Numerical simulation of shear band patterning in biaxial compression tests

1993 ◽  
Vol 20 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Jacek Tejchman ◽  
Wei Wu
2019 ◽  
Vol 92 ◽  
pp. 16005
Author(s):  
Hansini Mallikarachchi ◽  
Kenichi Soga

When saturated granular materials which are dilative in nature are subjected to the undrained deformation, their strength increases due to the generation of negative excess pore pressure. This phenomenon is known as dilative hardening and can be witnessed in saturated dense sand or rocks during very fast loading. However, experimental evidence of undrained biaxial compression tests of dense sand shows a limit to this dilative hardening due to the formation of shear bands. There is no consensus in the literature about the mechanism which triggers these shear bands in the dense dilative sand under isochoric constraint. The possible theoretical reasoning is the local drainage inside the specimen under the globally undrained condition, which is challenging to be monitored experimentally. Hence, both incept of localisation and post-bifurcation of the saturated undrained dense sand demand further numerical investigation. Pathological mesh dependency hinders the ability of the finite element method to represent the localisation without advanced regularisation methods. This paper attempt to provide a macroscopic constitutive behaviour of the undrained deformation of the saturated dense sand in the presence of a locally drained shear band. Discontinuation of dilatant hardening due to partial drainage between the shear band and the adjacent material is integrated into the constitutive model without changing governing equilibrium equations. Initially, a classical bifurcation analysis is conducted to detect the inception and inclination of the shear band based on the underlying drained deformation. Then a post-bifurcation analysis is carried out assuming an embedded drained or partially drained shear band at gauss points which satisfy bifurcation criterion. The smeared shear band approach is utilised to homogenise the constitutive relationship. It is observed that the dilatant hardening in the saturated undrained dense sand is reduced considerably due to the formation of shear bands.


2021 ◽  
Vol 8 ◽  
Author(s):  
Yan-Shuang Yang ◽  
Wei Cheng ◽  
Zhan-Rong Zhang ◽  
Hao-Yuan Tian ◽  
Kai-Yue Li ◽  
...  

The energy dissipation usually occurs during rock failure, which can demonstrate the meso failure process of rock in a relatively accurate way. Based on the results of conventional triaxial compression experiments on the Jinping marble, a numerical biaxial compression model was established by PFC2D to observe the development of the micro-cracks and energy evolution during the test, and then the laws of crack propagation, energy dissipation and damage evolution were analyzed. The numerical simulation results indicate that both the crack number and the total energy dissipated during the loading process increase with confining pressures, which is basically consistent with the experiment results. Two damage variables were presented in terms of the density from other researchers’ results and energy dissipation from numerical simulation, respectively. The energy-based damage variable varies with axial strain in the shape of “S,” and approaches one more closely than that based on density at the final failure period. The research in the rock failure from the perspective of energy may further understand the mechanical behavior of rocks.


2011 ◽  
Vol 243-249 ◽  
pp. 704-709
Author(s):  
Chun Yi Xu ◽  
Ming Liu ◽  
Bo Xu

To study the influence of slenderness on the compressive bearing capacity of autoclaved fly ash perforated brick masonry long columns and provide experimental evidences for making corresponding technical code, compression tests were conducted on 9 autoclaved fly ash perforated brick masonrys long columns of different slenderness. The damage patterns and compression performance are analyzed. The experimental results indicate that compressive capacity decreases proportionally as slenderness increases and the proposed formula of axial compressive bearing capacity for autoclaved fly ash perforated brick masonry columns is given. The nonlinear FEA program ANSYS is also adopted to simulate the behaviors of masonry columns. By comparing results find that the simulated results agree well with the test ones, the rationality and applicability of the model are verified.


