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ASME 2013 International Mechanical Engineering Congress and Exposition, IMECE 2013

作者： Tawakoli, Taghi Akbari, Javad Zahedi, A.M. Furtwangen University Schwenningen Baden-Württemberg Germany Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology Azadi Ave. 14588-89694 Tehran Iran Center of Advanced Manufacturing and Material Processing Department of Engineering Design and Manufacture University of Malaya 50603 Kuala Lumpur Malaysia

ISBN: (纸本)9780791856185

Due to its vast applications and stochastic nature, grinding has been the subject of investigations and modifications for decades. Applying ultrasonic vibration in grinding has been a successful innovation introducing benefits such as reduced forces and temperature, improved surface quality, and making higher removal rates possible. In this work a set-up is developed for utilizing ultrasonic vibrations in cylindrical grinding. This is done by rotating and simultaneously vibrating the workpiece material. The set-up is used for cylindrical grinding of Alumina-zirconia ceramic as a difficult-to-grind and widely used industrial ceramic. Optimized parameters for efficient grinding and surface characteristics of the ground ceramic are investigated and the effects of ultrasonic vibration are declared. Copyright © 2013 by ASME.

关键词： Surface roughness

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Anomalous diffusion of proteins in sheared lipid membranes

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Physical Review E 2013年第3期88卷 032705-032705页

作者： Atefeh Khoshnood Mir Abbas Jalali Computational Mechanics Laboratory Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

We use coarse grained molecular dynamics simulations to investigate diffusion properties of sheared lipid membranes with embedded transmembrane proteins. In membranes without proteins, we find normal in-plane diffusion of lipids in all flow conditions. Protein embedded membranes behave quite differently: by imposing a simple shear flow and sliding the monolayers of the membrane over each other, the motion of protein clusters becomes strongly superdiffusive in the shear direction. In such a circumstance, the subdiffusion regime is predominant perpendicular to the flow. We show that superdiffusion is a result of accelerated chaotic motions of protein-lipid complexes within the membrane voids, which are generated by hydrophobic mismatch or the transport of lipids by proteins.

关键词： Anomalous sheared lipid membranes Molecular Dynamics Simulation anomalous diffusion Shearing Proteins Anomalous Lipids Flow lipid membrane membrane

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Applying Ultrasonic Vibration to Decrease Drilling-Induced Delamination in GFRP Laminates

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Procedia CIRP 2013年 6卷 577-582页

作者： P. Mehbudi V. Baghlani J. Akbari A.R. Bushroa N.A. Mardi Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology AzadiAve. 14588-89694 Tehran Iran Center of Advanced Manufacturing and Material Processing - Micro Mechanism Research Group Department of Engineering Design and Manufacture Faculty of Engineering University of Malaya 50603 Kuala Lumpur Malaysia

Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, and ultrasonic vibration amplitude as control factors. The results show that applying ultrasonic vibration reduces the thrust force and therefore the drilling induced delamination dramatically.

关键词： Ultrasonic assisted drilling GFRP laminates Drilling induced delamination Taguchi method

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Analytical modeling of static behavior of electrostatically actuatednano/micromirrors considering van der Waals forces

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Acta Mechanica Sinica 2012年第3期28卷 729-736页

作者： Hamid Moeenfard Mohammad Taghi Ahmadian School of Mechanical Engineering Sharif University of Technology Center of Excellence in Design Robotics and AutomationSchool of Mechanical EngineeringSharif University of Technology

In this paper, the effect of van der Waals （vdW） force on the pull-in behavior of electrostatically actuated nano/micromirrors is investigated. First, the minimum po- tential energy principle is utilized to find the equation gov- erning the static behavior of nano/micromirror under electro- static and vdW forces. Then, the stability of static equilib- rium points is analyzed using the energy method. It is found that when there exist two equilibrium points, the smaller one is stable and the larger one is unstable. The effects of dif- ferent design parameters on the mirror＇s pull-in angle and pull-in voltage are studied and it is found that vdW force can considerably reduce the stability limit of the mirror. At the end, the nonlinear equilibrium equation is solved numer- ically and analytically using homotopy perturbation method （HPM）. It is observed that a sixth order perturbation approx- imation can precisely model the mirror＇s behavior. The re- suits of this paper can be used for stable operation design and safe fabrication of torsional nano/micro actuators.

