Representation of Crack-Tip Plasticity in Pressure Sensitive Geomaterials: Large Scale Yielding

2006 ◽  
Vol 139 (1) ◽  
pp. 137-144 ◽  
Author(s):  
Panos Papanastasiou ◽  
Colin Atkinson
Keyword(s):  
Large Scale ◽  
Crack Tip ◽  
Pressure Sensitive ◽  
Scale Yielding ◽  
Crack Tip Plasticity

Comparison of Strip Yield and Net Section Plasticity Models for a Bar in Bending With a Single Edge Crack

2017 ◽  
Author(s):  
Wolf Reinhardt ◽  
Don Metzger
Keyword(s):  
Edge Crack ◽  
Large Scale ◽  
Stress Singularity ◽  
Crack Tip ◽  
Small Scale ◽  
Single Edge ◽  
Yield Model ◽  
Strip Yield Model ◽  
Crack Tip Plasticity ◽  
Stress And Deformation

The strip yield model is widely used to describe crack tip plasticity in front of a crack. In the strip yield model the stress in the plastic zone is considered as known, and stress and deformation fields can be obtained from elastic solutions using the condition that the crack tip stress singularity vanishes. The strip yield model is generally regarded to be valid to describe small scale plasticity at a crack tip. The present paper examines the behavior of the strip yield model at the transition to large-scale plasticity and its relationship to net section plasticity descriptions. A bar in bending with a single edge crack is used as an illustrative example to derive solutions and compare with one-sided and two-sided plasticity solutions.

Comments on “A new procedure for measuring the decohesion energy for thin ductile films on substrates,” by A. Bagchi, G. E. Lucas, Z. Suo, and A. G. Evans [J. Mater. Res. 9, 1734 (1994)]

1996 ◽  
Vol 11 (8) ◽  
pp. 2109-2111 ◽  
Author(s):  
O. Jørgensen ◽  
A. Horsewell ◽  
B. F. Sørensen
Keyword(s):  
Closed Form ◽  
Large Scale ◽  
Crack Tip ◽  
Bilayer Film ◽  
Sufficient Condition ◽  
Elastic Analysis ◽  
Tensile Stresses ◽  
Linear Elastic ◽  
Additional Layer ◽  
Scale Yielding

A recently proposed method for measuring decohesion energy of ductile films on substrates is discussed. The loading mechanism that causes the decohesion of the ductile film is that of gradually depositing an additional layer, with large residual tensile stresses, on top of the film. Hence, the method involves the decohesion of a bilayer film on a substrate. The suggested method assumes that the unloading of the film is controlled entirely by elasticity. This assumption is a prerequisite for the suggested linear elastic analysis, from which the interfacial debond energy is derived in closed form. However, as is shown in the present comment, large scale yielding can occur in the wake of the crack tip and is prohibitive to the suggested linear elastic analysis. A sufficient condition for the occurrence of said large scale yielding is outlined in the present comment. Indeed it is shown that large scale plasticity must have occurred in the experiments described by Bagchi et al.1

scholarly journals Analysis of blunted crack tip field in large scale yielding.

1985 ◽  
Vol 51 (463) ◽  
pp. 824-830 ◽  
Author(s):  
Shigeru AOKI ◽  
Kikuo KISHIMOTO ◽  
Atsushi KIMURA ◽  
Masaru SAKATA
Keyword(s):  
Large Scale ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Scale Yielding

Constraint Quantification of Single Edge Notched Bend Specimens Under Large-Scale Yielding

2003 ◽  
Author(s):  
Yuh J. Chao ◽  
Xian-Kui Zhu ◽  
Yil Kim ◽  
M. J. Pechersky ◽  
M. J. Morgan ◽  
...  
Keyword(s):  
Large Scale ◽  
Crack Tip ◽  
Bending Moment ◽  
Additional Term ◽  
Small Scale ◽  
Bending Stress ◽  
Single Edge ◽  
Crack Tip Fields ◽  
Scale Yielding ◽  
Crack Tip Constraint

Because crack-tip fields of single edge notched bend (SENB) specimens are significantly affected by the global bending moment under the conditions of large-scale yielding (LSY), the classical crack tip asymptotic solutions fail to describe the crack-tip fields within the crack tip region prone to ductile fracture. As a result, existing theories do not quantify correctly the crack-tip constraint in such specimens under LSY conditions. To solve this problem, the J-A2 three-term solution is modified in this paper by introducing an additional term derived from the global bending moment in the SENB specimens. The J-integral represents the intensity of applied loading, A2 describes the crack-tip constraint level, and the additional term characterizes the effect of the global bending moment on the crack-tip fields of the SENB specimens. The global bending stress is derived from the strength theory of materials, and proportional to the applied bending moment and the inverse of the ligament size. Results show that the global bending stress near the crack tip of SENB specimens is very small compared to the J-A2 three-term solution under small-scale yielding (SSY), but becomes significant under the conditions of LSY or fully plastic deformation. The modified J-A2 solutions match well with the finite element results for the SENB specimens at all deformation levels ranging from SSY to LSY, and therefore can effectively model the effect of the global bending stress on the crack-tip fields. Consequently, the crack-tip constraint of such bending specimens can now be quantified correctly.

Numerical Analyses of Ductile Fracture Behavior in 2D Plane Strain and Axisymmetric Models Using the Complete Gurson Model

2009 ◽  
Author(s):  
Jie Xu ◽  
Zhiliang Zhang ◽  
Erling O̸stby ◽  
Ba˚rd Nyhus ◽  
Dongbai Sun
Keyword(s):  
Crack Growth ◽  
Fracture Behavior ◽  
Large Scale ◽  
Crack Tip ◽  
Ductile Crack ◽  
Geometry Dependence ◽  
Ductile Crack Growth ◽  
Scale Yielding ◽  
Resistance Curves ◽  
Crack Tip Constraint

Ductile crack growth plays an important role in the analyses of fracture behavior of structures. A strong geometry dependence of ductile crack growth resistance emerges under large scale yielding conditions. This geometry dependence is associated with different levels of crack tip constraint. However, an independent relationship between the fracture resistance and crack tip constraint has also been observed in experimental studies for selected specimen geometries. To verify these results, crack growth resistance curves for plane strain, mode I crack growth under large scale yielding have been computed using the complete Gurson model. Single edge notched bending (SENB) and tension (SENT) specimens with three different crack geometries have been selected for the numerical analyses. Specimen size effect on ductile crack growth behavior has also been studied. In addition, the SENT specimen appears as an alternative to conventional fracture specimens to characterize fracture toughness of circumferentially cracked pipes due to its similar geometry constraint ahead of the crack tip with that of cracks in pipes. 2D axisymmetric models have been carried out to investigate the effect of biaxial loading (axial tension combined with internal pressure) on the resistance curves for pipes with long internal circumferential cracks under large scale yielding conditions.

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