En
  • دکتری (1392)

    مهندسی مکانیک

    دانشگاه تربیت مدرس، تهران، ایران

  • کارشناسی‌ارشد (1387)

    مهندسی مکانیک

    دانشگاه تربیت مدرس، تهران، ایران

  • کارشناسی (1385)

    مهندسی مکانیک

    دانشگاه علم و صنعت ایران، تهران، ایران

  • مکاترونیک
  • عملگرها و سنسورها
  • مهندسی فراصوت (طراحی ترانسدیوسرها، ابزارهای ارتعاشی و منابع تغذیه برای کاربردهای مختلف امواج فراصوتی)
  • فرآیندهای الکتروفیزیکی (طراحی و ساخت تجهیزات فرآیندی و منابع تغذیه)
  • آزمایشگاه فناوری های الکتروفیزیکی

دکتر محمدرضا کرفی در سال 1363 در شهرستان نوشهر استان مازندران متولد شده است. وی درجه کارشناسی مهندسی مکانیک را از دانشگاه علم و صنعت ایران در سال 1385 اخذ نموده است. همچنین درجه کارشناسی ارشد و دکتری مهندسی مکانیک را از دانشکده مهندسی مکانیک دانشگاه تربیت مدرس به ترتیب در سالهای 1387 و 1392 دریافت نموده است. ایشان فرصت مطالعاتی دوره دکتری خود را در دانشگاه بریتیش کلمبیا در ونکوور کانادا گذرانده است. وی از سال 1393 تا کنون به عنوان عضو هیئت علمی تمام وقت در دانشکده مهندسی مکانیک مشغول به فعالیت است. زمینه های تحقیقاتی مورد علاقه ایشان شامل : مکاترونیک، سنسورها و عملگرهای ساخته شده با مواد هوشمند، سنسورهای کوانتومی، مهندسی آلتراسونیک و کاربردهای آن (طراحی و ساخت تراسدیوسرها و ابزارهای ارتعاشی و منابع تغذیه آلتراسونیک)، و نیز ساخت تجهیزات الکترومکانیکی فرآیندهای الکتروفیزیکال است.

A continuum electro-mechanical model of ultrasonic Langevin transducers to study its frequency response

Mohammadreza Karafi, Sobhan Kamali
Journal PapersApplied Mathematical Modelling , Volume 92 , 2021 April 1, {Pages 44-62 }

Abstract

In this paper, a continuum mathematical electro-mechanical model of ultrasonic Langevin transducers has been developed by considering three factors: 3D vibrations, piezoelectric effects, and elements damping. Since the equivalent-circuit methods simulate a continuous system with discrete components, they are valid near one resonance frequency. However, a continuum model is valid in broader frequency ranges. It can also describe the effect of geometries and material properties on the frequency response of transducers. By using the mathematical model, the amplitude of vibrations, mode shape, resonant and anti-resonant frequencies, mechanical quality factor, and frequency response can be achieved for a transducer with a specific geometry and m

An electromagnetic arrayed pump to create arbitrary velocity profiles in fluid

SP Hashemi, MR Karafi, MH Sadeghi, VR Esfedan
Journal Papers , , {Pages }

Abstract

A New Method to Detect and Track the Resonance Frequency of Piezoelectric Transducers in Ultrasonic Power Supplies

E Taghvayi, MR Karafi
Journal Papers , , {Pages }

Abstract

An introduction to a bulk magnetostrictive bending actuator using a permendur rod

Mohammad Reza Karafi, Reyhaneh Sadat Nejabat
Journal PapersSN Applied Sciences , Volume 2 , Issue 2, 2020 February 1, {Pages 290 }

Abstract

In this paper, a new bulk magnetostrictive bending actuator is presented using a permendur rod. By applying an axial magnetic field in a thin layer of the magnetostrictive rod, the tensile deformation of the layer would cause bending of the actuator. The generation of the magnetic field in the layer is carried out by coils and a comb-shaped magnetic core. The Comsol software is used to calculate the magnetic field. Following the fabrication of the actuator, deflection values are measured at different currents and compared with results of the simulation. The actuator has been tested with constant and alternating magnetic fields. The actuator is excited with an alternating magnetic field at the resonance frequency of the actuator to increase

An Analytical Approach to Design of Ultrasonic Trans-ducers Considering Lateral Vibrations

