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Investigation of the Effects of Process Damping on Chatter Instability in Micro End Milling

Procedia CIRP 2012年 1卷 156-161页

作者： S. Ahmad Tajalli Mohammad R. Movahhedy Javad Akbari Center of Excellence in Design Robotics and Automation (CEDRA) Department of Mechanical Engineering Sharif University of Technology Tehran Iran

In this paper, chatter instability of micro end mill tools is studied by taking into account the process damping effect. The actual geometry of the micro tool including shank, taper part and fluted section is considered in the analysis. Timoshenko beam theory is utilized to consider the shear deformation and rotary inertia effects due to short and thick beam-type structures of each parts of the micro tool. The extended Hamilton's Principle is used to formulate a detailed dynamical model of the rotating micro end mill. The governing equations are solved by assumed mode model expansion. An exact dynamic stiffness method is developed to investigate modal characteristics of the tool including mode shapes to be utilized as base functions for the solution. In micro milling, the process damping affects the chatter especially at low spindle speeds. So, the process damping parameters are used to investigate chatter instability.

关键词： Micromachining Chatter Modeling Finite element Method

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Tool condition monitoring based on sound and vibration analysis and wavelet packet decomposition

Tool condition monitoring based on sound and vibration analy...

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2012 8th International Symposium on Mechatronics and its Applications, ISMA 2012

作者： Rafezi, Hamed Akbari, Javad Behzad, Mehdi Sharif University of Technology International Campus School of Science and Engineering Kish Island Iran Sharif University of Technology Department of Mechanical Engineering Center of Excellence in Design Robotics and Automation Tehran Iran

ISBN: (纸本)9781467308625

Tool Condition Monitoring (TCM) is a vital demand of advanced manufacturing in order to develop automated unmanned production. Continuing the machining operation with a worn or damaged tool will result in damages to the workpiece. This problem becomes more important in supplementary machining processes like drilling which the workpiece usually has passed a lot of machining processes and any damage to workpiece at this stage results in high production losses. In this research features of sound pressure and vibration signals in drilling process are recorded and analyzed in order to detect tool wear. Signal statistical features are extracted in time domain, and the features trends as the tool becomes worn are extracted. Frequency spectrum of signals is calculated and Wavelet Packet Decomposition (WPD) is applied to focus on specific frequency bands. In this research capability of both sound and vibration signals for drill wear detection are shown and the most informative features of the signals for wear detection are evaluated and introduced. The results showed that the wavelet packets features make a better contrast between the sharp and the worn tool compared to the primary time domain signal. © 2012 IEEE.

关键词： Vibration analysis

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TEMPERATURE DEPENDENCE STUDY OF NONCONTACT AFM IMAGES USING MOLECULAR DYNAMICS SIMULATIONS

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International Journal of Modern Physics: Conference Series 2012年第5期ijmpcs卷 418-432页

作者： HOSSEIN NEJAT PISHKENARI ALI MEGHDARI Nano-Robotics Laboratory Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology Tehran P.O. Box: 11365-9465 Iran

The effect of temperature on the noncontact atomic force microscopy (NC-AFM) surface imaging is investigated with the aid of molecular dynamics (MD) analysis based on the Sutton-Chen (SC) interatomic potential. Particular attention is devoted to the tip and sample flexibility at different temperatures. When a gold coated probe is brought close to the Au (001) surface at high temperatures, the tip and surface atoms are pulled together and their distance becomes smaller. The tip and sample atoms displacement varies in the different environment temperatures and this leads to the different interaction forces. Along this line, to study the effect of temperature on the resulting images, we have employed the well-known NC-AFM model and carried out realistic non-equilibrium MD 3D simulations of atomic scale imaging at different close approach positions to the surface.

关键词： NC-AFM molecular dynamics simulation Sutton-Chen potential tip-surface interaction force temperature effect

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Kinematics and force analysis of a 6 degrees of freedom 3-UPS mechanism with triangular platform for haptic applications

Kinematics and force analysis of a 6 degrees of freedom 3-UP...

