An atomistic–continuum multiscale analysis for heterogeneous nanomaterials and its application in nanoporous gold foams

, Article Applied Mathematical Modelling ; Volume 107 , 2022 , Pages 353-378 ; 0307904X (ISSN) Nikravesh, Y ; Sameti, A. R ; Khoei, A. R ; Sharif University of Technology

Elsevier Inc 2022

Abstract

In this paper, an atomistic–continuum homogenization multiscale method is developed to study the nonlinear behavior of heterogeneous nanomaterials. The atomistic representative volume element (RVE) with vacancy and/or void defects are analyzed by employing the fully atomistic method, in which the nucleation, migration, and elimination of dislocation, as well as the dislocation-vacancy interaction, are captured. The coarse-scale material domain is modeled within the framework of the nonlinear finite element method, and the impression of nanoscale material defects is investigated by upscaling the stress tensor and tangent modulus from the atomistic RVE based on the Hill-Mandel principle. The...

Modeling the Nonlinear Behavior of Nano-Materials Via Hierarchical RVE-based Multi-Scale Method

, M.Sc. Thesis Sharif University of Technology Nikravesh Kazerooni, Yousef (Author) ; Khoei, Amir Reza (Supervisor)

Abstract

In this paper, a hierarchical RVE-based continuum-atomistic multiscale framework is established on the basis of the nonlinear finite element method and molecular dynamics simulation in order to model the geometric and material nonlinearities of deformable solids. In this framework, the coarse scale material properties required for nonlinear finite element method are directly exploited via fine scale atomistic simulation of atomic RVEs designated for each coarse scale integration point and required boundary conditions for atomic RVE simulation are achieved from the coarse scale kinematical response. In order to ensure the kinematical and energetic consistency between the two scales, the...

Optimal preview control design of an active suspension based on a full car model

, Article Scientia Iranica ; Volume 10, Issue 1 , 2003 , Pages 23-36 ; 10263098 (ISSN) Marzbanrad, J ; Hojjat, Y ; Zohoor, H ; Nikravesh, S. K ; Sharif University of Technology

Sharif University of Technology 2003

Abstract

In this paper, an approach to the synthesis of optimal preview control laws for active vehicle suspension has been studied. A basic three-dimensional, seven-degree of freedom car riding model, subjected to two road inputs, is considered. To obtain an enhanced control scheme, the input senses and measures road irregularities, using the contactless sensors fixed on the vehicle front bumper. The suspension systems are optimized, with respect to ride comfort, road holding and suspension rattle space. The performance of active, active and delay and active and preview, are compared with a passive system by numerical simulation in the time domain. The results show that optimal preview control...

Mechanical and microstructural investigation of friction stir processed Al1100

, Article Welding in the World ; Volume 53, Issue SPECIAL ISSUE , 2009 , Pages 253-258 ; 00432288 (ISSN) Nasiri, A. M ; Pouraliakbar, H ; Nikravesh, M ; Kokabi, A. H ; Sharif University of Technology

2009

Abstract

Surfaces of cast 1100 aluminum were treated by multi-pass friction stir processing (MP-FSP), which is a solid-state microstructural modification technique using frictional heat and stirring action. An improvement in the mechanical properties was accomplished due to the microstructural modification and reduction of porosities. The yield strengths of the MP-FSPed specimens were significantly increased to about 1.4 times versus that of the base metal. The elongation of MP-FSP sample is about 30% higher than that of the base metal. Also the ultimate tensile strength and hardness of MP-FSPed specimens are improved. Moreover the effect of tool rotation rate and tool travel speed on the mechanical...

Study and Synthesis of Biocompatible Polymer and Loading of Peptide Drug for using in Drug Delivery

, M.Sc. Thesis Sharif University of Technology Nikravesh, Niusha (Author) ; Vosoughi, Manouchehr (Supervisor) ; Alemzadeh, Iran (Co-Advisor)

Abstract

With the rapid development of biotechnology, peptide and protein drugs are now playing an increasingly important role in therapeutics. Compared with chemical drugs, peptide and protein drugs have some limitations such as low stability and rapid deactivation. Biodegradable and biocompatible polymeric micro carriers have been shown to have a high potential for the delivery of peptides and proteins. Among these polymers, alginate has been widely investigated as a biomaterial. Alginates are natural polysaccharide polymers isolated from brown seaweed. Bovine serum albumin (BSA) loaded calcium alginate microspheres produced in this study by a modified w/o emulsification method. The influence of...