4 research outputs found
Microstructure of surface zones subjected to high-velocity parting-off
A hydraulic high-velocity pressing machine with a
parting-off tool was used for adiabatic cutting with impact velocities
ranging from 5 to 10 m/s. In this study the associated fracture mechanisms
and microstructures of three different materials (100Cr6, 100CrMn6 and C56)
in the form of wire or bar were investigated. It was concluded that the
parting-off is initiated through a shearing effect resulting in ductile
shear fracture being responsible for the cutting. In all of the samples
microcracks were found in the severely deformed region around the cut, which
became larger with increasing sample diameter. Evidence of heating was not
observed in the cut zone of samples having 6 mm diameter. However, for
samples with a diameter of 70 mm and above, a white-etching band could be
found, indicating that the temperature had increased considerably in this
region. Analysis of the fracture surfaces using scanning optical microscopy
showed that the fracture mode had mostly been ductile shear, with exception
of the largest samples where some evidence of tensile fracture could be
observed