Implications of stress concentrators and work hardening in flat tensile samples subjected to milling and abrasive water jet machining

Abstract

AbstractThe milling process is the standard method for producing flat tensile test specimens from sheet metal. However, alternative methods employed in the industry for cutting sheet metal include abrasive water jet cutting, laser cutting, punching, and, to a lesser extent, electrical discharge machining. Among these, abrasive water jet cutting stands out for its superior material integrity, versatility, precision, and efficiency, making it a preferred choice. Previous studies consistently show that specimens cut by abrasive water jetting exhibit lower ultimate tensile strength and higher percent elongation than those obtained by milling in standardized tensile tests. This study investigates this behavior across different types of steel and alloys. Both steel types were subjected to milling and water jetting processes, followed by an analysis of their experimental and simulated mechanical behavior to identify discrepancies between the two methods. The findings suggest that milling, influenced by factors such as feed per tooth and cutter diameter, introduces geometric stress concentrators. This relative increase in ultimate tensile strength and decrease in percent elongation are observed consistently in milled tensile specimens compared to those cut by water jet, regardless of material type or thickness. Additionally, the effects of perimeter hardening resulting from superficial plastic deformation caused by the cutting edge, likely due to its small thickness, do not influence the observed trends significantly.