Detonation loading of tubes in the modified shear wave speed regime
We performed experiments and numerical simulations on a thin-wall aluminum tube with internal gaseous detonation loading in the modified shear wave speed regime. Strain gauges were used to determine the time-dependent hoop strain on the surface of the tube. The experimental results were compared with analytical models and numerical simulations with explicit finite element computation treating the detonation as a traveling load. Hoop strain amplification factors (defined as the ratio of the dynamic strain to the equivalent static strain) close to two were obtained both in the present experiments and simulations. No resonance phenomena in the hoop strain were found in either experiments or simulations. Computations reveal the existence of a resonance in the shear strain.
Shock Loading and Failure of Fluid-filled Tubular Structures
We consider the response of fluid-filled tubes to internal shock waves and explosions. The emphasis is on the fluid–solid coupling aspects. The coupling of axial wave propagation in the fluid to flexural waves in the tube may be characterized by a single parameter that depends only on the tube and fluid material properties and dimensions. Using this parameter as a figure of merit, we discuss the limiting cases of weak and strong coupling between the fluid wave motion and tube structural motion. Examples discussed include detonation and shock waves in gas and liquid-filled tubes of metal, polymers, and composites. The results of experiments on elastic and plastic deformation are presented as well as selected results on fracture and rupture. Detonation in gas-filled tubes usually falls in the weak coupling regime except for very thin tubes or cases of deformation that lead to tube rupture. Impact generated axial waves in liquid-filled tubes can range from weak-to-strong coupling cases depending on the tube wall thickness and material. These cases include the well-known phenomenon of water hammer and we describe the relationship of impact studies to previous work on wave-propagation in water-filled pipes.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).