ششمین کنفرانس بین المللی آکوستیک و ارتعاشات - 17 و 18 آذر ماه 1395، تهران، دانشگاه صنعتی خواجه نصیرالدین طوسی ISAV K. N. Toosi Universitz of Technology

ششمین کنفرانس بین المللی آکوستیک و ارتعاشات

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  سخنرانی‌های کلیدی کنفرانس
Dr. Seyed M. Hashemi,
Department of Aerospace Engineering,
Ryerson University, Toronto (ON),
Canada

Dr. Seyed M. Hashemi is a Professor at Ryerson University, Department of Aerospace Engineering. His research revolves around developing novel analytical, semi-analytical and numerical models and mesh-reduction techniques in order to achieve higher convergence rates in the dynamic analysis of intact and defective, flexible, composite/sandwich structural elements.
Dr. Hashemi has a Bachelor of Science in Mechanical Engineering from Sharif University of Technology (SUT), Tehran/Iran (1990), and a Diplôme D’Études Profondis (DEA) en Mécanique from the Université de Lille I, Flandre Androit, Lille (1992), France. He received his Doctor of Philosophy in 1998 from Laval University, studying numerical modelling of blades and rotating beam-structures. In particular, this work focused on developing a highly convergent Dynamic Finite Element (DFE) method, with applications to the vibration analysis of rotary blades and beam-structures.
Later, he worked as a research associate in the Department of Mechanical Eng., Laval University, and subsequently joined the University of Waterloo, where he worked on a variety of topics related to structural vibration analysis/ modelling/ control, including vibration control of a turbo-Prop engine, tall buildings, … . Dr. Hashemi also collaborated with the Kinesiology Department of the University of Waterloo on several projects, namely passive/active vibration control of Parkinson tremors.
Dr. Hashemi joined Ryerson University in September 2001, where he continues his research work on Finite Elements, Dynamic Finite Element (DFE) and other numerical methods in structural vibration, design, analysis and modelling. To date, he has (co-)authored over 160 publications, including some fifty journal papers, 12 chapters in books and edited volumes, and over 100 conference papers on DFE applications in the areas of structural dynamics, vibration, composites/sandwich structures, and the modeling of MEMS devices, Morphing Wings, Hyperloop Deployable Wheel Subsystem, etc.
Dr. Hashemi is also:
- A licensed Professional Engineer (P.Eng.) in Ontario, Canada,
- Adjunct Professor at the Department of Mechanical and Mechatronics Eng., University of Waterloo, Waterloo (ON), Canada,
- Member of the Centre of Excellence in Smart Structures and Dynamical Systems; Amirkabir University of Technology, I-R-Iran (since July 2013),
- Associate Member of Ryerson Institute for Aerospace Design and Innovation, (RIADI),
- Member of Professional Engineers Ontario (PEO), and OSPE
- Senior member of American Institute of Aeronautics and Astronautics (AIAA), and AIAA Student Branch’s Faculty Advisor (Ryerson University),
- Member of International Institute of Acoustics and Vibration (IIAV), Canadian Aeronautics and Space Institute (CASI), Iranian Society of Acoustics and Vibration (ISAV), Int. Association of Comp. Science and Information Tech (IACSIT), ...

Home page: http://www.ryerson.ca/aerospace/research/Research%20profiles/hashemi.html
E-mail address: smhashem@ryerson.ca


Dynamic Finite Element (DFE) Formulation for Vibration Modelling and Analysis of Structural Elements: Past, Present, and Future Directions

