Prediction of forming limits for anisotropic sheets containing prolate ellipsoidal voids

• Published in: International journal of mechanical sciences Vol. 45; no. 10; pp. 1625 - 1643
• Main Authors: Son, Hyun Sung, Kim, Young Suk
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2003; Elsevier
• Subjects: Exact sciences and technology; Forming limit diagrams; Fundamental areas of phenomenology (including applications); Marciniak and Kuczynski model; Physics; Prolate ellipsoidal void; Solid mechanics; Structural and continuum mechanics; Theory and numerical methods; Marciniak and Kuczynski model; Forming limit diagrams; Prolate ellipsoidal void; Plastic anisotropy; Probabilistic approach; Yield criterion; Forming limit diagram; Anisotropic material; Forming; Formability; Experimental study; Modeling; Axial symmetry; Optimization; Biaxial tension stress; Cavity; Sheet metal; Strain gradient; Ductile material; Neck; Ellipsoid; Damaging
• ISSN: 0020-7403; 1879-2162
• DOI: 10.1016/j.ijmecsci.2003.10.011

In sheet metal forming operations, the formability of sheet metals is limited by the occurrence of internal damage evolution that eventually yields a localized neck. Thus, designing and optimizing a sheet metal forming process, requires the precise prediction of the forming limits of the sheet materials. Accordingly, the current work attempts to theoretically predict the forming limit diagrams (FLDs) of voided anisotropic sheets using a new version of the Marciniak and Kuczynski (M–K) model. The analysis employs Gologanu–Leblond–Devaux's yield function for materials containing axisymmetric prolate ellipsoidal cavities with random orientations in conjunction with Barlat and Lian's 1989 anisotropic yield criterion. The effect of a void shape parameter on a ductile material under biaxial tensile loading is introduced and examined within the framework of the M–K model, along with the effect of including a first-order strain gradient term in the flow stress. To confirm the validity of the proposed M–K model, the predicted FLDs were compared with experimental results for steel sheets. The predicted forming limits for the voided sheets were found to agree well with the experimental data.