Loading...
Search for:
fld
0.01 seconds
Total 26 records
A New Method Based on Crystal Plasticity Finite Element to Predict the Formability of Steel Sheets with Spheroidal Cementites
, Ph.D. Dissertation Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
In this research, using the crystal plasticity finite element method, the effects of various microstructural features on behavior of spherical steel sheets have been investigated. The cementite phase ratio, the grain sizes of ferrite and cementite, and the percentage of residual pearlite in the steel structure due to incomplete annealing are the major microstructural parameters studied in this work. A grain generator software has been developed to generate ferrite grains as well as cementite particles distributed in the ferrite matrix. A hard coating with special properties as an intermediate layer around the cementite grains has been considered to simulate the contact between ferrite grains...
Extraction of the Forming Limit Diagram in Magnesium Microtubes Used in Stents by Modeling the Hydroforming Process in Abaqus Finite Element Software
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
One of the common methods of removing blood clots is angioplasty with stents. Due to the fact that the mechanical properties of the stent are directly related to the microtube it is made of. Therefore, investigating the mechanical properties of microtubes is very important. One of the ways used to evaluate the plasticity of microtubes; Drawing a graph is the limit of shaping. The purpose of this research is to extract the forming limit diagram of magnesium microtube by simulating the hydroforming process in Abaqus software. First, in order to confirm the modeling, the hydroforming process for aluminum has been simulated and compared with the existing experimental results. The comparison...
Numerical study on the effects of main BCC rolling texture components on the formability of sheet metals
, Article International Journal of Advanced Manufacturing Technology ; Volume 80, Issue 1-4 , March , 2015 , Pages 245-253 ; 02683768 (ISSN) ; Assempour, A ; Sharif University of Technology
Springer-Verlag London Ltd
2015
Abstract
Crystallographic texture considerably affects the formability of crystalline materials. In this paper, the effects of BCC ideal rolling fibers—including α, ε, η, γ, and ξ fibers—on the sheet formability are numerically studied. The simulations are based on the numerical procedure developed by the authors in [1] in which a rate dependent crystal plasticity model along with the power law hardening are employed in a user material subroutine to model the behavior of crystalline materials. In order to determine FLD—in a M-K type approach—second-order derivative of sheet thickness variations with respect to time is used as necking criterion. The calculated FLDs of the fibers are compared with each...
An Investigation on the Microstructure and Mechanical Properties of Almg6 Alloy-Carbon Nanotube Composite Produced by Accumulated Roll Bonding Process
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
In recent years, the use of high specific strength aluminum alloys in automotive and aerospace industries is in progress due to their energy savings. On the other hand, the carbon nanotubes (CNTs), due to their ultra-high strength and modulus of elasticity, have been considered as an excellent reinforcement for the metal matrix composites used in these industries. For production of these materials, the severe plastic deformation (SPD) has been known as a method of grain refinement to increase the strength and ductility. In this research, the composites of AlMg6 reinforced with CNT were produced by accumulated roll bonding (ARB) known as a SPD technique and their properties were compared...
Experimental and analytical studies on the prediction of forming limit diagrams
, Article Computational Materials Science ; Volume 44, Issue 4 , 2009 , Pages 1252-1257 ; 09270256 (ISSN) ; Eivani, A. R ; Akbarzadeh, A ; Sharif University of Technology
2009
Abstract
Metal forming processes are widely used in industrial productions, automobile bodies, food industries, oil refineries, and liquid and gas transmission systems. Analyzing these processes is very important to reduce wastes and optimize the processes. Study of some main factors such as physical and mechanical properties of material and its formability, die geometry, die material, lubrication and pressing speed has been the topic of many research projects. In this paper, forming limit diagrams (FLDs) for LC and ULC steels and the effect of different parameters like the work-hardening exponent, n, and the plastic strain ratio, r, on these diagrams have been evaluated and simulated using...
Analysis of P300 classifiers in brain computer interface speller
, Article 28th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'06, New York, NY, 30 August 2006 through 3 September 2006 ; 2006 , Pages 6205-6208 ; 05891019 (ISSN); 1424400325 (ISBN); 9781424400324 (ISBN) ; Fazel Rezai, R ; Shamsollahi, M. B ; Sharif University of Technology
2006
Abstract
In this paper, the performance of five classifiers in P300 speller paradigm are compared. Theses classifiers are Linear Support Vector Machine (LSVM), Gaussian Support Vector Machine (RSVM), Neural Network (NN), Fisher Linear Discriminant (FLD), and Kernel Fisher Discriminant (KFD). In classification of P300 waves, there has been a trend to use SVM classifiers. Although they have shown a good performance, in this paper, it is shown that the FLD classifiers outperform the SVM classifiers. FLD classifier uses only ten channels of the recorded electroencephalogram (EEG) signals. This makes them a very good candidate for real-time applications. In addition, FLD approach does not need any...