Loading...
Search for:
chattering
0.006 seconds
Total 60 records
Investigation of thermal effects on machining chatter based on FEM simulation of chip formation
, Article CIRP Journal of Manufacturing Science and Technology ; Vol. 7, issue. 1 , 2014 , p. 1-10 ; Movahhedy, M. R ; Moradi, H ; Sharif University of Technology
Abstract
In this paper, thermo mechanical finite element analysis of orthogonal machining process with a flexible tool is carried out to study the dynamic behaviour of the machining system and its stability against chatter vibration. By combining the simulation of chip formation in metal cutting with the dynamic phenomena leading to chatter development, the influence of various phenomena, including thermal effects resulting from friction and plastic deformations on the stability of the process are investigated. The novelty of this model is in its ability to evaluate the effect of temperature rise in the cutting zone on the stability of cutting process. Process stability is analyzed and compared for...
Investigation of the effects of process damping on chatter instability in micro end milling
, Article Procedia CIRP ; Volume 1, Issue 1 , 2012 , Pages 156-161 ; 22128271 (ISSN) ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
2012
Abstract
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...
Investigation of the internal resonance and regenerative chatter dynamics in nonlinear milling process
, Article ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 28 August 2011 through 31 August 2011 ; Volume 1, Issue PARTS A AND B , August , 2011 , Pages 141-150 ; 9780791854785 (ISBN) ; Vossoughi, G ; Movahhedy, M. R ; Ahmadian, M. T ; Sharif University of Technology
2011
Abstract
Peripheral milling is extensively used in manufacturing industry. To achieve more material removal rate, high precision and surface quality and increase tool life, chatter vibration must be suppressed. In this paper, an extended dynamic model of the peripheral milling process including both the structural nonlinearity and nonlinear cutting forces is presented. Using the multiple-scale approach, as a perturbation technique, internal resonance of the milling process is investigated. Transfer of the energy between the coupled x-y modes is studied. According to results obtained, it is possible to adjust the rate at which the x-mode (or y-mode) decays by implementation of the internal resonance...
Spindle speed variation for regenerative chatter suppression in turning process with tool wear effect
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 4 , 2010 , Pages 619-626 ; 9780791849187 (ISBN) ; Vossoughi, G ; Rahaeifard, M ; Movahhedy, M ; ASME Turkey Section ; Sharif University of Technology
Abstract
Chatter suppression in machining processes results in more material removal rate, high precision and surface quality. In this paper, a single degree of freedom model of orthogonal turning process is used to set up the delay differential equation of motion with considering the tool wear effect as a contact force between the workpiece and tool flank surfaces. Sinusoidal spindle speed variations with different frequencies around the mean speed are modulated to disturb the regenerative mechanism. The optimal amplitudes of the speed modulations are found based on a genetic algorithm such that the input energy to the turning process is minimized. Results of the stability analysis and the...
Robust control strategy for suppression of regenerative chatter in turning
, Article Journal of Manufacturing Processes ; Volume 11, Issue 2 , 2009 , Pages 55-65 ; 15266125 (ISSN) ; Movahhedy, M. R ; Vossoughi, G. R ; Sharif University of Technology
Elsevier BV
2009
Abstract
Chatter suppression is of great importance in machining processes for achieving more material removal rate, high precision and surface quality. In this paper, an H∞ control algorithm is proposed for chatter suppression in the presence of tool wear and parameter uncertainties. Orthogonal turning process is modelled as a single degree of freedom model that includes the effect of tool flank wear. Control input of the system is the force provided by a piezo-actuator.The turning process model includes the uncertainties in cutting velocity, tool wear and dynamic model parameters. Using the μ-synthesis technique, an H∞ optimal controller is designed based on a DK-iteration algorithm. The...
