However, when forming the GA DP600 without prephosphate coating, necking was not able to be detected and the shear fracture (typical fracture around the tight die radius
without necking for AHSS, Shih et al.
Many studies had been conducted and there are few parameters found to have effect on springback such as holding force and die radius
(Ouksi et al.
and its solution is the function of secondary coating die radius
at this time.
Bending and unbending over the die radius
is also provided by this tensile stress on the cup wall.
Influence factors Factors Levels of variations 1st 2nd 3rd level level level Punch radius Rp[mm] 54 55 56 Die radius
Rf[mm] 5 6 7 Blankholder force BHF[kN] 30 50 70 Clearance between 1 1.2 1.4 punch and die c[mm] Tab.
where R and L are the die radius
and die length, [DELTA]P is the driving pressure, and q is the volumetric flow rate.
The accuracy of the radial extrudate swell profile can be verified by averaging the values of the radial extrudate swell ([B.sub.r]) obtained across die diameter, and comparing with the overall extrudate swell ratio ([B.sub.overall]) directly measured at the die exit, the overall extrudate swell ratio being referred to as the ratio of the extrudate radius to the die radius
; a detailed description of the technique can be found in previous work (26).
Three parameters were taken into account in this design of experiment: blankholder force (A), punch radius (B) and die radius
Another subject of future research will be the solution of the inverse problem, consisting in the use of the springback angle [beta] and thickness g as input data, in order to find out the angle [[alpha].sub.s], punch radius [r.sub.p], die radius
[r.sub.pl] (as output parameters).
The [B.sub.overall] value was referred to as the ratio of the extrudate radius ([R.sub.ext]) to the die radius
([R.sub.d]) (as shown in Eq 2).
The BUR is defined as the ratio of the final film radius ([R.sub.f]) and the die radius
([R.sub.o]), thus [R.sub.f]/[R.sub.o].
We will decrease the outer die radius
to lower the DRB.