Vibration analysis of non-uniform tapered beams with nonlinear FGM properties

Alireza Keshmiri,Nan Wu,Quan Wang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11

This paper presents the free vibration analysis of a non-uniform cone beam with nonlinearly varying axial functionally graded material (FGM) properties. Based on the Adomian decomposition method and a proposed modified mathematical procedure, the vibration mode shapes and natural frequencies of a nonlinearly tapered FGM beam are analytically derived. Several vibration analyses for uniform and non-uniform FGM structures are presented and the results are compared with the existing ones to prove the effectiveness and accuracy of the proposed methodology. Additionally, vibration analysis of exponentially and trigonometrically tapered beams with nonlinearly axial varying FGM properties considering different geometry and material taper ratios was studied and presented. Based on this analytical model, ideal structural design can be efficiently achieved for many engineering applications, such as stability enhancement and energy harvesting.

Visual Servoing Using an Optimized Trajectory Planning Technique for a 4 DOFs Robotic Manipulator

Mohammad Keshmiri,Wen-Fang Xie,Ahmad Ghasemi 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3

Although visual servoing has been considered as a solution to increase dexterity and intelligence ofthe robotic systems specially in unstructured environments, some prominent deficiencies are preventing it frompractical employment. Trajectory planning is a solution to overcome the shortcomings of visual servoing andmakes it practical for industrial applications. In this paper, a new trajectory planning technique is developed toperform image-based visual servoing (IBVS) tasks for a 4 DOFs robotic manipulator system. In this method, thecamera’s velocity screw is parameterized using time-based profiles. The parameters of the velocity profile are thendetermined such that the velocity profile takes the robot to its desired position. This is done by minimizing theerrors between the initial and desired features. A depth estimation technique is proposed to provide the trajectoryplanning algorithm with an accurate initial depth. This algorithm is tested and validated via the experiment on a4 DOFs Denso robot in an eye-in-hand configuration. Experimental results demonstrate that the proposed methodprovides with a reliable visual servoing algorithm by overcoming the IBVS drawbacks such as surpassing the systemlimits and causing instability of the system in fulfilling the tasks which require a 180o rotation of the camera aboutits center.

A novel approach towards controlled growth of metal-organic framework ZIF-8 thin film on steel with excellent corrosion protection

Navid Keshmiri,Parisa Najmi,Mohammad Ramezanzadeh,Bahram Ramezanzadeh 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.117 No.-

The control over the in-situ growth of metal-organic framework (MOF) thin films on a metal surface isstill challenging. As an interesting subdivision of MOFs, the zeolite imidazole framework (ZIF) has beenthe research hotspot in various research areas, from separation to sensing in the form of nanocrystals,thin films, and membranes. Continuous thin films of ZIF crystals need binding sites for desirable heterogeneousnucleation. This study proposed a novel and facile surface treatment at room temperature basedon zinc-phosphate conversion coating to provide nucleation sites for the intergrown ZIF-8 crystals onmild steel as a corrosion protective layer. The successful growth of ZIF-8 crystals on the modified carbonsteel was characterized using FT-IR, Raman, GIXRD, XPS, and FE-SEM tests. This thin layer led to a superprotective barrier film for up to 10 days in a harsh corrosive environment of salt spray. On the other hand,EIS reported almost 100 kO.cm2 total resistance after 72 h immersion in 3.5% wt. NaCl solution which is agreat achievement compared to conventional primer coatings. The total resistance of an epoxy coatingwith the proposed primer was improved by 135% when there was a deep mechanical scratch in the coating. The ZIF-8 thin film could significantly improve the epoxy coating’s anti-corrosion ability. The goodnews is that this concept is transferable to other ZIF-based MOFs.

