scholarly journals Strain-Softening Analyses of a Circular Bore under the Influence of Axial Stress

2021 ◽  
Vol 11 (17) ◽  
pp. 7937
Author(s):  
Xuechao Dong ◽  
Mingwei Guo ◽  
Shuilin Wang
Keyword(s):  
Rock Mass ◽  
Plane Stress ◽  
Strain Softening ◽  
Hydrostatic Stress ◽  
Axial Stress ◽  
Perfectly Plastic ◽  
Out Of Plane ◽  
Softening Process ◽  
Elastic Perfectly Plastic ◽  
Proper Consideration

Strain-softening analyses were performed around a circular bore in a Mohr–Coulomb rock mass subjected to a hydrostatic stress field in cross section and out-of-plane stress along the axis of the bore. Numerical procedures that simplify the strain-softening process in a step manner were employed, and on the basis of the theoretical solutions of the elastic–brittle–plastic(EBP) medium, the strain-softening results of the displacements, stresses and the plastic zones around the circular bore were obtained. The numerical solution was validated based on the fact that the strain-softening process became EBP when the softening slope was very steep and elastic-perfectly plastic(EP) when the softening slope was near zero. The results illustrated that the stresses and displacements in the rock mass surrounding the bore was affected by axial stress and that a proper consideration of out-of-plane stress is necessary. Moreover, the presented results can be used for the verification of numerical codes.

Analytical Solutions of Crack Tip Plasticity Zone Shape for a Semi-Infinite Crack

2003 ◽  
Author(s):  
Peihua Jing ◽  
Tariq Khraishi ◽  
Larissa Gorbatikh
Keyword(s):  
Plane Strain ◽  
Plane Stress ◽  
Analytical Solutions ◽  
Yield Criterion ◽  
Plasticity Zone ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Classical Plasticity ◽  
Elastic Perfectly Plastic ◽  
Von Mises

In this work, closed-form analytical solutions for the plasticity zone shape at the lip of a semi-infinite crack are developed. The material is assumed isotropic with a linear elastic-perfectly plastic constitution. The solutions have been developed for the cases of plane stress and plane strain. The three crack modes, mode I, II and III have been considered. Finally, prediction of the plasticity zone extent has been performed for both the Von Mises and Tresca yield criterion. Significant differences have been found between the plane stress and plane strain conditions, as well as between the three crack modes’ solutions. Also, significant differences have been found when compared to classical plasticity zone calculations using the Irwin approach.

Effect of Yield Strength to Elastic Modulus Ratio on Finite Element Based Plastic Loads for Elbows Under Bending

2008 ◽  
Author(s):  
Kuk-Hee Lee ◽  
Yun-Jae Kim
Keyword(s):  
Elastic Modulus ◽  
Yield Strength ◽  
Modulus Ratio ◽  
Yield Strain ◽  
Perfectly Plastic ◽  
Plastic Materials ◽  
Out Of Plane ◽  
Asme Code ◽  
Elastic Perfectly Plastic ◽  
Experimental Values

This paper quantifies the effect of the yield strength-to-elastic modulus ratio (yield strain) on plastic loads (defined by the twice-elastic-slope according to the ASME code) for 90° elbows under in-plane and out-of-plane bending. Results are based on extensive and systematic FE limit analyses assuming elastic-perfectly plastic materials. Based on FE results, a simple approximation of plastic loads of pipe bends, incorporating the yield strength-to-elastic modulus ratio effect, is proposed. To validate the proposed approximation, predicted plastic moments are compared with published full-scale pipe test data, showing that the proposed approximation gives overall lower than the FE results and close to experimental values.