关键词： Nano/micromirror Electrostatic actuation vdW force Pull-in. Homotopy perturbation method （HPM）

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Nonlinear Observer design for Turbocharger in a SI Engine

Nonlinear Observer Design for Turbocharger in a SI Engine

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American Control Conference

作者： R. Salehi M. Shahbakhti A. Alasty G.R. Vossoughi Center of Excellence in Design Robotics and Automation (CEDRA) Mechanical Engineering Department Sharif University of Technology Tehran Iran Mechanical Engineering-Engineering Mechanics Department Michigan Technological University Houghton MI 49931USA

ISBN: (纸本)9781479901777

Estimation of major turbocharger variables is essential for proper control and monitoring of a turbocharged engine. This work presents a novel algorithm to estimate turbocharger rotator speed, air temperature downstream a compressor and flow rate over the compressor using mean value models of engine subsystems. A nonlinear Luenberger observer is designed for a 1.7-lit gasoline turbocharged engine. The designed observed is shown analytically to be asymptotically stable. Performance of the designed observer is experimentally validated with the data collected from the engine. The results indicate the observer can capture major turbocharger's rotational dynamics and estimated turbocharger variables are in a good agreement with the experimental measurements.

关键词： compressor designed experimental Turbochargers Compressors Engines Observers Turbocharged Engines

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Control Oriented Modeling of a Radial Turbine for a Turbocharged Gasoline Engine

Control Oriented Modeling of a Radial Turbine for a Turbocha...

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American Control Conference

ISBN: (纸本)9781479901777

This paper presents a control oriented model for predicting turbine major variables in a turbocharged spark ignition engine. The turbine is simulated as a two-nozzle chamber where the pressure ratio over the two nozzles is not the same. A convex nonlinear estimation algorithm is formulated to determine the relation between these pressure ratios. The new model is experimentally validated with transient and steady state data collected from a 1.7 liter gasoline engine. The results show the new model can predict the turbine mass flow with an average error of 1.4%. In addition, the application of the turbine model is illustrated for the design of a nonlinear observer to estimate the turbocharger non-measured variables. The designed observer is tested against experimental data and the results confirm the observer capability to estimate the turbine rotor speed, flow over the compressor and temperature downstream the compressor.

关键词： gasoline engine PresRto turbines Turbochargers radial flow turbine Compressors key variable MASS FLOW Oriented

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A new calibration method for FLCs in the M-K frame-work

A new calibration method for FLCs in the M-K frame-work

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2011 2nd International Conference on Material and Manufacturing Technology, ICMMT 2011

作者： Ghazanfari, Amir Assempour, Ahmad Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

ISBN: (纸本)9783037852521

The main drawback of the method proposed by Marciniak and Kuczynski for prediction of the limit strains in sheet metal forming processes is requirement of an experimental point of the forming limit curve (FLC) in order to calibrate the curve. The purpose of this work is to introduce a new method to calibrate the FLC using the M-K model in which no experimental data is needed. To achieve this goal, many experimental FLCs were collected from the literature and the values of the initial inhomogeneity factors were determined for them with trial and error aproach. Using these data, an empirical law was developed to predict the value of inhomogeneity factor. The resultant curves show good agreement with the experiments. © (2012) Trans Tech Publications, Switzerland.

关键词： Sheet metal

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Determination of geometrical parameters of the dead metal zone and exit curvature profile in the extrusion process of non-symmetrical flat dies

Determination of geometrical parameters of the dead metal zo...

