RT journal article T1 Convergence Analysis of the Straightforward Expansion Perturbation Method for Weakly Nonlinear Vibrations A1 Moreno Pulido, Soledad A1 García Pacheco, Francisco Javier A1 Sánchez Alzola, Alberto A1 Rincón Casado, Alejandro A2 Estadística e Investigación Operativa A2 Ingeniería Mecánica y Diseño Industrial A2 Matemáticas K1 numerical analysis K1 approximation theory K1 nonlinear vibration K1 perturbation method K1 Banach space K1 unitary algebra K1 sup norm AB There are typically several perturbation methods for approaching the solution of weakly nonlinear vibrations (where the nonlinear terms are "small" compared to the linear ones): the Method of Strained Parameters, the Naive Singular Perturbation Method, the Method of Multiple Scales, the Method of Harmonic Balance and the Method of Averaging. The Straightforward Expansion Perturbation Method (SEPM) applied to weakly nonlinear vibrations does not usually yield to correct solutions. In this manuscript, we provide mathematical proof of the inaccuracy of the SEPM in general cases. Nevertheless, we also provide a sufficient condition for the SEPM to be successfully applied to weakly nonlinear vibrations. This mathematical formalism is written in the syntax of the first-order formal language of Set Theory under the methodology framework provided by the Category Theory. PB MDPI SN 2227-7390 YR 2021 FD 2021-05 LK http://hdl.handle.net/10498/24993 UL http://hdl.handle.net/10498/24993 LA eng DS Repositorio Institucional de la Universidad de Cádiz RD 08-nov-2026