WRC 443:1999

$34.45

External Pressure: Effect of Initial Imperfections and Temperature Limits

Published By	Publication Date	Number of Pages
WRC	1999	52

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Description

Part 1: External Pressure: Effect Of Initial Imperfections And Temperature Limits: The Effect of Intitial Imperfections on the Buckling of Cylinders Subjected to External Pressure

This report presents a new method for estimating the effects of deviations from a true circular form on external pressure capacity of cylinders. The new, improved method is based on analytical work and test results that have become available since earlier Code rules were developed. The new method is based on a more rational basis than earlier rules, and the new method provides better correlation with test results. The method could be adopted by ASME Code Committees as a replacement for the existing rules and as a means of providing some flexibility on specified tolerances, so that a reduced allowable external pressure may be calculated if tolerance limits are exceeded.

Part 2: External Pressure: Effect Of Initial Imperfections And Temperature Limits: Design Limits for Elevated-Temperature Buckling

Section II of the ASME Boiler & Pressure Vessel Code provides design limits for buckling due to compressive loads, but the limits do not account for time-dependent effects that reduce the buckling strength for long-term loads at elevated temperatures. A method is presented here for determining limits to avoid creep buckling based on classical bifurcation creep buckling theory and the design factors of Section III, Division 1 – Subsection NH. The method is applied to develop temperature limits that define the limits of applicability of the Section II external pressure design charts without consideration of creep. The temperature limits are presented in the form of design charts for the three load cases – cylinders under axial compression, and spheres and cylinders under external pressure – covered by Section II, and for the four elevated-temperature materials – types 304 and 316 stainless steel, Alloy 800H, and 2 ¼ Cr-1 Mo Steel – included in Subsection NH.

Part 3: External Pressure: Effect Of Initial Imperfections And Temperature Limits: Temperature Limits for ASME Boiler and Pressure Vessel Code Section VIII Application of External Pressure Charts

These reports establish temperature limits for the ASME Boiler and Pressure Vessel Code External Pressure Design Charts. The methodology is based on classical stability theory developed by Gerard and simplified by Griffin by replacing the constant strain rate stress-strain curves with isochronous stress-strain curves for determining the tangent and secant moduli. The theory has been validated by both test and analysis methods. The method is applied to develop temperature limits that define the limits of applicability of external pressure design charts without consideration of creep. Design charts for three load cases are presented: cylinders under axial compression; spheres under external pressure; cylinders under external pressure. Four elevated temperature materials are included; type 304 and 316 stainless steel, Alloy 800H and 2 ¼ Cr-1 Mo. Additional materials include 9Cr, SA-533, 2 ¼ Cr – 1Mo annealed, 2 ¼ Cr – 1Mo N&T and SA-516/55.

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