Influence of the rolling direction on ductile damage during deep drawing of dual-phase steel

The spatial distribution as well as the amount of the accumulated damage within a component significantly affects its performance in terms of fatigue and crash behavior. One effective approach to control the amount of the accumulated damage is through precise adjustments of process parameters and setup. This paper explored the impact of sheet metal alignment with respect to the forming tools relative to the rolling direction of cold rolling on damage accumulation in sheet metal during deep drawing of a rectangular cup and a U-profile. Firstly, numerical analysis was performed to evaluate the load paths in form of stress and strain states that occur during deep drawing. Subsequently, experimental investigations were conducted to examine the effect of different alignments of the sheet metal with respect to the rolling direction on ductile damage. Therefore, the damage accumulation in the form of void area fraction in workpiece areas that are critical to performance was quantified and compared. Overall, the results have shown that the damage accumulation in form of void area fractions is dependent on the alignment of the sheet metal with respect to the rolling direction. The void area fraction of the rectangular cup could be reduced by 22.4% when considering a sheet metal that is aligned with the rolling direction parallel to the longest, straight sides of the geometry instead of a perpendicular orientation. For the U-profile it was demonstrated that a 45°-orientation of the rolling direction to the bending radius leads to the lowest damage accumulation reducing it by 50.38% compared to a 0°-orientation.