On the non-conservativeness of a class of anisotropic damage models with unilateral effects

2006 ◽  
Vol 334 (7) ◽  
pp. 414-418 ◽  
Author(s):  
Noël Challamel ◽  
Damien Halm ◽  
André Dragon
Keyword(s):  
Anisotropic Damage ◽  
Damage Models ◽  
Unilateral Effects

Failure Predictions for DP Steel Cross-die Test using Anisotropic Damage

2011 ◽  
Vol 21 (5) ◽  
pp. 713-754 ◽  
Author(s):  
M. S. Niazi ◽  
H. H. Wisselink ◽  
T. Meinders ◽  
J. Huétink
Keyword(s):  
Strain Rate ◽  
Damage Evolution ◽  
Damage Model ◽  
Anisotropic Damage ◽  
Continuum Damage ◽  
Anisotropic Plasticity ◽  
Continuum Damage Model ◽  
Damage Models ◽  
Isotropic Damage ◽  
Failure Predictions

The Lemaitre's continuum damage model is well known in the field of damage mechanics. The anisotropic damage model given by Lemaitre is relatively simple, applicable to nonproportional loads and uses only four damage parameters. The hypothesis of strain equivalence is used to map the effective stress to the nominal stress. Both the isotropic and anisotropic damage models from Lemaitre are implemented in an in-house implicit finite element code. The damage model is coupled with an elasto-plastic material model using anisotropic plasticity (Hill-48 yield criterion) and strain-rate dependent isotropic hardening. The Lemaitre continuum damage model is based on the small strain assumption; therefore, the model is implemented in an incremental co-rotational framework to make it applicable for large strains. The damage dissipation potential was slightly adapted to incorporate a different damage evolution behavior under compression and tension. A tensile test and a low-cycle fatigue test were used to determine the damage parameters. The damage evolution was modified to incorporate strain rate sensitivity by making two of the damage parameters a function of strain rate. The model is applied to predict failure in a cross-die deep drawing process, which is well known for having a wide variety of strains and strain path changes. The failure predictions obtained from the anisotropic damage models are in good agreement with the experimental results, whereas the predictions obtained from the isotropic damage model are slightly conservative. The anisotropic damage model predicts the crack direction more accurately compared to the predictions based on principal stress directions using the isotropic damage model. The set of damage parameters, determined in a uniaxial condition, gives a good failure prediction under other triaxiality conditions.

Lode angle dependency due to anisotropic damage

2020 ◽  
pp. 105678952094856
Author(s):  
A Mattiello ◽  
R Desmorat
Keyword(s):  
Plastic Strain ◽  
Damage Evolution ◽  
Time Integration ◽  
Anisotropic Damage ◽  
Proportional Loading ◽  
Isotropic Materials ◽  
Damage Models ◽  
Evolution Laws ◽  
Lode Angle ◽  
Fully Coupled

The lode angle dependency introduced by anisotropic damage evolution laws is analyzed in detail for initially isotropic materials. Many rupture criteria are obtained, under the proportional loading assumption, by the time integration of different anisotropic damage evolution laws [Formula: see text] among the three existing families: strain governed, stress governed and plastic strain governed. The cross-analysis of path independent rupture criteria and of anisotropic damage evolution laws finally allows us to improve the Lode angle dependency of (fully coupled) anisotropic damage models.

Maximal Crack Tip Shielding by Microcracking

1989 ◽  
Vol 56 (2) ◽  
pp. 279-283 ◽  
Author(s):  
M. Ortiz ◽  
A. E. Giannakopoulos
Keyword(s):  
Crack Tip ◽  
Asymptotic Solutions ◽  
Shielding Effect ◽  
Mode I ◽  
Anisotropic Damage ◽  
Maximum Tension ◽  
Damage Models ◽  
Singular Field ◽  
Crack Tip Shielding

It is shown here that the shielding effect of a distribution of microcracks, i.e., the extent to which they alleviate the severity of a near-tip singular field, is maximized when the microcracks develop normal to the direction of maximum tension. In passing, we derive mode I asymptotic solutions for a class of anisotropic damage models.

