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LETTERS TO THE EDITOR

J. Pressure Vessel Technol. 1990;112(1):1-3. doi:10.1115/1.2928580.
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Abstract
Topics: Titanium , Artillery
Commentary by Dr. Valentin Fuster

RESEARCH PAPERS

J. Pressure Vessel Technol. 1990;112(1):4-19. doi:10.1115/1.2928586.

Creep-fatigue interaction and its effect on damage of components in service have been a major concern to analysts. To deal with this problem, several criteria have been proposed and used, such as: cycle-time fraction summation rule, strain limit, fracture maps where damage mechanisms are based on crack initiation or propagation, and ductility exhaustion. These concepts are reviewed in this paper so that one can interpret the damage mechanisms caused by creep and by fatigue. If a long period of dwell-time at elevated temperature is imposed on a component under strain conditions, stress relaxation occurs. Relaxation data can be used, for example, in austenitic steels, in predicting creep stages; however, interpretation of data obtained from such tests could be misleading in assessing damage. An example is given for life prediction on the basis of two selected criteria: the fraction rule and ductility exhaustion.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):20-27. doi:10.1115/1.2928581.

A methodology for assessing the remaining life of hot reheat steam pipe with longitudinal flaws, such as those typically associated with the longitudinal seam welds, has been developed. The approach uses three levels of analysis. Level 1 employs handbook data, assumed flaw sizes, and design parameters. Level 2 employs handbook data, assumed flaw sizes, and actual operating parameters. Level 3 is tailored to a specific case and uses measured data, inspection results, and actual operating parameters. A computer code was developed to apply this approach to hot reheat steam pipe of 2-1/4Cr-1Mo and 1-1/4Cr-1/2Mo-Si steel. Using data from an EPRI survey (RP2596-7), the results of Level 1 analysis were found to predict the potential for creep damage and fracture and to correlate well with past experience, whereas the traditional lower-bound Larson-Miller approach was generally overly optimistic in predicting remaining service life. The approach predicts creep-crack-growth life and assesses the potential of rapid, unstable fracture occurring before a significant amount of leaking takes place. The usefulness of the methodology is illustrated by means of example analyses of a typical cases that might be expected in service. The parameters that were varied in these analyses include type of material (base metal or weld metal), pressure, temperature, pipe wall thickness, and initial flaw size. The approach provides a preliminary tool to help make inspection, operating, and replacement decisions; but additional work is required to validate it as a general tool.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):28-33. doi:10.1115/1.2928582.

A three-dimensional analysis of the dynamic behavior of liquid-filled elastic cylindrical tanks based on flexible grounds, undergoing horizontal and vertical earthquake excitation is presented. The interaction of the ideal fluid with the elastic shell and with the flexible ground yields a problem of linear potential theory which must be solved together with the equations of motion of the shell and of the ground. With the unknown modal shapes of vibration developed in Fourier and in Fourier-Bessel series, the partial differential equations are transformed into coupled generalized equations of vibration by a weighted residual approach. The results show the strong influence of the flexible ground characterized by a remarkable shifting of natural frequencies, by the existence of additional natural frequencies, and by high damping ratios.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):34-38. doi:10.1115/1.2928583.

Improving the reliability of the piping systems can be achieved by eliminating the mechanical snubber and by reducing the response of the piping. In the seismic design of piping system, damping is one of the important parameters to reduce the seismic response. It is reported that the energy dissipation at piping supports contributes to increasing the damping ratio of piping system. Visco-elastic damper (VED) and elasto-plastic damper (EPD) were developed as more reliable, high-damping piping supports. The dynamic characteristics of these dampers were studied by the component test and the full-scale piping model test. Damping effect of VED is independent of the piping response and VED can be modeled as a complex spring in the dynamic analysis. On the other hand, damping ratio of piping system supported by EPD increases with the piping response level. So, these dampers are helpful to increase the damping ratio and to reduce the dynamic response of piping system.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):39-45. doi:10.1115/1.2928584.

Considering the effect of the interaction between piping and support systems in the piping design is a more integrated approach to improve the reliability of piping systems. So, it is important to clarify the dynamic characteristics of the piping and the restraint structure during the seismic events. It may be desirable to investigate the effect of the gap on the response and the local stress of the piping systems. The dynamic characteristics of a simplified piping model with gaps was investigated by the tests and the analysis. Three-dimensional piping model test was performed to estimate the effect of the gap on the response of the piping system. It can be found that the local stress and the stiffness of the piping and the restraint structure under the seismic loadings should be considered in the seismic design. The gap size was not so effective on the response of the 3-dimensional piping system in the high-level response.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):46-49. doi:10.1115/1.2928585.

Flow-induced vibration of rod arrays in a jet flow was studied experimentally. The rod arrays tested were on square layout with a pitch-to-diameter ratio of 1.32. The rods were found to vibrate with large whirling trajectories when the jet velocity exceeds a critical value. The effects of axial flow velocity and stand-off distance of the rod array from jet exit were also investigated. A design guide for rod arrays subjected to a jet flow is proposed.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):50-56. doi:10.1115/1.2928587.

Design Rules in the ASME Code, Section VIII, Division 1, cover the design of unreinforced and reinforced rectangular pressure vessels. These rules are based on “infinitely long” vessels of non-circular cross section and stresses calculated are based on a linearized “small deflection” theory of plate bending. In actual practice, many pressure vessels can be found which are of finite length, often operating successfully under pressures two to three times as high as those permitted under the Code rules cited. This paper investigates the effects of finite length on the design formulae given by the ASME Code, and also a design method based on “large deflection” theory coefficients for short rectangular pressure vessels. Results based on analysis are compared with values obtained from finite element computations, and with experimental data from strain gage measurements on a test pressure vessel.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):57-64. doi:10.1115/1.2928588.

