Iranian Society of Acoustics and Vibration and Avecina Journal of Theoretical and Applied Vibration and Acoustics 2423-4761 5 2 2019 07 01 Hybrid method for studying the effect of the material change on the blade vibration behavior 85 94 39786 10.22064/tava.2019.78721.1092 EN Ali Salehzadeh Nobari Professor, Aerospace Department, Amirkabir University of Technology, Tehran, Iran Kamal Jahani Associate Professor, Mechanical Engineering Department, University of Tabriz, Tabriz, Iran Journal Article 2018 05 27 To increase the production efficiency of a typical turbine blade, it is necessary to change its material and hence its production technology. In this respect and in order to make sure that new material will not bring about the blade resonant vibrations, the common practice is to use the Campbell diagram approach. This approach only indicates the potential dangers for blade forced vibration. The purpose of this paper is to demonstrate the efficiency of a proposed hybrid procedure for the development of a reliable Campbell diagram, using an updated finite element model and a simplified test setup.

https://tava.isav.ir/article_39786_59ddf60f6efb7a194b24a392215fb222.pdf

Iranian Society of Acoustics and Vibration and Avecina Journal of Theoretical and Applied Vibration and Acoustics 2423-4761 5 2 2019 07 01 Finite element model updating of a geared rotor system using particle swarm optimization for condition monitoring 95 114 39787 10.22064/tava.2020.104852.1134 EN Morteza Farrokhnia School of Mechanical Engineering,College of Engineering, University of Tehran, Tehran, Iran Farzad A. Shirazi School of Mechanical Engineering,College of Engineering, University of Tehran, Tehran, Iran Maryam Mahnama School of Mechanical Engineering,College of Engineering, University of Tehran, Tehran, Iran Mohammad Mahjoob School of Mechanical Engineering,College of Engineering, University of Tehran, Tehran, Iran Journal Article 2019 04 04 In this paper, condition monitoring of a geared rotor system using finite element (FE) model updating and particle swarm optimization (PSO) method is onsidered. For this purpose, employing experimental data from the geared rotor system, an updated FE model is obtained. The geared rotor system under study consists of two shafts, four bearings, and two gears. To get the experimental data, iezoelectric accelerometers are mounted on the bearings to extract the natural frequencies. Also, mass, stiffness and gyroscopic matrices can be obtained using FE method. By extracting these matrices, natural frequencies and mode shapes are also obtained from solutions of an eigenvalue problem. Having the first flexural four natural frequencies from experimental modal analysis as the objective, FE model of the geared rotor structure is to be updated. Solving sensitivity equations iteratively, model updating is performed to predict the required changes in parameters of the model. In the next stage, some defects are introduced into the experimental setup and the resulting natural frequencies are set as the reference for model updating purpose. Therefore, the changes in the model parameter with respect to a healthy system is monitored. Using PSO method, fault detection in a geared rotor system is performed. Model updating and PSO are able to predict the types and values of damages created in the geared rotor system. In general, the model updating method is simpler and computationally more efficient for industrial equipment. However, particle swarm optimization provides more accurate results with higher computations.

https://tava.isav.ir/article_39787_d98fac2ea99d25f055f9ae52e49dd46d.pdf

Iranian Society of Acoustics and Vibration and Avecina Journal of Theoretical and Applied Vibration and Acoustics 2423-4761 5 2 2019 07 01 Experimental investigation of the gyroscopic and rotary inertia effects on the chatter boundary in a milling process 115 130 39849 10.22064/tava.2020.96841.1120 EN Ali Mokhtari PhD Candidate, Department of Mechanical Engineering, Yazd University, Yazd, Iran Mohammad Mahdi Jalili Associate Professor, Department of Mechanical Engineering, Yazd University, Yazd, Iran Abbas Mazidi Assistant Professor, Department of Mechanical Engineering, Yazd University, Yazd, Iran Journal Article 2018 11 02 Experimental examination of the gyroscopic and rotary inertia effects on the chatter boundary in a milling operation is the chief aim of this article. The equations of motion of the tool vibration are derived based on Timoshenko beam theory and Hamilton principle by considering gyroscopic moment, rotary inertia, velocity-dependent process damping and radial immersion effect. For a range of depth of cuts and spindle velocities, the stability of the milling process is determined by using the method of multiple scales and creating a so-called stability lobe diagram (SLD) in which boundaries separate stable area and unstable or chatter area. Then the newly obtained SLD with the effects of rotary inertia and gyroscopic moments is verified experimentally. Indeed, the verification of the lobes at the speeds where the distinction is sound between the conventional lobes and the newly obtained lobes is presented. Here, the SLD obtained without the effects of rotary inertia and gyroscopic moments is so-called conventional SLD. For this purpose, some experiments are conducted to demonstrate the progressive move into the unstable zone at the locally optimum point of SLD. Finally, a parametric study is presented as a validation of the newly obtained lobes from the sense that the effects of different parameters on these limits are as expected.

