scholarly journals Damage Zone Size Limit During the Crack Propagation

2020 ◽  
Author(s):  
Hamid Hamli Benzahar ◽  
Mohamed Chabaat
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Damage Zone ◽  
Stress Fields ◽  
Mode I ◽  
Zone Size ◽  
Zone Length ◽  
Dislocation Stress ◽  
Rectangular Element

The principal goal of this work is to limit the damage zone length during the crack propagation in brittle materials. This study is based on the determination of stress fields by varying the distance between a semi-infinite crack and a neighboring dislocation. The model suggested is a rectangular element (a dish), having a semi-infinite crack in one of its ends and a dislocation located in the vicinity of a crack-tip, subjected to a tensile stress on mode I. The problem is treated numerically using Finite Element Method.For each distance between the two cracks (semi-infinite crack and dislocation), stress fields are given. On the basis of these stress fields, a limiting damage zone length is obtained.

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.

Fully Automated SCC and Fatigue Crack Propagation Analyses on Deep Semi-Elliptical Flaws

2013 ◽  
Author(s):  
Kota Sugawara ◽  
Hirohito Koya ◽  
Hiroshi Okada ◽  
Yinsheng Li ◽  
Kazuya Osakabe ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Flaw ◽  
Stress Fields

In this paper, some results of crack propagation analyses of deep initially semi-elliptical flaws under assumed residual stress fields are presented. The crack propagation analyses were performed by using a software system that has been developed by Okada and his colleagues. It is based on a conventional finite element program but uses the quadratic tetrahedral finite elements to model the structure with the crack. The finite element model with the crack can be generated in an automated manner. The stress-intensity factor computations are performed by using the virtual crack closure-integral method (VCCM) for the quadratic tetrahedral finite element which was also proposed by Okada and his colleagues. The automatic meshing scheme for the crack propagation analyses has also been developed by the authors. By the authors’ previous publication, it was shown that the stress intensity factor of deep semi-elliptical surface flaw under assumed residual stress field reached its maximum value at the mid-depth of the crack. Hence, in present study, in order to investigate the feature of the crack propagation of deep surface cracks, we are conducting crack propagation analyses that can predict the crack extension from each point along the crack front for an arbitrary shaped surface flaw. It can also account for material anisotropy in the crack propagation behavior. Then, the SCC crack propagation analyses for a deep semi-elliptical surface flaw in a plate under assumed residual stress fields are being conducted. The results of the crack propagation analyses suggest that the shapes of the crack after the SCC crack propagation may not be exact semi-elliptic in its shape. In this paper, the analytical procedures and some results are presented. The same analytical procedures can be adopted to perform fatigue crack propagation analyses.

scholarly journals Crystallographic crack propagation rate in single-crystal nickelbase superalloys

2018 ◽  
Vol 165 ◽  
pp. 13012
Author(s):  
Christian Busse ◽  
Frans Palmert ◽  
Paul Wawrzynek ◽  
Björn Sjödin ◽  
David Gustafsson ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Crack Growth ◽  
Driving Force ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Mode I ◽  
Force Parameter ◽  
Intensity Factors ◽  
Crack Driving Force

Single-crystal nickel-base superalloys are often used in the hot sections of gas turbines due to their good mechanical properties at high temperatures such as enhanced creep resistance. However, the anisotropic material properties of these materials bring many difficulties in terms of modelling and crack growth prediction. Cracks tend to switch cracking mode from Mode I cracking to crystallographic cracking. Crystallographic crack growth is often associated with a decrease in crack propagation life compared to Mode I cracking and this must be taken into account for reliable component lifing. In this paper a method to evaluate the crystallographic crack propagation rate related to a crystallographic crack driving force parameter is presented. The crystallographic crack growth rate is determined by an evaluation of heat tints on the fracture surface of a specimen subjected to fatigue loading. The complicated crack geometry including two crystallographic crack fronts is modelled in a three dimensional finite element context. The crack driving force parameter is determined by calculating anisotropic stress intensity factors along the two crystallographic crack fronts by finite-element simulations and post-processing the data in a fracture mechanics tool that resolves the stress intensity factors on the crystallographic slip planes in the slip directions. The evaluated crack propagation rate shows a good correlation for both considered crystallographic cracks fronts.

scholarly journals Determination of mode I and mode II fracture toughness of walnut and cherry in TR and RT crack propagation system by the Arcan test

Holzforschung ◽  
2017 ◽  
Vol 71 (12) ◽  
pp. 985-990 ◽  
Author(s):  
Koji Murata ◽  
Erik Valentine Bachtiar ◽  
Peter Niemz
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Release Rate ◽  
Strain Energy ◽  
Shear Plane ◽  
Mode I ◽  
Mode Ii ◽  
Mode Ii Fracture ◽  
Mode Ii Fracture Toughness

AbstractTwo specimen types, each from walnut and cherry wood, were prepared for tangential-radial (TR) and radial-tangential (RT) crack propagation systems at 65% of RH and 20°C before mode I and mode II fracture toughness was determined through Arcan tests. It was found that fracture toughness in mode I is in agreement with literature data. In the mode II test, however, the crack propagated in the direction normal to the shear plane and not parallel to it. The release rate of strain energy in terms of the opening failure in mode II was lower than that in mode I. It can be concluded that it is difficult to determine the fracture toughness of RT or TR propagation in hardwood specimens in mode II.

Semi-Analytical Finite Element Method for Bilinear Cohesive Crack Model in Mode I Crack Propagation

2006 ◽  
Vol 324-325 ◽  
pp. 755-758
Author(s):  
Cheng Qiang Wang ◽  
Zhong Hua Chen ◽  
Chang Liang Zheng
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Propagation ◽  
Cohesive Crack ◽  
Stress Fields ◽  
Crack Model ◽  
Cohesive Crack Model ◽  
Precise Description ◽  
Hamiltonian Theory ◽  
Element Method

Based on the Hamiltonian theory and method of elasticity, a ring and a circular hyper-analytical-elements are constructed and formulated. The hyper-analytical-elements give a precise description of the displacement and stress fields in the vicinity of crack tip for the bilinear cohesive crack model. The new analytical element can be implemented into finite element method program systems to solve crack propagation problems for plane structures with arbitrary shapes and loads. Numerical results for typical problems show that the method is simple, efficient and accurate.

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