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WSRC-MS-2006 -00146 Proceedings of Insert Conference Abbreviation: Insert Conference Name Insert Conference Date and Location Put Paper Number Here PREDICTION OF FRACTURE STRESSES OF HIGH PRESSURE GAS CYLINDERS CONTAINING CRACK LIKE FLAWS USING VARIOUS METHODS
Mahendra D. Rana P.E. ASME Fellow Praxair, Inc. 175 East Park Drive Tonawanda, NY, 14151 e-mail: Mahendra Rana a)Praxair.com
George B. Rawls Senior Fellow Engineer Savannah River National Laboratory. Bldg. 773-41A, Rm. 173 Aiken, SC 29808-0001 e-mail georqe. rawls@srnl. doe. gov
ABSTRACT Full scale tests were conducted on high pressure gas cylinders containing crack like flaws. The cylinders were then pressurized to destruction and the membrane stress at failure in the cylinder wall was calculated from the failure pressure. Mechanical properties including tensile and fracture data were obtained on specimens representing the heats of the tested cylinders. Analyses were performed to predict the failure stresses using several methods available in the open literature. This paper presents the results of the predicted and measured fracture stresses. 1.0 INTRODUCTION Considerable progress has been made in the development of standards for fitness-for-service applications. Two examples of such standards are API 579 [1] and BS 7910[2]. Both these standards provide methods to assess the components containing cracks and local thin areas (LTA). Full scale fracture tests were conducted on high pressure (4500 psi) gas cylinders in 1988 [3]. A subset of the data obtained from the tested cylinders have been used in this paper to predict the fracture stresses using various fracture mechanics based methods available in the open literature. The methods used to predict the failure stress level include: API 579[1], BS 7910[2] and Battelle [4]. The results of these analyses indicated the LEFM based FAD approach predicted much lower
fracture stress compared to those measured. The Battelle's API 579 Level 1 LTA and modified LEFM methods predicted the fracture stresses higher than those by BS7910, but lower than those measured stresses. In summary, all the above listed methods predictability is not very accurate, but it is on the conservative side. 2.0 NOMENCLATURE a = surface crack depth I = surface crack length d = cylinder inside diameter D = cylinder outside diameter is = thickness at machined flaw Kic(J) = plane-strain fracture toughness obtained from J tests using ASTM E-813 test method Kc = plane stress fracture toughness J = elastic plastic fracture parameter J-R= J vs. Aa curve obtained LTA= local thin area LEFM= linear elastic fracture mechanics 6u =UTS = ultimate tensile strength 6y =YS = yield strength 6P = predicted fracture stress, 6f = measured fracture stress 6fiow = flow strength = 0.5x (UTS + YS) Mt = stress intensity magnification factor for a thru wall crack Mp = stress intensity magnification factor for a part thru wall crack
Rawls, George & Rana, Mahendra D.Prediction of Fracture Stresses of High Pressure Gas Cylinders Containing Crack Like Flaws Using Various Methods,
article,
June 1, 2006;
[Aiken, South Carolina].
(https://digital.library.unt.edu/ark:/67531/metadc874767/m1/2/:
accessed July 16, 2024),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
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