Harmonic analysis three frequency response with views of the number of members of the series "FFT" transformation

In this paper, a 1D dynamical model with substrate resistance was imposed with three frequencies of displacement amplitudes with two amplitudes with frequencies in the resonant region. If the external excitation is treated as a continuous periodic real function with two variables (the basic oscillation period - the first and the ratio of the frequency of the external excitation and the response of the model - the second) then we can present the final solution of the motion of the 1D model in conjugated complex form. Applying FFT algorithms with MathCAD, the treated displacement amplitudes in the frequency and time domains respect the mapping suggested by the transfer function (I.M. Miličić, 2015) and with a smaller number of order members. Computer simulations confirmed that the harmonic response of a 1D dynamic model system can be successfully modeled based on the equivalent solution which shown here.