Modeling and active control of chatter vibrations of piezoelectric stacked machining arm in micro-turning process
, Article Meccanica ; Volume 55, Issue 9 , 18 July , 2020 , Pages 1707-1731 ; Moradi, H ; Movahhedy, M. R ; Sharif University of Technology
Springer
2020
Abstract
Self-excited vibrations known as chatter are considered as the most detrimental issue in micro-turning processes. Occurring unpredictably, they adversely affect the tool life, productivity rate and surface quality of the machining processes. In this paper, a novel machining arm is modeled as a piezoelectric stacked rod which is subjected to a chatter force in the orthogonal micro-turning process. Due to the fact that machining processes are affected by various sources of uncertainties, H∞ robust control approach is used to suppress the chatter vibrations of the machining arm in the presence of tool wear and dynamic model parameter variations. Also, input control force of the system is...
A PID controller design to suppress chatter vibrations in the turning process studying its effect in nonlinear delayed process
, Article 10th International Conference on Modern Circuits and Systems Technologies, MOCAST 2021, 5 July 2021 through 7 July 2021 ; 2021 ; 9781665418478 (ISBN) ; Moradi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
High-quality, high-production-rate machining operations are significantly hindered by the regenerative chatter. Therefore, chatter suppression is of great significance; and active control is one of the best ways to curb it. In this paper, the orthogonal turning process is modeled as a single-degree-of-freedom system that includes the effect of tool wear; and described through a delay differential equation (DDE). Based on the model, stability lobes diagrams are obtained by the trial and error. The actuator force is the input for the control system and the tool vibration is the output. A classical PID controller is designed to improve the stability of the process and curb the self-excited...
Prediction of Machining Chatter Based on 2 Dimensional FE Dynamic Modeling of Chip Formation
, M.Sc. Thesis Sharif University of Technology ; Movahhedi, Mohammad Reza (Supervisor)
Abstract
In machining processes, chip formation is one of the most important methods to obtain the final shape of a work-piece. Improving the machining processes leads to the increase in the material removal rate (MRR) and reduction of high economical costs. Vibration is an undesirable phenomenon in machining processes because it results in reduction of material removal rate (MRR), poor surface finish and increased tool wear. Among various types of vibration, self-excited vibration or chatter is the most important one. It is obvious from previous investigations that for prediction of machine tools vibration, many simplifications were assumed while the linear and non-linear effects are not considered...
Performance Analysis of Proximate Time-Optimal Control for Undamped Harmonic Oscillator in the Presence of Unmodelled Dynamics
, M.Sc. Thesis Sharif University of Technology ; Tavazoei, Mohammad Saleh (Supervisor)
Abstract
A servomechanism is a system with the objective of to controlling the position or velocity of a mechanical device. In many servomechanisms, one of the major performance measures is tracking the reference input in the shortest time possible. In practice, due to reasons such as modeling error and existence of disturbances, time-optimal control strategy, which is obtained using the classical calculus of variations methods, leads to the undesirable chattering phenomenon. The Proximate Time-Optimal Servomechanism control method is among the practical approaches proposed to obtain responses arbitrarily close to time-optimal, and at the same time avoid chattering. This methodology has found...
Chatter instability analysis of spinning micro-end mill with process damping effect via semi-discretization approach
, Article Acta Mechanica ; Vol. 225, issue. 3 , 2014 , pp. 715-734 ; ISSN: 00015970 ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
Abstract
In this paper, the stability of delay differential equations (DDEs), describing self-excited vibrations in a micro-milling process, is investigated based on semi-discretization (SD) method. Due to the stubby geometry of micro-tools, the shear deformation and rotary inertia effects are considered for modeling the structure. The extended Hamilton's principle is used to derive a detailed dynamical model of the spinning micro-tool with the support of misalignment in which the gyroscopic effects cause coupling of equations. Considering the actual geometry of the micro-end mill, exact dynamic stiffness (DS) formulations are developed to investigate the tool's free vibration characteristics. The...
Experimental dynamic modelling of peripheral milling with process damping, structural and cutting force nonlinearities
, Article Journal of Sound and Vibration ; Volume 332, Issue 19 , 2013 , Pages 4709-4731 ; 0022460X (ISSN) ; Vossoughi, G ; Movahhedy, M. R ; Sharif University of Technology
2013
Abstract
In this paper, an extended dynamic model of peripheral milling process including process damping, structural and cutting force nonlinearities is presented. Cutting forces are described through a third-order polynomial function of chip thickness while a cubic nonlinear function is considered for the structural stiffness. Under stable and regenerative chatter conditions and using Fourier series components, closed form expressions for the nonlinear cutting forces are derived. Parameters of the proposed model are identified through a set of experiments. For this purpose, modal experiments and measurement of cutting forces (at various feed rates) are performed to determine the modal parameters...
