SURFACE WAVE PROPAGATION FOR LINEAR VISCOELASTIC SOLIDS.
BROWN UNIV PROVIDENCE R I DIV OF APPLIED MATHEMATICS
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Experiments were carried out to observe the surface waves produced on large blocks of polyethylene and polymethylmethacrylate p.m.m. when specimens of these materials have been subjected to surface impacts of steel balls or when small lead azide charges have been detonated on the free surfaces. It was shown that if Poissons ratio is taken to be a real constant the shapes of surface waves can be calculated if the shape of the initial disturbance and the viscoelastic properties of the medium are known. It was shown that the complex nature of Poissons ratio results in only second order effects for the materials used. It was found possible to forecast the shape of surface waves produced by the impact of steel balls. The agreement with experimentally observed shapes was found to be excellent for the p.m.m. specimen. The theoretical predictions were less accurate for the polyethylene specimen, but the predictions here agreed reasonably well with the experiments.