MR Karafi, SA Mirshabani
Journal Papers , 2019 March 3, {Pages }

Abstract

The purpose of this paper is to develop a design procedure for Langevin ultrasonic transducers with lateral dimensions larger than a quarter of the longitudinal wave length. In this case, the assumption of the one-dimensional design is not valid, and this method cannot predict the experimental resonance frequency. Some researchers have considered radial and longitudinal normal stresses by means of the apparent elasticity method and reduced the error between the design and experimental resonance frequency. In this research, 3D normal stresses of a transducer’s components ie longitudinal, radial and circumferential were considered in the design procedure. The apparent elasticity method was used to modify the elastic modulus and the wave num

Design and fabrication of a novel vibration-assisted drilling tool using a torsional magnetostrictive transducer

Mohammad Reza Karafi, Soroush Korivand
Journal PapersThe International Journal of Advanced Manufacturing Technology , 2019 January , {Pages 12-Jan }

Abstract

In this paper, a vibrational drilling tool using a magnetostrictive torsional transducer is designed and fabricated. The torsional transducer is a hollow cylinder, which is made up of “2 V permendur.” Passing an alternating current through the material creates a variable circular magnetic field and exciting a coaxial coil with a direct current generates a constant axial field in the material. According to the Wiedemann effect, the magnetic domains of the material rotate helically in the direction of the external field and cause a shear strain in the material. To utilize the maximum torque and amplitude of the transducer as well as to maintain the transducer’s resonance conditions, a wave transmitter is designed to connect the transduc

Evaluation of mechanical and electric power losses in a typical piezoelectric ultrasonic transducer

Mohammad Reza Karafi, Farshad Khorasani
Journal PapersSensors and Actuators A: Physical , Volume 288 , 2019 April 1, {Pages 156-164 }

Abstract

In this paper, contributions of the mechanical and electric power losses have been studied in a typical piezoelectric ultrasonic transducer under free conditions. The losses in a Langevin ultrasonic transducer can be divided into three parts: dielectric loss of piezoelectric, structural damping loss of the transducer’s mechanical components, and losses due to the friction of contact surfaces. In order to estimate dielectric losses, loss factor or t a n δ of the piezoelectric ceramic have been measured. Dielectric power loss is obtained by calculating the electrical energy stored in a piezoelectric and using the loss factors. The structural damping of the mechanical components of the transducer is calculated using the mechanical quality f

Effects of film viscoelasticity on dynamic behavior of dielectric elastomer minimum energy structure

Hamed Vatanjou, Yousef Hojjat, MohammadReza Karafi
Journal PapersModares Mechanical Engineering , Volume 19 , Issue 11, 2019 November 15, {Pages 0-0 }

Abstract

This open-access journal is published under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License which permits Share (copy and redistribute the material in any medium or format) and Adapt (remix, transform, and build upon the material) under the Attribution-NonCommercial terms.

Nonlinear dynamic analysis of dielectric elastomer minimum energy structures

H Vatanjou, Y Hojjat, M Karafi
Journal PapersApplied Physics A , Volume 125 , Issue 9, 2019 September 1, {Pages 583 }

Abstract

This paper presents a theoretical study of nonlinear dynamic behavior of a dielectric elastomer minimum energy structure (DEMES). While planar Dielectric Elastomer Actuators (DEA) solely poses material nonlinearity in their model, geometrical nonlinearity imposes additional challenge to model DEMES. Considering dielectric elastomer and bending frame, respectively, as a hyper-elastic film and an elastic beam, Euler–Lagrange equation is employed to derive the equation of motion of actuator subject to a harmonic voltage. Fixed point analysis of the equation of motion demonstrates supercritical pitchfork bifurcation with respect to film pre-stretch as bifurcation parameter. It is shown by simulation results that the system poss

Effects of Dielectric Film Viscoelasticity on Dynamic Behavior of Dielectric Elastomer Minimum Energy Structure

H Vatanjou, Y Hojjat, MR Karafi
Journal Papers , , {Pages }

Abstract

An Analytical Approach to Design of Ultrasonic Transducers Considering Lateral Vibrations

MR Karafi, SA Mirshabani
Journal Papers , , {Pages }

Abstract

Development of a hybrid DEP-SAW device for trapping/sensing target cells

R Ghayour, Y Hojjat, MR Karafi, H Sadeghiyan
Journal PapersApplied Acoustics , Volume 141 , 2018 December 1, {Pages 355-361 }

