The flying wedge: a method for high strain rate tensile testing. Part 2: Characteristics of the device

The flying wedge concept, and the design and commissioning of the device have been described in the first part of this paper. In this second paper the operation of the device is analysed using a rigid-body mechanics model, to gain an understanding of its dynamic behaviour, in particular, the effects of the mass ratio of wedge to sliders, their elastic behaviour at impact, the wedge semi-angle, the influence of friction, multiple or “clattering” impact effects, etc. The model is built up in three sections; firstly, for the case where no separation of the wedge and sliders occurs after impact. The second section takes account of the fact that such separation may occur, and introduces the concept of a “coefficient of bulk kinetic energy restitution ‘c’ ” and the final section deals with the effect of the restraint offered by the deforming test piece in giving rise to “clattering” impact. Inertia and stress wave effects are briefly dealt with, and finally, the behaviour of the apparatus during the commissioning trials, and comparison with the model are discussed.