Single-point incremental formability of Monel 400: Coupled grey relational and principal component analyses

Abstract

This study reports the effects of single-point incremental forming (SPIF) process variables like vertical step down (0.2, 0.4, 0.6 mm), tool diameter (6, 8, 10 mm), feed rate (300, 600, 900 mm/min), spindle speed (300, 450, 600 rpm), lubricant (dry, oil, grease) and sheet thickness (0.6, 0.8, 1.0 mm) on the formability of Monel 400. Based on the varying wall angle tests conducted, it was found that the vertical step down was the parameter most influential in achieving maximum wall angle. The forming limit diagram constructed with the data obtained from straight groove tests revealed the parameter combination for low, moderate, and high formability while forming along different directions (0°, 45°, 90°). Also, it was observed that the formability has been positively influenced by increased tool diameter in the case of 0° orientation, spindle speed in the case of 45° orientation, and vertical step down in the case of 90° orientation. Based on the fractography study, it is concluded that more number of voids enhanced the forming limit. This may be due to the coalescence of voids and their slow aggregation. Based on the combined grey relational analysis and principal component analysis, it is obtained that the order of influencing parameters is vertical step down, tool diameter, sheet thickness, spindle speed, lubricant, and feed rate for obtaining the maximum sum of strains (0°, 45° 90°) and maximum wall angle.