Latin American Journal of Solids and Structures, Volume: 12, Issue: 10, Published: 2015
• ## Uncertainty analysis of flexible rotors considering fuzzy parameters and fuzzy-random parameters Articles

Lara-Molina, Fabian Andres; Koroishi, Edson Hideki; Steffen, Valder

Abstract in English:

Abstract The components of flexible rotors are subjected to uncertainties. The main sources of uncertainties include the variation of mechanical properties. This contribution aims at analyzing the dynamics of flexible rotors under uncertain parameters modeled as fuzzy and fuzzy random variables. The uncertainty analysis encompasses the modeling of uncertain parameters and the numerical simulation of the corresponding flexible rotor model by using an approach based on fuzzy dynamic analysis. The numerical simulation is accomplished by mapping the fuzzy parameters of the deterministic flexible rotor model. Thereby, the flexible rotor is modeled by using both the Fuzzy Finite Element Method and the Fuzzy Stochastic Finite Element Method. Numerical simulations illustrate the methodology conveyed in terms of orbits and frequency response functions subject to uncertain parameters.
• ## Concrete road barriers subjected to impact loads: An overview Articles

Zain, Muhammad Fauzi Bin Mohd.; Mohammed, Hasan Jasim

Abstract in English:

Abstract Concrete barriers prevent vehicles from entering the opposite lane and going off the road. An important factor in the design of concrete barriers is impact load, which a vehicle exerts upon collision with a concrete barrier. This study suggests that a height of 813 mm, a base width of 600 mm, and a top width of 240 mm are optimum dimensions for a concrete barrier. These dimensions ensure the stability of concrete barriers during vehicle collisions. An analytical and experimental model is used to analyze the concrete barrier design. The LS-DYNA software is utilized to create the analytical models because it can effectively simulate vehicle impact on concrete barriers. Field tests are conducted with a vehicle, whereas laboratory tests are conducted with machines that simulate collisions. Full-scale tests allow the actual simulation of vehicle collisions with concrete barriers. In the vehicle tests, a collision angle of 25°, collision speeds of 100 km per hour, and a vehicle weighing more than 2 t are considered in the reviewed studies. Laboratory tests are performed to test bridge concrete barriers in static condition.
• ## Flow behavior of unsteady incompressible Newtonian fluid flow between two parallel plates via homotopy analysis method Articles

Hoshyar, H.A.; Ganji, D.D.; Borran, A.R.; Falahati, M.

Abstract in English:

Abstract An analysis has been performed to study the problem of the flow of incompressible Newtonian fluid between two parallel plates where the upper plate is impermeable and can move up or down and the lower one is fixed and has a porous surface. The governing equations for this problem are reduced to an ordinary form and is solved using Homotopy Analysis Method (HAM) and numerically by fourth order Runge-Kutta technique. Also, Velocity fields have been computed and shown graphically for various values of physical parameters. As an important outcome, HAM is able to solve a large class of nonlinear problems effectively, more easily and accurately; and thus it has been widely applicable in engineering and physics.
• ## Reflection/refraction at the interface of an elastic solid and a partially saturated porous solid containing liquid filled bound pores and a connected pore space saturated by two-phase fluid Articles

Saini, Rajesh

Abstract in English:

Abstract The phenomena of reflection and refraction of plane waves incident obliquely at a plane interface between uniform elastic solid half-space and porous solid containing liquid filled bound pores and two-phase fluid in connected pores has been analyzed. The amplitude ratios of the reflected and refracted waves to that of the incident wave are calculated as a non- singular system of linear algebraic equations. These amplitude ratios are used further to derive the expressions for the partition of incident energy among the reflected and refracted waves. Partition of incident energy among the reflected and refracted waves is studied for incidence of P and SV waves. The conservation of the energy across the interface is verified. The effect of gas saturation, wave frequency, capillary pressure and bound liquid film on the amplitude ratios and energy partitions are studied in the numerical example.
• ## DQ thermal buckling analysis of embedded curved carbon nanotubes based on nonlocal elasticity theory Articles

