SURFACE-TREATMENT OF HIGH-STRENGTH STEEL PLATES DUE TO BALL-DROP FORMING

Experimental results pertaining to the ball-drop forming of carbon-alloyed and high-strength steel plates are reported. The authors' research is mainly focused on the correlation of the residual stresses induced and the hardness changes developed with the operational parameters that govern the ball-drop forming process. Ball-drop forming is a multiple impact process and the theories pertaining to single and/or multiple indentations are critically reviewed and compared with experimental results. It is shown that the depth of plastic zone can be determined from measurements of the indentation crater diameter d(c). Residual stress fields and strained zones are related to the process parameters, that is, drop height, shot size, accumulated mass dropped and material thickness for various grades of steel strips.