2018 ◽  
Vol 323 ◽  
pp. 385-392 ◽  
Author(s):  
Dong Lei ◽  
Jinfeng Huang ◽  
Wenxiang Xu ◽  
Wenchao Wang ◽  
Pei Zhang

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Suifeng Wang ◽  
Fei Tan ◽  
Minglong You ◽  
Yu-Yong Jiao ◽  
Fubin Tu

Investigating the crack initiation stress of rocks is vital for understanding the gradual damage process of rocks and the evolution law of internal cracks. In this paper, the particle flow code method is used to conduct biaxial compression tests on a marble model with an elliptical crack under different confining pressures. According to the evolution status of microcracks in the rock during compression, four characteristic stresses are defined to reflect the gradual damage process of the marble. Two different methods are used to obtain crack initiation stress of rocks, and the calculation results are compared with those based on Griffith’s strength theory to verify the accuracy of this theory under compressive stress. Based on the numerical simulation results, the evolution law for the strength parameters of marble with the degree of damage is described. According to the proportional relationship between the peak stress and crack initiation stress, a new method for predicting the initiation stress is proposed, whose effectiveness is verified. Overall, the results of this study can serve as a useful guide for solving the important problems of slab cracking and rockburst encountered in underground space engineering.


2018 ◽  
Vol 941 ◽  
pp. 1391-1396 ◽  
Author(s):  
Nitish Bibhanshu ◽  
Satyam Suwas

The hot workability of gamma titanium aluminide alloy, Ti-48Al-2V-2Nb, was assessed in the cast condition through a series of compression tests conducted over a range of temperatures (1000 to 1175 °C) and at the strain rate of 10 S-1. The mechanism of dynamics recrystallization has been investigated from SEM Z-contrast images and from the Electron backscattered diffraction EBSD as well. It has been observed that volume fraction of the recrystallized grains increases with increasing the deformation temperature. The major volume fraction of the recrystallized grains was observed in the shear band which was forming at an angle 45 ̊ with respect to the compression direction. The mechanism of breaking of the laths and the region of the dynamic recrystallization were also investigated from the SEM Z-contrast image and EBSD. The dynamic recrystallization occurred in the region of the broken laths and shear bands. The breaking of the laths was because of the kinking of the lamellae. The shear band, kinked lamellae and dynamic recrystallized region where all investigated simultaneously.


Author(s):  
Tao Cheng ◽  
Renjie Hu ◽  
Wanhui Xu ◽  
Yi Zhang

In this paper, the mechanical properties and engineering applicationof electric furnace (EAF) slag mixed soil are investigated.The samples of steel slag are taken from a steel manufacturingcompany in Huangshi, a city of China. The mixed soilwas firstly prepared by mixing the steel slag and clay mixturein different proportions. The optimal moisture content for mixingthe soil is investigated from the experiment through directshear test. Based on three axial compression tests, the optimumsteel slag ratio is determined. Finally, the mechanical propertiesof steel slag mixed soil are tested in a practical engineeringproblem through a numerical simulation. The steel slag mixedsoil is used to replace the original soil of the embankment andcompared with that of the original one. The comparison studyshows that the method proposed in this paper is simple andeffective. Moreover, from the practical problem analysis, theoptimal utilization of electric furnace slag can be achieved.


2017 ◽  
Vol 898 ◽  
pp. 79-85
Author(s):  
Tao Lin ◽  
Ji Xue Zhou ◽  
Bai Chang Ma ◽  
Yun Teng Liu ◽  
Di Zhang ◽  
...  

Based on the stress-strain curves at the temperature of 300-450 °C with strain rate of 0.01-1 s−1 by hot compression tests, the empirical dynamic recrystallization models for the semi-continuous AZ31magnesium alloy were developed. The dynamic recrystallization evolution during the seamless tube extrusion of the AZ31 Mg alloy was simulated by numerical method with the derived models and validated by experiment measurements. The results show that at certain extrusion speed the influence of the extruding temperature on the dynamic recrystallization fraction was significant. With the increase of the extruding temperature the volume fraction of dynamic recrystallization increase obviously. The predicted dynamic recrystallization fraction was in an excellent agreement with the experimental results.


2007 ◽  
Vol 344 ◽  
pp. 955-962
Author(s):  
E. Szczurek ◽  
M. Dubar ◽  
R. Deltombe ◽  
A. Dubois ◽  
L. Dubar

This paper deals with an industrial three rolls coater. The behaviour law of the elastomer roll cover in different environments is first established in order to be taken into account in the numerical simulation of the process. Cyclic compression tests are performed and compared to the corresponding numerical simulation to precisely determine the viscoelastic parameters. With the identified parameters, a finite element simulation of the process is then performed to evaluate the meniscus stability in real contact conditions. The influence of the determined elastomer behaviour laws on the free surface position is discussed.


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