New high-speed precise shearing method of hard-to-cut metal bars with stress concentration

The cropping of metal bars is the first process for forming most mechanical parts. Due to the inferior section quality and low efficiency in traditional cropping methods, a new high-speed precise shearing method has been proposed for hard-tocut metal bars with prefabricated surface notches. The stress concentration effect of the surface notch is theoretically analyzed, and the fracture behavior and section quality are investigated by finite-element simulation and experimental tests for notched and unnotched high-strength 42CrMo steel and high-toughness 304 steel bars. The results show that the new method effectively inhibits the plastic deformation and high precision sections are obtained with roundness error of 2.3%-3.8%, flatness error of 0.6-1.0 mm, and maximum plastic bending deformation of 1.6-1.8 mm. Moreover, the shearing load and fracture energy also decrease significantly. The new method shows the advantages of high precision and efficiency, and low energy consumption.