Coupling Analysis between Stress Induced Anisotropic Damage and Permeability Variation in Brittle Rocks

2007 ◽  
Vol 340-341 ◽  
pp. 1133-1138 ◽  
Author(s):  
Hui Zhou ◽  
Jian Fu Shao ◽  
Xia Ting Feng ◽  
Da Wei Hu
Keyword(s):  
Damage Model ◽  
Coupling Model ◽  
Mechanical Analysis ◽  
Effective Porosity ◽  
Anisotropic Damage ◽  
Permeability Evolution ◽  
Coupling Analysis ◽  
Brittle Rocks ◽  
Permeability Variation ◽  
Set Up

In this paper, a coupling constitutive model is proposed for anisotropic damage and permeability variation in brittle rocks before cracks fully coalesce. In this coupling model, an anisotropic damage model is employed to perform the mechanical analysis, and a statistical penetration model is set up to describe the effective porosity and permeability evolution in brittle rocks. For the coupling analysis, anisotropic damage model offers statistical penetration model the crack length in various directions, and statistical penetration model inversely provides anisotropic damage model with permeability of rock for coupling hydro-mechanical analysis. The proposed coupling model is applied to Lac du Bonnet granite, and generally a good agreement is obtained between numerical simulations and experimental data.

scholarly journals A Micromechanical Anisotropic Damage Model for Brittle Rocks With Non-Associated Plastic Flow Rule Under True Triaxial Compressive Stresses

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuangshuang Yuan ◽  
Qizhi Zhu ◽  
Wanlu Zhang ◽  
Jin Zhang ◽  
Lunyang Zhao
Keyword(s):  
Plastic Flow ◽  
Damage Model ◽  
Local Stress ◽  
Inclusion Problem ◽  
Flow Rule ◽  
Model Parameters ◽  
Anisotropic Damage ◽  
True Triaxial ◽  
Brittle Rocks ◽  
Plastic Flow Rule

A micromechanical anisotropic damage model with a non-associated plastic flow rule is developed for describing the true triaxial behaviors of brittle rocks. We combine the Eshelby’s solution to the inclusion problem with the framework of irreversible thermodynamics. The main dissipative mechanisms of inelastic deformation due to the frictional sliding and damage by microcrack propagation are strongly coupled to each other. A Coulomb-type friction criterion is formulated in terms of the local stress applied onto the microcracks as the yielding function. The back-stress term contained in this local stress plays a critical role in describing the material’s hardening/softening behaviors. With a non-associated flow rule, a potential function is involved. Some analytical analysis of the non-associated micromechanical anisotropic damage model are conducted, which are useful for the model parameters calibration. The proposed model is used to simulate the laboratory tests on Westerly granite under true triaxial stresses. Comparing the numerical simulation results provided by the models with associated/non-associated plastic flow rule and experimental results, it is clear that the proposed non-associated model gives a better prediction than the previous associated model.

On Damage and Fracture Mechanics of Shaft Lining under Complicated Loads with Freezing Method

2010 ◽  
Vol 452-453 ◽  
pp. 549-552
Author(s):  
Bin Liu ◽  
Quan Sheng Liu
Keyword(s):  
Fracture Mechanics ◽  
Damage Model ◽  
Evolutionary Process ◽  
Additional Stress ◽  
Anisotropic Damage ◽  
Mine Shaft ◽  
Aggregate Gradation ◽  
Damage And Fracture ◽  
Shaft Lining ◽  
Set Up

Based on the stress characteristics of freeze shinking shaft lining at construction and operation stages, it is set up that The anisotropic damage model including initial damage, which suit to make Damage and Fracture Mechanics analysis for the shaft lining. A 3 dimensional anisotropic damage program is compiled using FEPG software, which take the following factors into consideration: temperature, conduction conditions, concrete facture energy and its aggregate gradation. Take the liangbosi mine shaft lining for example, its damage evolutionary process under complicated stresses such as permanence field stress, the gravity and vertical additional stress changed with time is obtained. It is discussed that the facture’s position and its development process, and the mechanical mechanics of the shaft lining structure failure.

Comparison of Two Time-Integration Algorithms for an Anisotropic Damage Model Coupled with Plasticity

2015 ◽  
Vol 784 ◽  
pp. 292-299 ◽  
Author(s):  
Stephan Wulfinghoff ◽  
Marek Fassin ◽  
Stefanie Reese
Keyword(s):  
Evolution Equations ◽  
Damage Model ◽  
Time Integration ◽  
Three Dimensional ◽  
Anisotropic Damage ◽  
Euler Scheme ◽  
The Finite Element Method ◽  
Time Step ◽  
Implicit Euler Scheme ◽  
Integration Algorithms

In this work, two time integration algorithms for the anisotropic damage model proposed by Lemaitre et al. (2000) are compared. Specifically, the standard implicit Euler scheme is compared to an algorithm which implicitly solves the elasto-plastic evolution equations and explicitly computes the damage update. To this end, a three dimensional bending example is solved using the finite element method and the results of the two algorithms are compared for different time step sizes.

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.

scholarly journals Modeling of Hydraulic Fracture of Concrete Gravity Dams by Stress-Seepage-Damage Coupling Model

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Sha Sha ◽  
Guoxin Zhang
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Hydraulic Fracture ◽  
Carrying Capacity ◽  
Damage Model ◽  
Coupling Model ◽  
Propagation Path ◽  
Concrete Dams ◽  
Gravity Dams ◽  
Concrete Gravity Dams

High-pressure hydraulic fracture (HF) is an important part of the safety assessment of high concrete dams. A stress-seepage-damage coupling model based on the finite element method is presented and first applied in HF in concrete dams. The coupling model has the following characteristics: (1) the strain softening behavior of fracture process zone in concrete is considered; (2) the mesh-dependent hardening technique is adopted so that the fracture energy dissipation is not affected by the finite element mesh size; (3) four coupling processes during hydraulic fracture are considered. By the damage model, the crack propagation processes of a 1 : 40 scaled model dam and Koyna dam are simulated. The results are in agreement with experimental and other numerical results, indicating that the damage model can effectively predict the carrying capacity and the crack trajectory of concrete gravity dams. Subsequently, the crack propagation processes of Koyna dam using three notches of different initial lengths are simulated by the damage model and the coupling model. And the influence of HF on the crack propagation path and carrying capacity is studied. The results reveal that HF has a significant influence on the global response of the dam.

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