Spall Strength Comparison of High Strength Steels

Kiara Stephanie Penman


Defining steel’s dynamic behaviour is important for armoured applications. The material characteristics dictate the appropriate application for the material. A pertinent dynamic behaviour that should be considered in impact dynamics is a material’s spall strength. Understanding how a material reacts dynamically to an impact force can aid in selecting and possibly improving steel to withstand large dynamic forces. Two different grades of armoured steel were supplied by Bisalloy®. Bisalloy ultra-high toughness (UHT) 440 and Bisalloy ultra-high-hardness (UHH) 600 are compared in spall strength and Hugoniot Elastic Limit (HEL) to determine which material is more suitable for military applications. This was done through flyer plate impact testing with 70mm high-velocity single stage light gas gun at UNSW Canberra. From impact tests and microstructural analysis, UHT440 had the higher spall strength than UHH600. Relationships between the grain sizes, ductility and effect on the spall peak gradient demonstrated a relationship for the higher spall strength. Theory suggests that higher yield stress characteristics in a material correlate to a higher HEL. In this case, UHH600 was determined to achieve a higher HEL than compared to UHT440. It was concluded that UHT440 is more resistant to high impact stresses such as blast waves, where UHH600 would be more suitable against ballistic penetration.


Materials; Spall Strength; Hugoniot Elastic Limit

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