RESIDUAL FORMABILITY OF SINGLE POINT INCREMENTALLY FORMED PART

Single point incremental forming is a potential manufacturing process under sheet metal forming which promises various advantages over other manufacturing processes. Single point incremental forming is a die-less manufacturing process. In this process the sheet metal is clamped in the fixture and then a single point, incrementally form each point by sliding the material forward and downward. As at each point the single point is formed, the uniform deformation can be achieved in the whole part and due to which the part can show much higher formability as compared to the conventional forming. The process has these other advantages over conventional forming like complex shapes can be created, and higher flexibility in the process as it depends on the forming program. Enormous research on the subject are available in the literature on formability, process variation, process parameters and their influence, but limited research are available on residual formability on single point incrementally formed parts. The previously published paper in IMECE2019 by the author studied the residual formability of single point incrementally formed part with four cone angles. It was found that the 30 and 45° cone angle did not survive during single point incremental forming but 60 and 90° did. Further 60 and 90° cones were conventionally restrike with spherical dome punch to determine the residual formability, however the 60° cone failed without conforming the dome shape, but 90^o deformed to full shape of dome and then fractured. In this paper the aim is to construct the whole section of forming limit point from uniaxial to equal-biaxial deformation mode restrike and measure the forming limits. These points will construct the whole residual forming limit curve of a single point incrementally formed part. For this, the successfully formed part by incremental forming were restrike with hemispherical tool in tensile, plane and biaxial deformation mode and limits were plotted. It was found that the maximum deformation is due to the single point incremental forming and less deformation are left in the part if it would be restrike by the conventional forming method.