https://tava.isav.ir/article_39849_21b12b67cb6ff82b0d5e9e1d96d4b56c.pdf

Iranian Society of Acoustics and Vibration and Avecina Journal of Theoretical and Applied Vibration and Acoustics 2423-4761 5 2 2019 07 01 Nonlinear lap joint interface modeling and updating strategies for assembled structures 131 152 39876 10.22064/tava.2020.127915.1168 EN Ehsan Shahabi Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16844, Iran Hamid Ahmadian Center of Excellence in Experimental Solid Mechanics and Dynamics, School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16844, Iran 0000-0002-2383-672X Journal Article 2019 09 08 A comparison between two known strategies of modeling lap joint interfaces, namely, zero-thickness and thin layer interface theories and their associated updating procedures, is made. Finite element models capable of accurately representing nonlinear behavior of assembled structures with localized nonlinearities in their bolted lap joint are developed. A practical strategy is employed in updating of these structures that initially parameters describing linear behavior are updated based on the low-amplitude excitation experimental observations. In the next step, parameters representing nonlinear effects are updated using stepped-sine excitations near the structure resonance frequency. In both steps, the Particle Swarm Optimization (PSO) algorithm is used to reduce the discrepancies between experimental observations and model predictions<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: Calibri; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="AR-SA" dir="RTL">. The identified contact interface models are validated by comparing their predictions with the experimental data not included in the updating procedure. In what concerns the updating process, the convergence rate of parameter identification in a model with zero thickness frictional contact elements was lower and more time-consuming compared to the model with thin layer interfaces.This study shows assigning appropriate material properties for the thin interface layer results in contact forces with comparable accuracy to the ones obtained by zero thickness elements with less computational efforts.

https://tava.isav.ir/article_39876_6c75af1b54121e4804210955262ec032.pdf

Iranian Society of Acoustics and Vibration and Avecina Journal of Theoretical and Applied Vibration and Acoustics 2423-4761 5 2 2019 07 01 Wave propagation analysis of magneto-electro-thermo-elastic nanobeams using sinusoidal shear deformation beam model and nonlocal strain gradient theory 153 176 40346 10.22064/tava.2020.104267.1128 EN Ahad Amiri School of Mechanical Engineering, Iran University of Science and Technology, Narmak, 16765-163, Tehran, Iran Arian Masoumi School of Mechanical Engineering, Iran University of Science and Technology, Narmak, 16765-163, Tehran, Iran Roohollah Talebitooti Associate Professor, School of Mechanical Engineering, Iran University of Science and Technology, Narmak, 16765-163, Tehran, Iran Mir Saeed Safizadeh Associate Professor, School of Mechanical Engineering, Iran University of Science and Technology, Narmak, 16765-163, Tehran, Iran Journal Article 2019 03 07 <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">The main goal of this research is to provide a more detailed investigation of the size-dependent response of magneto-electro-thermo-elastic (METE) nanobeams subjected to propagating wave, employing sinusoidal shear deformation beam theory (SSDBT). With the aim to consider the size influences of the structure, the nonlocal strain gradient theory (NSGT) is utilized. Hamilton’s principle within constitutive relations of METE materials is incorporated to derive the governing equations. Utilizing Maxwell’s relation and magnet-electric boundary conditions, proper distributions for magnetic and electric potentials along the nanobeam are obtained. Thereafter an exact analysis is used to obtain the axial and flexural dispersion relations of METE nanobeams. In numerical results, detailed investigations of wave dispersion behavior related to three modes are addressed. In addition, a relation is introduced to determine the cut-off frequency of the system. Moreover, the effectiveness of various parameters including length scale and nonlocal parameters, nanobeam thickness, and the loadings due to imposed thermo-electro-magnetic field on the response of propagating wave in METE nanobeams are examined.

https://tava.isav.ir/article_40346_e866f5b284008f65db1641dae437f9c2.pdf

Iranian Society of Acoustics and Vibration and Avecina Journal of Theoretical and Applied Vibration and Acoustics 2423-4761 5 2 2019 07 01 A new multi-switch circuit with adaptive capacitance for semi-active piezoelectric shunt damping 177 190 40446 10.22064/tava.2020.108853.1138 EN Saber Mohammadi Associate Professor, Mechanical Engineering Department, Engineering Faculty, Razi University, Kermanshah, Iran Akram Khodayari Assistant Professor, Mechanical engineering department, Engineering faculty, Razi university, Kermanshah, Iran Salar Hatam PhD Candidate, Mechanical Engineering Department, Engineering Faculty, Razi University, Kermanshah, Iran Journal Article 2019 05 31 Piezoelectric-based shunt dampers are developed in recent years because of simplicity in comparison with other methods. In these methods, a part of converted mechanical energy is stored in the internal electrostatic field of the piezoelectric and a minor portion is dissipated in the load resistor of damping circuits. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: KO; mso-bidi-language: AR-SA; mso-bidi-font-size: 9.5pt;">In recent methods, the electrostatic field of piezoelectric elements is reduced (not eliminated) and a portion (not whole) of the stored energy is extracted and dissipated in the resistor. In this paper, using a new adaptive multi-switch network and RLC resonance concept, the electrostatic field of piezoelectric is eliminated (not reduced) and almost the whole converted energy (not a portion) is extracted and dissipated in the load resistor. Using the proposed network, self-tuning ability provides electrical resonance in the circuit for almost all excitation types in a wide frequency band and also any mass and stiffness of the structure. Most of the electronic damping techniques are presented just for harmonic excitations, but the proposed technique in the current work is suitable for both harmonic and random excitations. In mechanical structures with variable mass such as vehicles, airplanes and missiles, structure mass will be changed while motioning. For such systems, resonance frequencies will change by structure mass during operation. Recent RLC dampers are not self-tuning for different mechanical stiffness or mass, but, the proposed technique is completely adaptive with variable mechanical characteristics of the vibrating structure. Consequently, significant damping is obtainable in comparison with other electronic damping techniques.

https://tava.isav.ir/article_40446_560003ffda27cda2328b3e17a0ed7f0f.pdf