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mechanical properties of blank sheet (Table 1) are measured using uniaxial tensile
testing method according to ASTM standards (ASTM M8).
2.2 Design of Forming Tools
Preform tool of hemispherical shape having 50 mm radius is used for the stretching
process and it is made of wood. SPIF tools are also hemispherical in shape and
are made of high carbon high chromium (HCHCr) die steel. Figure 2a depicts the
preform tool and Fig. 2b depicts the SPIF tools used for experimental work.
Three process parameters namely preforming depth (P d ), SPIF tool diameter (d)
and pitch (P) are considered for experimental work. The process parameters and their
levels as given in Table 2 are selected based on the literature review and available
machine capabilities.
Fig. 2 a Wooden preforming tool. b SPIF tools
Table 2 Process parameters and their levels
Parameter
Unit Actual values
Coded values
Preforming depth (P d ) mm
10
12
14
16
18 −2 −1 0
1
2
Tool diameter (d)
mm
4
6
8
10
12 −2 −1 0
1
2
Pitch (P)
mm
0.2 0.4 0.6 0.8 1
−2 −1 0
1
2