Fourier Method

a0 =  Integral(2*sweep_frequency*fx)

a1 =  Integral(2*sweep_frequency*cos(2*pi*sweep_frequency*time)*fx)

b1 =  Integral(2*sweep_frequency*sin(2*pi*sweep_frequency*time)*fx)

loss_angle = atan(a1/b1)

f_ampl = a1 /sin(loss_angle)

f_min = a0/2 - f_ampl

f_max = a0/2 + f_ampl

dyn_stiffness  =  fabs((fmax - fmin) / (2.0*amp_max))

loss_energy = a1 * f_ampl * PI