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Research Papers: Design and Analysis

J. Pressure Vessel Technol. 2018;140(4):041201-041201-14. doi:10.1115/1.4039844.

The paper is a review work devoted to dished heads of various meridian shapes. Geometry of the shells of revolution, the membrane state, and the edge effect occurring in the shells are described. Exemplary analytical and numerical finite element method (FEM) studies of torispherical, ellipsoidal, Cassini-ovaloidal, and untypical special dished heads are presented. The results of the above-mentioned two methods are compared. Moreover, numerical research of elastic buckling of the above-mentioned selected heads under external pressure is carried out. Literature related to each of the considered head types is quoted and discussed, with special attention paid to the works developed in the 21st century. In concluding remarks, the stress concentration and buckling of these structures are commented, with consideration of the head meridian shapes.

Commentary by Dr. Valentin Fuster

Research Papers: Materials and Fabrication

J. Pressure Vessel Technol. 2018;140(4):041401-041401-11. doi:10.1115/1.4039843.

In the course of the service of long-distance oil/gas pipelines, due to corrosion, abrasion, and other reasons, the possibility of pipeline leakage is growing. In-service welding is an advanced technique employed in the repair of pipelines, and it has wide application in guaranteeing the safe transmission of petroleum or gas. The present studies on in-service welding, including experiments and numerical simulations, all assumed that the inner wall of the pipeline was in good condition without considering the influence of defects. This paper started from internal corrosive defects, through the finite element simulation method, investigated how the pressure of inner medium and defect size influence the burn-through of in-service welding. The results show that, compared with the intact pipe, pipeline with internal corrosive defect is more prone to burn-through. With the increase of medium pressure, the maximum radial deformation, the von Mises stress, and hoop stress at the defect area increase. The radial deformation has a certain time effect. The depth of defect has an evident impact on the radial deformation and the stresses. The radial deformation, the von Mises stress, and hoop stress increase with the deepening of the defect, while the impacts of the defect's length and width are less obvious.

Commentary by Dr. Valentin Fuster

Research Papers: Pipeline Systems

J. Pressure Vessel Technol. 2018;140(4):041701-041701-13. doi:10.1115/1.4039698.

This paper investigates the rupture of thin-walled ductile cylinders with isolated corrosion defects, subject only to internal pressure. It aims to propose a new solution for predicting the maximum load limit that will rupture a corroded pipeline, regardless of its material, its geometric ratio, or the dimensions of the existing corrosion defect. This solution is the result of several numerical simulations by variation of the length and depth of the defect with the assumption that the width of the defect has a negligible marginal effect. In all our numerical simulation analyses, the rupture was controlled by the Tresca failure criterion which is expressed in terms of material hardening exponent and the ultimate material stress. The proposed solution was then compared with the currently used coded methods, first B31.G, its improved version 0.85dL, and then DNV-RP F101, using an experimental database compiled from the existing literature. As a result, our proposed solution has been validated and has resulted in rupture ratios ranging from approximately 0.7 to 1. Furthermore, it has a tight prediction range compared to the B31.G, 0.85dL, and the DNV-RP F101 methods.

Commentary by Dr. Valentin Fuster

Technical Brief: Technical Briefs

J. Pressure Vessel Technol. 2018;140(4):044501-044501-3. doi:10.1115/1.4039882.

Documented thermowell failures designed to PTC 19.3TW and earlier, when evaluated with the drag crisis invoked, reveals the potential for enhanced reliability of the current standard in reducing the risk of failure. The code calculation remains largely intact apart from a conservative Strouhal number in conjunction with Reynolds number criteria marking the onset and terminus of the drag crisis.

Commentary by Dr. Valentin Fuster

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