Dynamics and Strength of Metal-Composite Cylinders on Internal Explosion Against the Thickness and Properties of Metallic and Composite Layers. Part 1. Numerical Simulation of Thin- and Medium-Thickness Cylinders

The effect of the metallic layer thickness on the stress-strain state and strength of metal-composite cylinders of the total constant thickness under internal dynamic pressure produced by the explosion of a charge evenly distributed along its axis in air at the constant total-to-running charge mass ratio (ξ = 1.421 mm was numerically investigated. The strength of the cylinders was evaluated by the generalized Mises criterion. The strength of shells with a unidirectionally circularly reinforced outer composite layer for the composites of low tensile strength in the isotropy plane is shown to be mainly governed by the wave processes across the shell width. Under this condition, its dependence on radial and axial stresses is much higher than on the circumferential ones, which are usually much larger than the first two components of the stress tensor. The four composites and two designs of the cylinders: thin-walled and medium-thickness are examined. The cylinders are double-layered: the inner layer is steel (St20) and the outer layer is a circularly reinforced composite. At given (ξ and the total constant cylinder thickness H , the optimum in strength terms ratio ( β opt of the metalliclayer thickness h to H is strongly dependent on H , a composite (i.e., its physicomechanical characteristics) and varies within 0.4–0.7 for thin-walled cylinders and 0.6–0.7 for medium-thickness ones. Irreversible plastic energy losses in the inner steel layer have a significant impact on the shell strength, as a result the shock wave travelling to the outer composite layer is of lower intensity and the strength of the object as a whole can be ensured. The inclusion of the plastic steel layer deformation in thin-walled cylinder calculations significantly changes the dynamics of objects qualitatively but insignificantly increases the strength quantitatively, the Mises strength function can be reduced by less than 5% compared to an ideally elastic calculation. If the plastic metal deformation is accounted for medium-thickness cylinders, it significantly changes the wave patterns both qualitatively and quantitatively, the strength function can be reduced by almost 50% compared to the elastic calculation.