Discussions on Zonal Disintegration around Tunnel in Deep Rock Mass

2012 ◽  
Vol 594-597 ◽  
pp. 2285-2289 ◽  
Author(s):  
Peng Jia ◽  
Tian Hong Yang ◽  
Chun Ming Zhang
Keyword(s):  
Rock Mass ◽  
Laboratory Test ◽  
Stress Level ◽  
Hydrostatic Stress ◽  
Axial Stress ◽  
Numerical Code ◽  
Zonal Disintegration ◽  
Heterogeneous Rock ◽  
Deep Rock ◽  
Adjacent Fractures

Questions related to zonal disintegration such as difference between results from laboratory test and field monitoring test, as well as the effect of multi-axial stress level on zonal disintegration were discussed through numerical modeling by using a 3D numerical code called RFPA3D. Results show that the much smaller fracture spacing captured by laboratory test on zonal disintegration is due to the heterogeneity extent of the tested material. Zonal disintegration is an inherent character of heterogeneous rock mass, the more the heterogeneous the rock is, the larger the spacing between the adjacent fractures will be. The configuration of zonal disintegration is influenced by combination of stress level in three directions. Intact fracture rings can not be formed unless a nearly hydrostatic stress state exists in directions perpendicular to tunnel axis.

scholarly journals The yield condition strongly influences the formation of Dugdale plastic strips ahead of crack tips under tensile plane stress loading conditions

2012 ◽  
Vol 21 (1-2) ◽  
pp. 37-39
Author(s):  
David J. Unger
Keyword(s):  
Plane Stress ◽  
Plastic Material ◽  
Yield Condition ◽  
Loading Conditions ◽  
Element Analysis ◽  
Plastic Strip ◽  
Tresca Yield Condition ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Von Mises

AbstractA finite element analysis indicates a good correlation between the Dugdale plastic strip model and a linear elastic/perfectly plastic material under plane stress loading conditions for a flow theory of plasticity based on the Tresca yield condition. A similar analysis under the von Mises yield condition reveals no plastic strip formation.

Asymptotic Fields of a Perfectly-Plastic, Plane-Stress Mode II Growing Crack

1986 ◽  
Vol 53 (4) ◽  
pp. 831-833 ◽  
Author(s):  
P. Ponte Castan˜eda
Keyword(s):  
Plane Stress ◽  
Velocity Fields ◽  
Mode I ◽  
Mode Ii ◽  
Perfectly Plastic ◽  
Stress Mode ◽  
Mode Ii Crack ◽  
Growing Crack ◽  
Elastic Perfectly Plastic ◽  
Elastic Unloading

The asymptotic near-tip stress and velocity fields are presented for a plane-stress Mode II crack propagating quasi-statically in an elastic-perfectly plastic Mises solid. The solution is found to have fully continuous stress and velocity fields, and a configuration similar to that of the anti-plane strain problem: a singular centered fan plastic sector ahead of the crack, followed by an elastic unloading sector and a constant stress plastic sector extending to the crack flank. The impossibility of a plane-stress Mode I crack solution having these properties is also discussed.

Specimen Design for Creep Characterization Under Multiaxial Stress

2005 ◽  
Author(s):  
Douglas L. Marriott ◽  
Peter Carter
Keyword(s):  
Plastic Material ◽  
Hydrostatic Stress ◽  
Creep Damage ◽  
Constitutive Law ◽  
Approximate Methods ◽  
Complex Material ◽  
Perfectly Plastic ◽  
Computationally Intensive ◽  
Material Conditions ◽  
Elastic Perfectly Plastic

This paper describes part of an ongoing study to develop a simple tensile test which will maximize the effects of hydrostatic constraint. The test for such purposes is the notched bar test. Two notch geometries are in common use, the ASTM Standard notch, and the Bridgman blunt notch. Both of these tests have shortcomings, which are described in the paper. Alternative geometries, including notches, plane strain holes and slots have been evaluated, using the ratio of hydrostatic stress to Mises stress in a bar made of an elastic, perfectly plastic material. Examples are given of the stress evolution in selected geometries under creep according to a simple Bailey/Norton power law model, and comparison is made with the behavior when a more complex material constitutive law is used, which includes continuum creep damage. The model used in this case is a simplified version of the MPC Omega model, described in API 579 [1]. Since creep calculations involving damage are both computationally intensive and difficult to carry to completion due to numerical convergence problems, approximate methods of predicting specimen behavior under such complex material conditions is being explored. One promising method, based on isochronous stress/strain curves is described and the results compared with detailed predictions using a more accurate constitutive model.

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