Influence of processing temperature on formability of thin-rolled DP590 steel sheet

DP590 steel is used as an alternative material in automobile applications due to its high strength and considerably good other mechanical properties. However, major concern of DP590 steel forming is limited ductility and malleability. Warm forming is used as an effective alternative process to produce complex shape components from such high strength material. The present work is mainly focused on the investigation of processing temperatures (room temperature [RT], 200 degrees C, and 400 degrees C) on stretch forming behavior of DP590 thin-rolled sheet. The formability of the material increased by approximately 26% as the forming temperature increased from RT to 400 degrees C. Further, six ductile fracture criteria were calibrated in order to predict the fracture locus of material in effective plastic strain versus triaxiality space. Oh's model is found to have best predictability of fracture locus with least average absolute error at RT and 200 degrees C while Cockcroft and Latham model best predicted at 400 degrees C. Furthermore, fracture behavior of DP590 steel has been analyzed in the biaxial, plane strain, and uniaxial regions. The specimens in the biaxial region fractured without any prior hint of necking while predominantly ductile type of fracture has been observed for specimen lying in the uniaxial region.