Abstract

For detecting cells by Surface Acoustic Wave sensors, a sacrificial layer with antigens is usually used to trap cells. This paper introduces a new idea where Dielectrophoresis force traps target cells instead of a sacrificial layer that reacts with target cells and sensed by the surface acoustic wave. Therefore, one can use the sensors more than once, and it is possible to trap different types of cells with different dielectric properties. The device is simulated, and the main parameters of a Dielectrophoresis trapping system and Surface Acoustic Wave sensor, have been introduced and optimized. The effects of focused and unfocused electrode are studied numerically on the displacement of the sensor. Eventually, the feasibility of using the h

Introduction of a hybrid sensor to measure the torque and axial force using a magnetostrictive hollow rod

Mohammad Reza Karafi, Seyyed Javad Ehteshami
Journal PapersSensors and Actuators A: Physical , Volume 276 , 2018 June 15, {Pages 91-102 }

Abstract

In this paper, a hybrid sensor to measure the torque and axial force using a magnetostrictive hollow rod is presented. The magnetostrictive material is made up of vanadium permendur alloy. Axial and circular magnetic fields are used in order to excite the sensor. An axial coil and a single wire passing through the material are used in order to generate axial and circular magnetic field, respectively. In order to detect axial and circular flux changes, two orthogonal pickup coils are used. Theoretical modeling of the sensor has been done using piezomagnetic equations of magnetostrictive materials. In order to achieve an estimation of applied magnetic fields to the material, the sensor has been simulated numerically. Then, the sensor has been

The effect of temperature on tensile behavior and microstructure of Al-3 vol% SiC nanocomposite

Mohammadreza Soltani, Amir Atrian
Journal PapersIranian Journal of Manufacturing Engineering , Volume 5 , Issue 2, 2018 October 23, {Pages 08-Jan }

Abstract

In this study, high-temperature tensile behavior of Al-3 vol% SiC nanocomposite is investigated. To fabricate the samples, SiC nano reinforcements and Al matrix were mixed using an attrition milling. The mixed powders were then subjected to cold pressing and hot extrusion at temperature of 500? C. Tensile behavior at different temperatures along with density measurement and microstructural examinations were studied. The results represent a 40% improvement in ultimate tensile strength of Al-3vol% SiC nanocomposite in comparison with non-reinforced sample at ambient temperature. Also, a rise in temperature up to 270 ? C during the tensile test led to an increase of the maximum elongation. Moreover, this temperature rise caused to 50% and 44%

Reduction of magneto rheological dampers stiffness by incorporating of an eddy current damper

Ali Asghar Maddah, Yousef Hojjat, Mohammad Reza Karafi, Mohammad Reza Ashory
Journal PapersJournal of Sound and Vibration , Volume 396 , 2017 May 26, {Pages 51-68 }

Abstract

In this paper, a hybrid damper is developed to achieve lower stiffness compared to magneto rheological dampers. The hybrid damper consists of an eddy current damper (ECD) and a Magneto Rheological Damper (MRD). The aim of this research is to reduce the stiffness of MRDs with equal damping forces. This work is done by adding an eddy current passive damper to a semi-active MRD. The ECDs are contactless dampers which show an almost viscous damping behavior without increasing the stiffness of a system. However, MRDs increase damping and stiffness of a system simultaneously, when a magnetic field is applied. Damping of each part is studied theoretically and experimentally. A semi-empirical model is developed to explain the viscoelastic behavior

An approach to design and fabrication of resonant giant magnetostrictive transducer

Mohammad R Sheykholeslami, Yousef Hojjat, Simone Cinquemani, Mojtaba Ghodsi, M Karafi
Journal PapersSmart Structures and Systems , Volume 17 , Issue 2, 2016 February 1, {Pages 313-325 }

Abstract

The paper provides a comprehensive procedure for the mechanical and magnetic design of Langevin transducer based on giant magnetostrictive material. The the transducer is designed to work at its second mode of vibration, having high mechanical quality factor and low damping coefficient. The design procedure is based on an analytical model and it is verified by finite-element analysis. Experimental tests based on impedance response analysis in first and second modes are carried out on the prototype. Results confirm the appropriate design of this transducer, demonstrating the highest mechanical quality factor between the resonant transducers in the literature.

