error of the predicted contact spot size is in the range of experi- mental and measurement deviations. The predicted height of the smaller bulge is 13.7 mm which differs with the experimental value
on about 7%.
The thickness of specimen was measured in the points corre- sponding to the apex of smaller bulge and the center of contact spot of the larger one at 0.90 ± 0.5 and 0.79 ± 0.5 mm. The predicted
values for the same points are: 0.919 and 0.869 mm.
The photograph of the sample formed by the pressure regime
№2 is presented in Fig. 12. It can be seen, that the specimen did not come in to a contact with the die. The heights of the bulges were measured at 22.7 mm and 11.9 mm. The results of computer simulation of this forming process are presented in Fig. 13. In this simulation the heights of larger and smaller bulges were predicted at 26.9 mm and 13.4 mm. The fact that there is no contact between the specimen and the die in the simulation is explained by the smoothening of forming pressure curve which reduces the pressure values. The results of experiment and predictions made by FEM for the larger bulge differ by 4.2 mm which is more than 18% of the measured height. The deviation between the experiment and the model for the smaller bulge is 1.5 mm or 13% of the measured value. The comparison between the models and experimental results for the both pressure regiems is shown in Fig. 14. The meashured height of both cavities is denoted by green markers and dushed lines.