High strain rate forming using an underwater shock wave focusing technique

This paper proposes an effective method for controlling the morphology of i mpulsive pressure waves in hydro-spark forming, making use of the technique of underwater shock wave focusing. Free forming experiments using ellipsoi dal reflectors with two kinds of minor-to-major axis ratios b/a = 0.6 and 0 .8 are performed under several blank-setting conditions. The height of the formed product depends solely on the impulse of the shock wave, regardless of its focusing behavior, while the shape of the product is controlled by d istribution of the applied pressure wave. It is demonstrated that the refle ctor having b/a = 0.8 yields a wide range of pressure distribution, which c an be estimated from the shock wave front distribution calculated consideri ng the effect of non-linear reflection. (C) 1999 Elsevier Science S.A. All rights reserved.