scholarly journals Analysis of the Crack Initiation and Growth in Crystalline Materials Using Discrete Dislocations and the Modified Kitagawa–Takahashi Diagram

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 358
Author(s):  
Kuntimaddi Sadananda ◽  
Ilaksh Adlakha ◽  
Kiran N. Solanki ◽  
A.K. Vasudevan
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Dislocation Dynamics ◽  
Internal Stresses ◽  
Stress Concentrations ◽  
Crystalline Materials ◽  
Discrete Dislocation ◽  
Continuous Crack ◽  
American Society

Crack growth kinetics in crystalline materials is examined both from the point of continuum mechanics and discrete dislocation dynamics. Kinetics ranging from the Griffith crack to continuous elastic-plastic cracks are analyzed. Initiation and propagation of incipient cracks require very high stresses and appropriate stress gradients. These can be obtained either by pre-existing notches, as is done in a typical American Society of Testing and Materials (ASTM) fatigue and fracture tests, or by in situ generated stress concentrations via dislocation pile-ups. Crack growth kinetics are also examined using the modified Kitagawa–Takahashi diagram to show the role of internal stresses and their gradients needed to sustain continuous crack growth. Incipient crack initiation and growth are also examined using discrete dislocation modeling. The analysis is supported by the experimental data available in the literature.

Simple Models for Surface Cracking

1988 ◽  
Vol 130 ◽  
Author(s):  
Paul Meakin
Keyword(s):  
Thin Films ◽  
Surface Layer ◽  
Simple Model ◽  
Crack Initiation ◽  
Crack Growth ◽  
Growth Kinetics ◽  
Growth Process ◽  
Surface Cracking ◽  
Cracking Process ◽  
Initiation Period

AbstractA simple model for crack growth in thin films deposited onto a substrate has been developed. This model results in the generation of cracking patterns which have a remarkably realistic appearance. In the simulations a slow crack initiation period is followed by a period of rapid crack growth in which quite linear cracks are formed. Later on the crack growth process becomes slower and less regular as the cracking process relieves much of the stress in the surface layer. In this model pre-existing defects have a large effect on the crack growth kinetics and morphology.

Crack growth behavior of 4340 steel under corrosion and corrosion fatigue conditions

2015 ◽  
Vol 33 (6) ◽  
pp. 335-349 ◽  
Author(s):  
K. Sadananda ◽  
A.K. Vasudevan
Keyword(s):  
Crack Initiation ◽  
Driving Forces ◽  
Peak Stress ◽  
Growth Behavior ◽  
Internal Stresses ◽  
Crack Growth Behavior ◽  
Stress Concentrations ◽  
4340 Steel ◽  
Stress Dependent ◽  
Parameter Approach

AbstractCrack initiation and growth behavior in 4340 steel under static and cyclic loads in various environments are examined using the two-parameter approach developed by the authors. It is shown that environmental effects can be time dependent, stress dependent, or both, depending on the amplitude, peak stress, and aggressiveness of the environment. It is shown that the tests under vacuum are required to establish the reference state for the quantification of the chemical driving forces involved in crack initiation and growth in aggressive environments. Failure diagrams are proposed by extending the Kitagawa-Takahashi diagram for fatigue. It is shown that these can be used to quantify the mechanical and chemical internal stresses required to cause both initiation and growth of an incipient crack in a smooth as well as notched specimens. Conditions for propagating and nonpropagating incipient cracks that are initiated under stress concentrations are also discussed, taking the example of the 4340 steel data available.

Advances in Discrete Dislocations Dynamics and Multiscale Modeling

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
S. Groh ◽  
H. M. Zbib
Keyword(s):  
Multiscale Model ◽  
Plasticity Theory ◽  
Dislocation Dynamics ◽  
Dislocation Model ◽  
Atomistic Modeling ◽  
Crystalline Materials ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Crystal Plasticity Theory ◽  
Discrete Dislocations

Discrete dislocation dynamics is a numerical tool developed to model the plasticity of crystalline materials at an intermediate length scale, between the atomistic modeling and the crystal plasticity theory. In this review we show, using examples from the literature, how a discrete dislocation model can be used either in a hierarchical or a concurrent multiscale framework. In the last section of this review, we show through the uniaxial compression of microcrystal application, how a concurrent multiscale model involving a discrete dislocation framework can be used for predictive purposes.

A Discrete Dislocation Analysis of Crack Growth under Cyclic Loading

1999 ◽  
Vol 578 ◽  
Author(s):  
H.H.M. Cleveringa ◽  
E. Van Der Giessen ◽  
A. Needleman
Keyword(s):  
Stress Intensity ◽  
Cyclic Loading ◽  
Crack Growth ◽  
Elastic Solid ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Small Scale ◽  
Loading Conditions ◽  
Dislocation Interaction ◽  
Discrete Dislocation

