Fig. 3

Schematic representation of the geometry when shearing with angled tools, with definition of the rake angle θ and sheet strip width and thickness 2w and h, respectively. Position C is the vertex of the v-shaped tool and D is the strip edge. The load carrying interaction area (the plastic zone) between sheet and tools is confined between positions A and B. a–d Four stages of the shearing process: a is when contact is established between sheet and both tools; b a plastic zone has formed at the strip edge but no material is fractured; c a plastic zone of constant length propagates toward the sheet middle, with fractured material from the right zone boundary (position B) to the strip edge (position D); and d the plastic zone front (position A) has reached the sheet middle (position C), the zone length decreases, and final fracture follows as the fracture front has reached the sheet middle. The plastic zone is shown magnified in e, with definition of the load per unit sheet width P(u) and the local penetration u