THE INFLUENCE OF LOADING RATE ON SHEAR DEFORMATION-BEHAVIOR OF TUNGSTEN COMPOSITE

This paper aimed to study 93% W-4.54% Ni-2.46% Fe tungsten composite l oaded at high strain rates ranging from 2200 s(-1) to 4200 s(-1) in si mple shear by means of a torsional split Hopkinson bar. The flow stres s and stress-strain response are measured by a proposed method. The st rain rate sensitivities and deformation mechanism are also investigate d with macroscopic results. Compared with those of low strain rate tes ts performed at 4 x 10(-3) s(-1), the results showed that the flow str ess, strain rate sensitivities and deformation mechanisms of tungsten composite are strongly sensitive to strain rate. Microstructural obser vations revealed by quantitative metallographic techniques found that the deformation of tungsten grains varied with strain rate levels and that microcracks are visible under dynamic loading conditions. Fractur e appearance is analyzed by a scanning electron microscope (SEM) to fi nd out the reason why both the binding strength between the tungsten g rains and the binder phase, and the fracture characteristics change wi th increasing loading rate.