AbstractCyclic loading of a plane strain mode I crack under small scale yielding is analyzed using discrete dislocation dynamics. The dislocations are all of edge character, and are modeled as line singularities in an elastic solid. At each stage of loading, superposition is used to represent the solution in terms of solutions for edge dislocations in a half-space and a nonsingular complementary solution that enforces the boundary conditions, which is obtained from a linear elastic, finite element solution. The lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and dislocation annihilation are incorporated into the formulation through a set of constitutive rules. An elastic relation between the opening traction and the displacement jump across a cohesive surface ahead of the initial crack tip is also specified, which permits crack initiation and crack growth to emerge naturally. It is found that crack growth can occur under cyclic loading conditions even when the peak stress intensity factor is smaller than the stress intensity required for crack growth under monotonic loading conditions.

scholarly journals First Steps of Crack Initiation and Propagation in Fatigue of FCC Crystals Studied by Dislocation Dynamics

2012 ◽  
Author(s):  
C. Déprés ◽  
G. V. Prasad Reddy ◽  
L. Tabourot ◽  
R. Sandhya ◽  
S. Sankaran
Keyword(s):  
Stress Field ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Crack Tip ◽  
Dislocation Dynamics ◽  
Crack Initiation And Propagation ◽  
Dislocation Dynamic ◽  
Discrete Dislocation ◽  
Initiation And Propagation

3D discrete dislocation dynamic (DDD) simulations are performed to simulate stage-I fatigue crack initiation and propagation along the surface, in the primary grain and its neighbouring grain, in 316L stainless steel. The scenario of crack propagation in primary grain and the evolution of dislocation structure ahead of crack tip are discussed, and in addition crack tip sliding displacement is estimated. Probable mechanisms of crack propagation from primary grain to neighbouring grain are evaluated. In this process, surface relief in the neighbouring-grain under the influence of crack stress field in the primary grain is studied for varying neighbouring-grain orientations. An enhanced evolution of surface extrusions in the neighbouring grain, are observed in the presence of heterogeneous stress field (i.e., in the presence of crack in the primary grain), compared to that in the case of homogeneous stress field. In addition, influence of crack stress field on prior cyclic-deformed substructure is presented.

Subcritical crack growth and crack tip driving forces in relation to material resistance

2017 ◽  
Vol 35 (4-5) ◽  
pp. 251-265 ◽  
Author(s):  
Kuntimaddi Sadananda ◽  
Kiran N. Solanki ◽  
Asuri K. Vasudevan
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Driving Force ◽  
Subcritical Crack Growth ◽  
Driving Forces ◽  
Crack Tip ◽  
Crack Arrest ◽  
Internal Stresses ◽  
Continuous Growth ◽  
Elastic Plastic

AbstractBasic concepts, related to the crack tip driving forces in relation to the material resistance, are analyzed for the elastic and elastic-plastic crack growth condition. This defines the crack initiation and growth conditions, as well as for crack arrest. Environment provides an additional driving force, thereby reducing the mechanical driving force required for the crack to grow. It is shown that (a) crack initiation and its growth are inseparable and (b) the magnitude of the applied and/or internal stresses; their gradients are also important for initiation and continuous growth of a crack. Elastic-plastic crack growth is also analyzed using the discrete dislocation models. The results show that its behavior is similar to that of an elastic crack. These concepts are valid for all subcritical crack growth. Mechanical and mechanical equivalent of chemical forces are defined for estimating the life prediction of a component in service. Failure diagrams are defined based on the extension of classical Kitagawa-Takahashi diagram that bridges the behavior of smooth and fracture mechanics specimens. Connections between crack initiation, growth, arrest, and overload fracture are established via these failure diagrams. Application of these diagrams for engineering components in service is outlined for diagnostic and prognostic purposes.

A discrete dislocation analysis of fatigue crack growth

2001 ◽  
Vol 11 (PR5) ◽  
pp. Pr5-69-Pr5-75
Author(s):  
V. S. Deshpande ◽  
H. H.M. Cleveringa ◽  
E. Van der Giessen ◽  
A. Needleman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Discrete Dislocation

Equilibrium Profile of Modern Belted Radial Ply Tires: Its Determination and Performance Benefits

2013 ◽  
Vol 41 (2) ◽  
pp. 127-151
Author(s):  
Rudolf F. Bauer
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
Finite Element Methods ◽  
Mathematical Analysis ◽  
Internal Stresses ◽  
Stress Concentrations ◽  
Equilibrium Profiles ◽  
Equilibrium Profile ◽  
And Performance ◽  
Beneficial Property

ABSTRACT The benefits of a tire's equilibrium profile have been suggested by several authors in the published literature, and mathematical procedures were developed that represented well the behavior of bias ply tires. However, for modern belted radial ply tires, and particularly those with a lower aspect ratio, the tire constructions are much more complicated and pose new problems for a mathematical analysis. Solutions to these problems are presented in this paper, and for a modern radial touring tire the equilibrium profile was calculated together with the mold profile to produce such tires. Some construction modifications were then applied to these tires to render their profiles “nonequilibrium.” Finite element methods were used to analyze for stress concentrations and deformations within all tires that did or did not conform to equilibrium profiles. Finally, tires were built and tested to verify the predictions of these analyses. From the analysis of internal stresses and deformations on inflation and loading and from the actual tire tests, the superior durability of tires with an equilibrium profile was established, and hence it is concluded that an equilibrium profile is a beneficial property of modern belted radial ply tires.

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