Fatigue Crack Growth and Retardation Due to Overloads in Metal-Matrix Composites. Volume 2. Finite Element Analysis of Cracks in Metal Matrix Composites.

摘要

The general three dimensional flow rule for anisotropic plasticity is derived and explicitly defined for the special case of plane stress. Parametric studies of orthotropic elastoplastic behavior and the corresponding yield surfaces are investigated. A finite element program, ANPLAST, is developed to analyze non-linear orthotropic elastic-plastic problems. An in depth elastoplastic study of a sheet with a circular hole is conducted. A detailed investigation of the elastoplastic response of center and edge cracked panels is thoroughly addressed. The anisotropic plasticity formulation is extended to a multi-layer laminates and implemented in ANPLAST. It was found that the isoparametric quadrilateral and constant strain triangle finite elements both performed adequately with neither element demonstrating any significant advantages in efficiency or accuracy. Analysis of the sheet with a circular hole and the cracked panels demonstrated the strong influence of anisotropy on plastic zone growth. The character of residual stress distributions due to unloading was not affected by plastic anisotropy. The effect of transverse remote loading on plastic zone growth was also shown to be significant. The advantages of an incremental plasticity formulation for problems consisting of complex loading paths were clearly demonstrated. Elastoplastic laminates displayed complex distortions of their initial yield surface during plastic work-hardening. Analysis of a laminated sheet with a circular hole demonstrated vastly different plastic zone growth within each layer.