Influence of mesh size, stress triaxiality and damage induced softening on ductile fracture of large-scale shell structures

• We study influence of mesh size, stress triaxiality and damage softening on ductile fracture prediction in panels.
• Fracture strain is adjusted simultaneously according to mesh size as well as stress state.
• Employed approach effectively removes the mesh size effects and reduces the scatter in results.
• Softening delays the element removal, but has only minor influence on the force–displacement curves.

In this investigation, ductile fracture in stiffened and unstiffened panels is simulated employing the fracture criterion, which depends on the mesh size, stress state and damage induced softening. The aim of the study is to show that employed fracture criterion removes mesh size effects more efficiently than traditional fracture criteria adjusted only on the basis of uniaxial tension. Fracture model is implemented into Finite Element software ABAQUS using user-defined material, VUMAT-subroutine, available for shell elements. Mesh size sensitivity analysis is carried out. Finite element simulation results are validated with experimental measurements available in literature. Comparison of numerical and experimental results shows that simulations effectively capture most of the experimentally observed features, especially when considering different mesh densities. In most cases, mesh size effects are considerably reduced compared with the fracture criteria adjusted on the basis of a uniaxial tension.