Setoodeh, AliReza; Derahaki, Morteza; Bavi, Navid

Abstract in English:

Abstract To investigate the thermal buckling of curved carbon nanotubes (CCNTs) embedded in an elastic medium, nonlocal elasticity theory is employed in combination with the theory of thin curved beams. Differential quadrature (DQ) method is implemented to discretize the resulted governing equations. Solving these equations enables us to estimate the critical temperature and the critical axial buckling load for CCNTs surrounded by an elastic medium and under the effect of a uniform temperature change. The elastic interaction between the nanotube and its surrounding medium is modeled as a Winkler-Pasternak elastic foundation. The fast convergence of the DQ method is demonstrated and also its accuracy is verified by comparing the results with available solutions in the literature. The effects of various parameters such as different boundary conditions, nonlocal parameter, Winkler and Pasternak elastic modulus, temperature and nanotube curvature on the critical buckling temperature and load are successfully studied. The results reveal that the critical buckling load depends significantly on the curvature of the CCNT.
• ## Large amplitude free vibration of micro/nano beams based on nonlocal thermal elasticity theory Articles

Wang, Yong-Gang; Song, Hui-Fang; Lin, Wen-Hui; Wang, Jin-Ke

Abstract in English:

Abstract This paper is concerned with the nonlinear free vibration of a heated micro/nano beam modeled after the nonlocal continuum elasticity theory and Euler-Bernoulli beam theory. The governing partial differential equations are derived from the Hamilton variational principle and von Kármán geometric nonlinearity, in which the effects of the nonlocality and ambient temperature are inclusive. These equations are converted into ordinary forms by employing the Kantorovich method. The solutions of nonlinear free vibration are then sought through the use of shooting method in spatial domain. Numerical results show that the proposed treatment provides excellent accuracy and convergence characteristics. The influences of the aspect ratio, nonlocal parameter and temperature rise parameter on the dimensionless radian frequency are carefully investigated. It is concluded that the nonlocal and temperature rise parameters lead to reductions of the nonlinear vibration frequency, while the influence of the nonlocal effect decreases with an increase in the aspect ratio.
• ## Dispersion of Love wave in an isotropic layer sandwiched between orthotropic and prestressed inhomogeneous half-spaces Articles

Kakar, Rajneesh

Abstract in English:

Abstract An in-depth study has been carried out for the dispersion of Love waves in an isotropic elastic layer sandwiched between orthotropic and prestressed inhomogeneous elastic half-spaces. The inhomogeneities in density and rigidity of the lower half-space are space dependent and an arbitrary function of depth. Simple mathematical techniques are used to obtain dispersion relation for Love wave propagation in an isotropic layer. An extensive analysis is carried out through numerical computation to explore the effect of inhomogeneity and initial stress the lower half on the phase velocity of the Love waves. The numerical analysis of dispersion equation manifests that the phase velocity of the Love wave increases with the increase of stress parameter. The results further indicate that the inhomogeneity of the half space affect the wave velocity significantly. These results can be useful to study geophysical prospecting and understanding the cause and estimation of damage due to earthquakes.
• ## Experimental and numerical investigation of lattice-walled cylindrical shell under low axial impact velocities Articles

Hatami, H.; Nouri, M. Damghani

Abstract in English:

Abstract This research was an experimental and numerical investigation of the cylindrical expanded Sheets under impact loading. Two types of absorbers with different cell angles were examined (i.e. α = 0 and α = 90). The experiments were performed using the drop hammer setup, and the numerical simulations were conducted by ABAQUS. In this study, the type of collapse, force-displacement diagrams, the crushing length, and the absorbed energy were investigated. The experimental and numerical results were compared, and it was observed that they were in good agreement. Results showed that the absorbers with the cell angle of α = 0 had a symmetric collapse and a high energy absorption capacity. Also, various heights of fall were considered for the impact mass to examine the type of collapse in the models. The crushing amounts of the models were also compared in different heights. Multi-walled expanded metal tubes were studied, and the effect of being multi-walled in collapse was examined.