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:

Notching

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 blade

Cutting

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 blade

Tearing

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 blade

Figure 20. Sheared joint face

1 upper notch, 2 smooth cut face, 3 rough torn face, 4 lower notch