Numerical Study of the Influence of the Crack Front Curvature in the Evolution of the Plastic Zone along the CT Specimen Thickness

2011 ◽  
Vol 465 ◽  
pp. 119-122 ◽  
Author(s):  
Daniel Camas ◽  
Pablo Lopez-Crespo ◽  
Antonio González-Herrera
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Plastic Zone ◽  
Crack Closure ◽  
Crack Front ◽  
Numerical Study ◽  
Load Level ◽  
Specimen Thickness ◽  
Aluminum Specimen ◽  
Front Curvature

This paper presents a numerical study of the influence of the load level and the crack front curvature on the plastic zone in the area close to the crack front. The aim of the work is to determine the influence of these parameters on fatigue crack closure. For this, a CT aluminum specimen has been modelled tri-dimensionally and several finite elements calculations have been made considering a large combination of the variables under consideration.

The Effect of Sheet Thickness on Near-Threshold Fatigue Crack Propagation and Oxide and Roughness-Induced Crack Closure

1987 ◽  
Vol 109 (1) ◽  
pp. 86-91 ◽  
Author(s):  
K. Tokaji ◽  
Z. Ando ◽  
K. Nagae
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Closure ◽  
Growth Rates ◽  
Sheet Thickness ◽  
Specimen Thickness ◽  
Low Carbon ◽  
Wide Range ◽  
Near Threshold

Characteristics of fatigue crack propagation have been investigated in a low carbon steel and a high tensile strength steel to evaluate the effect of sheet thickness. Crack propagation data are generated over a wide range of growth rates, from 10−8 to 10−3 mm/cycle, for load ratios of 0.05 and 0.70 at room temperature in laboratory air. Particular emphasis is placed on behavior at near-threshold growth rates. Near-threshold fatigue crack propagation behavior is found to show a marked sensitivity to sheet thickness, and near-threshold growth rates decrease and threshold values increase with increasing sheet thickness. Oxide and roughness-induced crack closure models are proposed as a mechanism for the effect of sheet thickness on near-threshold fatigue crack propagation. It is also shown that the requirement for specimen thickness recommended by ASTM, W/20≤B≤W/4, is not always valid for near-threshold fatigue crack propagation.

An Efficient Way to Characterize the Fatigue Crack Growth Based on Numerical Analysis

2009 ◽  
Vol 417-418 ◽  
pp. 653-656
Author(s):  
Ya Zhi Li ◽  
Jing He ◽  
Zi Peng Zhang
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Length ◽  
Crack Growth ◽  
Crack Closure ◽  
Load Ratio ◽  
Specimen Thickness

The behavior of plasticity induced fatigue crack closure (PICC) in middle tension specimen was analyzed by the elastic-plastic finite element method. For the constant-K (CK) loading cases, the opening stress intensity factor are independent of crack length. The level of increases with the maximal applied stress intensity factor for given load ratio and increases with for fixed . The in plane strain state is much smaller than that in plane stress state. The results under CK loadings can be deduced to constant amplitude cyclic loading case during which the load ratio, maximal load level, crack length and specimen thickness are all the factors affecting the crack closure effect. The phenomena revealed in the analysis are beneficial in understanding the driving force mechanism of the fatigue crack growth.

Plastic Zone Study by Means of Tri-Dimensional Finite Element Models on Fatigue Crack Closure

2006 ◽  
Vol 324-325 ◽  
pp. 555-558 ◽  
Author(s):  
Antonio González-Herrera ◽  
J. Garcia-Manrique ◽  
A. Cordero ◽  
Jose Zapatero
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Plastic Zone ◽  
Crack Closure ◽  
Plastic Zone Size ◽  
Important Change ◽  
Element Analysis ◽  
Fatigue Crack Closure ◽  
Fine Mesh ◽  
Dimensional Finite Element

This paper focuses on the study of the plastic zone in fatigue crack closure based on the results obtained by means of 3D Finite Element Analysis (FEA). These results show the crack behavior through the thickness. The plastic zone is visualized and quantified. It does not correspond to the classical shape. The plastic zone in the interior surface is similar to those obtained in 2D plane strain conditions and a reduced effect of closure is observed. However, close to the external surface, 2D plane stress results are not reproduced, the plastic zone size is smaller and an important change is observed. This transition is developed in a thin external portion of the specimen and it can only be captured if a fine mesh of the thickness is done.

Numerical Study of the Crack-Front Constraint for SENT Specimens of X80 Pipeline Steel

2017 ◽  
Vol 898 ◽  
pp. 735-740
Author(s):  
Ting Zhong ◽  
Lin Zhu ◽  
Yan Zhou ◽  
Jian Shuai ◽  
Lan He
Keyword(s):  
Crack Front ◽  
Numerical Study ◽  
Pipeline Steel ◽  
Crack Depth ◽  
Stress Triaxiality ◽  
Width Ratio ◽  
Specimen Thickness ◽  
X80 Pipeline Steel ◽  
Specimen Width ◽  
Average Measure

This work presents a numerical study of crack-front constraint for SENT specimens of X80 pipeline steel, to examine geometry effect on the correlation of crack-front stress field and constraint. An average measure of constraint over crack-front Am was employed to characterize the crack-front constraint. SENT specimens with varying geometries (different crack depth to specimen width ratio, a/W, and different specimen width and thickness, W/B) were analyzed by Gurson-Tvergaard-Needleman model (GTN model). Results showed that the stress triaxiality Am can characterize the crack-front constraint of X80 pipeline steel very well. The level of the Am-△a curve rises with the decrease of crack depth, and increases first and then decreases with the increase of SENT specimen thickness.

scholarly journals An Analytical Model for Fatigue Crack Propagation Prediction with Overload Effect

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Shan Jiang ◽  
Wei Zhang ◽  
Xiaoyang Li ◽  
Fuqiang Sun
Keyword(s):  
Fatigue Crack ◽  
Plastic Zone ◽  
Crack Growth ◽  
Crack Closure ◽  
Retardation Effect ◽  
Crack Growth Behavior ◽  
Zone Model ◽  
Constant Amplitude ◽  
Proposed Model ◽  
Single Overload

In this paper a theoretical model was developed to predict the fatigue crack growth behavior under the constant amplitude loading with single overload. In the proposed model, crack growth retardation was accounted for by using crack closure and plastic zone. The virtual crack annealing model modified by Bauschinger effect was used to calculate the crack closure level in the outside of retardation effect region. And the Dugdale plastic zone model was employed to estimate the size of retardation effect region. A sophisticated equation was developed to calculate the crack closure variation during the retardation area. Model validation was performed in D16 aluminum alloy and 350WT steel specimens subjected to constant amplitude load with single or multiple overloads. The predictions of the proposed model were contrasted with experimental data, and fairly good agreements were observed.

Effect of the free surface on the fatigue crack front curvature at high stress asymmetry

2019 ◽  
Vol 118 ◽  
pp. 249-261 ◽  
Author(s):  
Tomáš Oplt ◽  
Pavel Hutar ◽  
Pavel Pokorný ◽  
Luboš Náhlík ◽  
Zdeněk Chlup ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Free Surface ◽  
Crack Front ◽  
High Stress ◽  
Stress Asymmetry ◽  
Front Curvature
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