A Visco-plastic Damage Model For High
Temperature Creep Of Single-crystal Superalloys
Author(s)
A. Staroselsky & B. Cassenti
Abstract
The micromechanics of the high temperature creep and damage accumulation in
single crystal nickel base superalloys is important for the design of turbine
blades and vanes in advanced commercial and military gas turbines. We have
developed a robust predictive tool to relate single crystal macroscopic behaviour
and fracture initiation to micromechanical events. A crystallographic-based
model for non-isothermal high temperature cyclic deformation has been fully
coupled with the damage kinetics. The model significantly improves the quality
of material deformation predictions on cyclic and thermal-cyclic loading.
Keywords: super-alloys, single crystal, constitutive modeling, dislocation
kinetics.
1 Introduction
Historically, secondary creep effects with associated modelling techniques
(Larson-Miller, etc.) were used in engineering calculations. However, during the
thermal-mechanical loading of high temperature single crystal turbine parts, all
three creep stages: primary, secondary and tertiary, manifest themselves and
none of them can be neglected. A creep law is especially important in the case of
non-homogeneous thermal loading which results in intensive stress redistribution
and relaxation.
Several damage mechanisms, namely multiplication of mobile dislocations,
void and micro-crack growth and the scale effects caused by dislocation
extrusions/intrusions and necking, have been considered. Our damage model
bridges the gap between dislocation dynamics and continuum mechanics scales.
Damage accumulation causes tertiary creep and shear localization around local
concentrators, which is essential for airfoil life prediction.
Keywords
super-alloys, single crystal, constitutive modeling, dislocation
kinetics.
Related Book
Other papers in this volume
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