Computational modelling and simulation of ductile damage in metals
Loading...
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Alternative Title(s)
Abstract
This thesis deals with the development of a novel continuum damage modelling framework which enables the accurate prediction of the phenomenological effects of ductile damage on the mechanical properties of metals.
The proposed modelling framework establishes a relation between the macroscopic strain and stress states and is embedded into a finite element method regularised by adopting the micromorphic approach.
Thereby, the simulation of (cold) forming processes with more accurate predictions of the resulting mechanical properties and, especially, of the safety margin of the produced part becomes possible.
The process of developing the modelling framework is set forth by means of three separate models which increase in complexity.
At first, a regularised, isotropic, three-dimensional, ductile damage model is established at finite strains.
The analysis focuses on the coupling of damage and plasticity by means of a multisurface approach as well as on the applicability of the material model to resemble the behaviour of the dual-phase steel DP800, i.e.\ experiments are performed and parameters are identified by using full-field displacement data.
Secondly, a regularised anisotropic ductile damage model is implemented by adopting the fictitious configuration concept, where damage is described by a mapping related to a fictitiously undamaged configuration.
The coupling of damage and plasticity is further enriched by introducing effective driving forces controlling onset and evolution of damage and plasticity, respectively.
Different possibilities of regularisation are analysed and the results are underlined by illustrative examples.
The final stage of material model development incorporates the micro-crack closure and reopening effect.
Motivated from micro-mechanical considerations where mechanical stiffness in tension and in compression may evolve differently, two separate damage variables are introduced.
Previous stages of the material model are formulated with thermodynamically consistent associated evolution equations.
In contrast, the recovery of stiffness on crack closure is modelled in terms of a non-associated approach where special attention is paid towards fulfilling the dissipation inequality.
For all discussed models, the algorithmic implementation encompasses an implicit and monolithic solution of the model equations.
Furthermore, the characteristic behaviour of the developed models is demonstrated in terms of illustrative examples.
Description
Table of contents
Keywords
Damage, Plasticity, Regularisation, Gradient-enhancement, Anisotropy, Dual-phase steel, Finite Element Methode
Subjects based on RSWK
Werkstoffschädigung, Plastizität, Regularisierung, Gradientenverfahren, Anisotropie, Dualphasenstahl, Finite-Elemente-Methode, Duktilität, Modellierung, Simulation