Askari, H.Saadatnia, Z.Younesian, D.Yildirim, A.Kalami-Yazdi, M.2019-10-272019-10-2720110898-12211873-76680898-12211873-7668https://doi.org/10.1016/j.camwa.2011.09.042https://hdl.handle.net/11454/45914Approximate periodic solutions for the Helmholtz-Duffing oscillator are obtained in this paper. He's Energy Balance Method (HEBM) and He's Frequency Amplitude Formulation (HFAF) are adopted as the solution methods. Oscillation natural frequencies are analytically analyzed. Error analysis is carried out and accuracy of the solution methods is evaluated. (C) 2011 Elsevier Ltd. All rights reserved.en10.1016/j.camwa.2011.09.042info:eu-repo/semantics/openAccessHelmholtz-Duffing oscillatorHe's Energy Balance MethodHe's Frequency Amplitude FormulationArticle621038943901WOS:000297140300022N/AQ1