Mixed variational principles in space and time for elastodynamics analysis

Nonlinear elastodynamics problems are approached from the point of view of a mixed variational principle. Tt is shown that four different functionals lead to different formulations of the problem with different independent fi elds. One of the functionals is specialized to the case of spatial beams un dergoing large deformations, and small strains. The extension of these func tionals to the case in which kinematic constraints are presented leads to t he useful concept of dual constraints, which can be advantageously employed in treating problems involving contact, impact, and changing topology.