In this work, the analogous treatment between coupled temperature-displacement problems and material failure models is explored within the context of a commercial software (Abaqus®). The implicit gradient Lemaitre damage and phase field models are implemented utilizing the software underlying capabilities for coupled temperature-displacement problems. The heat conduction equation is made compatible with the diffusive regularization of such material models and calculations are carried out at the material point level. This bypasses the need to implement explicitly the weak form resultant from the coupling between the momentum conservation and the evolution of the diffusive field. Throughout benchmarking examples, the proposed methodology is assessed and validated by investigating typical issues risen from the considered local inelastic-based deformation models, such as mesh dependency and the difficulties to predict cracked regions.

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Utilization of the phase-field diffusive crack approach in prediction of crack evolution in materials containing voids is investigated herein. It has been established that the ductile failure occurs predominantly due to nucleation, growth and coalescence of micro-voids and micro-cavities, which lead to initiation and propagation of cracks till final material collapse. This study is an attempt to model the material internal degradation with the Rousselier pressure-dependent plasticity law, assisted with the phase field diffusive crack approach for the first time, in order to account for the post-critical softening regime. Such treatment requires the utilization of a damage evolution law and a crack initiation criterion which triggers the succeeding crack propagation, whereby a modified crack driving force based on the sequence of internal damage is employed. In numerical terms, the proposed model is integrated within a fully-staggered framework for the mechanical and diffusive fields and is implemented via the finite element method. The verification tests on the model is processed by several examples with the focus on both qualitative monitoring of pathological crack patterns and the quantitative analysis on the material response, particularly in the post-critical range, complemented by relevant comparisons with the existing data from literature.

The present contribution addresses the micromechanical and thermal analysis of directed energy deposition-manufactured, stainless steel 316L components by utilizing experimental and numerical analyses. It has been established that a combination of controlling process parameters, manufacturing environment and microstructural anisotropies could adversely affect the quality of as-deposited parts. Among other factors, the shape, size, and distribution of the microvoids and porosities could, to some extent, have deteriorating effects on the mechanical properties of the additively manufactured components. In this work, the micromechanically motivated Gurson–Tvergaard–Needleman damage model is utilized and the performance of the model is evaluated by observing the damage accumulation in the loaded additively manufactured specimens. By relying to the laboratory-based material data and fractographic imagery from nonstandard tensile testing on fabricated samples in different building directions, numerical model predictions are found to be in a good agreement with the experimental observations. Furthermore, by resorting to the finite element software capabilities, the thermal analyses are carried out on the manufactured cube component and the influence of the process parameters on the temperature distribution is revealed.

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Additive manufacturing (AM) of metals proved to be beneficial in many industrial and non-industrial areas due to its low material waste and fast stacking speed to fabricate high performance products. The present contribution addresses several known challenges including mechanical behaviour and porosity analysis on directed energy deposition (DED) manufactured stainless steel 316L components. The experimental methodology consisting of metal deposition procedure, hardness testing and fractographic observations on manufactured mini-tensile test samples is described. A ductile fracture material model based on the Rousselier damage criterion is utilized within a FE framework for evaluation of material global response and determination of initial porosity value representing the structure’s nucleating void population. Alternatively, the initial pore sizes are characterized using the generalized mixture rule (GMR) analysis and the validity of the approach is examined against the experimental results.

Abstract. Traditionally, combination of equivalent plastic strain and stress triaxiality parameters are taken into account when performing characterization of material ductility. Some well-established models like Lemaitre model, GTN based models and many others perform relatively well at high-triaxiality stress states but fail to give adequate answers to low-triaxiality states. In this work, three damage models are presented, applied and assessed to a crossshaped component. Concerning material, AA5182-O, corresponding damage parameters are characterized by an inverse analysis procedure for each damage model.

In an effort to simulate the involved thermal physical effects that occur in direct energy deposition (DED) a thermodynamically-consistent of phase-field method is developed. Two state parameters, characterizing phase change and consolidation, are used to allocate the proper material properties to each phase. The numerical transient solution is obtained via a finite element analysis. A set of experiments for single tracks scanning were carried out to provide dimensional data of the deposited cladding lines. By relying on a regression analytical formulation to establish the link between process parameters and geometries of deposited layers from experiments, an activation of passive elements in the finite element discretization is considered. The single-track cladding of Inconel 625 powder on tempered steel 42CrMo4 was printed with different power, scanning speed and feed-rate to assess their effect on the morphology of the melt pool and the solidification cooling rate. The predicted dimensions of melt pools were compared with experiments reported in the literature. In addition, this research correlated the used process parameter in the modelling of localized transient thermal with solidification parameters, namely, the thermal gradient (𝐺) and the solidification rate (𝑅).