Sample preparation and testing: Samples of 0.12" (3mm) and 0.24” (6mm) thick plate were subjected to controlled denting using a compression testing machine. Prior to denting, the samples were stress relieved at 500oC for three hours to remove any pre-existing residual stresses. Dents were produced using a cylindrical tool with a rounded tip, which was pushed into the plate. A die containing a larger hole was located below the tool. Dents of two different diameters were produced. For ease of reference these were termed ‘small’ and ‘large’ dents, defined as below:
Small dents: A 20mm diameter cylindrical tool was used to produce these dents in 0.12” (3mm) thick plate samples. Dents from 0.02" to 0.12" (0.5mm deep to 3mm deep) were produced, with varying diameters from 0.14" to 0.43" (3.5mm to 11mm).
Large dents: A 40 mm diameter cylindrical tool was used to produce dents of approximately 1-1.5” diameter (25- 36mm) in the 0.24” (6mm) plate samples. Dent depths ranged from 0.12” – 0.35” (3 – 8mm).