The Experts below are selected from a list of 1857 Experts worldwide ranked by ideXlab platform
Oana Cazacu - One of the best experts on this subject based on the ideXlab platform.
-
effect of the third invariant on the formation of necking instabilities in ductile plates subjected to plane strain tension
Meccanica, 2021Co-Authors: J A Rodriguezmartinez, Oana Cazacu, N Chandola, K E NsougloAbstract:In this paper, we have investigated the effect of the third invariant of the Stress Deviator on the formation of necking instabilities in isotropic metallic plates subjected to plane strain tension. For that purpose, we have performed finite element calculations and linear stability analysis for initial equivalent strain rates ranging from $$10^{-4}\,\text {s}^{-1}$$ to $$8 \cdot 10^{4}\,\text {s}^{-1}$$ . The plastic behavior of the material has been described with the isotropic Drucker (J Appl Mech 16:349–357, 1949) yield criterion, which depends on both the second and third invariant of the Stress Deviator, and a parameter c which determines the ratio between the yield Stresses in uniaxial tension and in pure shear $$\sigma _T / \tau _Y$$ . For $$c=0$$ , Drucker (J Appl Mech 16:349–357, 1949) yield criterion reduces to the von Mises (ZAMM J Appl Math Mech/Zeitschrift fur Angewandte Mathematik und Mechanik 8(3):161–185, 1928) yield criterion while for $$c=81/66$$ , the Hershey–Hosford (J Appl Mech 76:241–249, 1954; Proceedings of the seventh North American metalworking research conference, 1979) $$\left( m=6\right)$$ yield criterion is recovered. The results obtained with both finite element calculations and linear stability analysis show the same overall trends and there is also quantitative agreement for most of the loading rates considered. In the quasi-static regime, while the specimen elongation when necking occurs is virtually insensitive to the value of the parameter c, both finite element results and analytical calculations using Considere (Ann Ponts et Chaussees 9:574–775, 1885) criterion show that the necking strain increases as the parameter c decreases, bringing out the effect of the third invariant of the Stress Deviator on the formation of quasi-static necks. In contrast, at high initial equivalent strain rates, when the influence of inertia on the necking process becomes important, both finite element simulations and linear stability analysis show that the effect of the third invariant is reversed, notably for long necking wavelengths, with the specimen elongation when necking occurs increasing as the parameter c increases, and the necking strain decreasing as the parameter c decreases.
-
The effect of tension-compression asymmetry on the formation of dynamic necking instabilities under plane strain stretching
International Journal of Plasticity, 2020Co-Authors: K.e. N’souglo, J.a. Rodríguez-martínez, Oana CazacuAbstract:Abstract This paper brings to light the effect of tension-compression asymmetry in flow Stresses on the formation of dynamic necking instabilities in isotropic metallic plates subjected to plane strain stretching. For that purpose, a two-pronged approach which includes finite element calculations and linear stability analysis has been used. In both approaches, for the description of the plastic behavior the isotropic form of Cazacu et al. (2006) criterion and isotropic hardening was assumed. It is shown that although this criterion involves dependence of the third-invariant of the Stress Deviator, it is possible to develop a linear stability analysis and obtain the value of the growth rate of the perturbation at different loading times, and track the history of the growth rate of all the growing modes during the post-critical deformation process. Furthermore, an original procedure for calibration of linear stability analysis from finite element calculations was developed. Both linear stability analysis and finite element results indicate an important effect of the tension-compression asymmetry on the necking behavior and the same overall trends. In particular, the results show that while the necking time, and thus the specimen elongation when necking occurs, is roughly the same irrespective of the tension-compression asymmetry ratio, the necking strain and the necking energy are significantly greater for a material that displays a larger flow Stress in uniaxial compression than in uniaxial tension. A key outcome of this investigation is to demonstrate that such behavior is due to the larger plastic dissipation undergone, under plane strain stretching, by such a material as compared to a von Mises material and a material with larger flow Stress in uniaxial tension than in uniaxial compression.