Real-time estimation of the volumetric efficiency in spark ignition engines using an adaptive sliding-mode observer
, Article Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering ; Volume 229, Issue 14 , December , 2015 , Pages 1925-1933 ; 09544070 (ISSN) ; Salehi, R ; Salarieh, H ; Alasty, A ; Vossoughi, G ; Sharif University of Technology
SAGE Publications Ltd
2015
Abstract
Proper operation of an engine requires accurate measurement or estimation of the engine's air charge provided to the control unit which reduces both the engine's fuel consumption and the emissions. The volumetric efficiency of the engine is a key variable in computations using the engine control unit to estimate the air charge using the speed-density equation. This paper presents a new approach for real-time estimation of the volumetric efficiency using the sliding-mode methodology. An adaptive sliding-mode observer is proposed which relies on measurements from the engine's conventional sensors. The observer is shown to estimate asymptotically the volumetric efficiency of the engine for...
Dynamic stability of a Hexaglide machine tool for milling processes
, Article International Journal of Advanced Manufacturing Technology ; Volume 86, Issue 5-8 , 2016 , Pages 1753-1762 ; 02683768 (ISSN) ; Movahhedy, M. R ; Zohoor, H ; Alasty, A ; Sharif University of Technology
Springer-Verlag London Ltd
Abstract
One of the major issues related to parallel kinematic machine tools (PKMs) is their structural dependency on their configuration. In this paper, the machine configuration effect on its stability is investigated for the case of a Hexaglide machine tool. An FEM model of the Hexaglide machine tool is developed. The frequency response function (FRF) at the tool tip is obtained by a modal analysis. The numerical results are validated through comparison with those of an experimental modal test. The pose dependency of the PKM stability over its workspace is investigated. It is shown that the machine stability over the workspace is dependent on the spindle/tool/holder system characteristic. For...
A new method for multi-objective optimal design of milling parameters by considering chatter vibrations
, Article 2019 SAE Automotive Technical Papers, WONLYAUTO 2019, 1 January 2019 through 1 January 2019 ; Volume 2019-January, Issue January , 2019 ; 01487191 (ISSN) ; Khodaygan, S ; Sohani, A ; Sharif University of Technology
SAE International
2019
Abstract
The desired milling process with high material removal rate (MRR) and low surface roughness of the product can be achieved only if machining chatter is absent. Incorporating chatter into the optimal selection of the machining parameters leads to a complex problem. Therefore, the approach of selecting conservative intervals for the machining parameters is usually employed instead. In this paper, a practical approach is proposed to specify the optimal machining parameters (depth of cut and spindle speed) in order to maximize MRR and minimize forced vibrations by considering machining chatter. Firstly, the worst-case scenario-based optimization problem in terms of the surface quality is solved...
Adaptive control of regenerative chatter in turning process with tool wear effect
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings ; Vol. 10, Issue PART B , 2010 , pp. 1023-1030 ; ISBN: 9780791843833 ; Moradi, H ; Vossoughi, G. R ; Alasty, A ; Movahhedi, M. R ; Sharif University of Technology
Abstract
Chatter suppression is of great importance for achieving high precision and surface quality in machining processes. A single degree of freedom model of orthogonal turning process is used to set up the nonlinear delay differential equation of motion. Tool wear effect is considered as the contact force between the workpiece and tool flank surfaces. Uncertainties in parameters of dynamic model and machining conditions are included in the model. An adaptive control strategy is applied for chatter suppression in cutting process. The force provided by a piezoactuator is the control input of the system. Results of stability analysis and adaptive control for two distinct cases of sharp and worn...
