عنوان مقاله [English]
In this paper, the optimum values of stiffness coefficients of elastomer engine for EF7 engine have been determined. For this purpose, at first, a six_ degree_ freedom model of engine has been considered. This engine includes three engine mounts named: hydraulic engine mount, gear box engine mount, and torque engine mount. Using Lagrange method, the equations of motion have been derived and the stiffness matrix and mass matrix of the system have been determined. Then, the torque roll axes of the engine considering the output torque along the crank shaft have been determined. Decoupling the vibrational modes along this axes causing the best values of stiffness coefficient have been calculated. According to some constrains in design and manufacturing of the engine and engine mount position, the complete decoupling of vibrational modes is impossible; the optimization methods have been used for maximum decoupling of modes. So, by defining a relation named distribution of kinetic energy of modes, the percentage of decoupling the vibrational modes has been calculated. Then, four strategies for the optimization of stiffness coefficient of engine mounts, considering the percent of decoupling of modes, have been defined. A sensitive analysis has been done to determine the effective stiffness coefficient in each strategy. Using MODEFRONTIER software, which is adaptable with the MATLAB software, and is based on genetic algorithm method, the optimum values of effective stiffness coefficient for engine mount have been calculated. Then, the frequency response function of the center of mass for engine using these evaluated stiffness coefficients have been plotted and compared with the current values.By comparison of these graphs, finally, the best values for the stiffness coefficient have been selected. The results show that using the new optimum values of stiffness of engine mount, the displacement of mass center for engine and transferred forces have been reduced, and vibrational behavior of engine has been improved properly.