By analyzing the forming characteristics of open die forging and the shape of spiral bevel gear forging, the plastic deformation is divided into upsetting deformation zone and extrusion deformation zone. As shown in the figure, zones 1, 2 and 3 are upsetting deformation zone and zone 4 is extrusion deformation zone. The forging deformation force in the upsetting deformation zone can be calculated by the upper bound method; Since the deformation of zone 4 in extrusion deformation zone is the same as that in zone 4 in non flash die forging, its calculation process will be given. The following mainly calculates the forming force in upsetting deformation zone.
According to the calculation formula given, the unit deformation force consumed in the upsetting deformation area is:
Where:
HC — thickness of connecting skin, mm (taken as 12mm);
HF — flash thickness, mm (taken as 4mm);
RC — outer diameter of connecting skin, mm (taken as 54mm);
R — inner diameter of flash, mm (taken as 116mm);
B – width of flash bridge, mm (taken as 14mm);
σ S — flow stress, MPa (taken as 80MPa).
According to the formula, the unit forging deformation force required for upsetting deformation zone is 556.4mpa. Then the forging deformation force PA required for upsetting deformation area is:
Where s — Horizontal projected area of spiral bevel gear forging, mm2.
The required deformation force in the extrusion deformation zone Pb = 3480 kn. Therefore, the total forging deformation force P required for open die forging is:
