Modeling of Wedge-Shaped Anisotropic Piezocomposite Transducer for Guided Wave-based Structural Health Monitoring

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77008/1/AIAA-2007-1723-966.pd

Numerical simulation of plastic deformation and fracture in polysynthetically twinned (PST) crystals of TiAI

Plastic deformation and fracture in polysynthetically twinned (PST) crystals of TiAl have been simulated by using periodic unit cells representing the relaxed-constraint model recently proposed by Lebensohn et al. for the co-deformation of the lamellar compound of PST-TiAl. The unit cells contain both intermetallic phases, #alpha#_2-(Ti_3Al) and #gamma#-(TiAl). Furthermore, the six orientation variants of the #gamma#-phase are also considered. The constitutive behaviour of both phases is described by crystal plasticity, and the damage behaviour has been implemented by means of cohesive elements. The unit cells have been used as submodels for multi-scale finite element simulations of compression tests and fracture mechanics tests of notched micro-bend specimens. It is shown that the anisotropy of plastic deformation and damage in PST-TiAl can be well represented. (orig.)Also published in: Computational Materials Science 19 (2000), 97-107Available from TIB Hannover: RA 3251(2000/50) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Local strain fields and global plastic response of continuous fiber reinforced metal-matrix composites under transverse loading

The influence of fiber arrangement on the local plastic strain fields and the resulting mechanical response of continuous fiber reinforced metal-matrix composites under transverse loading has been studied systematically by means of finite element analyses. Random, hexagonal and square fiber arrangements were investigated. The composite material examined consisted of isotropic linear-elastic fibers which are perfectly bonded with an isotropic elastic-plastic matrix with power-law hardening behavior. The random arrangements were analyzed with representative material elements containing approximately 50 fibers. The internal strain fields are highly influenced by the fiber arrangements. Three different strengthening mechanisms are proposed for composites with perfectly plastic matrix material: the orientation, bowing-out and bending mechanisms. Simple analytical estimates are given for the orientation and the bending mechanisms. The influence of matrix work-hardening is explained by means of an effective deformable matrix volume fraction. (orig.)Also published in 'Computational Materials Science 12, 1998 p. 124-136'Available from TIB Hannover: RA 3251(98/E/58) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Critical Stresses Estimation by Crystal Viscoplasticity Modeling of Rate-Dependent Anisotropy of Al-rich TiAl Alloys at High Temperature

Determining critical stresses for different slip systems is one of the most important parts in crystal plasticity modeling of anisotropy. However, the task of finding individual critical resolved shear stress (CRSS) for every single slip system, if not impossible, is formidable and a delicate one especially if the microstructure is very complex. Slip family-based, mechanism-based and morphology-based (e.g., phase interface) slip systems classification and hence determining CRSS consistent with experimental measurements are often used in crystal plasticity. In this work, a novel approach to determining CRSS at high homologous temperature has been proposed by crystal plasticity modeling of rate-dependent anisotropy. Two-internal-variable-based phenomenological crystal viscoplasticity model is adopted for simulating isothermal, two-phase, single-crystal-like Al-rich lamellar Ti–61.8at.%Al binary alloy at high-temperature compression state (1050∘C) by employing finite strain and finite rotation framework. To the best of authors’ knowledge, this is the first micromechanical modeling attempt with long-period superstructures. Conventional approaches related to CRSS estimation are also compared with the proposed one. Our material parameters are based on calibrating three different sets of compressive stain rate-controlled plasticity data taken from the loading of two different lamellar directions. It is revealed that the proposed approach works fine for rate-dependent anisotropy modeling, while other conventional approaches highly under- or overestimate available anisotropic experimental behavior of this alloy