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SAE 2012 World Congress and Exhibition

作者： Rastegar, Meysam Assempour, Ahmad Ghazanfari, Amir Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

To determine the curvature of the exit profile in the extrusion process of non-symmetrical flat dies, the dead metal zone profile was predicted using the energy minimization method. The dead zone is a natural non-linear die for the process and it is pragmatic to use this non-linear die to estimate the value of the exit profile curvature and the required bearing length for reducing this deviation. The velocity field is calculated based on Hermite cubic spline and some additional assumptions. In non-symmetrical dies the entrance section of the deformation region is not flat. Considering this fact, axial velocity decreases with increasing the distance to die center line which is in agreement with experiment. After determination of the velocity field, the strain rates in different directions are calculated. Subsequently, the required power for the process is estimated using the upper bound method. Since the material tends to consume less energy, to determine the profile of the dead zone, the coefficients of the curve are set so as to minimize the consumed power. Finally, using this curve, the value of the exit profile curvature is estimated. Dead metal zone for different angles of the deformation region at entry and different friction constant coefficients was determined and compared with the results of simulations of the finite element software (ABAQUS v6.9). Additionally, the deviation calculated from theoretical method was verified with the results of the commercially available bulk forming simulation software (Deform-3D v5). This method does not depend on the exit section and is applicable to non-symmetrical dies as well. The analytical results for non-symmetrical T-die are in good agreement with results of the finite element simulations. Copyright © 2012 SAE International.

关键词： Velocity

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A critical assessment of forming limit prediction models and beneficial modifications to them

A critical assessment of forming limit prediction models and...

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SAE 2012 World Congress and Exhibition

作者： Ghazanfari, Amir Assempour, Ahmad Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran

Major forming limit prediction models and calibration methods are reviewed briefly and their advantages and disadvantages are discussed. Two modified Marciniak-Kuczynski (M-K) models and one modified NADDRG (Keeler-Brazier) model are also presented which have some advantages over conventional models. In the first modified M-K model, material non-homogeneity has been substituted for geometrical non-homogeneity to reduce the sensitivity of the traditional model to variations of the initial non-homogeneity. Using this important advantage, a semi-empirical relation is proposed to predict the value of the initial material non-homogeneity. In the second modified M-K model, the conventional calibration method (which requires an experimental point, corresponding to plain strain condition, to find the initial non-homogeneity and calibrate the model) is revised and the uniaxial tensile point, which is easily obtained, is proposed to be used in the calibration process. Finally, a modified NADDRG relation is suggested which predicts the Forming Limit Curve (FLC) much more accurately and for various types of materials (i.e. not only low carbon steel). This new relation uses the value of strain rate sensitivity index. The results obtained from these models and calibration methods are compared with experimental results. The proposed modifications are very easy to implement;could be applied to various materials;require few and easily measurable parameters and are in good agreement with experiments. Copyright © 2012 SAE International.

关键词： Low carbon steel

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Forming limit diagrams of ground St14 steel sheets with different thicknesses

Forming limit diagrams of ground St14 steel sheets with diff...

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SAE 2012 World Congress and Exhibition

作者： Hashemi, Ramin Ghazanfari, Amir Abrinia, Karen Assempour, Ahmad University of Tehran Iran Center of Excellence in Design Robotics and Automation Department of Mechanical Engineering Sharif University of Technology Azadi Avenue Tehran Iran Tehran Univ Iran

The influence of sheet thickness on sheet metal forming limits is a controversial issue;while some investigations indicate the considerable influence of thickness on forming limit diagrams (FLDs), others suggest that it is of negligible importance. In the present work, it has been demonstrated that if the thickness-reduction process is chosen so as not to alter the micro structure of the material, the forming limits do not change with variations of thickness. A material which has extensive usage in sheet metal forming processes of automotive industry (St14) has been provided. The initial thickness of the sheet is 1.5mm and using grinding process (which does not alter the microstructure) the initial thickness is reduced to different thicknesses, namely 1 and 0.5mm. Afterwards, the FLDs for all three thicknesses were determined using standard test methods. The FLDs for specimens which were ground to various thicknesses differ slightly. This small difference is attributed to bending effects resulted from curvature of the punch. Thus, the results strongly support the conclusion that the absolute value of thickness has no influence on forming limits of St14 steel sheet. Copyright © 2012 SAE International.

关键词： Microstructure

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