جستجوی مقالات مرتبط با کلیدواژه "تحریک پایه" در نشریات گروه "فنی و مهندسی"

The purpose of the present research is to investigate the damage analysis mechanisms of the Dam-Reservoir-Foundation system using the Finite Element Method (FEM). The study focuses on the Koyna dam-reservoir-foundation system, which is a two-dimensional model that has been subjected to the horizontal and vertical components of ground acceleration in the Koyna earthquake using ABAQUS software and the Concrete Damage Plasticity (CDP) model. The comparison of models in linear and linear analysis shows that considering the bottom of the foundation for applying the load increases the seismic damage compared to applying the bottom of the dam. The results indicate that applying foundation excitation at the contact surface of the dam-foundation in the condition of foundation without mass, as well as applying foundation excitation at the level of the rock foundation in the condition of massed foundation can lead to a more accurate prediction of the response of the structure during an earthquake. However, the level of seismic damage in the dam is greatly affected by how the base excitation is applied and the mechanism of the modeling Dam-Reservoir-Foundation system. Therefore, it is crucial to consider the correct application of base excitation and the modeling mechanism while analyzing the damage analysis of the Dam-Reservoir-Foundation system.

In this study, global sensitivity analysis of nanomachining parameters by using a dynamic scanning thermal microscope is investigated. Thus, the cross-section of a nanomachined sample by sweeping with different tip radius on the vibrational response of the system at different speeds and temperatures are simulated. It is shown that by increasing temperature, the depth of nanomachining decreases, and by increasing tip radius, the depth of nanomachining increases. Also, it is declared that the final quality of the nanomachining decreases by increasing speed traveling. Then, the Sobol indices for the mean depth and surface finish of the nanomachined sample are studied. It is shown that traveling speed is not affected the mean depth of nanomachining in its physical range and so the effects of the probe traveling speed and interaction between parameters are negligible. It is declared that the effect of interaction between temperature, traveling speed and tip radius is important on the final surface finish of the sample, however, the most important parameter is still the temperature difference. Then, the total indices and Sobol indices are compared. It is stated that the total indices are significantly higher than the Sobol indices for the final surface of ​​the nanomachining. For the mean depth of the nanomachining the total indices and Sobol indices for temperature and tip radius are approximately equal and the effect of probe traveling speed is negligible.

In this article the vibration analysis of a viscoelastic cantilever beam with piezoelectric layers under aeroelastic force and base excitation is investigated. The beam viscoelastic material is assumed to obey the Kelvin-Voight model. Also the piezoelectric layers are located at the top and bottom beam surfaces with series connections. The aeroelastic force based on piston theory is considered to act as an external force on the beam and also the base excitation is assumed to be random. In this research the cantilever beam with two piezoelectric layers are considered as a mechanism to harvest the bending vibration energy. First, the Galerkin method is used to convert the governing partial differential equation into a set of ordinary differential equations. Then the resulted nonlinear ordinary differential equation coupled with electrical circuit equation of piezoelectric layer are solved numerically by Rung-Kutta method. Finally, by analyzing the response of the governing equations, the influence of the system parameters on the vibration behavior of beam and output voltage are discussed. Results show that the increase of fluid velocity increases vibrational energy system which leads to increase of both vibration amplitude and output voltage. In addition, it was shown that structural damping has a significant impact on the output voltage.