Abstract
This paper reveals the effectiveness of the homotopy perturbation method for strongly nonlinear oscillators. A generalized Duffing oscillator is adopted to elucidate the solving process step by step, and a nonlinear frequency-amplitudefrequency–amplitude relationship is obtained with a relative error of 0.91% when the amplitude tends to infinity, the solution morphology is also discussed, and the zero-th approximate approximate solution is enough for conservative nonlinear oscillators, while the accuracy of the frequency can be improved if the iteration continues.