عنوان مقاله [English]
Time-dependent deformation and critical load of viscoelastic thick plates were evaluated in the present study. The ordinary finite
strip method was used with trigonometric functions in longitudinal direction and polynomial functions in transverse direction.The stiffness and geometric matrices were calculated based on virtual work principle and the finite strip formulations were constructed. The material properties were considered to be linear viscoelastic in the form of Prony series. In addition, the time discretization method was used to evaluate the time integral appeared in viscoelastic formulation. Maximum deflection of viscoelastic plates during the time of loading was calculated and the effect of plate thickness was considered on viscoelastic behavior. The results show that deformation of viscoelastic materials increases by the lower rate as the time of loading increases. The maximum deflections of viscoelastic plate in the first time of loading were compared with those of elastic deformation of plate, and the accuracy of results was evaluated. The maximum deflections of plates were calculated by present method with various time steps to assess the integration error induced in viscoelastic integral. The results show that using small time step, the results obtained from discretization method converge to each other. In addition, the results show that deformation of viscoelastic materials increases by the lower rate as the time of loading increases. Also, the buckling factor of was increased by increasing the plate thickness, whilst it contracts with thin plates in which was independent of plate thickness. Effect of unloading on viscoelastic response of thick plates was studied using the presented method. The results show that viscoelastic plates recover its original state when the time tends to infinity once the applied load was removed. The results show that HSDT predicts the plate deformation more than FSDT and classical plate theory for all of the time of loading and this difference increases by increasing in plate thickness.