An investigation of failure mechanisms in forming of monolithic and composite sheets

Viac o knihe

The forming behavior of novel lightweight construction materials, such as advanced high strength steel and composite sheets, is gaining significant attention. This thesis investigates the failure mechanisms of DP1000, CP1000, aluminum alloy, and an aluminum/low density polyethylene half sandwich sheet during blanking and bending processes. It employs the shear-enhanced Lemaitre's damage model, Drucker-Prager model, and cohesive zone model to describe the mechanical behavior of the respective materials. These materials are characterized through various tests, including tensile, in-plane torsion, compression, and delamination tests, with a successful application of an inverse parameter identification procedure. The study examines the microstructure deterioration of DP1000 and CP1000 under tensile and shear stress, highlighting their differing mechanical behaviors. The characterized material model is then applied to the blanking of DP1000 and AA6082-T6 sheets, exploring the influence of punch-die clearances on the morphology of the sheared parts. Additionally, the mechanical behavior of the Al/LDPE half sandwich sheet during the blanking process is investigated. A fully characterized finite element model is used to analyze the effects of cutting clearance on cutting force-displacement curves and cutting edge morphology, with the experimental cutting edge imperfections quantitatively described by three feature values. The stress