Analysis of Mode II Crack Growth Behavior in Spalling Failure of Backup Roll

Abstract

The crack in spalling failure of steel making backup rolls propagates mostly in Mode II. Mode II crack growth rate (ΔK_II-da/dN) and Mode II threshold stress intensity factor range (ΔK_IIth) for a backup roll steel were measured by using the newly developed testing system with a conventional closed-loop type tension-compression fatigue testing machine. The Mode II fatigue crack fracture surface morphology of the specimen was very similar to that of an actual backup roll. The crack growth behavior of the fractured backup roll was investigated based on fracture mechanics by using the laboratory test data of ΔK_IIth for the backup roll steel.