Entire deformational characteristics and strain localization of jointed rock specimen in plane strain compression

2006 ◽  
Vol 13 (3) ◽  
pp. 300-306 ◽  
Author(s):  
Xue-bin Wang
Keyword(s):  
Plane Strain ◽  
Strain Localization ◽  
Rock Specimen ◽  
Jointed Rock ◽  
Plane Strain Compression

Polycrystal Plasticity Based Predictions of Strain Localization in Metal Forming

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Joel V. Bernier ◽  
Nathan R. Barton ◽  
Jaroslaw Knap
Keyword(s):  
Plane Strain ◽  
Strain Localization ◽  
Metal Forming ◽  
Adaptive Sampling ◽  
Material Model ◽  
Plane Strain Compression ◽  
Bulge Test ◽  
Fine Scale ◽  
Compression Tests ◽  
Polycrystal Plasticity

In this study, a multiscale material model is employed to simulate two metal forming processes: 2D plane strain compression and a 3D biaxial bulge test. A generalized Taylor-type polycrystal model is employed to describe the fine scale viscoplastic response of the material, while the coarse scale response is computed using a multiphysics finite element code. The coupling between the local responses of the textured polycrystal and the continuum level is achieved via an adaptive sampling framework, which is shown to greatly reduce the total number of fine scale evaluations required to achieve a specified error tolerance. The anisotropy represented at the fine scale is sufficient to observe strain localization in both forming processes. For the case of idealized plane strain compression, a fairly diffuse yet distinct patterning of plastic strain localization develops in a manner consistent with experimental observations. The application of friction constraints to the compression surfaces—as is present in channel die compression tests—dramatically strengthens and redistributes the localization patterns. The simulated biaxial bulge test also demonstrates strain localization that is in agreement with the locations of diffuse necks in experimental observations. The tests are conducted using a federated multiple-program multiple-data simulation, which allows for load balancing between the coarse and fine scale calculations. Such a simulation framework is capable of efficiently embedding physically robust, but computationally expensive material models in component scale simulations appropriate to design decisions.

Effects of Joint Width on Strength, Stress-Strain Curve and Strain Localization of Rock Mass in Uniaxial Plane Strain Compression

2007 ◽  
Vol 353-358 ◽  
pp. 1129-1132 ◽  
Author(s):  
X.B. Wang
Keyword(s):  
Plane Strain ◽  
Inclination Angle ◽  
Rock Specimen ◽  
Strain Curve ◽  
Plane Strain Compression ◽  
Intact Rock ◽  
Peak Strength ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Joint Width

Effects of joint width (JW) on the macroscopic stress-strain curve, the failure process and mode of jointed rock specimen (JRS) in plane strain compression are modeled by use of FLAC. The failure criterion of intact rock outside the inclined joint is a composite Mohr-Coulomb criterion with tension cut-off and the linear strain-softening post-peak constitutive relation is adopted. The joint is treated as quadrate elements of ideal plastic material beyond the peak strength. A written FISH function is used to automatically find elements in the joint. Numerical results show that the peak strength of JRS depends on JW and is lower than that of intact rock specimen without joint. For JRS, the shear strains are concentrated into the joint or the new generated shear bands (NGSBs); the peak strength decreases with an increase of JW. At lower or higher joint inclination angle (JIA), the failure mode and pattern of NGSBs are not related to JW. The post-peak response becomes ductile at wider JW and higher JIA. The post-peak slope of stress-strain curve at lower JIA is not dependent on JW since the width and inclination angle of NGSBs are not affected by JW.

scholarly journals Nonlocal regularization of an anisotropic critical state model for sand

2021 ◽  
Author(s):  
Zhiwei Gao ◽  
Xin Li ◽  
Dechun Lu
Keyword(s):  
Plane Strain ◽  
Strain Localization ◽  
Critical State ◽  
Regularization Method ◽  
Strain Softening ◽  
Plane Strain Compression ◽  
Strip Footing ◽  
Nonlocal Model ◽  
Nonlocal Regularization ◽  
Force Displacement

AbstractMany advanced constitutive models which can capture the strain-softening and state-dependent dilatancy response of sand have been developed. These models can give good prediction of the single soil element behaviour under various loading conditions. But the solution will be highly mesh-dependent when they are used in real boundary value problems due to the strain-softening. They can give mesh-dependent strain localization pattern and bearing capacity of foundations on sand. Nonlocal regularization of an anisotropic critical state sand model is presented. The evolution of void ratio which has a significant influence on strain-softening is assumed to depend on the volumetric strain increment of both the local and neighbouring integration points. The regularization method has been implemented using the explicit stress integration method. The nonlocal model has been used in simulating both drained plane strain compression and the response of a strip footing on dry sand. In plane strain compression, mesh-independent results for the force–displacement relationship and shear band thickness can be obtained when the mesh size is smaller than the internal length. The force–displacement relationship of strip footings predicted by the nonlocal model is much less mesh-sensitive than the local model prediction. The strain localization under the strip footing predicted by the nonlocal model is mesh independent. The regularization method is thus proper for application in practical geotechnical engineering problems.

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