-
plastic potentials for isotropic porous materials influence of the particularities of plastic deformation on damage evolution
2019Co-Authors: Oana Cazacu, Benoit Revilbaudard, Nitin ChandolaAbstract:In Chap. 7, key contributions toward elucidating the role of the plastic deformation on damage evolution in isotropic metallic materials are introduced. The ductile damage models presented are derived using rigorous upscaling techniques and limit-analysis methods. Previously unrecognized combined effects of the mean Stress and third-invariant of the Stress Deviator on yielding of porous materials with matrix described by von Mises and Tresca yield criteria are presented. It is shown that the fastest rate of void growth or collapse occurs in a porous Tresca material. Most importantly, it is revealed that depending on the yield criterion for the matrix, the third-invariant effects (or Lode effects) on void evolution can be either enhanced or completely eliminated.
-
new analytic criterion for porous solids with pressure insensitive matrix governed by an yield criterion involving the third invariant of the Stress Deviator
ECF21, 2016Co-Authors: Oana Cazacu, Benoit RevilbaudardAbstract:First, a new versatile isotropic yield criterion is proposed. This yield criterion is pressure-insensitive and predicts the same response in tension and compression. Its expression is a smooth function of both invariants J 2 , J 3 , of the Stress Deviator, and involves a unique material parameter b . Depending on the sign of the parameter b , the new criterion is either interior ( b >0) or exterior ( b 0. Of notable interest is that for certain values of b 0 (Lode parameter positive).
-
importance of the consideration of the specificities of local plastic deformation on the response of porous solids with tresca matrix
European Journal of Mechanics A-solids, 2014Co-Authors: Oana Cazacu, Nitin Chandola, J L Alves, Benoit RevilbaudardAbstract:Abstract Based on rigorous limit-analysis theorems, very recently, Cazacu et al. (2014) have deduced an analytic plastic potential for porous solids with Tresca matrix. Key in the model development was the consideration of the specificities of the plastic flow of the matrix. In this paper, finite element calculations are conducted for a voided cubic cell obeying Tresca's criterion and compared with the predictions of the new model. The numerical calculations confirm the centro-symmetry of the yield locus of the porous Tresca material and the combined effects of the mean Stress and the third-invariant of the Stress Deviator on void evolution. In particular, it is shown that the rate of void growth is faster for axisymmetric loading histories corresponding to the third-invariant J 3 Σ ≥ 0 than for those corresponding to J 3 Σ ≤ 0 , while void collapse occurs faster for loadings such that J 3 Σ ≤ 0 than for those characterized by J 3 Σ ≥ 0. Irrespective of the loading history, it is found that neglecting the local plastic heterogeneity leads to a drastic underestimation of the rate of void evolution.
Benoit Revilbaudard - One of the best experts on this subject based on the ideXlab platform.
-
plastic potentials for isotropic porous materials influence of the particularities of plastic deformation on damage evolution
2019Co-Authors: Oana Cazacu, Benoit Revilbaudard, Nitin ChandolaAbstract:In Chap. 7, key contributions toward elucidating the role of the plastic deformation on damage evolution in isotropic metallic materials are introduced. The ductile damage models presented are derived using rigorous upscaling techniques and limit-analysis methods. Previously unrecognized combined effects of the mean Stress and third-invariant of the Stress Deviator on yielding of porous materials with matrix described by von Mises and Tresca yield criteria are presented. It is shown that the fastest rate of void growth or collapse occurs in a porous Tresca material. Most importantly, it is revealed that depending on the yield criterion for the matrix, the third-invariant effects (or Lode effects) on void evolution can be either enhanced or completely eliminated.
-
new analytic criterion for porous solids with pressure insensitive matrix governed by an yield criterion involving the third invariant of the Stress Deviator
ECF21, 2016Co-Authors: Oana Cazacu, Benoit RevilbaudardAbstract:First, a new versatile isotropic yield criterion is proposed. This yield criterion is pressure-insensitive and predicts the same response in tension and compression. Its expression is a smooth function of both invariants J 2 , J 3 , of the Stress Deviator, and involves a unique material parameter b . Depending on the sign of the parameter b , the new criterion is either interior ( b >0) or exterior ( b 0. Of notable interest is that for certain values of b 0 (Lode parameter positive).
