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Viscoplastic and Creep Crack Growth Analysis by the Finite Element Method.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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Creep crack growth in a nickel base alloy at elevated temperatures was analyzed through a hybrid experimental-numerical HEN procedure. This HEN procedure consisted of simultaneous use of creep crack growth test displacement data from center cracked plate specimens of IN-100 at 1350 F and a theoretical finite element model of the test specimen. A two-dimensional constant strain triangular finite element program was developed which accounts for both nonlinear viscoplactic material behavior and changing boundary conditions due to crack growth. Three viscoplastic material models -- 1 Malvern Flow Law, 2 Nortons Creep Law, and 3 Bodner-Partom Flow Law -- were incorporated into the program. These time dependent material models were numerically integrated through time by a linear Euler extrapolation technique. A variable time step algorithm was included that maximized time step size during the analysis while maintaining good accuracy. This program was used as the plane stress theoretical model for the HEN procedure to analyze sustained load creep crack growth.
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