SCHOOL OF MECHANICAL ENGINEERING SEMINAR Wednesday, march 15, 2017 at 14:00 Wolfson Building of Mechanical Engineering, Room 206
Incorporating micro-mechanical model into FEM for predicting fatigue failure of a unidirectional composite structure Limor BurshteinMSc Student of Prof. Rami Haj-Ali

This study presents a generic fatigue model of laminated composite materials and structures. The model incorporates a method for predicting fatigue failure of unidirectional laminate under multiaxial tension-tension loading into a multi-scale framework for the fatigue analysis of composite structures. Towards that goal, the unidirectional fatigue model is implemented in the Abaqus finite-element (FE) software. The simplified micromechanical method of cells (MOC) model is used within the fatigue framework to represent stress field inside the RUC for each of the layers in the shell elements. The analysis involves the examination of the local stresses, in the fiber and the matrix regions, induced by the applied external loading. Explicit matrix and fiber failure criteria are used to determine these failure modes and perform elastic degradation beyond this level for fatigue progressive analysis. The fiber and matrix fatigue failure functions are calibrated using data extracted from three S-N experimental curves under uniaxial tension, transverse tension and axial shear loading modes.
The Abaqus FE shell elements model are linked to UMAT subroutine which describes the material elastic properties during the loading cycles. In this subroutine material property are updated with correspondence to fatigue failure criteria in each constituent.
The layered fatigue framework is shown to be capable of predicting the S-N fatigue life for different laminated coupons under tension-tension loading. In addition, the proposed fatigue framework is applied for the fatigue analysis of a laminated plate with an open hole. This work can be extended for future application of damage tolerance.

School of Mechanical Engineering Seminar
Wednesday, March 15, 2017 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

CONTROLLING TORQUED ORTHOTROPIC METALLIC NANOPARTICLES IN AN ELECTROLYTE  BY MEANS OF AC ELECTRIC FORCING

Ben Weis Goldstein

MSc. Student of Professor Touvia Miloh

A theoretical study is provided for determining the angular velocity of an ideally polarized (metallic) nano-particle freely suspended in a symmetric electrolyte under ambient AC electric field excitations. First, we discuss electro-rotation (ROT) and electro-orientation (EOR) of nano-particles, of prolate spheroid shape, excited by two orthogonal electric field components which may be in or out of phase. The analytic expressions obtained are valid for a conducting prolate spheroid with arbitrary eccentricity including the limiting cases of isotropic spheres and slender rods. The total dipolophoretic (DIP) angular velocity is decomposed  from  contributions due to dielectrophoresis  (DEP) induced by the dipole-moment within the particle and  by  the induced-charge electrophoresis (ICEP) caused by the Coulomb force density within the Debye layer in the solute surrounding the conducting particle. Some comparisons with available known solutions and experimental data are also provided. In the second part, we present a novel theoretical study of 3D electro-rotation of ideally polarizable nano orthotropic particles. Comparisons to known solutions of sphere and prolate spheroid are presented and a new solution for oblate spheroid is derived, which could be reduced to the case of a ‘flat disk’. Furthermore, two specific 3D excitation problems are presented, showing the potential in controlling both velocity and direction using 3D forcing.

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Multiscale modeling of fibrous tissues

Prof. Gal deBotton
Department of Biomedical Engineering, Ben-Gurion University, Israel

Modern analyses and modeling require highly accurate and efficient methods for characterizing the mechanical response of biological tissues. We make use of 3D finite-element micromechanics based unit-cells models for soft connective tissues. The models account for the histologies and the individual constituents of the tissues. Subsequently, the overall responses of the models are determined under different types of loadings. The predictions of the micromechanics based models, experimental measurements and available phenomenological model are compared and analyzed. Our findings suggest that to develop accurate models that account for the structure of the connective tissues under arbitrary loading conditions micromechanics motivated models should be employed.

ההרצאה תתקיים ביום ראשון 08.01.17, בשעה 15:00

בחדר 315, הבניין הרב תחומי, אוניברסיטת תל אביב

ISOGEOMETRIC BOUNDARY ELEMENT METHODS

By:

Gregory J. Rodin

Institute for Computational and Engineering Sciences

University of Texas at Austin, Austin, TX 78712

Abstract

This talk is concerned with isogeometric boundary element methods for solving boundary-value problems governed by Laplace’s equation and equations of classical elasticity theory. These methods are based on discretizing boundary integral equations using basis functions widely used in computer-aided design. From the practical standpoint, this approach is advantageous because it requires neither additional meshing nor any geometric approximations. Further, we were able to exploit smooth basis functions to formulate numerical schemes with optimal convergence rates and many superior properties inaccessible to conventional boundary element methods based on finite element basis functions.