Unsteady Creep of Layered Rods of Irregular Structure from Nonlinear-Hereditary Materials

The unsteady creep of homogeneous and metal-composite beams with irregular layered structure is considered. Beams consist of thin walls and shelves attached to them at top and bottom (bearing layers). The walls and bearing layers made of homogeneous isotropic materials. The mechanical behavior of these materials is described by a nonlinear hereditary theory of creep (Yu. Rabotnov). On the basis of the hypotheses of the Timoshenko theory with involvement of the ideas of method of steps in time the problem is formulated for the inelastic flexural deformation of such beams with account of their weakened resistance of their walls to the transverse shear. It is shown that in discrete moments of time the mechanical behavior of these materials layers obeys formally the defining relations of nonlinearelastic isotropic body with an initial stress state that is known. The secant modulus method is used for linearization of the task at each discrete time moment. Characteristics of the flexural behavior of three- and five-layer homogeneous and metal-composite beams under short-and long-term loading are studied. Statically determinate double-seat and cantilever beams are considered under the action of uniformly distributed transverse load of Heaviside type. It is found that the use of the classical theory of calculation of such beams leads to the prediction of unreasonably understated their flexibility, especially under creep conditions. In beams with reinforced bearing layers it is shown that the creep mainly develops due to the shear strain which actively accumulates in the walls of such structures