This paper presents a nonlinear analysis of compliant mechanisms (CMs ) using finite element method. The case of a compliant four-bar mechanism, where the coupler link is to be guided by flexible input and follower links is developed. Previous works on this type of compliant mechanism are based on linear formulation thereby neglecting the shear stress induced in the links. An investigation on the influence of geometric nonlinearity in the analysis of compliant mechanisms where all flexible links are considered as two dimensional beams with shear deformation is presented. The energy equations were developed first; the discretization and the lagrangian dynamics that produced the motion equation were thereafter established. The automatic derivation of formulae needed in numerical procedure were done using symbolic programming module, AceGEN and implemented in a compiled back end, AceFEM. Finally, the numerical results reveal the deviation that exists with linear formulation assumption, showing that this approach is more encompassing.
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