-
importance of the consideration of the specificities of local plastic deformation on the response of porous solids with tresca matrix
European Journal of Mechanics A-solids, 2014Co-Authors: Oana Cazacu, Nitin Chandola, J L Alves, Benoit RevilbaudardAbstract:Abstract Based on rigorous limit-analysis theorems, very recently, Cazacu et al. (2014) have deduced an analytic plastic potential for porous solids with Tresca matrix. Key in the model development was the consideration of the specificities of the plastic flow of the matrix. In this paper, finite element calculations are conducted for a voided cubic cell obeying Tresca's criterion and compared with the predictions of the new model. The numerical calculations confirm the centro-symmetry of the yield locus of the porous Tresca material and the combined effects of the mean Stress and the third-invariant of the Stress Deviator on void evolution. In particular, it is shown that the rate of void growth is faster for axisymmetric loading histories corresponding to the third-invariant J 3 Σ ≥ 0 than for those corresponding to J 3 Σ ≤ 0 , while void collapse occurs faster for loadings such that J 3 Σ ≤ 0 than for those characterized by J 3 Σ ≥ 0. Irrespective of the loading history, it is found that neglecting the local plastic heterogeneity leads to a drastic underestimation of the rate of void evolution.
-
importance of the coupling between the sign of the mean Stress and the third invariant on the rate of void growth and collapse in porous solids with a von mises matrix
Modelling and Simulation in Materials Science and Engineering, 2014Co-Authors: J L Alves, Benoit Revilbaudard, Oana CazacuAbstract:Recently, Cazacu et al (2013a J. Appl. Mech. 80 64501) demonstrated that the plastic potential of porous solids with a von Mises matrix containing randomly distributed spherical cavities should involve a very specific coupling between the mean Stress and , the third invariant of the Stress Deviator. In this paper, the effects of this coupling on void evolution are investigated. It is shown that the new analytical model predicts that for axisymmetric Stress states, void growth is faster for loading histories corresponding to than for those corresponding to . However, void collapse occurs faster for loadings where than for those characterized by . Finite-element (FE) results also confirm these trends. Furthermore, comparisons between FE results and corresponding predictions of yielding and void evolution show the improvements provided by the new model with respect to Gurson's. Irrespective of the loading history, the predicted rate of void growth is much faster than that according to Gurson's criterion.
-
new analytical criterion for porous solids with tresca matrix under axisymmetric loadings
International Journal of Solids and Structures, 2014Co-Authors: Oana Cazacu, Benoit Revilbaudard, Nitin Chandola, Djimedo KondoAbstract:Abstract In this paper, a new analytic criterion for porous solids with matrix obeying Tresca yield criterion is derived. The criterion is micromechanically motivated and relies on rigorous upscaling theorems. Analysis is conducted for both tensile and compressive axisymmetric loading scenarios and spherical void geometry. Finite element cell calculations are also performed for various triaxialities. Both the new model and the numerical calculations reveal a very specific coupling between the mean Stress and the third invariant of the Stress Deviator that results in the yield surface being centro-symmetric and void growth being dependent on the third-invariant of the Stress Deviator. Furthermore, it is verified that the classical Gurson’s criterion is an upper bound of the new criterion with Tresca matrix.
D. Kondo - One of the best experts on this subject based on the ideXlab platform.
-
Static limit analysis and strength of porous solids with hill orthotropic matrix
International Journal of Solids and Structures, 2017Co-Authors: I. El Ghezal, I. Doghri, D. KondoAbstract:The present study deals with a strength criterion for ductile porous materials consisting in a Hill type orthotropic matrix containing spherical voids. The originality of the study lies into an attempt to develop an approximate static Limit Analysis for this class of materials, based on the recent work of Cheng et al. (2014) initially proposed for isotropic von Mises matrix. To this end, we considered, in the framework of a statical limit analysis framework, a trial Stress field complying with the boundary conditions of the homogenization problem. Interestingly, the proposed procedure delivers an anisotropic macroscopic criterion which is not only pressure dependent, but exhibits an original sensitivity to the sign of the third invariant of the Stress Deviator. The obtained results are discussed and compared to existing theoretical models, to numerical bounds and to recently available Finite Element results. Finally, we provide the plastic strain rate equations and the void evolution law which are crucial for formulating the failure of anisotropic ductile metals. The influence of the plastic anisotropy on these constitutive equations is illustrated.
