4. Mode of Operation of the Shearing Process
In shearing, two wedge-shaped shear blades closely pass by each
other. The workpiece that is placed between the two shear blades is cut under
continued effect of force. The shearing process is performed in 3 stages:
When the blades touch down, the material springs back a bit
under the effect of force. As soon as its elastic limit has been overcome, the
blades notch the workpiece.
Figure 17. Notching
1 upper blade, 2 notched sheet, 3 lower
In further penetrating, the shear blades overcome the internal
resistance of the metal structure and cut the workpiece.
Figure 18. Cutting
1 upper blade, 2 cut-in sheet, 3 lower
The penetrating shear blades squeeze the material together
between the blades, resulting in a material solidification. Since the blades are
not able to further penetrate the material, they tear the residual material
apart under continued effect of force.
These stages can be seen at joint faces of thick sheets.
Figure 19. Tearing
1 upper blade, 2 torn sheet, 3 lower
Figure 20. Sheared joint face
1 upper notch, 2 smooth cut face, 3 rough torn
face, 4 lower