Tuneable vibration absorber design to suppress vibrations: An application in boring manufacturing process
, Article Journal of Sound and Vibration ; Volume 318, Issue 1-2 , 2008 , Pages 93-108 ; 0022460X (ISSN) ; Bakhtiari Nejad, F ; Movahhedy, M. R ; Sharif University of Technology
2008
Abstract
Dynamic vibration absorbers are used to reduce the undesirable vibrations in many applications such as electrical transmission lines, helicopters, gas turbines, engines, bridges, etc. Tuneable vibration absorbers (TVA) are also used as semi-active controllers. In this paper, the application of a TVA for suppression of chatter vibrations in the boring manufacturing process is presented. The boring bar is modeled as a cantilever Euler-Bernoulli beam and the TVA is composed of mass, spring and dashpot elements. In addition, the effect of spring mass is considered in this analysis. After formulation of the problem, the optimum specifications of the absorber such as spring stiffness, absorber...
Global optimization and design of dynamic absorbers for chatter suppression in milling process with tool wear and process damping
, Article Procedia CIRP ; Volume 21 , 2014 , Pages 360-366 ; ISSN: 22128271 ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
Abstract
Peripheral milling is extensively used in manufacturing processes, especially in aerospace industries where end mills are used for milling of wing parts and engine components. The generation of complex shapes with high quality for various types of materials is the main advantage of milling in contrast to other machining processes. During the milling process, the occurrence of self-excited vibrations or chatter may cause reduction in material removal rate (MRR), damage to the tool and spindle bearing or may result in poor dimensional accuracy and surface finish of the work-piece. In this paper, milling process is modeled as two degrees of freedom (2DOF) system in which the tool wear and...
Application of FEM simulation of chip formation to stability analysis in orthogonal cutting process
, Article Journal of Manufacturing Processes ; Volume 14, Issue 3 , 2012 , Pages 188-194 ; 15266125 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
Elsevier
2012
Abstract
Models for chatter prediction in machining often use a mechanistic force model that calculate the force as the product of a material dependent cutting constant and chip area. However, in reality, the forces are the result of complex interaction between the tool and the chip, and are affected by many factors. The effects of these complex, and often nonlinear, factors on the machining dynamics may only be included in chatter prediction if the chip formation process is simulated concurrently with simulation of the machining dynamics. In this paper, finite element simulation of the chip formation process is combined with simulation of chatter dynamics and the inter-relationship between the chip...
Dynamics of regenerative chatter and internal resonance in milling process with structural and cutting force nonlinearities
, Article Journal of Sound and Vibration ; Volume 331, Issue 16 , 2012 , Pages 3844-3865 ; 0022460X (ISSN) ; Movahhedy, M. R ; Vossoughi, G ; Sharif University of Technology
Elsevier
2012
Abstract
In this paper, internal resonance and nonlinear dynamics of regenerative chatter in milling process is investigated. An extended dynamic model of the peripheral milling process including both structural and cutting force nonlinearities is presented. Closed form expressions for the nonlinear cutting forces are derived through their Fourier series components. In the presence of the large vibration amplitudes, the loss of contact effect is included in this model. Using the multiple-scales approach, analytical approximate response of the delayed nonlinear system is obtained. Considering the internal resonance dynamics (i.e. mode coupling), the energy transfer between the coupled x-y modes is...
Geometry control of the deposited layer in a nonplanar laser cladding process using a variable structure controller
, Article Journal of Manufacturing Science and Engineering, Transactions of the ASME ; Volume 130, Issue 3 , 2008 , Pages 0310031-03100311 ; 10871357 (ISSN) ; Khajepour, A ; Durali, M ; Toyserkani, E ; Sharif University of Technology
2008
Abstract
This paper presents a closed-loop laser cladding process used in nonplanar deposition of desired metallic materials. In the proposed system, the deposited layer geometry is continuously controlled via a sliding mode controller (SMC). The controller, which uses the scanning speed as the control input, is designed based on a parametric Hammerstein model. The model is a parametric dynamic model with several unknown parameters, which are identified experimentally using the recursive least squares method. The designed SMC is robust to all model parameters' uncertainties and disturbances. The results showed that the tracking accuracy improves and the chattering effect reduces if an integrator on...