158
R. Jagtap et al.
Table 4 Process parameters and their levels for full factorial design
Parameters
Levels
−1
0
+1
Preform tool radius (P r ) (mm)
50
70
90
Preforming depth (P d ) (mm)
10
14
18
Table 5 ANOVA table for T min using full factorial design of experiment plan
Source
DF
Seq SS
Adj SS
Adj MS
F
P
P r
2
0.0014889
0.0014889
0.0007444
7.88
0.041
P d
2
0.0029556
0.0029556
0.0014778
15.65
0.013
Residual Error
4
0.0003778
0.0003778
0.0000944
Total
8
0.0048222
R 2 = 0.9217; Adjusted R 2 = 0.8433
Preforming is a plastic deformation process. Hence increase in preforming or
stretching results in increased plastic deformation and reduced thickness of blank
sheet as discussed in Sect. 3.1. As preform tool radius increases, improvement in
minimum thickness is observed as shown in Fig. 6. It is observed from the thickness
profiles of preformed sheet and conical frustum that, while using preform tool radius
of 50 mm, plastic deformation is localized and bending deformation is spread over
a small area. Hence, slight improvement in the thickness reduction is observed in
conical frustum along with more uniform thickness distribution as compared to SPIF
process. It is observed that minimum thickness reduction along the formed surface
is obtained at 10 mm preforming depth. It is observed that as the preform tool radius
increases to 70 mm, the area of contact between tool and sheet increases. Therefore,
more bending is observed near clamped edge where thinning band appears. Increased
bending due to 70 mm preform tool radius causes improvement in minimum thickness
near clamped edge, hence uniform thickness distribution is observed along the formed
surface as shown in Fig. 7. Further, as the preform tool radius increases to 90 mm, the
Fig. 6 Preform tool radius
versus minimum thickness
R. Jagtap et al.
Table 4 Process parameters and their levels for full factorial design
Parameters
Levels
−1
0
+1
Preform tool radius (P r ) (mm)
50
70
90
Preforming depth (P d ) (mm)
10
14
18
Table 5 ANOVA table for T min using full factorial design of experiment plan
Source
DF
Seq SS
Adj SS
Adj MS
F
P
P r
2
0.0014889
0.0014889
0.0007444
7.88
0.041
P d
2
0.0029556
0.0029556
0.0014778
15.65
0.013
Residual Error
4
0.0003778
0.0003778
0.0000944
Total
8
0.0048222
R 2 = 0.9217; Adjusted R 2 = 0.8433
Preforming is a plastic deformation process. Hence increase in preforming or
stretching results in increased plastic deformation and reduced thickness of blank
sheet as discussed in Sect. 3.1. As preform tool radius increases, improvement in
minimum thickness is observed as shown in Fig. 6. It is observed from the thickness
profiles of preformed sheet and conical frustum that, while using preform tool radius
of 50 mm, plastic deformation is localized and bending deformation is spread over
a small area. Hence, slight improvement in the thickness reduction is observed in
conical frustum along with more uniform thickness distribution as compared to SPIF
process. It is observed that minimum thickness reduction along the formed surface
is obtained at 10 mm preforming depth. It is observed that as the preform tool radius
increases to 70 mm, the area of contact between tool and sheet increases. Therefore,
more bending is observed near clamped edge where thinning band appears. Increased
bending due to 70 mm preform tool radius causes improvement in minimum thickness
near clamped edge, hence uniform thickness distribution is observed along the formed
surface as shown in Fig. 7. Further, as the preform tool radius increases to 90 mm, the
Fig. 6 Preform tool radius
versus minimum thickness