جستجوی مقالات مرتبط با کلیدواژه « mechanical vibration » در نشریات گروه « مکانیک »

Material properties of a structure can be estimated using destructive and non-destructive methods. Experimental vibration data of the structure can be used to conduct a non-destructive procedure to identify material properties. In this research, experimental modal parameters obtained from modal testing are utilized to estimate the Young’s modulus and the density of different components of a car seat frame. To do so, the finite element model of the structure is constructed and the modal parameters are evaluated by performing modal analysis. The obtained modal parameters are then used in an inverse identification procedure and compared with the experimental counterparts to estimate the material properties of the structure in an optimization framework. The objective function is defined by comparing the numerical and experimental natural frequencies where the material properties are considered as the design parameters of the optimization process. To find the optimum design parameters, the response surface optimization technique is employed to alleviate the computational costs of direct optimization. To this end, the design of experiment method using the Box-Behnken design is conducted to create the design points. The kriging method is then utilized to construct the response surfaces. Finally, the nonlinear programming quadratic Lagrangian method is employed to evaluate the best estimations for the material properties using the response surface optimization method.

In this paper, the effect of the temperature change on the vibration frequency of mono-layer graphene sheet embedded in an elastic medium is studied. Using the nonlocal elasticity theory, the governing equations are derived for single-layered graphene sheets. Using Levy and Navier solutions, analytical frequency equations for single-layered graphene sheets are obtained. Using Levy solution, the frequency equation and mode shapes orthotropic rectangular nanoplate are considered for three cases of boundary conditions. The obtained results are subsequently compared with valid result reported in the literature. The effects of the small scale, temperature change, different boundary conditions, Winkler and Pasternak foundations, material properties and aspect ratios on natural frequencies are investigated. It has been shown that the non-dimensional frequency decreases with increasing temperature change. It is seen from the figure that the influence of nonlocal effect increases with decreasing of the length of nanoplate and also all results at higher length converge to the local frequency. The present analysis results can be used for the design of the next generation of nanodevices that make use of the thermal vibration proper ties of the nanoplates.