Forming, fracture and corrosion behaviour of stainless steel 202 sheet formed by single point incremental forming process

Abstract

This work aims to determine the forming limit of stainless steel 202 sheet having 0.8 mm thickness during Single Point Incremental sheet metal Forming (SPIF) process. A L18 orthogonal array was designed using taguchi method for performing SPIF. The process parameters used were spindle speed, feed rate and vertical step down having three levels each and ball diameter having two levels. A straight groove test was conducted for 18 samples and strain based Forming Limit Diagrams (FLD) and stress based FLDs were plotted. Stress triaxiality and strain triaxiality were determined. The fractographs were analyzed and dislocation density was measured from x-ray diffraction line profile analysis. The corrosion behaviour of both undeformed sample and deformed sample were also studied. It was found that the formability is increased with increasing the spindle speed, decreasing the vertical step down and feed rate. The sum of strain was found to be 0.91 which is twice greater than that of conventional forming process. It is also found that the dislocation density is 2.35 times greater for the sample possesses higher formability than the sample possesses least formability. The goodness of fit in strain based FLD and stress based FLD are found to be 0.989 and 0.968 respectively.