Experimental Investigation of the Strain-Strengthen Effect on the Existed I+II Mixed Mode Fatigue Crack Transformation Propagation in an Austenite Stainless Steel

2013 ◽  
Author(s):  
Huifang Li ◽  
Zhenbei Wang ◽  
Xiaoju Sun ◽  
Caifu Qian
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Compressive Stress ◽  
Mixed Mode ◽  
Crack Tip ◽  
Residual Compressive Stress ◽  
Strengthening Effect ◽  
Strain Strengthening

In this paper, I+II mixed mode fatigue crack transformation propagation in austenitic stainless steel 06Cr19Ni10 was tested. Finite element method with displacement approach was employed to calculate stress intensity factors at the crack tip. Strain-strengthening effect on the new crack initiation and propagation of the existed pre-crack was investigated. It is found that under the uni-axial loading, the inclined pre-crack grows in a direction perpendicular to the applied load, making crack mode transferred from I+II mixed mode to Mode I. When strain-strengthened, the new crack initiation from the pre-crack tip is much more difficulty and crack propagation is slower. Finite element non-linear analysis shows that a residual compressive stress distribution is formed around pre-crack tip after strain-strengthening. The residual compressive stress is responsible for the difficult initiation and slow propagation of the new crack.

Analytical Prediction Model for Fatigue Crack Propagation Rate under Tension-Compression Loading

2013 ◽  
Vol 842 ◽  
pp. 455-461
Author(s):  
Yu Sha ◽  
Shi Gang Bai ◽  
Ya Hui Wang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Plastic Zone ◽  
Crack Propagation ◽  
Compressive Stress ◽  
Fatigue Crack Propagation ◽  
Crack Tip ◽  
Plastic Zone Size ◽  
Zone Size ◽  
Compression Loading

Elastic–plastic finite element analyses have been performed to study the compressive stress effect on fatigue crack growth under applied tension–compression loading. The near crack tip stress, crack tip opening displacement and crack tip plastic zone size were obtained for a kinematic hardening material. The results have shown that the near crack tip local stress, displacement and reverse plastic zone size are controlled by the maximum stress intensity factors Kmax and the applied compressive stress σmaxcom under tension–compression. Based on the finite element analysis results, a fatigue crack propagation model using Kmax and σmaxcom as a parameters under tension–compression loading has been developed.The models under tension–compression loading agreed well with experimental observations.

Finite Element Analysis of the Effect of the Compressive Loading on Fatigue Crack Growth under Different Loading

2009 ◽  
Vol 16-19 ◽  
pp. 269-272 ◽  
Author(s):  
Yu Sha ◽  
Hui Tang ◽  
Xin Song ◽  
Jia Zhen Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Crack ◽  
Compressive Stress ◽  
Compressive Loading ◽  
Crack Tip ◽  
High Strength ◽  
Stress Cycle ◽  
Element Analysis ◽  
Compression Loading

In this paper, elastic-plastic finite element analysis has been performed in order to obtain the fatigue crack tip parameters under tension-compression loading. Two centre-cracked high-strength aluminum alloy with a crack length of 2mm under different tension-compression loading are analyzed. The analysis shows that the compressive loading has a significant contribution towards the crack tip plasticity and the crack tip stress. In a tension-compression loading the crack tip displacement increases with the increase of the compressive stress and the crack tip compress stress increases with the increase of the compressive stress. The maximum stress intensity Kmax in the tension part of the stress cycle and the maximum compressive stress in the compression part of the stress cycle are the main factors controlling the near crack tip parameters.

Cyclic Plasticity of a Cracked Structure Subjected to Mixed Mode Loading

2007 ◽  
Vol 348-349 ◽  
pp. 105-108 ◽  
Author(s):  
Sylvie Pommier
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Mixed Mode ◽  
Crack Tip ◽  
Cyclic Plasticity ◽  
Loading Conditions ◽  
Mixed Mode Loading ◽  
Crack Tip Plasticity

Cyclic plasticity in the crack tip region is at the origin of various history effects in fatigue. For instance, fatigue crack growth in mode I is delayed after the application of an overload because of the existence of compressive residual stresses in the overload’s plastic zone. Moreover, if the overload’s ratio is large enough, the crack may grow under mixed mode condition until it has gone round the overload’s plastic zone. Thus, crack tip plasticity modifies both the kinetics and the crack’s plane. Therefore modeling the growth of a fatigue crack under complex loading conditions requires considering the effects of crack tip plasticity. Finite element analyses are useful for analyzing crack tip plasticity under various loading conditions. However, the simulation of mixed mode fatigue crack growth by elastic-plastic finite element computations leads to huge computation costs, in particular if the crack doesn’t remain planer. Therefore, in this paper, the finite element method is employed only to build a global constitutive model for crack tip plasticity under mixed mode loading conditions. Then this model can be employed, independently of any FE computation, in a mixed mode fatigue crack growth criterion including memory effects inherited from crack tip plasticity. This model is developed within the framework of the thermodynamics of dissipative processes and includes internal variables that allow modeling the effect of internal stresses and to account for memory effects. The model was developed initially for pure mode I conditions. It was identified and validated for a 0.48%C carbon steel. It was shown that the model allows modeling fatigue crack growth under various variable amplitude loading conditions [1]. The present paper aims at showing that a similar approach can be applied for mixed mode loading conditions so as to model, finally, mixed mode fatigue crack growth.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