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International Conference on Control, automation and Systems ( ICCAS)

作者： Mohammad Khodabakhsh Mehdi Sadeghpour Soroosh Hassanpour Gholamreza Vossoughi Department of Mechanical Engineering Center of Excellence in Design Robotics and Automation (CEDRA) Sharif University of Technology Tehran Iran University of Waterloo Ontario Canada

This paper presents inverse dynamics equations for a 3-UPS mechanism using virtual work principle. This mechanism has three UPS legs connecting the base to a triangular platform. By changing the orientation of leg's actuators a non-symmetric mechanism with a suitable workspace near the origin without any singularity is obtained. Direct and inverse kinematics Jacobian matrices of the mechanism are obtained by the Newton-Euler approach. Then the inverse dynamics problem is solved using the principle of virtual work, so that the force and torque of active actuators have been obtained by having external forces (force and torque) acted on the platform. Force analysis of the 3-UPS mechanism has been done in the whole workspace without any singularity. Studying several situations of the platform shows that the ranges of the magnitudes of the forces and torques of the active actuators in this mechanism are reasonable, and typical actuators can support them.

关键词： Joints Force Kinematics Torque Vectors Equations Actuators

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Tool Condition Monitoring based on sound and vibration analysis and wavelet packet decomposition

Tool Condition Monitoring based on sound and vibration analy...

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International Symposium on Mechatronics and Its Applications, ISMA

作者： Hamed Rafezi Javad Akbari Mehdi Behzad School of Science and Engineering Sharif University of Technology Kish Island Iran Department of Mechanical Engineering Center of Excellence in Design Robotics and Automation Sharif University of Technology Tehran Iran

关键词： Vibrations Wavelet packets Feature extraction Drilling machines Time domain analysis Condition monitoring Wavelet analysis

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Predicting average velocity of a non-linear sliding microrobot

Predicting average velocity of a non-linear sliding microrob...

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作者： Eigoli, A. Kamali Vossoughi, G.R. Center of Excellence in Design Robotics and Automation Sharif University of Technology 11365-9567 Tehran Iran

Among the locomotion concepts employed in the microrobotics, friction-based locomotion principles are of considerable importance. In this study, the dynamic modelling of friction drive microrobots subjected to the tangential and normal excitations is investigated, which have the same frequency, but are shifted in phase. The motion equation of the microrobot reveals a strongly non-linear differential equation with discontinuity for which the elastic force term is proportional to a signum function. Using the homotopy perturbation method, simple expressions are derived for predicting average velocity of the slider. The obtained results are in good agreement with those achieved from numerical integration of the full equation and experimental results, reported in the literature. Using the concept of step efficiency, some useful guidelines for the design and control of this type of microrobots are provided. © Authors 2011.

关键词： Friction

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Taguchi's optimization in ultrasonic drilling of alumina ceramic

Taguchi's optimization in ultrasonic drilling of alumina cer...

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6th International Conference on Leading Edge Manufacturing in 21st Century, LEM 2011

作者： Hoseini, S. Mehdi Akbari, Javad Department of Mechanical and Engineering Science and Research Branch Islamic Azad University Tehran Iran Center of Excellence in Design Robotics and Automation School of Mechanical Engineering Sharif University of Technology Tehran Iran

This paper outlines the effectiveness of the ultrasonic machining of alumina in terms of tool wear rate of the tool used and the material removal rate of work piece produced. The optimum combination of various input factors as type of abrasive slurry, their size and concentration, power and feed rate, in the machining of alumina has been determined by applying the Taguchi technique, also analysis is used to choose the best shape for horn. The study shows that among input parameters, power has the highest effect on MRR (material removal rate). Effects of grit size and feed rate on TWR (tool wear rate) also investigated.

关键词： Taguchi methods

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Development of a penetration model for an erosive long rod considering strength effects of colliding materials

Development of a penetration model for an erosive long rod c...