Department of Aerospace Eng., Ryerson University, in general, and recent research and developments the within the speaker’s research group, in particular, will be first briefly presented. The speaker’s research mainly revolves around developing novel analytical, semi-analytical and numerical models and mesh-reduction techniques in order to achieve higher convergence rates in the dynamic analysis of intact and defective, flexible structural elements, made of conventional and advanced materials. The development of a highly convergent, frequency-dependent, Dynamic Finite Element (DFE) formulation and its application to vibration analysis of various structural elements will be presented. The hybrid DFE method is a fusion of the Galerkin weighted residual formulation and the so-called ‘exact’ Dynamic Stiffness Matrix (DSM) method, where the basis functions of approximation space are assumed to be the closed form solutions of the differential equations governing uncoupled vibrations of the system. The use of resulting (dynamic) trigonometric interpolation (shape) functions leads to a frequency dependent stiffness matrix, representing both mass and stiffness properties of the element. Assembly of the element matrices and the application of the boundary conditions then leads to a frequency dependent nonlinear eigenproblem. A Wittrick-Williams (W-W) algorithm, based on a Sturm sequence root counting technique, is then used to extract the system natural frequencies and modes. The DFE formulation, developed by the presenter in mid-nineties, was originally applied to the free vibration analysis of rotating (i.e., centrifugally stiffened) beams. Incorporating different accelerations, due to the presence of gyroscopic, or Coriolis forces, has been possible considering the fact that the resulting stiffness matrix, in this case, is Hermitian. It has been demonstrated that the DFE can be advantageously used when the multiple and/or higher modes of vibrations have to be evaluated. The DFE formulation was then applied to the free vibration analysis of (geometrically) coupled bending-torsion beam-structures, without and with warping, and was later further extended to triply coupled bending-bending-torsion vibration of centrifugally stiffened, nonuniform beams and blades. The effects of variable geometric parameters were taken into account by introducing the so-called ‘deviator terms”, leading to a Refined formulation (RDFE), which results in very high convergence rates; it can be justifiably called a “Mesh Reduction Method (MRM)”. Coupled extension-torsion vibration analysis of such structural elements as helical springs, braided/twisted wire ropes and cables were also investigated. The same procedure is equally applicable to the dynamic analysis of flexible, Circumferentially Uniform Stiffness (CUS), laminated composite box beams and tubes, exhibiting materially coupled extension-torsion behavior. The bending-extension vibrations of both straight and curved symmetric/asymmetric sandwich beams have also been investigated, where the face layers follow the Rayleigh beam assumptions, while the core is governed by Timoshenko beam theory. The first four natural frequencies of an asymmetric soft-core sandwich beam, obtained using a single-element DFE model, were found to match with ‘exact’ Dynamic Stiffness Matrix (DSM) data; a Quasi-Exact (QE-DFE) method. The DFE has also been applied to the vibration and aeroelastic analysis of intact and defective laminated composite wing configurations, exhibiting both material and geometric bending-torsion couplings. The effects of single and multiple crack and delamination defects on the vibration response of sandwich/composite and various prestressed beam configurations, subjected to combined axial load and end moments, have also been investigated. In all case studies, the comparison between the DFE, exact DSM and FEM results, and those available in literature has validated the proposed formulation and confirmed its practical applicability and general superiority over the conventional FEM. Finally, the preliminary results for the Dynamic Finite Element (DFE) formulation, and its application to the free vibration analysis of isotropic thin (Kirchhoff) rectangular plate configurations are promising. Further research is presently underway to extend the DFE formulation to the dynamic/stability analysis of general (i.e., non-rectangular) and multilayer plates, as well as thick and anisotropic plate/shell elements.

Martine Davy,
Area Sales Manager,
Brüel & Kjær, Denmark

- June 2016 – Area Sales Manager at Brüel & Kjær, Denmark
- 2011 – 2016 Regional Export Manager at Dantec Dynamics, Denmark
- 2009 – 2011 Field worker and Team leader for Geophysical surveys at COWI, Denmark
- 2006 – 2009 MSc. Mech. at Ecole Centrale Nantes, France


Reflex Acoustic Camera for NVH Measurements Svend Gade, Bernard Ginn, Jesper Gomes, Jørgen Hald
 Brüel & Kjær Sound & Vibration Measurements A/S, Skodsborgvej 307,
DK-2850 Nærum, Denmark (E-mail: sgade@bksv.com)

Together with a hand held sector wheel array, the PULSE Reflex Array Analysis forms the PULSE Reflex Acoustic Camera. It is a complete system for real-time noise source identification (NSI) used for both stationary and non‐stationary measurements. It is eminently suitable for investigating moving and transient noise sources. The acoustic camera is a versatile tool designed for use in the automotive and aerospace industries, but has applications in many other industrial environments. PULSE Reflex Acoustic Camera is equally suited to NSI troubleshooting on powertrains; buzz, squeak, and rattle (BSR) detection in vehicle cabins; and high‐frequency leak detection.

Thomas Eutebach,

Our speaker is Diplom Ingenieur Thomas Eutebach, born 1971 in Cologne (Germany).
He has more than 15 years automotive engineering experience: he started at the Formula1 team of Toyota in Germany, worked for Ford Motor Company in Australia. Nearly 10 years ago he joined a supplier, Sika Automotive in Switzerland. Sika Automotive is a global supplier providing acoustic solutions. Today he is the Head of Engineering Europe leading a team of 50+ engineers and coordinator of global engineering activities of Sika Automotive. In this position he is responsible for all baffle and reinforcer projects in Europe as well as working on new solutions for the future.


Options for noise reduction in car bodies

Todays, car buyers become more and more demanding: design, safety, fuel economy and NVH. At the beginning the typical noise issues in a car are categorized - and based on the defined categories options of noise reduction will be shown. Products types will be described in general: dampers, absorbers, reinforcers/isolators, barriers. For all treatments their technical mechanism is described and the related measurement method summarized. With this approach the presentation will give an overview of todays typical treatments for noise issues. With this a guidance is given to give a first answer to the question: how do I improve the NVH behavior of a car?

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