Finite Element Simulation of Stable Fatigue Crack Growth Using Critical CTOD Determined by Preliminary Finite Element Analysis

2014 ◽  
Vol 891-892 ◽  
pp. 1675-1680
Author(s):  
Seok Jae Chu ◽  
Cong Hao Liu
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Finite Element Simulation ◽  
Crack Growth ◽  
Crack Tip ◽  
Stress Intensity Factor Range ◽  
Crack Tip Opening Displacement ◽  
Element Analysis ◽  
Element Simulation

Finite element simulation of stable fatigue crack growth using critical crack tip opening displacement (CTOD) was done. In the preliminary finite element simulation without crack growth, the critical CTOD was determined by monitoring the ratio between the displacement increments at the nodes above the crack tip and behind the crack tip in the neighborhood of the crack tip. The critical CTOD was determined as the vertical displacement at the node on the crack surface just behind the crack tip at the maximum ratio. In the main finite element simulation with crack growth, the crack growth rate with respect to the effective stress intensity factor range considering crack closure yielded more consistent result. The exponents m in the Paris law were determined.

Atomistic Study of Cleavage and Dislocation Emission in NiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
M. Ludwig ◽  
P. Gumbsch
Keyword(s):  
Finite Element ◽  
Mixed Mode ◽  
Crack Tip ◽  
Mode I ◽  
Crack Plane ◽  
Dislocation Emission ◽  
Dislocation Generation ◽  
Embedded Atom ◽  
Atomistic Study ◽  
Eam Potential

AbstractThe atomistic processes during fracture of NiAl are studied using a new embedded atom (EAM) potential to describe the region near the crack tip. To provide the atomistically modeled crack tip region with realistic boundary conditions, a coupled finite element - atomistic (FEAt) technique [1] is employed. In agreement with experimental observations, perfectly brittle cleavage is observed for the (110) crack plane. In contrast, cracks on the (100) plane either follow a zig-zag path on (110) planes, or emit dislocations. Dislocation generation is studied in more detail under mixed mode I/II loading conditions.

A Novel Singular Finite Element on Mixed-Mode Dugdale Model Based Crack

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
W. A. Yao ◽  
X. F. Hu
Keyword(s):  
Finite Element ◽  
Analytical Solutions ◽  
Mixed Mode ◽  
Crack Tip ◽  
Dugdale Model ◽  
Dual Approach ◽  
Singular Finite Element ◽  
Crack Tip Opening ◽  
Method Show ◽  
Dugdale Crack

The symplectic dual approach is employed to obtain the analytical solutions of displacements and stresses around the mixed-mode Dugdale crack tip. Based on the analytical solutions, a novel singular finite element is developed to study the problem. The singular finite element can be applied to determine the sizes of crack tip opening/sliding displacement of a mixed-mode Dugdale model. Numerical results obtained by the present method show excellent agreement with the existing analytical solutions.

A Simplified Method Study of Aluminium Alloy Fatigue Crack Tip Parameters Computed by Elastic-Plastic Finite Element Model

2010 ◽  
Vol 97-101 ◽  
pp. 2748-2751
Author(s):  
Xin Song ◽  
Jing Zhong Xiang ◽  
Jia Zhen Zhang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Aluminium Alloy ◽  
Crack Tip ◽  
Element Model ◽  
Crack Model ◽  
Dynamic Crack ◽  
Elastic Plastic ◽  
Static Crack ◽  
Element Computation

Fatigue crack propagation of aluminium alloy 7049-OA has been studied by non-linear finite element business-oriented software ABAQUS, and elastic-plastic finite element models of static fatigue crack and dynamic fatigue crack of center crack panel (CCP) specimens are also built. Based on the finite element computation results, the differences of stress and crack opening displacement around crack tip of static crack model have been compared with those of dynamic crack model. The compared results showed that the finite element computation results of dynamic crack model can be replaced by the results calculated by the static crack model. Fatigue crack tip parameters of aluminium alloy CCP specimens can be calculated by elastic-plastic finite element model of static crack. This is an effective method to cut down the computation expense and promote the computational efficiency.

The Area Fracture Criterion of Iso-εθ Line for Mixed Mode Crack

2012 ◽  
Vol 193-194 ◽  
pp. 708-711
Author(s):  
Si Li Chen ◽  
Tao Yu ◽  
Jian Jun Shi ◽  
Jie Huang ◽  
Kai He Dong
Keyword(s):  
Crack Initiation ◽  
Mixed Mode ◽  
Fracture Criterion ◽  
Shape Change ◽  
Crack Tip ◽  
Fracture Line ◽  
Mixed Mode Crack ◽  
Engineering Significance ◽  
Crack Initiation Angle ◽  
Predicted Values

In practice, the crack in some engineering materials is often compound crack. Therefore, it is important engineering significance to study on fracture problem. Based on the shape change energy near crack tip portion, the area fracture criterion of Iso-εθ line for compound crack was proposed. A crack initiation angle formula and the fracture criterion were established. The results showed that the theoretical predicted values and the measured values are consistent. The compound crack fracture line area of fracture criterion was established.Tthe formulas are easy to be derived and convenient to apply.

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