## 3 Results and Discussion  
### Strip Test  
Table 4 shows the values of blankholding forces F\({}_{\text{N}}\) set during experiments and the measured values of drawing forces F\({}_{\text{P}(\text{2-0})}\) and F\({}_{\text{P}(\text{2-0})}\) during the strip drawing test. The friction coefficient under the blankholder is evaluated by the regression analysis (the first method--Equations (1) and (2)), as is shown in Figure 6. The friction coefficient f1,2 for experimental materials calculated according to Equation (2) was f1,2 = 0.11 \(\pm\) 0.012, with R\({}^{2}\) = 0.993 for DC 05 and f1,2 = 0.23 \(\pm\) 0.049 with R\({}^{2}\) = 0.997 for AISI 304 steel.  
Figure 5: Cup test: (**a**) Scheme, (**b**) simulation model, (**c**) course of force for DC 05, f = 0.1.  
When the friction coefficient under the blankholder f\({}_{1,2}\) and on the drawing edge f\({}_{3}\) were evaluated by the analytical model according to Equations (3) and (4), respectively, the values varied from 0.149 to 0.11 for the friction coefficient under the blankholder f\({}_{1,2}\) and from 0.139 to 0.117 for the friction coefficient on the drawing edge f\({}_{3}\) for DC 05 material. It can be seen that by increasing the pressure of the blankholder from 2 to 5.3 MPa (except 4 MPa) there was a slight reduction in the friction coefficient. This reduction in the friction coefficient is strengthened by using Anticorit 3802-39 S lubricant with a high-pressure additives (EP). The effectiveness of EP additives increases with the increasing pressure on the contact surfaces.  
When material AISI 304 was applied, the unambiguous tendency was not recorded--the friction coefficient under the blankholder f\({}_{1,2}\) evaluated by the analytical model according to Equation (3) varied from 0.201 to 0.187 and the friction coefficient on the drawing edge f\({}_{3}\) evaluated by the analytical model according to Equation (4) varied from 0.229 to 0.197 (Figure 7). It is assumed that lubricant during drawing the strip was not retained well on the contact surfaces because the blank surface was very smooth (Ra = 0.07 \(\pm\) 0.02 \(\upmu\)m). This also correlates to the Abbott-Firestone curve (bearing area curve) and the roughness profile are shown in Figure 2.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Material**} & **Normal** & **Specific** & **Drawing Force F\({}_{\text{P}}\) (N)** & \multicolumn{2}{c}{**Friction Coefficient f (–)**} \\  & **Force** & **Pressure** & **f\({}_{3}\) = 0** & **f\({}_{3}\) > 0** & **f\({}_{1,2}\)** & **f\({}_{1,2}\)** & **f\({}_{3}\)** \\  & **F\({}_{\text{N}}\) (kN)** & **p (MPa)** & **f\({}_{3}\) = 0** & **f\({}_{3}\) > 0** & **Equation (2)** & **Equation (3)** & **Equation (4)** \\ \hline \multirow{8}{*}{DC 05} & 2 & 1.3 & 673 & 816 & & - & 0.123 \\  & 3 & 2.0 & 970 & 1176 & & 0.149 & 0.123 \\  & 4 & 2.7 & 1142 & 1400 & & 0.117 & 0.120 \\  & 6 & 4.0 & 1654 & 1977 & & 0.123 & 0.139 \\  & 8 & 5.3 & 1993 & 2367 & & 0.110 & 0.117 \\ \hline \multirow{8}{*}{AISI 304} & 2 & 1.3 & 1398 & 1860 & & - & 0.182 \\  & 3 & 2.0 & 1779 & 2550 & & 0.191 & 0.229 \\ \cline{1-1}  & 4 & 2.7 & 2145 & 3017 & & 0.187 & 0.217 \\ \cline{1-1}  & 6 & 4.0 & 2930 & 3995 & & 0.192 & 0.197 \\ \cline{1-1}  & 8 & 5.3 & 3808 & 5282 & & 0.201 & 0.208 \\ \hline \end{tabular}
\end{table}
Table 4: Measured values of forces and calculated values of friction coefficient.  
Figure 6: Evaluation of the friction coefficient by linear regression.