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Foundation ::
Crack Growth and Fatigue Analysis ::
LAYER
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LAYER
a program for predicting the thermomechanical fatigue life of metallic coated pwa 1480 single crystal superalloy
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SOURCE CODE AVAILABLE
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LAYER performs thermomechanical fatigue life prediction for coated nickel-based anisotropic materials. Metallic coatings are routinely used in gas turbine engines to protect hot section airfoils from environmental degradation. With the addition of the coating, however, turbine airfoil life prediction is complicated because the coating is a primary fatigue crack initiation site. LAYER is intended to provide gas turbine airfoil designers with a means to accurately project service lifetimes.
Given the differences in thermal expansion and creep between the coating and substrate alloys, nonlinear analysis of the coating-substrate composite cyclic history is considered necessary for accurate life prediction. Although nonlinear turbine airfoil analyses have been executed for uncoated airfoils, the highly nonlinear coating behavior essentially eliminates the possibility of conducting coated airfoil analyses within an acceptable time frame. LAYER, a simplified structural analysis technique, has been developed to analyze the nonlinear composite behavior at a predetermined critical location.
The base airfoil material considered is the Pratt & Whitney Aeronautics alloy PWA-1480. Two different generic oxidation resistant metallic coating types are considered. The first, PWA-286, is a low pressure plasma sprayed (LPPS) NiCoCrA/Y overlay coating. The second coating is a diffusion aluminide, NiAl, designated PWA-273. Although LAYER has been developed for predicting crack initiation of metallic coated PWA-1480, it can be extended to other materials as well.
Input to the LAYER code can come from any available elastic or nonlinear component cyclic analysis: finite element, boundary integral element, or hand calculation. The LAYER code can readily include the influence of multiaxial loading on crack initiation life such as the biaxial effect of coating-substrate thermal expansion mismatch which occurs during thermal cycling.
This version of LAYER was released in 1994.
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Copyright (c) K.K. Gupta 2010, 2011. All rights reserved.
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