ANISOTROPIC DAMAGE MODELS FOR GEOMATERIALS: THEORETICAL AND NUMERICAL CHALLENGES

2014 ◽  
Vol 11 (02) ◽  
pp. 1342007 ◽  
Author(s):  
HAO XU ◽  
CHLOÉ ARSON
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Damage Model ◽  
Damage Threshold ◽  
Yield Function ◽  
Flow Rule ◽  
Anisotropic Damage ◽  
Damage Models ◽  
Associate Flow Rule

A new anisotropic damage model for rock is formulated and discussed. Flow rules are derived with the energy release rate conjugate to damage, which is thermodynamically consistent. Drucker–Prager yield function is adapted to make the damage threshold depend on damage energy release rate and to distinguish between tension and compression strength. Positivity of dissipation is ensured by using a nonassociate flow rule for damage, while nonelastic deformation due to damage is computed by an associate flow rule. Simulations show that the model meets thermodynamic requirements, follows a rigorous formulation, and predicts expected trends for damage, deformation and stiffness.

scholarly journals Simplified damage models applied in the numerical analysis of reinforced concrete structures

2012 ◽  
Vol 5 (1) ◽  
pp. 26-37 ◽  
Author(s):  
J. J. C. Pituba ◽  
M. M. S. Lacerda
Keyword(s):  
Reinforced Concrete ◽  
Structural Engineering ◽  
Damage Model ◽  
Concrete Structures ◽  
Numerical Analyses ◽  
Anisotropic Damage ◽  
Reinforced Concrete Structures ◽  
Damage Models ◽  
Tension And Compression ◽  
Elastic Responses

This work presents one and two-dimensional numerical analyses using isotropic and anisotropic damage models for the concrete in order to discuss the advantages of these modeling. Initially, it is shortly described the damage model proposed by Mazars. This constitutive model assumes the concrete as isotropic and elastic material, where locally the damage is due to extensions. On the other hand, the damage model proposed by Pituba, the material is assumed as initial elastic isotropic medium presenting anisotropy, plastic strains and bimodular response (distinct elastic responses whether tension or compression stress states prevail) induced by the damage. To take into account for bimodularity two damage tensors governing the rigidity in tension and compression regimes, respectively, are introduced. Damage activation is expressed by two criteria indicating the initial and further evolution of damage. Soon after, the models are used in numerical analyses of the mechanical behavior of reinforced concrete structures. Accordingly with comparison of the obtained responses, considerations about the application of the isotropic and anisotropic damage models are presented for 1D and 2D reinforced concrete structures modeling as well as the potentialities of the simplified versions of damage models applied in situations of structural engineering.

Off-Diagonal Elastic Constants and Anisotropic Damage

1992 ◽  
Vol 114 (3) ◽  
pp. 244-249 ◽  
Author(s):  
S. Baste ◽  
A. Gerard
Keyword(s):  
Orthotropic Material ◽  
Ultrasonic Method ◽  
Ceramic Matrix Composite ◽  
Nonlinear Behavior ◽  
Ceramic Matrix ◽  
Anisotropic Damage ◽  
Strain Measurements ◽  
First Order ◽  
Classical Strain ◽  
Damage Models

Various anisotropic damage models are investigated to take into account the nonlinear behavior of a ceramic matrix composite. A critical analysis of classical strain metrology results proves that it is unfeasible to evaluate the damage in a direction orthogonal to the stress one, because the nine elasticity constants of an orthotropic material are independent and Poisson’s ratios are strain’s second order, whereas Young’s modulus are first-order ones. An ultrasonic method provides the necessary stiffness variations, inaccessible by classical strain measurements, required to identify the anisotropic damage.

Validation of Modified Lemaitre’s Anisotropic Damage Model with the Cross Die Drawing Test

2011 ◽  
Vol 488-489 ◽  
pp. 49-52 ◽  
Author(s):  
M.S. Niazi ◽  
H. H. Wisselink ◽  
T. Meinders
Keyword(s):  
Strain Rate ◽  
Automotive Industry ◽  
Damage Model ◽  
Anisotropic Damage ◽  
Rate Dependency ◽  
Damage Models ◽  
Rate Dependent ◽  
Drawing Test ◽  
Dp Steels ◽  
The Cross

Dual Phase (DP) steels are widely replacing the traditional forming steels in automotive industry. Advanced damage models are required to accurately predict the formability of DP steels. In this work, Lemaitre’s anisotropic damage model has been slightly modified for sheet metal forming applications and for strain rate dependent materials. The damage evolution law is adapted to take into account the strain rate dependency and negative triaxialities. The damage parameters for pre-production DP600 steel were determined. The modified damage models (isotropic and anisotropic) were validated using the cross die drawing test. The anisotropic damage model predicts the crack direction more accurately.

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