Computational methods coupling peridynamics with classical mechanics: out-of-balance forces in overall structural equilibrium

The paper investigates an often-overlooked issue in the use of coupled computational techniques: the assessment of overall static equilibrium. The analysis is focused on a peridynamic and FEM coupling computational method recently proposed by the authors. The magnitude of the out-of-balance forces obtained in all the examples is a fraction of a per cent of the applied forces, but it cannot be considered as a numerical error. The paper shows that the main reason for the occurrence of the out-of-balance forces is the presence of a highly nonlinear rate of change of displacements in the coupling zone of the models.