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Research Papers: Design and Analysis

Methodology for the Optimization of Bolting Sequences for Wind Generator Flanges

[+] Author and Article Information
Mikel Abasolo

Department of Mechanical Engineering,
ETSI-BILBAO,
University of the Basque Country,
Bilbao 48013, Spain
e-mail: mikel.abasolo@ehu.es

Josu Aguirrebeitia, Rafael Avilés, Igor Fernández de Bustos

Department of Mechanical Engineering,
ETSI-BILBAO,
University of the Basque Country,
Bilbao 48013, Spain

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received April 30, 2012; final manuscript received May 2, 2014; published online September 4, 2014. Assoc. Editor: Hakim A. Bouzid.

J. Pressure Vessel Technol 136(6), 061202 (Sep 04, 2014) (13 pages) Paper No: PVT-12-1051; doi: 10.1115/1.4027597 History: Received April 30, 2012; Revised May 02, 2014

In bolted joints, bolts are tightened to a uniform preload in order to improve their operational behavior. This preload is not easy to achieve due to several phenomena that occur during the tightening sequence; in the case of wind generator bolted joints, which present a gap between the contact surfaces of the flanges, the elastic interaction is by far the most prejudicial of them. As a consequence, the tightening sequence is very costly, typically consisting on a large number of passes. Based on a metamodel created in previous work, this work presents methodology for the optimization of the tightening sequence, which consists on calculating the load to be applied to each bolt so as to achieve the target uniform preload at the end of the sequence in only one pass or two at the most. This methodology is based on optimization methods used for pressure vessel bolted joints has provided satisfactory results (validated via FE analyses) with a very low computational cost.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Welded and bolted joints in wind generator towers

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Fig. 2

Gap between the flanges of bolted joints in wind generator towers [6]

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Fig. 3

(a) Bolt 2 is tightened, (b) tightening of bolt 1 causes loss of preload in bolt 2, and (c) tightening of bolt 3 causes loss of preload in bolts 1 and 2

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Fig. 5

Characteristic dimensions of the flange [18]

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Fig. 6

Tested tightening patterns

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Fig. 7

Bolt loads at the end of the clockwise pattern (initial load 500 kN)

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Fig. 8

Steps to follow in the inverse sequence method

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Fig. 9

Forces acting on the upper and lower master nodes

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Fig. 10

Forces on the master nodes

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Fig. 11

Situation of the flange at the end of step k − 1

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Fig. 12

Initial loads for final load of 300 kN in one-pass sequence: (a) clockwise pattern and (b) four-point star pattern

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Fig. 13

Initial loads for final load of 600 kN in one-pass sequence: (a) clockwise pattern and (b) four-point star pattern

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Fig. 14

Initial loads for final load of 900 kN in one-pass sequence: (a) clockwise pattern and (b) four-point star pattern

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Fig. 15

Initial loads for final load of 300 kN in a two-pass sequence following a clockwise pattern using intermediate load values of (a) 100 kN and (b) 200 kN

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Fig. 16

Maximum initial loads in the first and second passes in a two-pass sequence using different intermediate loads for final load of 300 kN

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Fig. 17

Initial loads for final load of 600 kN in a two-pass sequence following a clockwise pattern using intermediate load values of (a) 200 kN and (b) 400 kN

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Fig. 18

Maximum initial loads in the first and second passes in a two-pass sequence using different intermediate loads for final load of 600 kN

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Fig. 19

Initial loads for final load of 300 kN in two-pass sequence: (a) clockwise pattern and (b) four-point star pattern

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Fig. 20

Initial loads for final load of 600 kN in two-pass sequence: (a) clockwise pattern and (b) four-point star pattern

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Fig. 21

Initial loads for final load of 900 kN in two-pass sequence: (a) clockwise pattern and (b) four-point star pattern

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Fig. 22

Maximum initial load needed to achieve several final uniform loads in one-pass and two-pass tightening sequences

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Fig. 23

Algorithm for the optimization of the tightening sequence for the bolted joints of wind generator flanges

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Fig. 24

Final load distribution in the FE model with the initial loads of Fig. 12(a) (target final load 300 kN)

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Fig. 25

Final load distribution in the FE model with the initial loads of Fig. 13(a) (target final load 600 kN)

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Fig. 26

Final load distribution in the FE model with the initial loads of Fig. 14(a) (target final load 900 kN)

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Fig. 27

Final load distribution in the FE model with the initial loads of Fig. 20(a) (target final load 300 kN)

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Fig. 28

Final load distribution in the FE model with the initial loads of Fig. 21(a) (target final load 600 kN)

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Fig. 29

Final load distribution in the FE model with the initial loads of Fig. 22(a) (target final load 900 kN)

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