@phdthesis{,
    author = {Koirala, Sanjeev},
    title = {A continuum damage model for anisotropic ductile metals based on experiments and numerical simulations},
    editor = {},
    booktitle = {},
    series = {},
    journal = {},
    address = {},
    publisher = {},
    edition = {},
    year = {2024},
    isbn = {},
    volume = {},
    number =  {},
    pages = {},
    url = {},
    doi = {},
    keywords = {Continuum damage mechanics, Material anisotropy, Digital Image Correlation, Biaxial specimens, User defined material subroutine},
    abstract = {The doctoral thesis centers on exploring the damage and failure behavior of anisotropic ductile metals through a combined approach of experimental and numerical analyses. The research involves a series of experiments with both uniaxially and biaxially loaded specimens, emphasizing different loading ratios and loading directions. Digital image correlation is used to analyze the strain fields in critical areas of the specimens, while scanning electron microscopy is employed to analyze fractured surfaces, providing insights into various damage mechanisms. The thermodynamically consistent anisotropic continuum damage model, developed by Brünig [22], is further enhanced to incorporate the influence of plastic anisotropy on the damage behavior. Hoffman yield criterion, taking strength-differential into account, is used to model the anisotropic plastic behavior of the investigated aluminum alloy sheets. Using this yield criterion, generalized anisotropic stress invariants along with the generalized stress triaxiality and the generalized Lode parameter are introduced to characterize the stress state in the anisotropic ductile metal. 
Moreover, a damage criterion expressed in terms of the anisotropic stress invariants is proposed. To understand the effect of plastic anisotropy on damage evolution on the micro-level, numerical simulations of a unit-cell containing a spherical void are performed. With the help of micro-mechanical studies, the stress-state and loading direction dependent parameters are determined, which describe the evolution of macroscopic damage strains. The constitutive relations of the proposed continuum damage model are implemented into the commercial software package Ansys Classic APDL through a user-defined subroutine (UMAT). This involves employing a numerical algorithm based on the inelastic predictor-elastic corrector approach. The results obtained from experiments are then compared with corresponding numerical simulations, demonstrating the utility of the experimental-numerical methodology in gaining insights into the impact of plastic anisotropy on ductile damage and fracture behavior.},
    note = {},
    
    school = {Universität der Bundeswehr München},
    
}