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Table 1 Design rules of DDI process [23, 24]

From: Deep Drawing Process Using a Tractrix Die for Manufacturing Liners for a CNG High-Pressure Vessel (Type II)

Rule 1 t0 \(\ge\) 2 \(\times\) twall \(\times\) 1.05 (5%: Thickness reduction ratio caused by erosion
t0: Blank thickness, twall: Liner wall thickness
Rule 2 Vb (Blank volume) = VL (Liner volume)
Rule 3 Draw ratio in each drawing do not exceed LDR.
Rule 4 Draw ratio in 1st deep drawing process is smaller than 2.2.
Rule 5 Draw ratio in 2nd drawing process is smaller than 1.3 or 1.56 (1.3×1.2).
If intermediate annealing takes place after the first draw, then the values are higher by 20% (1.56).
Rule 6 Draw ratio in 3rd drawing process is smaller than 1.2.
Rule 7 Limit reduction ratio of cross-sectional area in ironing process (LRA ironing) is 35%.
Rule 8 When ironing processes are carried out two times in one stage, each reduction ratio of the cross-sectional area (RA ironing) should be the same.
Rule 9 Limit reduction ratio of the cross-sectional area (LRA) in each stage is 50%.