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作者： Nezamabadi, A.R. Vahedi, K. Zohoor, H. Tehran Sciences and Research Branch Department of Mechanical Engineering Islamic Azad University Arak Iran Department of Mechanical Engineering Imam Hossein University Tehran Iran Center of Excellence in Design Robotics and Automation Sharif University of Technology Iran

In this article a simple penetration model for the terminal ballistic of long rod penetrators is developed. The model is to predict the crater depth of a projectile penetrating into a semi-infinite target. A principle objective was to take an account of strength properties of colliding materials using erosive phenomena. The entire velocity regime from low to hypervelocity is analysed. The effect of the penetrator aspect ratio is also considered in the model. The model developed here is based on the steady-state penetration process and is used to compare with existing experimental measurements. The results of the comparison show very good agreement with experimental investigations of other researchers in this field. The study shows that it is possible to construct a very simple model to predict crater depth for a large range of materials with sufficient accuracy without recourse to high cost of experimentation. In fact, the biggest advantage of this model is simplicity and direct applicability to design process. Historically, penetration mechanics has relied very heavily on experimental investigation. This work gives a quick and easy result with sufficient accuracy which may be useful for many applications. To validate the analytical solution, an experimental method is employed.

关键词： Aspect ratio

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design and analysis of a novel two DOF thermal micromanipulator

Design and analysis of a novel two DOF thermal micromanipula...

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International Conference on Mechatronics (ICM)

作者： Hoorad Pourzand Reza Ghaemi Aria Alasty Center of Excellence in Design Robotics & Automation (CEDRA) Mechanical Engineering Department Sharif University of Technology Tehran Iran

In this paper, a novel thermal microactuator is designed which is capable of producing bi-directional lateral and rotational output and one of its applications as a two DOF micromanipulator is shown. Also, by carefully choosing the doping level, temperature distribution is determined by considering the dependency of silicon's resistivity and conductivity to temperature. Using variable separation method an equation in terms of elliptic integrals is reached and after imposing boundary conditions the exact temperature distribution is obtained numerically. Currents at each branch is updated due to the last temperature distribution and this process is repeated several times until the final thermal distribution is reached with less than 0.1 percent change in two following computed currents. Furthermore, By using equations of postbuckling behavior of a cantilever subjected to tip multiple loading, deflections of flexible joints and computed linear axial and flexural stiffness of a box spring, a numerical approach has been developed to find output displacement of the micromanipulator.

关键词： Heating Micromanipulators Voltage control Jacobian matrices Finite element methods Polymers

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Sensitivity Analysis Of Mouse Embryos In Needle Injection Experiment Using Artificial Neural Network

Sensitivity Analysis Of Mouse Embryos In Needle Injection Ex...

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2011 International Conference on Future Information Technology (ICFIT 2011)

作者： Ali A. Abbasi H. Sayyaadi G.R.Vossoughi school of mechanical engineering Sharif university of technology Tehran Iran Center of excellence in design robotics and automation(CEDRA) school of mechanical engineeringSharif university of technology Tehran Iran

In this paper sensitivity analysis is performed to investigate the influence of the significance of cell membrane deformation and dimple depth under needle injection using neural network modeling. To achieve these goals two neural network models are implemented. In the first model dimple depth, dimple radius and radius of the semi-circular curved surface of the cell are used as inputs of the neural network model and indentation force has been predicted. In the second model indentation force, dimple radius and radius of the semi-circular curved surface of the cell are used as inputs of the neural network model and dimple depth is predicted. Results of experimental data from literature are used to train the neural network models. Sensitivity analysis showed that output parameters were less sensitive to the rate of input parameters after training the neural network models while effect of semi-circular curved surface of the cell on prediction of indentation force and dimple depth is negligible. Results of theoretical formulation by other researchers also confirm these findings.

关键词： sensitivity analysis biological cells artificial neural network,needle injection experiment.

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