is emerging as a useful technique for determining multiaxial stress relaxation, follow-up, creep damage, inelastic strain concentrations and low-cycle fatigue estimates, limit analysis and issues pertaining to stress-classification

Fluidelastic Instability of Heat Exchanger Tube Bundles: Review and Design Recommendations

Abstract: This paper reports that fluidelastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to cross-flow. Most of the available data on this topic have been reviewed from the perspective of the designer. Uniform definitions of critical flow velocity for instability, damping, natural frequency and hydrodynamic mass were used. Nearly 300 data points were assembled. The authors found that only data from experiments where all tubes are free to vibrate are valid form a design point of view. In liquids, fluid damping is important and should be considered in the formulation of fluidelastic instability. From a practical design point of view, we conclude that fluidelastic instability may be expressed simply in term of dimensionless flow velocity and dimensionless mass-damping. There is no advantage in considering more sophisticated models at this time. Practical design guidelines are discussed.

A Stress Analysis of Pipe Flange Connections

Abstract: The use of pipe flange connections is standardized in the codes of JIS, ASME, DIN and so on. However, these codes are almost entirely dependent on experience, and subsequently some problems concerning pipe flange connections have been encountered. In the present paper, the distribution of contact stresses which governs the sealing performance is analyzed as a three-body contact problem, using an axisymmetrical three-dimensional theory of elasticity. The effects of the stiffness and the thickness of raised face metallic gaskets on the contact stresses and the effective gasket seating width are shown by numerical calculation. Moreover, stresses produced on the hub, the load factor (the relationship between an increment of bolt axial force and an internal pressure), and the maximum stress caused in bolts are analyzed. For verification, experiments are carried out. The analytical results are satisfactorily consistent with the experimental results.

A Weight Function Technique for Estimating Stress Intensity Factors for Cracks in High Pressure Vessels

Abstract: This paper describes a computationally efficient weight function technique which can be used to estimate the opening-mode stress intensity factor around the perimeter of planar surface or embedded cracks. The accuracy of the weight function itself and of the numerical quadrature schemes adopted are verified for elliptical cracks with a wide range of aspect ratios. The technique is then applied to longitudinal-radial cracks at the inner surface, including crossbores, of thick-walled pressure vessels. The results obtained for a wide range of crack depths, aspect ratios and vessel diameter ratios agree well with the predictions obtained by others using finite element, boundary element and modified mapping collocation methods, as well as with previously unpublished experimental data. The paper also considers the applicability of the ASME Boiler and Pressure Vessel Code procedures for estimating K 1 for these defects.

Longitudinal Motion of a Thick Transversely Isotropic Hollow Cylinder

Abstract: The propagation of a longitudinal harmonic wave in a transversely isotropic shell has been investigated in the development of ultrasonic techniques for thick hollow composite cylinders. The characteristic equation for satisfying the stress-fee inner and outer cylindrical boundaries has been obtained in an exact form in terms of the wavelength, the cylinder radii and the material constants. The phase velocity of the fundamental mode is calculated for a wide range of the wavelength for various cylinder radii for some typical sample materials. The shell wave speeds for the second mode of vibration are also presented. Comparisons are made between shell wave speeds and plate wave speeds. The spread of the wave speeds for the composite shells is shown to be much wider than that for an isotropic shell.

Recent Advances in Dynamic Buckling Analysis of Liquid-Filled Shells

Abstract: The dynamic buckling of liquid-filled shells is reviewed. Comparison of the analysis with experimental results is presented. The governing equations of dynamic buckling of liquid-filled imperfect shells are then derived. A simple imperfection pattern is chosen to explain the additional buckling modes encountered in the experiments.

Some Results on the Analytical Solution of Cylindrical Shells With Large Openings

Abstract: In comparison with previous analytical solutions obtained by Eringen, Van Dyke and Lekkerkerker, the following three areas have been improved by the present method: 1) The modified Morley's equation is used instead of Donnell's shallow shell equation; 2) the accurate expression of boundary curve of hole is expanded in terms of powers of p o =r o /R; 3) the accurate boundary conditions for generalized forces are expanded in terms of powers of p o and truncated after the terms of p o 3 . The stress analysis of cylindrical shells connected with nozzles has been developed by using the present solution

Displacements in Oil Storage Tanks Caused by Localized Differential Settlement

Abstract: This paper presents design charts for predicting the maximum radial distortion of open-topped storage tanks caused by localized differential settlement of the tank foundations. It is well known that differential settlement can produce radial deflection of the tank shell sufficient to cause jamming of the floating roof. Predictions of shell deflections have often assumed the shell to be inextensional, and assumption which may not always be valid, particularly where the settlement is localized. Consequently, the authors have recently completed a more refined analysis of the deflections and stresses in the shell and the primary wind girder in which the shell is considered to act as a membrane. They concluded that this membrane analysis is valid for all practical applications and proposed a procedure for predicting shell displacements caused by any general differential settlement profile using Fourier analysis.