Charles Roe - One of the best experts on this subject based on the ideXlab platform.
-
On Stress-state dependent plasticity modeling: Significance of the hydrostatic Stress, the third invariant of Stress Deviator and the non-associated flow rule
International Journal of Plasticity, 2011Co-Authors: Xiaosheng Gao, Tingting Zhang, Jun Zhou, Stephen M. Graham, Matthew Hayden, Charles RoeAbstract:It has been shown that the plastic response of many materials, including some metallic alloys, depends on the Stress state. In this paper, we describe a plasticity model for isotropic materials, which is a function of the hydrostatic Stress as well as the second and third invariants of the Stress Deviator, and present its finite element implementation, including integration of the constitutive equations using the backward Euler method and formulation of the consistent tangent moduli. Special attention is paid for the adoption of the non-associated flow rule. As an application, this model is calibrated and verified for a 5083 aluminum alloy. Furthermore, the Gurson–Tvergaard–Needleman porous plasticity model, which is widely used to simulate the void growth process of ductile fracture, is extended to include the effects of hydrostatic Stress and the third invariant of Stress Deviator on the matrix material.
-
effects of the Stress state on plasticity and ductile failure of an aluminum 5083 alloy
International Journal of Plasticity, 2009Co-Authors: Xiaosheng Gao, Tingting Zhang, Matthew Hayden, Charles RoeAbstract:Abstract The experimental and numerical work presented in this paper reveals that Stress state has strong effects on both the plastic response and the ductile fracture behavior of an aluminum 5083 alloy. As a result, the hydrostatic Stress and the third invariant of the Stress Deviator (which is related to the Lode angle) need to be incorporated in the material modeling. These findings challenge the classical J2 plasticity theory and provide a blueprint for the establishment of the Stress state dependent plasticity and ductile fracture models for aluminum structural reliability assessments. Further investigations are planned to advance, calibrate and validate the new plasticity and ductile fracture models.
Joel B Stewart - One of the best experts on this subject based on the ideXlab platform.
-
analytical criterion for porous solids containing cylindrical voids in an incompressible matrix exhibiting tension compression asymmetry
Philosophical Magazine, 2013Co-Authors: Oana Cazacu, Joel B StewartAbstract:A new analytic plastic potential is developed using a rigorous limit analysis approach. Conditions of homogeneous boundary strain rate are imposed on every cylinder concentric with the cavity. It is shown that, due to the tension–compression asymmetry of the incompressible matrix, the third invariant of the Stress Deviator has a strong influence on the yielding of the porous solid. New and intriguing results are obtained; namely, for axisymmetric loadings and plane strain conditions, the Stress state at yielding is not hydrostatic. In the case when the matrix has the same yield in tension as in compression, the new criterion reduces to Gurson’s criterion for cylindrical voids.
-
Analytic plastic potential for porous aggregates with matrix exhibiting tension-compression asymmetry
Journal of the Mechanics and Physics of Solids, 2009Co-Authors: Oana Cazacu, Joel B StewartAbstract:Abstract This paper is devoted to modeling the effects of the tension–compression asymmetry of the matrix on yielding of the void–matrix aggregate. The matrix plastic behavior is described by the Cazacu et al. [2006. Orthotropic yield criterion for hexagonal closed packed metals. Int. J. Plasticity 22, 1171–1194] isotropic yield criterion, which captures strength differential effects. Using an upper-bound approach, a new analytic isotropic plastic potential for a random distribution of spherical voids is obtained. The derived analytic potential is sensitive to the third invariant of the Stress Deviator and displays tension–compression asymmetry. In the case when the matrix material has the same yield in tension and compression, it reduces to Gurson's [1977. Continuum theory of ductile rupture by void nucleation and growth: Part I: Yield criteria and flow rules for porous ductile media. J. Eng. Mater. Technol. Trans. ASME Ser. H 99, 2–15.] criterion. Furthermore, the proposed criterion predicts the exact solution of a hollow sphere loaded in hydrostatic tension or compression. The accuracy of the proposed analytical criterion is assessed through comparisons with finite-element cell calculations.
