Journal of Mechanical Science and Technology 31 (4) (2017) 1773~1787 www.springerlink.com/content/1738-494x(Print)/1976-3824(Online) DOI 10.1007/s12206-017-0325-8 Thermo-electro-mechanical buckling analysis of cylindrical nanoshell on the basis of modified couple stress theory † Fahimeh Mehralian 1 and Yaghoub Tadi Beni 2,* 1 Mechanical Engineering Department, Shahrekord University, Shahrekord, Iran 2 Faculty of Engineering, Shahrekord University, Shahrekord, Iran (Manuscript Received February 28, 2016; Revised November 7, 2016; Accepted December 14, 2016) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract In the present study, the buckling of piezoelectric cylindrical nanoshell subjected to an axial compression, an applied voltage and uni- form temperature change resting on Winkler-Pasternak foundation is studied analytically. The modified couple stress theory combined with the geometrical nonlinear shell model is employed to derive the equilibrium equations and boundary conditions. The numerical results are proposed for the buckling of simply supported cylindrical nanoshell using the Navier-type solution. Thus, the effects of differ- ent parameters such as dimensionless length scale parameter, length and thickness to radius ratio, temperature change, external electric voltage and Winkler and Pasternak foundation stiffness on critical buckling load are illustrated. It is shown that increase in dimensionless length scale parameter results in increasing critical buckling load and even intensifying the influence of other parameters, such as length and thickness, on critical buckling load. Keywords: Modified couple stress theory; Shell model; Size effect; Thermo-electro-mechanical buckling ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction Today, the advance of smart structures thanks the invention of piezoelectric nanostrutures due to its promising mechanical, thermal and electrical properties. ZnO piezoelectric nanowires was first reported by Pan et al. and opened a new field of re- search in various fields of nonamechanics and nanoelectronics [1]. The superior properties of piezoelectric nanostructures lead to its extensive usages in many nanodevices like nanore- sonators, nanogenerators, light-emitting diodes, and chemical sensors [2-4]. Indeed, the coupled electro-mechanical proper- ties of piezoelectric materials, generating electrical charge under external mechanical deformation, and reversely, de- forming under electrical charge, permits them to be used as sensors and actuators [5, 6]. Therefore, due to the various practical applications and further development of piezoelec- tric-based nanodevices, the study of their behavior, such as their deformation under different loads, is of both theoretical significance and practical value. Hence, the buckling behavior of the piezoelectric nanostucturs has attracted the attention of many researchers. For example, the axial buckling of piezo- electric nanowires under distributed transverse loading on the basis of Timoshenko beam theory and considering surface effect was investigated by Samaei et al. and the dependency of critical electric potential of buckling on both surface stresses and piezoelectricity was shown [7]. Yan et al. studied the vi- bration and buckling of piezoelectric nanoplate affected the surface effects, using the modified Kirchhoff plate model and the sensitivity of the critical electric voltage of buckling to the plate thickness and aspect ratio was discussed [8]. Arani et al. studied the thermo-mechanical-torsional and axial buckling of double-walled boron nitride nanotube using the nonlocal elas- ticity and piezoelasticity theories on Winkler-Pasternak me- dium and the effects of some parameters such as nonlocal parameter, temperature change, piezoelectric and dielectric constants on the critical buckling load were shown [9, 10]. In order to examine the piezoelectric nanostructures more precisely, an appropriate approach should be used. Both theo- retical and experimental approaches are utilized to investigate their behaviors. However, with regard to the difficulties of experiments at submicron size, the theoretical analysis, includ- ing atomistic simulations and continuum mechanics, are be- coming more important. As the molecular dynamic simulation is complicated and time consuming for large scale systems [11, 12]; thus, these limitations inspired researchers to use the con- tinuum based models which are computationally more effi- cient [13-15]. On the other hand, based on the experimental observation, the size effect in small scale structures due to impurities, crystal lattice mismatch and nano cracks plays an * Corresponding author. Tel.: +98 38 32324438, Fax.: +98 38 32324438 E-mail address: tadi@eng.sku.ac.ir † Recommended by Associate Editor Heung Soo Shin © KSME & Springer 2017