Research Papers: Design and Analysis

Investigation of Fatigue Strength of Welded Tube-to-Tubesheet Joint

[+] Author and Article Information
Wenxian Su, Ning Ma

Institute of Chemical Machinery and Process Equipment, University of Shanghai for Science and Technology, Shanghai 200093, P.R.C.

Zhifu Sang

Institute of Chemical Machinery and Process Equipment, Nanjing University of Technology, Nanjing, Jiangsu 210009, P.R.C.

G. E. O. Widera

Center for Joining and Manufacturing Assembly, Marquette University, Milwaukee, WI 53233

J. Pressure Vessel Technol 131(4), 041205 (Jul 14, 2009) (5 pages) doi:10.1115/1.3122024 History: Received April 28, 2008; Revised November 21, 2008; Published July 14, 2009

The tube-to-tubesheet joint of heat exchangers is an important aspect in the design and fabrication process. This paper discusses the fatigue strength of welded tube-to-tubesheet joint under a periodic axial load along the tube by test and by 3D finite element analysis. The testing shows that expanding, in addition to welding, may slightly enhance the fatigue strength of a welded joint. From a microscopic view, the fatigue crack begins at the half melt coarse grain zone of the welded seam on the outer wall of tube and then propagates to the zone of the welded seam on the inner wall of the tube. In the fracture zone, the fracture face is at an angle of 45 deg to the tube wall face and the explicit plastic deformation is present. The analysis, by electronic energy spectrum, shows that there exist many fatigue striations in the fracture face. A 3D finite element analysis correlates with the experimental results.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 2

Loading curve for welded tube-to-tubesheet

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Figure 3

The FE model of tube-to-tubesheet

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Figure 4

von Mises stress of tube-to-tubesheet under static load

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Figure 5

Specimen material S-N curve

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Figure 6

S-N fatigue curve of welded tube-to-tubesheet

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Figure 7

Fracture appearance

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Figure 8

Metallurgical structure of tube (×250): (a) metallurgical structure of heat affected zone (×50), (b) metallurgical structure of normalized (×125), and (c) incomplete metallurgical structure of normalized zone normalized zone (×250)

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Figure 9

Metallurgical structures of welded zone

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Figure 10

Microscopic structure of the last rapture zone (×125)

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Figure 11

Rupture origins

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Figure 12

Fatigue striation in the fracture appearance



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