https://hal.science/hal-03259382Vizzaccaro, AlessandraAlessandraVizzaccaroImperial College LondonShen, YichangYichangShenIMSIA - UMR 9219 - Institut des Sciences de la mécanique et Applications industrielles - CEA - Commissariat à l'énergie atomique et aux énergies alternatives - ENSTA Paris - École Nationale Supérieure de Techniques Avancées - Université Paris-Saclay - CNRS - Centre National de la Recherche Scientifique - EDF R&D - EDF R&D - EDF - EDFSalles, LoïcLoïcSallesImperial College LondonBlahoš, JiříJiříBlahošImperial College LondonTouzé, CyrilCyrilTouzéIMSIA - UMR 9219 - Institut des Sciences de la mécanique et Applications industrielles - CEA - Commissariat à l'énergie atomique et aux énergies alternatives - ENSTA Paris - École Nationale Supérieure de Techniques Avancées - Université Paris-Saclay - CNRS - Centre National de la Recherche Scientifique - EDF R&D - EDF R&D - EDF - EDFDirect computation of nonlinear mapping via normal form for reduced-order models of finite element nonlinear structuresHAL CCSD2021[SPI.MECA.VIBR] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph][SPI.MECA.STRU] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Structural mechanics [physics.class-ph][MATH.MATH-DS] Mathematics [math]/Dynamical Systems [math.DS][SPI] Engineering Sciences [physics]Touzé, Cyril2021-06-14 10:19:492023-03-24 14:53:222021-06-18 11:42:30enJournal articlesapplication/pdf1The direct computation of the third-order normal form for a geometrically nonlinear structure discretised with the finite element (FE) method, is detailed. The procedure allows to define a nonlinear mapping in order to derive accurate reduced-order models (ROM) relying on invariant manifold theory. The proposed reduction strategy is direct and simulation free, in the sense that it allows to pass from physical coordinates (FE nodes) to normal coordinates, describing the dynamics in an invariant-based span of the phase space. The number of master modes for the ROM is not a priori limited since a complete change of coordinate is proposed. The underlying theory ensures the quality of the predictions thanks to the invariance property of the reduced subspace, together with their curvatures in phase space that accounts for the nonresonant nonlinear couplings. The method is applied to a beam discretised with 3D elements and shows its ability in recovering internal resonance at high energy. Then a fan blade model is investigated and the correct prediction given by the ROMs are assessed and discussed. A method is proposed to approximate an aggregate value for the damping, that takes into account the damping coefficients of all the slave modes, and also using the Rayleigh damping model as input. Frequency-response curves for the beam and the blades are then exhibited, showing the accuracy of the proposed method.