0
Research Papers: Nuclear Power

The Influence of the Grain Structure Size on Microstructurally Short Cracks

[+] Author and Article Information
Igor Simonovski

Reactor Engineering Division, “Jožef Stefan” Institute, Jamova cesta 39, SI-1000 Ljubljana Slovenia

Leon Cizelj

Reactor Engineering Division, “Jožef Stefan” Institute, Jamova cesta 39, SI-1000 Ljubljana Slovenialeoncizelj@ijs.si

J. Eng. Gas Turbines Power 131(4), 042903 (Apr 15, 2009) (8 pages) doi:10.1115/1.3079610 History: Received October 01, 2008; Revised October 06, 2008; Published April 15, 2009

The dominant processes in the initialization and propagation of microstructurally short cracks include microstructural features such as crystallographic orientations of grains, grain boundaries, inclusions, voids, material phases, etc. The influence of the microstructural features is expected to vanish with distance from the crack tip. Also, the influence of the nearby microstructural features is expected to be smaller for a long than for a small crack. Finally, a crack of sufficient length can be modeled using classical fracture mechanic methods. In this paper the approach to estimate the crack length with vanishing influence from the microstructural feature is proposed. To achieve this, a model containing a large number of randomly sized, shaped, and oriented grains is employed. The random grain structure is modeled using a Voronoi tessellation. A series of cracks of lengths from about 1 to 7 grain lengths is inserted into the model, extending from a grain at the surface toward the interior of the model. The crack tip opening displacements are estimated and statistically analyzed for a series of random crystallographic orientation sets assigned to the grains adjacent to the crack. Anisotropic elasticity and crystal plasticity constitutive models are employed at the grain size scale. It is shown that the standard deviation of the crack tip opening displacement decreases from about 20% for a short surface crack embedded within a single grain to about 7% for a surface crack extending through seven grains. From the engineering point of view, a crack extending through less than about ten grain sizes is therefore considered to strongly depend on the neighboring microstructural features.

FIGURES IN THIS ARTICLE
<>
Copyright © 2009 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

The outline of the finite element model

Grahic Jump Location
Figure 2

Relation between the slip systems of a face centered cubic crystal and the crack for crystallographic orientation α=0 deg and crack direction θ=315 deg

Grahic Jump Location
Figure 3

Angles between the slip planes and the crack plane for crystallographic orientation α=0 deg and crack direction θ=315 deg

Grahic Jump Location
Figure 4

Details of the crack tip meshes for different crack lengths. The numbers indicate the grains containing the crack. Please refer to Fig. 1 for the global position of the crack in the model.

Grahic Jump Location
Figure 5

Possible effective crack shapes and effective crack length

Grahic Jump Location
Figure 6

Definition of crack tip opening displacement CTOD

Grahic Jump Location
Figure 7

Strain ε11 in a single crystal as a function of crystallographic orientation

Grahic Jump Location
Figure 8

Grain stiffness for an arbitrarily selected set of crystallographic orientations. Orientations of the crack-containing grains were kept constant for all analyses reported in this paper

Grahic Jump Location
Figure 9

Scatter of the CTOD values due to the random nature of crystallographic orientations of the surrounding grains

Grahic Jump Location
Figure 10

Normalized scatter of the CTOD values due to the random nature of crystallographic orientations of the surrounding grains

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In