Natural frequency extraction of a beam-moving mass system with periodic passages using its pseudo-natural frequencies

Esmaeil Ghorbani,Mehdi Keshmiri 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7

Wind turbines, helicopters, and turbo-machineries’ rotary motion, along with a variety of nonlinear structures linearized with their periodic limit cycles, may all contain time-periodic terms in their equations of motion even if the equations remain linear. The purpose of this study is to model these systems into a beam-moving mass system. Natural frequencies of the beam are calculated using past work in which pseudo-natural frequencies of a beam-moving mass system were extracted, followed by the homotopy perturbation method. The findings of this study are valuable to the industry, and they decrease error margin in resonance range assessment. This approach indicates that for beam-moving mass systems, extraction of natural frequencies that ignore the moving mass effect can lead to inaccurate results, whereas only a limited amount of physical data are needed obtain accurate calculations. Furthermore, this study used homotopy perturbation for operational modal analysis purposes and not for solving nonlinear equations.

Identification of pseudo-natural frequencies in a beam-moving mass system with periodic passages

Esmaeil Ghorbani,Mehdi Keshmiri 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.7

The response of a linear time-invariant (LTI) system to harmonic input generates a harmonic output with constant frequency but varyingmagnitude and phase. Many structural dynamic systems have been modeled as linear time-varying periodic (LTP) systems. Previousstudies have reported that the response of an LTP system to an exponential input establishes an infinite number of frequencies. Thesestudies have presented a new, exponentially modulated periodic signal space and a corresponding harmonic transfer function as usefultools in the operational modal analysis of LTP systems. In consideration of this new approach, this study mainly identifies the frequenciesof a typical LTP system, such as a beam that is subject to the intermittent passage of moving masses. Upon obtaining the harmonic transferfunction for the beam-moving mass system, conventional frequency domain methods for LTI systems are used to derive the frequencycharacteristics of the LTP system from the system response. These methods include the peak-picking method. As expected in anLTP system, an infinite number of pseudo-natural frequencies resonate in the beam-moving mass system.

Active structural acoustic control of a smart cylindrical shell using a virtual microphone

Loghmani, Ali,Danesh, Mohammad,Kwak, Moon K,Keshmiri, Mehdi Institute of Physics Publishing 2016 Smart materials & structures Vol.25 No.4

<P>This paper investigates the active structural acoustic control of sound radiated from a smart cylindrical shell. The cylinder is equipped with piezoelectric sensors and actuators to estimate and control the sound pressure that radiates from the smart shell. This estimated pressure is referred to as a virtual microphone, and it can be used in control systems instead of actual microphones to attenuate noise due to structural vibrations. To this end, the dynamic model for the smart cylinder is derived using the extended Hamilton’s principle, the Sanders shell theory and the assumed mode method. The simplified Kirchhoff–Helmholtz integral estimates the far-field sound pressure radiating from the baffled cylindrical shell. A modified higher harmonic controller that can cope with a harmonic disturbance is designed and experimentally evaluated. The experimental tests were carried out on a baffled cylindrical aluminum shell in an anechoic chamber. The frequency response for the theoretical virtual microphone and the experimental actual microphone are in good agreement with each other, and the results show the effectiveness of the designed virtual microphone and controller in attenuating the radiated sound.</P>

Design of a virtual acoustic sensor for estimating the radiated sound of cylindrical shells

A. Loghmani,M. Danesh,M.K. Kwak,M. Keshmiri 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10

In this paper, a virtual acoustic sensor is designed and evaluated experimentally to be used instead of microphones in active noise control of vibrating cylindrical shells. Dynamic motion equations of a cylindrical shell along with the effect of bonded piezoelectric patches are derived based on the Hamilton’s principle and Rayleigh-Ritz method. The Sanders shell theory is used to relate the strains to the displacements of the cylinder. Modal structural acoustic sensing technique estimates the far-field radiated sound pressure of the cylinder. Experimental frequency response function (FRF) of the actual microphone at various locations are obtained and compared to that of the virtual one. The theoretical estimated sound pressure is in good agreement with the experimental results.