Structural Engineering and Mechanics, Vol. 57, No. 1 (2016) 179-200 DOI: http://dx.doi.org/10.12989/sem.2016.57.1.179 179 Copyright © 2016 Techno-Press, Ltd. http://www.techno-press.org/?journal=sem&subpage=8 ISSN: 1225-4568 (Print), 1598-6217 (Online) An investigation into the influence of thermal loading and surface effects on mechanical characteristics of nanotubes Farzad Ebrahimi  , Gholam Reza Shaghaghi and Mahya Boreiry Mechanical Engineering Department, Faculty of Engineering, Imam Khomeini International University, Qazvin, P.O.B. 16818-34149, Iran (Received November 14, 2014, Revised December 15, 2015, Accepted December 16, 2015) Abstract. In this paper the differential transformation method (DTM) is utilized for vibration and buckling analysis of nanotubes in thermal environment while considering the coupled surface and nonlocal effects. The Eringen’s nonlocal elasticity theory takes into account the effect of small size while the Gurtin- Murdoch model is used to incorporate the surface effects (SE). The derived governing differential equations are solved by DTM which demonstrated to have high precision and computational efficiency in the vibration analysis of nanobeams. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of thermal loading, small scale and surface effects, mode number, thickness ratio and boundary conditions on the normalized natural frequencies and critical buckling loads of the nanobeams in detail. The results show that the surface effects lead to an increase in natural frequency and critical buckling load of nanotubes. It is explicitly shown that the vibration and buckling of a nanotube is significantly influenced by these effects and the influence of thermal loadings and nonlocal effects are minimal. Keywords: nanotube, surface effects; nonlocal elasticity theory; thermal effect; critical buckling load; differential transformation method 1. Introduction In recent years, nanomechanical and nano-electro-mechanical systems (NEMS) at nanoscale receive special attention from researchers. Among them nanobeams attracted more attention because of their potential usage (Eltaher et al. 2013). For difficulty of experiments at nanoscale, the mechanical behaviors of the nanostructures are usually investigated using mathematical simulations such as atomistic, atomistic-continuum mechanics and continuum mechanics approaches. Since performing atomistic and atomistic-continuum mechanics simulations in large scales experiments need much time and expenses, continuum mechanic approaches are often used (Malekzadeh et al. 2013). In the classical continuum theory the small scale effect and size dependence of material properties cannot be predicted, but in continuum approaches nonlocal effect can be simulated (Hosseini-Hashemi et al. 2013a). The nonlocal effect which first considered by Eringen expresses Corresponding author, Professor, E-mail: febrahimy@eng.ikiu.ac.ir