Numerical study of the geometric parameters effect on acoustic pressure of focal point of a linear phased array ultrasonic transducer

YOUSEF HOJJAT, Saeed Ansari, Mohammad Reza Karafi
Journal Papers , Volume 3 , Issue 100503, 2016 January 1, {Pages 33-40 }

Abstract

Phased array transducers because of their unique features, are used in many applications. Application of such transducers in non-destructive tests to detect defects such as porosity and crack, as well as stress measurement, in medicine for medical imaging and treatment of diseases, as well as in navigation range finder and acoustic (sonar), are some of the applications of this system. One of the important features of this type of transducer to other transducers, is the ability to focus waves at any distance and angle. The main objective of this paper is to study geometric parameters of a linear phased array transducer with 8 piezoelectric elements such as width and thickness, the distance between elements as well as excitation frequency and

An approach to design and fabrication of resonant giant magnetostrictive transducer

R Sheykholeslami Mohammad, Hojjat Yousef, Simone Cinquemani, Ghodsi Mojtaba, M Karafi
Journal Papers , Volume 17 , Issue 2, 2016 January , {Pages 313-325 }

Abstract

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Study on classical and excess eddy currents losses of Terfenol-D

Soheil Talebian, Yousef Hojjat, Mojtaba Ghodsi, Mohammad Reza Karafi
Journal PapersJournal of Magnetism and Magnetic Materials , Volume 388 , 2015 August 15, {Pages 150-159 }

Abstract

In the present paper, classical and excess eddy currents losses of Terfenol-D are studied and effects of magnetic field frequency, peak of magnetic flux density and diameter of Terfenol-D on the eddy currents losses are investigated. To provide reliable data for the purpose of the paper, an experimental laboratory is fabricated and used to obtain major and minor hysteresis loops of Terfenol-D at different frequencies. In theoretical study, initially an analytical model based on uniform distribution of magnetic flux is developed which yields to calculation of classical eddy currents losses. Then, another eddy currents model based on non-uniform distribution of magnetic flux and nonlinear diffusion of electromagnetic fields is presented. The

An in vitro study of thermal necrosis in ultrasonic-assisted drilling of bone

Ehsan Shakouri, Mohammad H Sadeghi, Mohammad R Karafi, Mehdi Maerefat, Mahmood Farzin
Journal PapersProceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine , Volume 229 , Issue 2, 2015 February , {Pages 137-149 }

Abstract

In case of human bone fracture, the best way to better and faster knitting is when a traumatologist fixes the fractured bone ends by drilling and setting the immobilization plates by screws. Heat generation during bone drilling may result in thermal injury due to exposure to elevated temperatures, with potentially devastating effect on the outcome of orthopedic surgery. A recent and promising method for reducing temperature in bone drilling is the use of ultrasonic assistance, where high-frequency and low-amplitude vibrations are added in feed direction during cutting process. In this research, experimental tests are carried out in five cutting speeds and three feed rates. The results demonstrate that ultrasonic-assisted drilling offered lo

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دروس نیمسال جاری

  • كارشناسي ارشد
    مكاترونيك 2 ( واحد)
    دانشکده مهندسی مکانیک، گروه مهندسي ساخت و توليد
  • كارشناسي ارشد
    مكاترونيك 2 ( واحد)

دروس نیمسال قبل

  • كارشناسي ارشد
    رياضيات مهندسي پيشرفته ( واحد)
    دانشکده مهندسی مکانیک، گروه مهندسي ساخت و توليد
  • كارشناسي ارشد
    رياضيات مهندسي پيشرفته ( واحد)
  • كارشناسي ارشد
    مكاترونيك 1 ( واحد)
  • كارشناسي ارشد
    مباحث پايه در مهندسي برق ( واحد)
  • 1400
    پورصدر, مينا
    طراحي و ساخت سنسور خمشي مگنتواستريكتيو حجمي
  • 1398
    عظيمي پيرسلطان, فائزه
    طيف سنجي خواص الكتريكي و مكانيكي يك بافت زيستي به منظور مدلسازي رفتارهاي رزونانسي فركانس پايين
  • مسئول کمیته ایمنی دانشکده مهندسی مکانیک
  • مدیر عامل شرکت دانش بنیان آفرینش لوازم فنی البرز (آلفا)، تولید کننده تجهیزات فرآیندهای الکتروفیزیکی/منابع تغذیه آلتراسونیک، منابع تغذیه پلاسما، ترانسدیوسرهای پیزوالکتریکی، دستگاه جوشکاری آلتراسونیک پلاستیک ها و فلزات، دستگاه ماشینکاری الکتروشیمیایی https://alfapower.ir
  • عضویت در هیئت تحریریه مجله علمی پژوهشی مهندسی مکانیک مدرس
  • مدیر گروه رشته مهندسی مکاترونیک (مشترک بین دپارتمان های برق و مکانیک)
  • مدیر گروه رشته مهندسی ساخت و تولید-دانشکده مهندسی مکانیک
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