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Technical Briefs

Improved Three-Dimensional Crowning Profiles for Dovetail Attachments

[+] Author and Article Information
J. R. Beisheim

Development Group, ANSYS Inc., Canonsburg, PA 15317

G. B. Sinclair

Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803

J. Eng. Gas Turbines Power 132(6), 064504 (Mar 30, 2010) (4 pages) doi:10.1115/1.4000142 History: Received April 14, 2009; Revised May 07, 2009; Published March 30, 2010; Online March 30, 2010

Dovetail attachments in gas turbines are subject to fatigue failures. These fatigue failures occur as a result of large fluctuations in hoop stresses near the edges of contact in attachments. The high hoop stresses available for fluctuating are, in turn, the result of high contact stress peaks near the edges of contact. One means of alleviating these stresses is via crowning. Such crowned configurations are inherently three-dimensional and consequently present some challenges to obtaining convergent contact stresses with finite elements. Such challenges are met in the work of Beisheim and Sinclair (2008, “Three-Dimensional Finite Element Analysis of Dovetail Attachments With and Without Crowning,” ASME J. Turbomach., 130, pp. 021012-1–021021-8), and crowning is shown to reduce contact stresses by about 40%. The crowning profile used in that paper is the natural Hertzian profile of a segment of an ellipsoid. This note investigates an alternative profile with a view to increasing the area of contact, and thereby further reducing contact stresses. Converged contact stresses are obtained for both profiles, and demonstrate that the alternative profile can indeed reduce contact stresses by an additional 10%.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

Grahic Jump Location
Figure 1

Dovetail attachment configuration: (a) section of attachment, (b) close up of disk near lower contact point with stresses acting, and (c) in-plane crown on blade flat

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Figure 4

Contact stress distributions with different crowning profiles

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Figure 3

Contact regions (a) with the original crowning profile of Eq. 5, and (b) with the alternative crowning profile of Eq. 6

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Figure 2

Contact stress distribution (two-dimensional analysis of Ref. 2)

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