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Ali Asghar Atai,Davood Lak 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1
In this work, the effect of electric potential on the mechanical (Stresses, strains, displacement) and electrical (electrical displacementand intensity) response of a Functionally graded piezoelectric (FGP) hollow sphere is analytically investigated. The sphere is under theaction of internal/external pressure and temperature gradient as well. The inhomogeneity is based on power law in radial direction. Theanalysis is done in two parts: elastic response and plastic response, using Tresca yield criterion. It is shown by illustrative example thatunder internal pressure and assumed model parameters, the commencement of plastic region is from outside surface towards inside in theplastic zone is extended with the increase of electric potential. Interestingly, radial stress and displacement have an extreme not on theboundaries, but on the inside.
Ali Asghar Atai,Mohammad Hassan Naei,Reza Eghtefari 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.11
Snap-through is an instability phenomenon that occurs in arch and dome-shaped structures, wherein the structure has to move from a stable equilibrium state through an unstable path into another stable equilibrated configuration in a jumping action. In this study, a linear elastic isotropic low arch is considered as a structure with power-law variable thickness. The phenomenon is investigated by considering the equation of the deflection for the variable thickness arch, solving it with an elegant analytical technique, and finding the snap-through critical load from an extreme condition. The effect of power-law exponent and geometry of the arch centerline on critical load is investigated and the constant thickness case and a very rare case of power-law thickness variation found in literature are considered for verification.
Ali Asghar Atai,Mohammad Hassan Naei,Shabnam Rahrovan 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.6
Thin shallow arches may become unstable under transverse loading if the built-up internal compressive forces reach a limiting value beyond which the structure undergoes a sudden large displacement towards a new stable configuration. This phenomenon could be both desirable (in toggle switches) and disastrous (collapse of a dome or truss). Hence, the so-called snap- or limit-load analysis becomes important as to which factors influence it to give guidelines in designing structures to behave favorably. By the introduction of functionally graded materials (FGMs) in recent years, and incorporating them into this phenomenon, interesting results can be obtained which can give structures with favorable instability properties. In this work, a thin shallow arch with a modulus that can be varied along the thickness or the arch length or both is considered. Based on the governing equations of the deflected arch, the snap load is obtained in a mixed analytical-numerical approach and a parameter study of the critical load is carried out. Several verifying and interesting examples are presented.
Application of impulse damper in control of a chaotic friction-induced vibration
Mansour Ataei,Ali Asghar Atai,Sajjad Mirjavadi,Mohammad Sahebnasagh,Mansour Nikkhah-Bahrami 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.2
Friction-induced vibration is an important phenomenon with adverse effects on many dynamic systems involving friction. In this study,a very simple and well-known one-dimensional friction-induced dynamic system is considered in which the novel PZT stack impulse damper is incorporated into the system. It has been shown that by appropriately tuning the damping parameters, the chaotic behavior is removed quickly and efficiently. It has also been demonstrated that the system is sensitive to parameter change, and minimal modification of these parameters can revert the chaotic or periodic motion.