Structure parameter optimization and bearing limit analysis of the expansion unit of three-roller tube expander

The critical technical issues for the structure design of three-roller tube expander were first studied and analysed in this paper. Then, the major design parameters of the expansion unit structure and the bearing limit of 12¼″ three-roller tube expander were optimized and investigated by finite-element numerical simulation method. Results from study show that the required expansion force increases when the taper angle of the roller outer surface gets larger, taking the axial expansion force as the quantitative indicators. It is suggested that the roller tape angle of the expansion unit should be in the range of 9–12° considering the proper length of the roller and the non-self-locking tube expansion process. The required expansion force of the bellows first decreases and then increases when the gauge length of the expansion unit becomes longer. The optimal value of the gauge length is 50 mm considering the proper length of the roller. And according to the numerical simulation results, the designed three-roller tube expander meets the strength requirements. The results of this study are of great significance to the expend bellows drilling technology.

1. Pay attention to the format specification of the pictures in the article, especially pictures 10 and 12. 2. Read through the full text carefully, and try to modify the words, sentences or paragraphs that are ambiguous or confusing, and strive to describe refinement, smoothness and accuracy. 3. The conclusion part of the manuscript should be rewritten to emphasize the importance of investigated subject. 4. Please keep the reference style uniform and add some recent references. 5. There are some Chinese words in Figure 15.
Decision letter (RSOS-191630.R0) 14-Feb-2020 Dear Professor Bi, The editors assigned to your paper ("Structure Parameter Optimization and Bearing Limit Analysis of the Expansion Unit of Three-roller Tube Expander") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. This paper studies and analyzes the critical technical issues for the structure design of three-roller tube expander. It is indicated that the expansion unit structure is the main influencing factor for the performance of three-roller tube expander. The major design parameters and key parts of the expansion unit structure of 12 1/4" three-roller tube expander was optimized by theoretical analysis and finite element numerical simulation method. The research results are of great significance and reference value for the development of expandable bellows drilling.
Overall, the article is well organized and its presentation is excellent. However, some minor issues still need to be improved: 1. Pay attention to the format specification of the pictures in the article, especially pictures 10 and 12. 2. Read through the full text carefully, and try to modify the words, sentences or paragraphs that are ambiguous or confusing, and strive to describe refinement, smoothness and accuracy. 3. The conclusion part of the manuscript should be rewritten to emphasize the importance of investigated subject. 4. Please keep the reference style uniform and add some recent references.
5. There are some Chinese words in Figure 15.

Comments to the Author(s)
This article is well modified and can be published as it is now.
Decision letter (RSOS-191630.R1) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Professor Bi, It is a pleasure to accept your manuscript entitled "Structure Parameter Optimization and Bearing Limit Analysis of the Expansion Unit of Three-roller Tube Expander" in its current form for publication in Royal Society Open Science. The comments of the reviewer(s) who reviewed your manuscript are included at the foot of this letter.
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Thank you for your fine contribution. On behalf of the Editors of Royal Society Open Science, we look forward to your continued contributions to the Journal. Response: According to reviewer's opinion, the abstract was revised and refined in detail, which were marked in red in the 1 st page of the revised manuscript.
(2) Introduction: another large market for tube expanders are heat exchangers -could your research be relevant for this market as well?
Response: In this paper, the expandable bellows technology is mainly applied in the field of oil drilling engineering. As for the heat exchangers, it may have common properties with the expandable bellows. However, I think they should be two different tools.
(3) What are the underlying formulars used for your calculations? I think you should mention at least 3 and compare the results to other results from the literature.
Response: According to reviewer's opinion, we have added related formulas for our calculations, which were marked in red in the 7 th page of the revised manuscript.