VistaDam – VistaMat

VistaDam is a ductile-fracture prediction module for large-scale, thin-walled metal structures. Reliable modeling of fracture on a structural scale restricts the type of the finite elements used in the analyses to shell elements. VistaDam was developed on the basis of a comprehensive constitutive formulation embedded in the shell mechanics framework. The formulation features a three-invariant plasticity model that accounts for dependence of the strain at fracture on both stress triaxiality and the third invariant of the deviatoric stress, which has a significant influence on shear-dominated fracture.

The shell-based ductile-fracture prediction method packaged into VistaDam represents the state of the art in ductile-fracture mechanics for large-scale, thin-walled structures. High levels of accuracy in fracture prediction can be achieved through VistaDam, while maintaining discretization levels and computational efforts that are realistic for structural applications. A consistent calibration and validation framework for VistaDam has also been developed, which significantly reduces the experimental effort necessary to calibrate the model.

VistaDam has been extensively validated for a variety of thin-walled metal structures. All investigated problems involved complex fracture mechanisms with significant degree-of-mode interaction, including through-thickness fracture (mode III). Both controlled static and fast dynamic events involving explosive loads were simulated, resulting in excellent correlation with the experimental test results. Selected examples are briefly discussed below.

Ductile Fracture Prediction – Examples

Shell Buckling and Implosion under Hydrostatic Pressure:

Buckling of shell structures and implosion under hydrostatic pressure often leads to ductile fracture under complex state of stress. Multiple fracture mechanisms are typically involved with interaction of tension and bending, as well as in-plane and out-of-plane shear, which leads to mixed-mode fracture (including mode III). A series of detailed analyses of the implosion problems was conducted to validate VistaDam and the underlying theoretical considerations. In all cases, excellent correlation with the experimental test results was obtained.

Experiment: T. Giagmouris, S. Kyriakides, Y.P. Korkolis, L.-H. Lee; International Journal of Solids and Structures 47 (2010) 2680–2692 Simulation: Pawel B. Woelke, Najib N. Abboud; Journal of the Mechanics and Physics of Solids 60 (2012) 2044–2063