Autor: Mohammadi, A. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Effect of high electrostatic actuation on thermoelastic damping in thin rectangular microplate resonators
Autorzy:: Mohammadi, A. K.
Ali, N. A.
Powiązania:: https://bibliotekanauki.pl/articles/280595.pdf
Data publikacji:: 2015
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:: microplate resonator
thermoelastic damping
high polarization voltage
Opis:: In this paper, a micro resonator is modeled as a thin rectangular microplate with thermoelastic damping that is actuated electrostatically. Large static deformation due to high polarization voltage is considered, and vibration of microplate occurs around the static de- flection. Due to the effect of thermoelastic damping, the frequency of vibration is a complex value that is used to determine the quality factor of thermoelastic damping. Also, the pull-in voltage is considered because nonlinear properties are more appeared when approaching the polarization voltage to the pull-in voltage.
Źródło:: Journal of Theoretical and Applied Mechanics; 2015, 53, 2; 317-329
1429-2955
Pojawia się w:: Journal of Theoretical and Applied Mechanics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Numerical and experimental study of the mechanical response of aluminum foams under compressive loading using CT data
Autorzy:: Mohammadi Nasrabadi, A. A.
Hedayati, R.
Sadighi, M.
Powiązania:: https://bibliotekanauki.pl/articles/281633.pdf
Data publikacji:: 2016
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:: metal foam
image processing
compression test
finite element method
CT scan
Opis:: Metal foams are relatively novel materials that due to excellent mechanical, thermal, and insulation properties have found wide usage in different engineering applications such as energy absorbers, bone substitute implants, sandwich structure cores, etc. In common numerical studies, the mechanical properties of foams are usually introduced to FE models by considering homogenized uniform properties in different parts of a foamy structure. However, in highly irregular foams, due to complex micro-geometry, considering a uniform mechanical property for all portions of the foam leads to inaccurate results. Modeling the micro-architecture of foams enables better following of the mechanisms acting in micro-scale which would lead to more accurate numerical predictions. In this study, static mechanical behavior of several closed-cell foam samples has been simulated and validated against experimental results. The samples were first imaged using a multi-slice CT-Scan device. Subsequently, experimental compression tests were carried out on the samples using a uniaxial compression testing machine. The CT data were then used for creating micro-scale 3D models of the samples. According to the darkness or brightness of the CT images, different densities were assigned to different parts of the micro-scale FE models of the foam samples. Depending on density of the material at a point, the elastic modulus was considered for it. Three different formulas were considered in different simulations for relating the local elastic modulus of the foam material to density of the foam material at that point. ANSYS implicit solver was used for the simulations. Finally, the results of the FE models based on the three formulas were compared to each other and to the experimental results to show the best formula for modeling the closed-cell foams.
Źródło:: Journal of Theoretical and Applied Mechanics; 2016, 54, 4; 1357-1368
1429-2955
Pojawia się w:: Journal of Theoretical and Applied Mechanics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: The combined heat transfer of radiation and mixed convection analysis in a lid-driven trapezoidal cavity
Autorzy:: Mohammadi, M.
Gandjalikhan Nassab, S. A.
Powiązania:: https://bibliotekanauki.pl/articles/279609.pdf
Data publikacji:: 2015
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:: mixed convection
radiation
lid-driven trapezoidal cavity
Opis:: In this paper, the effect of radiation heat transfer on mixed convection in a lid-driven trapezoidal cavity is studied numerically. The governing equations of mixed convection are solved based on the SIMPLE algorithm and the solution of the radiative transfer equation inside the participating medium is carried out using the discrete ordinates method, simultaneously. To study the heat transfer and flow characteristics, sensitivity analysis is carried out based on the two parameters including the optical thickness and radiation-conduction parameter. Several interesting results are obtained such as sweep behavior on the isotherms, streamlines and convective Nusselt number with optical thicknesses.
Źródło:: Journal of Theoretical and Applied Mechanics; 2015, 53, 3; 643-652
1429-2955
Pojawia się w:: Journal of Theoretical and Applied Mechanics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Effect of the multiple damages and temperature changes on the natural frequency
Autorzy:: Mohammadi Esfarjani, S.
Salehi, M.
Ghassemi, A.
Powiązania:: https://bibliotekanauki.pl/articles/279351.pdf
Data publikacji:: 2017
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:: structural health monitoring
damage detection
vibration response
temperature
natural frequency
Opis:: Damage detection based on structural dynamic characteristics, such as natural frequencies and mode shapes, is an important area of research. Obtaining accurate structural dynamic characteristics is perhaps the most challenging aspect. In particular, changes in environmental temperature due to seasonal weather or radiation from sunshine leads to changes in the dynamic characteristics of structures. An important conclusion is that changes in the dynamic characteristics of a structure due to damage may be smaller than changes in the dynamic characteristics due to variations in temperature. Also, damage can affect the frequency response. This is the first study of evaluation of the effect of changes in temperature and multiple damages on natural frequency at the same time. In this paper, the simultaneous effect of the multiple defects and temperature on the natural frequencies of 6063 aluminum alloy beam are assessed numerically. ABAQUS finite element software is used for the numerical analysis. The present paper aims to evaluate the temperature effect and multiple damages on vibration responses. The variations in the frequency have been analysed in simulation by using an aluminum specimen and obtaining impedance signatures at temperatures ranging from −200◦C to 204◦C. The results show that an increase in temperature leads to a decrease in structural frequency, and that a decrease in temperature leads to an increase in structural frequency. The evaluation of the effect of multiple defects on natural frequency shows that when damages are created in the structure, there is a significant decrease in the natural frequency responses of the 6063 aluminum alloy beam. The results show that damage causes a decrease in the natural frequency of the structure. This study highlights the importance of applying simulation methods to the evaluation of the effect of changes in environmental temperature and multiple damages on the dynamic characteristics such as natural frequencies and mode shapes, especially at the same time.
Źródło:: Journal of Theoretical and Applied Mechanics; 2017, 55, 3; 813-822
1429-2955
Pojawia się w:: Journal of Theoretical and Applied Mechanics
Dostawca treści:: Biblioteka Nauki

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