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An Investigation on the Behavior of Nanoparticle Filled Brake Friction Materialls
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor)
Abstract
The most common type of polymer based composite friction materials are usually in vehicles as the brake pads are used and must characteristics such as high wear resistance, low weight, durability, low noise and stable friction coefficient. Polymer matrix, in addition to providing other material suitable for storage, the final properties, including mechanical properties, heat, friction and wear is also effective. Thermoset resin polymer matrixes (usually phenolic resin) are used in the brake pads which used for automotive and in some cases, rubber particles as powder formulations may be entered, in order to achieve good properties of rubber and resin simultaneously. Nanofillers because of...
Mechanical properties and structure of solvent processed novolac resin/layered silicate: Development of interphase region
, Article RSC Advances ; Volume 5, Issue 98 , Jun , 2015 , Pages 80875-80883 ; 20462069 (ISSN) ; Shojaei, A ; Sharif University of Technology
Royal Society of Chemistry
2015
Abstract
Composites of phenol-formaldehyde (PF) resin with Closite Na+ and Closite 30B up to 20 wt% loadings were prepared by solution mixing. Tensile testing showed that both pristine and organically modified clays increased considerably the mechanical properties of PF resin at 2.5 wt% loading followed by marginal improvement or even sacrificed properties at high loadings. DMA and DSC analyses suggested development of a highly crosslinked and well adhered interphase around silicate layers. A novel three-phase model considering the interphase region was proposed to predict composite modulus. The model was successfully employed to correlate morphological characteristics and mechanical properties of...
Effect of alumina nanoparticle on the tribological performance of automotive brake friction materials
, Article Journal of Reinforced Plastics and Composites ; Vol. 33, issue. 2 , October , 2014 , pp. 166-178 ; ISSN: 07316844 ; Shojaei, A ; Jahanmard, P ; Sharif University of Technology
2014
Abstract
Brake friction materials filled with nanoalumina were produced by both conventional and solvent-assisted mixing methods. It was shown that nanoalumina loading led to the reduction of friction coefficient and improvement in mechanical, wear and thermal behaviors. Such behavior was attributed to the role of nanoalumina in producing stable friction layer and easy conduction path in matrix. It was postulated that nanoalumina is able to attach on the surface of microalumina facilitating the rolling of microalumina at interface. Solution-processed samples exhibited lower improvement in tribological and mechanical properties compared to the conventional mixing due to the limited interaction between...
Experimental and theoretical study on the mechanical properties of novolac phenolic resin nanocomposites: Effects of nanoclay and multiwallwed carbon nanotube
, Article ECCM 2012 - Composites at Venice, Italy, Proceedings of the 15th European Conference on Composite Materials, 24 June 2012 through 28 June 2012 ; 2012 ; 9788888785332 (ISBN) ; Shojaei, A ; Faghihi, M ; Sharif University of Technology
European Conference on Composite Materials, ECCM
2012
Abstract
The present work focused on the characterization of mechanical properties of novolac phenolic resin (PF) filled with two types of clays, including modified and unmodified ones, and multiwalled carbon nanotube (MWCNT). It was found that the solution mixing method is able to disperse the nanoparticles within the PF resin appropriately. It was also shown that the unmodified clay (Closite Na+) has the highest influence on the mechanical properties possibly due to the good level of dispersion as well as the good interfacial interaction. Theoretical analysis based on the rubber elasticity theory showed that the nanoparticles influence the evolution of crosslinking density and network structure
Experimental Study of Drying and Calcination of Simulated High-Level Waste (HLW)
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Zahakifar, Fazel (Supervisor) ; Zaheri, Parisa (Co-Supervisor)
Abstract
One of the novel methods of stabilization of nuclear waste is the use of vitrification technology. In order to stabilize high level wastes (HLLW) in glass, it is required that the elements are in their oxide form. Therefore, it is necessary to evaporate the waste and turn it into a solid form so that the elements can be converted into oxide form in the calcination furnace. Hence, one of the challenges of stabilization is the optimization of evaporation and calcination conditions. In this research, the parameters affecting evaporation were first investigated. Using laboratory measurements of application: temperature (110 to 180 °C), presence of nitric acid (0.5 to 4 mol/L), ratio of zirconium...
