Crack tip field andJ-integral with strain gradient effect

2004 ◽  
Vol 20 (3) ◽  
pp. 228-237 ◽  
Author(s):  
Xia Song ◽  
Wang Tzuchiang ◽  
Chen Shaohua
Keyword(s):  
Strain Gradient ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Gradient Effect

An Alternative Decomposition of the Strain Gradient Tensor

2001 ◽  
Vol 69 (2) ◽  
pp. 139-141 ◽  
Author(s):  
H. Jiang ◽  
Y. Huang ◽  
T. F. Guo ◽  
K. C. Hwang
Keyword(s):  
Strain Gradient ◽  
Strain Field ◽  
Numerical Study ◽  
Volumetric Strain ◽  
Crack Tip ◽  
Square Root ◽  
Crack Tip Field ◽  
Gradient Tensor ◽  
Classical Plasticity ◽  
Square Root Singularity

An alternative decomposition of the strain gradient tensor is proposed in this paper in order to ensure that the deviatoric strain gradient vanishes for an arbitrary volumetric strain field, which is consistent with the physical picture of plastic deformation. The theory of mechanism-based strain gradient (MSG) plasticity is then modified accordingly based on this new decomposition. The numerical study of the crack-tip field based on the new theory shows that the crack tip in MSG plasticity has the square-root singularity, and the stress level is much higher than the HRR field in classical plasticity.

Scale-Dependent Crack Modeling for Investigation the Effect of Geometrically Necessary Dislocations in Micro/Nano Grain Size of Copper

2016 ◽  
Vol 15 ◽  
pp. 1-16 ◽  
Author(s):  
Amin Zaami ◽  
Ali Shokuhfar
Keyword(s):  
Grain Size ◽  
Stress Concentration ◽  
Strain Gradient ◽  
Stress Concentration Factor ◽  
Size Effects ◽  
Crack Tip ◽  
Length Scale ◽  
State Variables ◽  
Dependent Model ◽  
Homogeneous Strain

In this study, a scale-dependent model is employed to investigate the size effects of copper on the behavior of the crack-tip. This model includes the homogeneous and non-homogeneous strain hardening based on the wavelet interpretation of size effect. Introducing additional micro/nano structural considerations together with decreasing grain size, different size effects can be obtained. As the size dependency is not taken into account in conventional plasticity, an enhanced theory which is related to the strain gradient introduces a length scale will give more realistic representations of state variables near the crack-tip. Accordingly, the contribution of geometrically necessary dislocations (GNDs) activity on strengthening and stress concentration factor is identified in the crack-tip. Finally, the affected zone which is dominated by presence of GNDs is identified

VARIATIONAL MULTISCALE ANALYSIS OF SOLIDS WITH STRAIN GRADIENT PLASTIC EFFECTS USING MESHFREE APPROXIMATION

2005 ◽  
Vol 02 (04) ◽  
pp. 601-626 ◽  
Author(s):  
JEOUNG-HEUM YEON ◽  
SUNG-KIE YOUN
Keyword(s):  
Strain Gradient ◽  
Partition Of Unity ◽  
Meshfree Method ◽  
Internal Variable ◽  
Plasticity Theory ◽  
Fine Scale ◽  
Meshfree Approximation ◽  
Gradient Effect ◽  
Classical Plasticity ◽  
Variational Form

A meshfree multiscale method is presented for efficient analysis of solids with strain gradient plastic effects. In the analysis of strain gradient plastic solids, localization due to increased hardening of strain gradient effect appears. Chen-Wang theory is adopted, as a strain gradient plasticity theory. It represents strain gradient effects as an internal variable and retains the essential structure of classical plasticity theory. In this work, the scale decomposition is carried out based on variational form of the problem. Coarse scale is designed to represent global behavior and fine scale to represent local behavior and gradient effect by using the intrinsic length scale. From the detection of high strain gradient region, fine scale region is adopted. Each scale variable is approximated using meshfree method. Meshfree approximation is well suited for adaptivity. As a method of increasing resolution, partition of unity based extrinsic enrichment is used. Each scale problem is solved iteratively. The proposed method is applied to bending of a thin beam and bimaterial shear layer and micro-indentation problems. Size effects can be effectively captured in the results of the analysis.

Mismatch Effect on the Mixed Mode Type Creep Crack within Weldment

2016 ◽  
Vol 853 ◽  
pp. 281-285
Author(s):  
Jun Hui Zhang ◽  
Yan Wei Dai
Keyword(s):  
Mixed Mode ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Loading Mode ◽  
The Difference ◽  
Engineering Practices ◽  
Mismatch Effect ◽  
Transient And Steady State

Creep crack within weldments are very common in engineering practices, and the cracking location in these welding structures always appears at the HAZ location. The mismatch effect on the mixed mode creep crack is still not clear in these available literatures. The aim of this paper is to investigate the mismatch influence on the creep crack of mixed mode thoroughly. A mixed mode creep crack within HAZ is established in this paper. The leading factor that dominates the creep crack tip field under mixed loading mode is studied. The influences of mismatch effect on mode mixity, stress distribution and stress triaxiality are proposed. The difference of mixed mode creep crack and normal mode I or mode II creep crack are compared. The influence of mixity factor on the transient and steady state creep of crack tip are also analyzed.

Gradient of Soil Constitutive Model

2010 ◽  
Vol 168-170 ◽  
pp. 1126-1129
Author(s):  
Wen Xu Ma ◽  
Ying Guang Fang
Keyword(s):  
Plastic Strain ◽  
Strain Gradient ◽  
Soil Analysis ◽  
Natural Material ◽  
Flow Rule ◽  
The Finite Element Method ◽  
Gradient Effect ◽  
Non Local ◽  
Associated Flow Rule ◽  
Plastic Strain Gradient

For the soil is a very complex natural material, significant strain gradient effect exist in soil analysis. Based on the "gradient" phenomenon, we add the plastic strain gradient hardening item into the traditional Cambridge yield surface. By using the consistency conditions and associated flow rule, we get the explicit expression of plastic strain gradient stiffness matrix. And the finite element method of plastic strain gradient is also shown in this article. Plastic strain gradient is actually a phenomenological non-local model containing microstructure information of the material. It may overcome the difficulties in simulating the gradient phenomenon by traditional mechanical model.

INVESTIGATIONS ON THE DYNAMIC NEAR-CRACK-TIP FIELD USING THE GRID METHOD

1988 ◽  
Vol 49 (C3) ◽  
pp. C3-307-C3-312
Author(s):  
K. KUSSMAUL ◽  
T. DEMLER ◽  
A. KLENK
Keyword(s):  
Crack Tip ◽  
Grid Method ◽  
Crack Tip Field

Linear strain-gradient effect on the energy bandgap in bent CdS nanowires

Nano Research ◽  
2010 ◽  
Vol 4 (3) ◽  
pp. 308-314 ◽  
Author(s):  
Qiang Fu ◽  
Zi Yue Zhang ◽  
Liangzhi Kou ◽  
Peicai Wu ◽  
Xiaobing Han ◽  
...  
Keyword(s):  
Strain Gradient ◽  
Linear Strain ◽  
Gradient Effect ◽  
Energy Bandgap ◽  
Cds Nanowires
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