Shakedown boundary and limit load determination of a 90-degree back to back pipe bend subjected to steady internal pressures and cyclic in-plane bending moments

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Mechanical Engineering Department

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Document Type

Research Article

Publication Title

American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP

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Shakedown analysis of 90-degree back-to-back pipe bends is scarce within open literature. According the author's knowledge, no shakedown analysis exists for such structure based on experimental data. Ninety degree back-to-back pipe bends are extensively utilized within piping networks of nuclear submarines and modern turbofan aero-engines where space limitation is considered a paramount concern. Additionally, on larger scales, 90-degree back-to-back pipe bend configurations are also found within piping networks of huge liquefied natural gas tankers. The structure analyzed is formed by bending a straight pipe to acquire the geometry of two 90-degree pipe bends set back-to-back each having a nominal pipe size (NPS) of 10 in. Schedule 40 Standard (STD). In the current research, the 90-degree back-to-back pipe bend setup analyzed is subjected to a spectrum of steady internal pressures and cyclic in-plane bending moments. A previously developed simplified technique for determining elastic shakedown limit loads is utilized to generate the elastic shakedown boundary of the 90-degree back-to-back pipe bend analyzed. In addition to determining the elastic shakedown boundary, elastic and post shakedown domains (Bree diagram), the maximum moment carrying capacities (limit moments) are also determined and imposed on the generated Bree diagram of the analyzed structure. The simplified technique outcomes showed excellent correlation with the results of full elastic-plastic cyclic loading finite element simulations. Copyright © 2013 by ASME.

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