The high strain-rate fracture behaviors of gray iron under compressive loading

This research studied the high strain-rate fracture behavior of a brittle metallic material under compressive loading. Gray cast iron was chosen as an ideal metal for such purpose. Split Hopkinson pressure bar test was used as experimental method for testing the specimens at the high strain-rate of 762–2526 S−1. Static compression test was performed at a slow rate of 2.4×10−4 S−1 for comparison purpose. The results indicated that the brittle metallic material does not clearly exhibit strain-rate sensitivity behavior, i.e. the difference between static and dynamic compression energy absorbed values tested at various strain-rates was insignificant. However, the fracture mechanisms were somewhat different. At slow rate, the fracture of gray iron was resulted from the crack propagating gradually and branching together along longitudinal directions of flake graphites. At high rate, it instantaneously appeared that large numbers of microvoids/cracks occurred and coalesced at the sites of flake graphites leading to the final fracture. Metallography and scanning electron microscopy (SEM) were performed to correlate the properties attained to the microstructural features.