Flow-Induced Vibration Analysis of Tube Bundles—A Proposed Section III Appendix N Nonmandatory Code

Abstract: This paper presents guidelines for flow-induced vibration analysis of tubes and tube bundles such as those commonly encountered in steam generators, heat exchangers, condensers and nuclear fuel bundles. It was proposed as a nonmandatory code to be included in Section III Appendix N (N-1300 series) of the American Society of Mechanical Engineers (ASME) Boiler Code. In preparing this code, the authors tried to limit themselves to the better-defined flow excitation mechanisms ― vortex-induced vibration, fluid-elastic instability and turbulence-induced vibration ― and include only the more-established methods. References are, however, given for other methods whenever justified. This guideline covers only design analysis

State-of-the-Art Review of Pressure Relief Valve Design, Testing and Modeling

Abstract: It is well known that the response of a rail tank car to exterior heating (e.g., fire engulfment) is significantly affected by the operating characteristics of the pressure relief valve (PRV). If the valve jams or fails in some way, it can lead to a violent vessel rupture; therefore, PRV failure modes and mechanisms must be understood. This paper investigates the studies which have been conducted in the area of PRV technology. The original focus of the paper was to conduct a literature search to find the state-of-the-art for the PRV’s which are presently installed on railway tank cars, highway tankers, and stationary LPG storage vessels. When few papers were found which had concentrated on this particular topic, the authors continued the search by considering both the nuclear power and chemical processing industries, where similar technologies are found. The results of the literature search suggest that the PRV’s currently installed on tank cars and highway tankers are based on designs more than 30 yr old. Controlled fire tests and industry’s maintenance programs suggest that PRV’s could be improved. Most experimental studies of PRV’s have concentrated on flow visualization techniques and have not considered PRV dynamic characteristics. The lack of understanding of valve dynamic characteristics has slowed the development of improved PRV dynamic computer models.

Rate Sensitivity and Short-Term Relaxation Behavior of AISI Type 304 Stainless Steel at Room Temperature and at 650°C; Influence of Prior Aging

Abstract: The strain rate sensitivity and short term relaxation behavior of Type 304 Stainless Steel were investigated in the uniaxial strain rate jump tests with intermittent periods of relaxation at room temperature and at 650/degree/C. At room temperature material exhibited conventional strain rate sensitivity and no strain rate history effect. The high-temperature experimental results revealed a complex and dramatically different material behavior. At 650/degree/C the pattern of strain rate sensitivity was not set as soon as the plastic flow was fully established, but continued to evolve with the further straining in the plastic range. Test results indicate that at 650/degree/C the material may exhibit a strain rate history effect. Both at room temperature and at 650/degree/C the relaxation behavior was independent of the stress and/or strain level at the beginning of the relaxation, but depended nonlinearly on the strain rate preceding the relaxation test. Prior aging had no significant influence on the rate-dependent material response. The irregular material behavior at 650/degree/C is attributed to dynamic strain aging as indicated by serrated stress-strain curves (the Portevin-LeChatelier effect). 20 refs., 9 figs., 1 tab.

A Simple Model for Fatigue Crack Growth Near Stress Concentrations

Abstract: Fatigue crack growth rates are often difficult to predict for short cracks growing near stress concentrations This paper presents a simple model to predict those growth rates which incorporates the phenomenon of crack closure Crack opening stresses are shown to change significantly as cracks grow away from notches, and the simple model is designed to describe those changes The effective stress range ratio, U , is assumed to be dependent on the local stress at the crack tip location in a corresponding uncracked body The value of U changes with the normalized maximum stress in unnotched bodies, and this dependence can be quantified with elastic-plastic finite element models or simpler modified-Dugdale crack analyses The local stress distribution is estimated with a Neuber analysis A semi-empirical stress intensity factor solution is constructed and calibrated with known exact solutions The crack growth rate is then calculated with the modified Paris law, taking crack growth constants from long crack data The model is illustrated with a specific case study, the growth of cracks from center notches in an SAE 1026 steel Experimental crack growth data for notches of different sizes and shapes compare favorably with the calculations The scheme is contrasted with previous models for notch fatigue cracks The implications of the simple model for other fatigue design problems are explored, highlighting the simplicity and generality of the model

Creep-Fatigue Evaluation Based on the Overstress

Abstract: There is summarized a series of creep-fatigue data on a normalized and tempered 2 1/4Cr-1Mo steel obtained at 550°C in a very high vacuum environment under a wide variety of a strain-time program. A special feature of a stress-strain response of the steel is described to give the overstress and the internal back stress. A damage equation is developed to predict a creep-fatigue behavior which is free from the environmental effect.

Use of On-Line Fatigue Monitoring of Nuclear Reactor Components as a Tool for Plant Life Extension

Abstract: In this paper the application of an on-line fatigue monitoring system for tracking fatigue usage in operating power plants is described. The system, like several others which have been developed, uses the influence function approach, operates on a microcomputer, and determines component stresses using temperature, pressure, and flow rate data that are typically available from plant computers. Using plant-unique influence functions developed specifically for each component location, the system calculates stresses as a function of time and computes the fatigue usage. Stress values are calculated at time internals defined by the user and the fatigue values are saved on files for use at a later time. The application of the GE Fatigue Monitoring System (GEFMS) to calculate fatigue usage in the feedwater nozzle of a GE boiling Water Reactor is described in this paper.