Constructing a Robust Least Squares Support Vector Machine Based on Lp-norm and L∞-norm
, M.Sc. Thesis Sharif University of Technology ; Mahdavi Amiri, Nezamoddin (Supervisor)
Abstract
In the last decades, Support Vector Machine (SVM) has been used for supervised classification due to its wide applications. In addition, SVM is a mathematical programming tool, that as other optimization-based approaches, turns to be useful for a successful development of supervised classification. Based on current research in the literature, we explain the extension of a developed method for SVM using L2-norm to the more general case of Lp-norms with p > 1. The Kernel function is used frequently in the L2-SVM model, but the multidimensional Kernel is used as a general function in Lp-SVM. Finally, we use Lp-LSSVM model, with 0
Fabrication Patient-Specific Drill Guide Templates for Cervical Pedicle Screw Placement
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor) ; Parnianpour, Mohammad (Supervisor) ; Azimi, Parisa (Co-Supervisor)
Abstract
One of the most common spinal surgeries involves spinal fusion or vertebral fixation, which is used to treat various conditions such as intervertebral disc disease, scoliosis (lateral deviation of the spinal column), fractures, infections, or the presence of tumors in the spinal column. In this surgical procedure, the use of pedicle screws and titanium rods prevents motion and friction between two vertebrae. Screws may enter the vertebrae in the wrong position and angle, causing bone weakening, rupture of nerve roots or blood vessels, weakness or lack of sensation in some parts of the body, spinal cord injury, and in severe cases, paralysis of the patient. For this reason, fusion surgery is...
Performance-based assessment of steel jacket platforms by wave endurance time method
, Article Ships and Offshore Structures ; Oct , 2015 , Page 1-11 ; 17445302 (ISSN) ; Diznab, M. A. D ; Mehdigholi, H ; Tabeshpour, M. R ; Seif, M. S ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
In this article, wave endurance time (WET) is addressed as an applicable method for performance-based assessment of fixed offshore structures under extreme waves. In this method, inspired by the endurance time method in the field of earthquake engineering, artificial wave records called wave functions are designed so that their excitations gradually increase with time. Therefore, the main advantage of the proposed method is that it can assess the structural performance under various wave load conditions through a single time-history analysis. Moreover, the reliability of structures can be evaluated on the basis of the time that the structural response is still acceptable. In this study,...
Performance-based assessment of steel jacket platforms by wave endurance time method
, Article Ships and Offshore Structures ; Volume 12, Issue 1 , 2017 , Pages 32-42 ; 17445302 (ISSN) ; Dastan Diznab, M. A ; Mehdigholi, H ; Tabeshpour, M. R ; Seif, M. S ; Sharif University of Technology
2017
Abstract
In this article, wave endurance time (WET) is addressed as an applicable method for performance-based assessment of fixed offshore structures under extreme waves. In this method, inspired by the endurance time method in the field of earthquake engineering, artificial wave records called wave functions are designed so that their excitations gradually increase with time. Therefore, the main advantage of the proposed method is that it can assess the structural performance under various wave load conditions through a single time-history analysis. Moreover, the reliability of structures can be evaluated on the basis of the time that the structural response is still acceptable. In this study,...
Developing Dynamic Increasing Amplitude and Period (DIAP)Method for Evaluation of Offshore Structures
, M.Sc. Thesis Sharif University of Technology ; Tabeshpour, Mohammad Reza (Supervisor) ; Dastan Diznab, Mohammad Ali (Co-Advisor)
Abstract
In this study, Wave Endurance Time (WET) is introduced as an applicable method for assessment of offshore structures under extreme waves. In this method, artificial records called Wave Functions (WFs) are used instead of usual extreme wave records. WFs are designed so that their excitations gradually increase with time. Therefore, one WF can be replaced by a large number of sea surface records with different excitation levels. The main advantage of proposed method is that it assesses the structural performance under various extreme waves with low computational cost especially in comparison with three-hour simulasions. Moreover, reliability of structures can be evaluated based on the time...