جستجوی مقالات مرتبط با کلیدواژه « تیر ساندویچی » در نشریات گروه « مواد و متالورژی »

In this paper, the vibration suppression capabilities of magnetorheological layer in smart beams is investigated. A three-layered beam including magnetorheological elastomer layer sandwiched between two elastic layers is considered. By assuming the properties of magnetorheological layer in the pre-yield region as viscoelastic materials behavior, the governing equations of motion and the corresponding boundary conditions are derived using Hamilton’s principle. Due to field-dependent shear modulus of magnetorheological layer, the stiffness and damping properties of the smart beam can be changed by application of magnetic field. This feature is utilized to suppress the unwanted vibration of the system. The appropriate magnetic field applied over the beam is chosen through a fuzzy controller for improving the transient response. The designed fuzzy controller uses the modal displacement and velocity of the beam as its inputs. The modal parameters of the sandwich beam including the natural frequencies and mode shapes are obtained and validated with existing results. Using the Galerkin method, the temporal equation governing beam’s motion is obtained and then the vibration of smart sandwich beam is investigated using numerical simulations. The results show that the magnetorheological layer along with the designed fuzzy controller can be effectively used to suppress the unwanted vibration of the system. The qualitative and quantitative knowledge resulting from this research is expected to enable the analysis, design and synthesis of smart beams for improving the dynamic performance of smart engineering structures.

In this paper, dynamic response of simply-supported composite sandwich beam with viscoelastic and transverse flexible core is investigated, analytically. Three-layered sandwich panel theory is used to analyze the beam. Hamilton's principle is employed to obtain governing equations of motion. In this paper, GHM method is used to model the viscoelastic core of the beam. Advantage of GHM model in according to classical models is including the frequency dependent characteristic of viscoelastic materials. Modal superposition method is used to convert partial differential equations of motion to ordinary differential equations with time varying coefficients. Newmark method is applied to solve the ODE with a numerical approach. Results of the present model are validated by analytical results published in the literatures. Innovation of this paper is considering frequency dependency of material property in viscoelastic core with using GHM model and utilizing three-layered sandwich panel theory in dynamic analysis of composite sandwich beam. The article investigates the dynamic response of beam with viscoelastic core by using GHM model to illustrate advantages of the GHM model over the Kelvin-Voigt model. As well as, a parametric study is also included in this paper to investigate the effect of different parameters such as thickness and density of core and stiffness of composite sandwich beam face sheets on the beam frequency and damping rate of beam dynamic response. The obtained results show that GHM model by considering the frequency dependency behavior of viscoelastic material presents a more accurate description of dynamic response of the beam with viscoelastic core.

In this paper, the two models of Modified Gibson and “Montanini” are used to predict failure behavior of sandwich beams with aluminum foam core at high temperatures. First, the geometrical and physical properties of the two models were considered to describe failure mode of the sandwich beam. Next, the failure load diagram of the beam in terms of beam geometrical properties as well as temperature was obtained using these two models and the results were compared with available experimental data. A good agreement was observed between theoretical results and experimental data. In both models, it can be seen that the theoretical failure loads are enhanced by increasing face and core thicknesses and are reduced by increasing span length. Moreover, according to the results of the two models, the failure loads decrease with temperature rise. In the “Montanini” model, the asymmetric deformation of the beam is considered (despite the geometrical and loading symmetry), while the Gibson’s model has no justification about it. Besides, in “Montanini” model at high temperatures, the amount of experimental failure load is closer to the load of one of the modes (mode IIB). However in Gibson’s model at high temperatures, the amount of experimental load is between failure load in two modes and the failure mode cannot be clearly specified in some temperature ranges. However, one of the drawbacks of the “Montanini” model as compared with Gibson’s model, is the lack of prediction of face yield failure mode.