Thesis Defense - Behnam Firoozi (MSME)

Behnam Firouzi - M.Sc.

Asst.Prof. Polat Şendur – Advisor

Date: 31.12.2020

Time: 12:00

Location: This meeting will be held ONLINE. Please send an e-mail to gizem.bakir@ozyegin.edu.tr in order to participate in this defense.

Development of Novel Methodologies for the Damage Detection in Mechanical Systems

Thesis Committee:

Asst.Prof. Polat Şendur, Özyeğin University

Asst.Prof. Göktürk Poyrazoglu, Özyeğin University

Asst.Prof. Birkan Tunç, Yeditepe University

Abstract:

The present study examines the capability of various optimization algorithms and proposes novel hybrid algorithms for the more precise prediction of open-edge cracks in mechanical systems. The natural frequencies of the beam with crack are obtained by modal analysis and experimentally validated from impact testing. In the first part of the paper, the performance of novel HHO, ESDA, PFA, and HGSO algorithms from literature are evaluated to determine the location and depth of an open-edge crack for an Euler–Bernoulli beam. More specifically, the accuracy of the crack dimensions and the number of function evaluations needed for the aforementioned algorithms are compared. Subsequently, hybrid algorithms such as HHO-NM, ESDA-NM, and PF-NM are proposed for improving the results. Optimization parameters are tuned systematically using the Taguchi design of experiments (DOE) method. Simulation results show that the proposed hybrid algorithms yield much more precise results with fewer function evaluations compared to previously introduced algorithms and, therefore, have a superior crack detection capability. Amongst the hybrid algorithms, PFA-NM algorithm emerges as the best algorithm in terms of precision and the number of function evaluations. Furthermore, the statistical post hoc analysis has shown that the proposed hybrid algorithm can be considered as a high-performance algorithm, which can significantly improve the performance of algorithms.

In the second part of this thesis, we study the static deflection, natural frequency, primary resonance of electrostatically actuated cracked gas sensor. Besides, a novel hybrid metaheuristic algorithm is proposed to detect the location and depth of possible cracks on the systems. The gas sensor configuration consists of a microcantilever with a rigid plate attached to its end. The nonlinear effects of the electrostatic force and fringing field are taken into account in the mathematical model. In the first part, the effect of crack on the static and dynamic pull-in instability are studied. The equations of motion are solved by the application of the perturbation method. Next, an inverse problem is formulated to predict the location and depth of the crack in the gas sensor. For that purpose, the weighted squared difference of the analytical and predicted frequency response is considered as the objective function. The location and depth of the crack in the microsystem are determined using the hybrid Harris Hawk and Nelder Mead optimization algorithms. The accuracy and efficiency of the proposed algorithm are compared with the HHO, DA, GOA, and WOA algorithms. Taguchi design of experiments method is used in order to tune the parameters of optimization algorithms systematically. It is shown that the proposed algorithm can predict the exact location and depth of the open-edge crack on an electrostatically actuated microbeam with proof mass.

Bio: 

Behnam Firouzi graduated from Kharazmi University of Tehran in Mechanical Engineering in 2016. He worked as a research assistant in a Microelectromechanical lab at Kharazmi University and accomplished several projects related to mechanical behavior Microelectromechanical systems (MEMS). After graduation, he worked in an oil refinery company as a mechanical expert. In February 2019, he joined the vibration and acoustic lab under the supervision of Dr. Polat Sendur in order to pursue his researches. In OZU vibration and acoustic lab he worked on several projects related to damage detection in mechanical systems, unbalance identification of rotary machines, design of tapered roller bearing, optimal design of microchannel heat sinks. His main research interests consist of nonlinear vibration and control, system identification, and optimization.