This paper is concerned with the nonlinear structural responses of steel liner-reinforced concrete penstocks of a concrete dam subjected to an internal pressure. The study reported herein consists of three major parts: 1) testing of two large penstock specimens, 2) a quasi-analytical solution for preliminary design, and 3) a detailed nonlinear finite element analysis. Each of the three parts are described in the paper with some detail. The quasi-analytical solution, although limited in geometric modeling, can give reasonable predictions on the overall deformation behavior and the ultimate failure strengths of penstocks in question. The finite element analysis, on the other hand, provided more detailed development and distribution of concrete cracking as a function of the applied pressure.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):65-70. doi:10.1115/1.2928589.

Loadings to cause severe accidents on containment buildings can include combinations of uniform internal pressure, dynamic pressure, and seismic. Most studies that have been conducted to predict containment building capacity have focused on the effect of over pressurization on containment performance. A simple methodology that permits rapid and reasonably accurate analysis for assessing the capacity of steel containment buildings; due to global or local uniform or spatially varying dynamic loading was developed. An axisymmetric model was used and the circumferential variation of the pressure, displacements, and stress resultants were represented by Fourier series. Shell vibration and buckling analysis were performed using modified versions of BOSOR4 and BOSOR5 finite difference codes. The modified version of BOSOR5 allows the input of pressures that vary along the meridional direction. These pressures were increased until failure of the containment occurred. Failure was defined to occur when membrane strains reached twice the yield strain or the bifurcation point was introduced. The axisymmetric analysis demonstrated a powerful tool to access the capacity of steel containment buildings.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):71-75. doi:10.1115/1.2928590.

A thermal ratcheting test was performed using an elbow model test specimen subjected to sustained primary load and cyclic thermal transient strains. Under severe loading conditions incremental longitudinal strains are observed in the region where a circumferential angle is around ± π/9 from the side of the elbow, while the elbow cross section was ovalized cycle by cycle causing large circumferential bending strain at around φ = π/2. It was shown by the test and analyses that the maximum primary membrane stress in an elbow is an essential parameter for thermal ratcheting behavior of elbows. Direct application of thermal ratcheting criteria in the ASME Code Case N-47 showed considerable conservative estimation and an improved thermal ratcheting criterion for elbows is recommended.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):76-84. doi:10.1115/1.2928591.

Temperatures, stresses, and deformations in a single-pass butt-welded pipe are studied with a full three-dimensional finite element model. The model covers the whole circumference and the complete welding sequence; i.e., no assumption of axi-symmetry is made. The pipe studied has an outer diameter of 114.3 mm and a wall thickness of 8.8 mm. The material is carbon-manganese steel. The MIG-welding simulated results in a very high cooling rate. Low-temperature solid-state phase transformations, therefore, become significant and of importance to the residual stress field. The material model in the FE-code used (ADINA) is extended for that purpose. Notable calculated results are the residual compressive hoop stresses in the weld and the residual circumferential stress variations, especially in the beginning and end regions of the weld.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):85-91. doi:10.1115/1.2928592.

Determination of residual stresses and the positive or negative effect that they may have on the component is an important consideration in design. Unexpected failure of components, latter determined to be attributable to residual stress, is not uncommon. In this paper, a theoretical study of the stresses in a long hollow circular cylinder subjected to rapid cooling of the exterior surface is presented. A quasi-static uncoupled thermoelastoplastic analysis, based on incremental theory of plasticity, is developed and a numerical procedure for successive approximation is formulated. For this analysis, it is assumed that the material has temperature-dependent properties and is characterized by linear strain hardening. The thermoelastoplastic and residual stress distributions are discussed in detail. The results are compared with related published work where a reasonable agreement is observed.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):92-97. doi:10.1115/1.2928593.
Abstract
Topics: Creep
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Pressure Vessel Technol. 1990;112(1):98-104. doi:10.1115/1.2928594.

Development of an annular finite element, for the linear elastic analysis of sandwich shells, is reported here. The derivation of stiffness and mass matrices is based on improved shell theory which takes into account the effects of rotary inertia and transverse shear deformation. Flexural rigidity of the faces is included in the formulation. The core of the sandwich shell is assumed to be incompressible in the radial direction. Numerical examples of spherical sandwich shells with two types of boundary conditions—(i) fixed and (ii) pinned along the outer periphery—have been presented. The results are generated for displacements and frequencies.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):104-108. doi:10.1115/1.2928577.

The computer simulation of forced vibrations induced on a water pool is presented in this paper. The complexity of the seismic fluid-structure interaction problem is accentuated by the large free surface motion. To overcome this difficulty, the arbitrary Lagrangian Eulerian (ALE) finite element formulation is employed. Moreover, the nonlinear behavior of the free surface motion is also taken into account. The results of the numerical simulation are compared with published experimental data and the effectiveness of the ALE algorithm is demonstrated.

Commentary by Dr. Valentin Fuster
J. Pressure Vessel Technol. 1990;112(1):108-114. doi:10.1115/1.2928578.

The finite element method is used to study stresses in two types of spherical pressure vessel heads having very wide range of applications in industries. The first problem involves a nozzle to sphere intersection reinforced by a pad and subjected to radial thrust load. The second problem deals with a pressurized thick hemispherical drumhead with a circular manhole. These structures are modeled using eight-node axisymmetric solid of revolution finite elements. Numerical values of circumferential and meridional stresses from the present analysis show excellent agreement with experimental data from the literature.

Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. Pressure Vessel Technol. 1990;112(1):115-116. doi:10.1115/1.2928579.
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Abstract
Commentary by Dr. Valentin Fuster

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