Showing papers in "Journal of Pressure Vessel Technology-transactions of The Asme in 1978"

Propagating Buckle Arrestors for Offshore Pipelines

Abstract: When an underwater pipeline is buckled in the presence of sufficient external pressure, a propagating buckle is initiated, and the buckle front will propagate along the pipeline until a region of much less external pressure is reached. This paper describes the results of experimental research on methods of arresting the advancement of a propagating buckle along the pipeline. The arresting capacities of three types of buckle arrestors conceived during this program, free-ring, welded-ring, and heavy-walled section arrestors, are described in detail. Results of propagating pressure experiments are also presented.

Stress Analysis of Pipe Bends by Ring Elements

Abstract: This paper proposes a new finite element method for treating the stress analysis of a piping system under general loading conditions. This finite element method will be referred as the finite ring method, since its elements are ring-shaped. This finite ring treatment is based on the general thin shell theory incorporating shear and distributed deformations along the pipe length. In this paper, emphasis is given to the theoretical aspects of the method. A comparison with other experimental and theoretical results is presented to substantiate the validity of the present method.

Stress Intensity Factors for Reactor Vessel Nozzle Cracks

Abstract: A method consisting of a marriage between frozen stress photoelasticity and a computerized least-squares data analysis for extracting stress intensity factor (SIF) distributions in three-dimensional cracked body problems is reviewed. Results from the application of the method to three programs dealing with nozzle corner cracks are discussed. The importance of using actual flaw shapes in analysis is stressed. It is concluded that the flaw growth in such problems is generally not self-similar due to the complexity and variety of boundary shapes. The experimental technique described appears to offer a viable independent estimate of SIF distributions for such problems.

Three-Dimensional Versus Axisymmetric Finite-Element Analysis of a Cylindrical Vessel Inlet Nozzle Subject to Internal Pressure—A Comparative Study

Abstract: This paper presents a comparative study between a three-dimensional and an axisymmetric finite-element analysis of a reactor pressure-vessel inlet nozzle subject to internal pressure. A quarter-symmetric section of the nozzle is modeled with a three-dimensional quadratic isoparametric finite element. This comparative study proves that the axisymmetric analysis is unconservative if based upon common axisymmetric modeling techniques. This inadequacy, for the PWR vessel inlet nozzle studied herein, can be offset by a modification of the modeling techniques, i.e., if the value of the radius of the equivalent spherical vessel is taken as 3.2 instead of, say, 2. The results of the three-dimensional finite-element analysis are also compared with those of a photo-elastic stress analysis and with the stress indices indicated by the ASME Section III Code. These additional comparisons, based upon a continuous distribution of hoop and tangential stress indices in both the transverse and longitudinal planes, shows good agreement between the three-dimensional finite-element and photoelastic analyses. The ASME Section III stress indices are found to be relatively conservative.

Embedded Elliptical Crack at a Corner

Abstract: A procedure for estimating the stress intensity factor of an embedded elliptical crack near the corner in a region of high stress concentration such as pressurized or thermally shocked nozzle-to-cylinder junction is discussed. The procedure is then used to analyze two hypothetical embedded circular cracks near the corner of a nozzle-to-cylinder junction where stress distributions in the uncracked junction are known. Also shown are two new stress intensity magnification factors for two embedded elliptical cracks, i.e., b/a = 0.2 and 0.982, close to a free corner, i.e., a/h = b/h = 0.9.

Thermoelastic Analysis of Nonaxisymmetrically Heated Thick Cylindrical Shells

Abstract: The thermoelastic problem of a thick cylinder subjected to nonaxisymmetric temperature distribution is considered. The temperature distribution may be harmonic or non-harmonic. The problem is formulated in terms of the in-plane displacements u and v and a solution is obtained by using Fourier series method. Two examples corresponding to a steady state and transient thermal distributions are solved. The steady-state case is compared to an exact solution and the transient problem is compared to a finite element solution. The transient problem considered is that of a solar superheater during startup after the departure of a cloud cover. The problem has applications in the conventional fossil-fired steam generators as well.

Shallow Formation Hydrofracture Mapping Experiment

Abstract: Geophysical diagnostic techniques are being developed to characterize massive hydraulic fractures. Sandia Laboratories is developing a system based on the measurement of surface electrical potentials. Model calculations indicate that the electrical potentials produced by direct electrical excitation of the fracture well and the fracture fluid can be used to determine the direction and asymmetry of a massive fracture. A small scale, shallow formation hydrofracture experiment was conducted by the AMOCO Production Company in an attempt to better correlate theoretical and experimental data.