The free vibration behavior of two fluid-conveying vertically-aligned single-walled boron nitride nanotubes are studied in the present paper via the nonlocal strain gradient piezoelectric theory in conjunction with the first-order shear deformation shell assumption in thermal environments. It is supposed that the two adjacent boron nitride nanotubes are coupled with each other in the context of linear deformation by van der Waals interaction according to Lennard–Jones potential function. To achieve a more accurate modeling for low-scale structures, both hardening and softening effects of materials are considered in the nonlocal strain gradient approach. Themotion equations and associated boundary conditions are derived by means of Hamilton’s variational principle, then solved utilizing differential quadrature method. Numerical studies are done to reveal the effect of different boundary conditions, size scale parameters, aspect ratio, inter-tube distance, and temperature change on the variations of dimensionless eigenfrequency and critical flow velocity. Manuscript profile

Based on the third-order shear deformation theory (TSDT), this paper numerically investigates the natural frequencies and time response of three-layered annular plate with functionally graded materials (FGMs) sheet core and piezoelectric face sheets, under initial external electric voltage. The impressive material specifications of FGM core are assumed to vary continuously across the plate thickness utilizing a power law distribution. The equilibriumequations are obtained employing Hamilton’s method and then solved applying differential quadrature method (DQM) in conjunction with Newmark-β. Numerical studies are carried out to express the influences of the external electric voltage, aspect ratio, and material gradient on the variations of the natural frequencies and time response curves of FGM piezoelectric sandwich annular plate. It is precisely shown that these parameters have considerable effects on the free vibration and transient response. Manuscript profile

Today, it is common to align broken bones using external bone fixators; ease of installation and adjustability are among the advantages of unilateral external bone fixators compared to circular and horseshoe models. The present study aimed to ensure the stability and strength of the motorized unilateral external bone fixator, equipped with four motors designed in SolidWorks software. The device was simulated and analyzed using the finite element method in Ansys software. The results were as follows: Simulation of compressive, bending, and torsional forces and reliability evaluation using the finite element method in each simulated experiment. The designed device has the necessary stability, rigidity, and desirable reliability to fix the long broken bones in place, with the possibility of displacing the bone when having a lost part. Precise bone displacement is possible since the device has four independent motorized units based on the patient's needs and the instructions of a specialist to rebuild bones. Manuscript profile