Issue 30

C.J.Su et alii, Frattura ed Integrità Strutturale, 30 (2014) 502-514; DOI: 10.3221/IGF-ESIS.30.61 511 As can be seen from Fig. 14, with the increase of radius of tooth pitch, changes are relatively stable. The euphotic zone decreases with the bright belt length down by 50%; the fracture zone increases thus the bright band increases. As teeth pitch does not increase linearly, the ring gear is closer to the die cutting edge (i.e. pitch is small), the shear zone will produce higher hydrostatic stress, and metal materials tend more to flow to the shear zone and improve the quality of the cross section. In conclusion, the quality of blanked parts is most ideal when the pitch is 3.5mm. Figure 14 : The effect of blanking quality by tooth pitch. The impact of blanking clearance on thick plate fine blanking The influence of different blanking clearances on the stress distribution is shown in Fig. 15. The equivalent stress concentrating near the shear zone when the clearance value is zero and its values vary from 19MPa to 100MPa. The stress values in the zone near the euphotic belt are basically uniform. When clearances are 0.8%t and 1.6%t, the equivalent stress distribution of the areas spreads and has no big changes. When clearance is 2.4%t, the areas of equivalent stress distribution decrease but still with no big changes. (a) 0 (b) 0.8%t (c) 1.6%t (d) 2.4%t Figure 15 : Equivalent stress of fine blanking 1/4 with different clearance. The effect of blanking quality by blanking clearance is shown in Fig. 16. The fault zone length increases as clearance does. The fault zone of cross section achieves the shortest and euphotic zone the longest when the clearance is 0.8%t. So 0.8%t is the best value optimum for blanking clearance. It is consistent with the theoretical value about 0.5%t. The euphotic zone proportion will decrease with the increase of clearance in the process of plate fine blanking. It is because compressive stress is delayed in deformation zone and its crack propagation velocity is less than that caused by tensile stress when the die clearance is too large.