Numerical Analysis of Damage Thermo-Mechanical Models (original) (raw)
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Meshfree simulations of thermo-mechanical ductile fracture
Computational Mechanics, 2006
In this work, a meshfree method is used to simulate thermo-mechanical ductile fracture under finite deformation. A Galerkin meshfree formulation incorporating the Johnson-Cook damage model is implemented in numerical computations. We are interested in the simulation of thermomechanical effects on ductile fracture under large scale yielding. A rate form adiabatic split is proposed in the constitutive update. Meshfree techniques, such as the visibility criterion, are used to modify the particle connectivity based on evolving crack surface morphology. The numerical results have shown that the proposed meshfree algorithm works well, the meshfree crack adaptivity and re-interpolation procedure is versatile in numerical simulations, and it enables us to predict thermo-mechanical effects on ductile fracture.
International Journal of Fracture, 2012
In this paper we assess a crack propagation criterion based on the notion of configurational force in the spirit of Gurtin (Configurational forces as basic concepts of continuum physics. Applied mathematical sciences. Springer, Berlin, 2000). We extend the theory of Gurtin to finite strain elasto-plastic fracture and in addition take thermal effects into account. The global model is a system of nonlinear and non-smooth equations which are solved directly with a finite element discretization. Comparison with laboratory experiments is provided, thereby showing that the concept of configurational force can be successfully used for computational damage-based fracture tests on ductile materials.
A damage model for ductile crack initiation and propagation
Computational Mechanics, 2011
Damage-induced ductile crack initiation and propagation is modeled using a constitutive law with asymmetrical contraction of the yield surface, and tip remeshing combined with a nonlocal strain technique. In practice, this means that the void fraction depends on a nonlocal strain. Finite strain plasticity is used with smoothing of the complementarity conditions. The prototype constitutive laws take into account pressure sensitivity and the Lode angle effect in the fracture strain. Two plane idealizations are tested: plane stress and plane strain. Thickness variation in the former is included by imposing a null out-of-plane stress. In plane strain, pressure unknowns and bubble enrichment are adopted to avoid locking and ensure stability of the equilibrium equations. This approach allows the representation of some 3D effects, such as necking. The nonlocal approach is applied to the strains so that the void fraction value evolves up to one and this is verified numerically. Two verification examples are proposed and one validation example is shown, illustrating the excellent results of the proposed method.
Computers & Structures, 2002
The continuum damage model for ductile damage and ductile fracture is applied to metal forming and crack propagation by finite element method. The highly nonlinear equilibrium equation is formulated in order to include geometric, material nonlinearities and frictional contact condition. The effect of friction on the damage concentration is shown in the upsetting process. Then it is verified that the ductile fracture using this damage model is reasonable by the comparison with the experimental result in CCT specimen. The influence of the hole at the crack tip is shown through the numerical simulations of edge-cracked plates with different hole size. Finally, the strain energy release rate in this damage model is compared with J-integral using ABAQUS to relate the result of damage analysis to the concept of fracture mechanics.
Ductile crack growth based on damage criterion: Experimental and numerical studies
2007
The continuum mechanical simulation of the microstructural damage process is important in the study of ductile fracture mechanics. In this paper, the continuum damage mechanics framework for ductile materials developed by Lemaitre has been validated experimentally and numerically for A533-B1 alloy steel under triaxial stress conditions. An experimental procedure to identify the damage parameters was established and the experimental calibrated damage parameters were then used in a finite element model. A fully coupled constitutive elastic-plastic-damage model has been developed and implemented inside the ABAQUS implicit FEA code. The model is based on a simplified Lemaitre ductile damage model whose return mapping stage requires the solution of only one scalar non-linear equation. A local crack growth criterion based on the critical damage parameter was proposed; the validity of this criterion was examined by comparing the simulation with the experimental results on standard three point bending (3PB) test. The critical load at crack growth initiation and the fracture toughness, J Ic , has also been predicted from the simulation. These numerically predicted values compared favourably with those obtained from experiments.
A ductile fracture analysis using a local damage model
International Journal of Pressure Vessels and Piping, 2008
In this study, the Gurson-Tvergaard-Needleman (GTN) model is used to investigate ductile tearing. The sensitivity of the model parameters has been examined from literature data. Three types of parameters have been reported: the ''constitutive parameters'' q 1 , q 2 and q 3 , the ''initial material and nucleation parameters'' and the ''critical and final failure parameters''. Each parameter in this model has been analysed in terms of various results in the literature.
Micromechanical Modeling of Crack Propagation with Competing Ductile and Cleavage Failure
Procedia Materials Science, 2014
Typical engineering metals exhibit a change of the failure mechanism with decreasing temperature. In the range of room temperature a ductile mechanism is observed. Thereby, voids nucleate, grow by plastic deformations of the surrounding matrix and finally the voids coalesce. In contrast in the low temperature regime, cleavage failure occurs, a mechanism which is associated with macroscopically brittle behavior. In the present study the crack initiation and propagation is investigated in the ductile-brittle transition region by means of a microscopic model. The voids in the process zone in front of the crack tip are resolved discretely. Possible void growth in the surrounding plastic zone, which may induce an important shielding effect, is taken into account in a homogenized way by means of the GTN-model. In contrast to comparable studies in the literature not only cleavage crack initiation is addressed but the material degradation by the cleavage mechanism is incorporated explicitly by means of a cohesive zone model. The limit case of smallscale yielding is investigated. This model allows to simulate all stages of crack initiation and propagation at all temperatures. A systematic study of the effects of the model parameters is performed.
2007
A new continuum damage model, the wing crack damage (WCD) model, was developed for the analysis of brittle failure of transversely isotropic solids. Special attention was paid to the analysis of axial splitting under compression and tensile cracking under tension. In addition to the WCD model a three-dimensional version of the damage model proposed by Murakami and Kamiya was enhanced and implemented in ABAQUS/Standard FE software. The proposed WCD model is based on the use of the damage vector. The vector represents both the normal direction of the surface of the plane crack and the size of the damaged area. Damaging induces anisotropy in an originally transversely isotropic material. The evolution equations for damage are motivated by the wing crack growth mechanism. The evolution is based on propagation of pre-existing damage. The proposed model enables modelling of pre-existing cracks. The feature can be exploited in studying the effect of orientation and size distribution of pre...