In this paper we establish the existence of solutions to a time-dependent problem for a linearly elastic body subjected to a confinement condition, expressing that all the points of the deformed reference configuration remain confined in a prescribed half space. This problem takes the form of a set of hyperbolic variational inequalities. The fact that any solution of the studied problem takes the form of a vector field instead of a real-valued function, the generality of the confinement condition under consideration, the fact that the integration domain is a subset of R 3 , and the choice of the function space where solutions are sought make the analysis substantially more complicated, thus requiring the adoption of new resolution strategies. external force. In this paper, we study the existence of solutions to an obstacle problem modelling the displacement of a three-dimensional linearly elastic body 5 confined in a half space.Obstacle problems arise in many applicative fields: For instance, the motion of three valves of the Aorta, that can be regarded as linearly elastic shells (cf., e.g., [1]), is governed by a mathematical model built up in a way such that each valve remains confined in a certain portion of space without colliding with the 10 remaining two valves. A substantial contribution to the theory of hyperbolic obstacle problems can be found in the seminal papers [2] and [3]. Other important contributions in this field can be found in the references [4], [5], [6], and [7], where the problems are set out as follows: the integration domain ω is a subset of R 2 , and the unknown 15 function, at almost all time instants, is a real-valued function that belongs to H 2 0 (ω). It is also worth mentioning the papers [8], [9], [10], [11], [12], [13], [14] and [15]. The nonlinear analysis tools used in this paper can be found in the recent monograph [16].The first main novelty of this paper is that the unknown, represented by 20 displacement of the linearly elastic body under consideration, is a vector field that, at almost all time instants, belongs to a nonempty, closed , and convex subset of the Sobolev space H 1 (Ω)×H 1 (Ω)×H 1 (Ω), where Ω ⊂ R 3 is a domain.This will require the implementation of a more general argument to recover the energy estimates in the Galerkin method.
25The second main novelty is given by the generality of the confinement condition under consideration, which comprises at once all of the three components of the displacement vector field. Such a confinement conditions were first considered in the papers [17], [18], [19], and [20]. Other types of confinement conditions which are more amenable in the context of numerical simulations are discussed 30 in the paper [21]. Finally, the method we propose here for recovering the initial condition for the first derivative in time of the displacement slightly differs from the one used in [4], [5], [6], and [7]. 2 The paper is organised as follows. First, some notations and background are 35 provided. Secondly, the main existence theorem for a dyna...