Abstract

Purpose - This paper aims to examine the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system (RFBS) with a crack in a fastening rod.Design/methodology/approach - Based on the 3D finite element method model and stress analysis of a cracked RFBS, a 3D dynamic model of the RFBS with a crack in a fastening rod is established with considering the initial bending and stress redistribution caused by the crack. A combined numerical simulation technology is used to investigate the dynamic behaviours of the system.Findings - The distribution of contact stress between the two disks will be not uniform, and the initial bending of the system will occur due to the presence of a crack. This will lead to the change of system stiffness and the dynamic behaviours such as vibration amplitude, and motion orbits will change significantly.Research limitations/implications - A 3D finite element method dynamic model is proposed for the study of dynamic characteristics of complex combined rotor bearing system with cracks.Practical implications - It is helpful and significant to master the dynamic behaviours of cracked RFBS. It is helpful to detect the presence of a crack of the rotor bearing system.Social implications - Some of the losses caused by crack failure may be reduced.Originality/value - The proposed 3D method can provide a useful reference for the study of dynamic characteristics of complex combined rotor bearing system with cracks.


Authors

Wang, Nanshan;  Liu, Heng;  Liu, Yi;  Wang, Qidan;  Qi, Shemiao;  Xu, Zhidong

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  • 1 reviewer
  • pre-publication peer review (FINAL ROUND)
    Decision Letter
    2020/09/01

    01-Sep-2020

    Dear Wang, Nanshan; Liu, Heng; Liu, Yi; Wang, Qidan; Qi, Shemiao; Xu, Zhidong

    It is a pleasure to accept your manuscript ilt-05-2020-0189.R2, entitled "Effect of a transverse crack on the dynamic behaviours of a 3D rod-fastening rotor bearing system" in its current form for publication in Industrial Lubrication and Tribology. Please note, no further changes can be made to your manuscript.

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    Thank you for your contribution. On behalf of the Editors of Industrial Lubrication and Tribology, we look forward to your continued contributions to the Journal.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/08/22

    In the present work, the dynamic behaviors of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using the infinite long bearing assumption. The numerical results are compared with the experimental results.

    Authors have addressed all queries in the revised manuscript. The efforts put by the authors is highly appreciated.
    Reviewer is thankful to the authors for implementing the suggestions. The paper may be accepted for publication.

    Cite this review
    Author Response
    2020/08/22

    Dear editors;
    We thank you very much for timely processing for two rounds of our manuscript entitled“ Effect of a transverse crack on the dynamic behaviours of a 3D rod-fastening rotor bearing system” (Paper ID. ilt-05-2020-0189).
    We are also grateful for you and reviewes’ worthwhile suggestion and comments. We have studied your and reviewers' comments carefully and have tried our best to revise our manuscript for each round. After two rounds of revision, the quality of our manuscript has been greatly improved.
    A new revised version has been submitted to the online paper submitted system. The main revisions are marked with green colour in revised manuscript. The main corrections of the manuscript and the responds to the reviewer’s comments are as followed.
    Please contact me by E-mail with any further questions referring to the revised manuscript.
    Looking forward to hearing from you.
    Thank you and best regards.

    Yours sincerely,
    Corresponding author: Nanshan Wang
    E-mail: tyus2012@163.com

    (1) Response to Reviewer: 1’ Comments:
    Thank you very much for your publication recommendation. I am still impressed by the meticulous and rigorous work in the first round of peer review
    The main revisions in latest revised manuscript are marked with green colour. The latest revised version has been submitted to the online paper submitted system.
    (2) Response to Reviewer: 2’ Comments:
    Thank you very much for your careful new comments which are helpful for the improvement of our manuscript. The corresponding corrections are marked with green colour in latest revised manuscript.

    1. In the final manuscript, it is suggested that the specification of rotor system (length of the shaft, mass of the disc, distance between the bearings, length to width ratio of the bearings, unbalance mass) should be included.
      A1:
      The specification of rotor system has been supplemented by Table I in section “2.1 Brief introduction of RFBS” in revised manuscript. Meanwhile the Figure 1 has been adjusted accordingly as well as some necessary symbols.
    2. Number of time steps used in the transient analysis should be mentioned.
    3. Initial conditions used in the analysis should be mentioned.
      A2-A3:
      The Number of time steps and Initial conditions have been supplemented in the beginning of section “4. Simulation results and dynamic analysis” in revised manuscript as follows
      “The initial values of all reserved nodes are 1x10-8m, 1x10-8m, and 0m in x, y, and z direction, respectively. The Integration accuracy, step length of integration, and integration time are 1x10-6m, 2π/100, and 800t (t=2π), respectively.
    4. Flow chart of the numerical solution may be included.
      A4:
      The basic flow chart of numerical solution has been supplemented as shown in Figure 5 in revised manuscript.
    5. In the conclusions section it is reported that, “The experiments of dynamic behaviours agree well with the numerical simulations.” However, from Fig. 10, it seems that numerical results are have large deviation as compared to experimental measurements.
      A5:
      For the numerical results of Figure 11 (that is the Figure 10 in first revised manuscript), there exists some differences between simulation and experiment mainly due to the practical experimental conditions. This point has been addressed in first revised manuscript.
      But for the sake of preciseness and reality, we have made a more accurate statement and correction In the conclusions section as follows:
      “The experiments of dynamic behaviours of disk location agree well with the numerical simulations, while there is some difference between the experiment and the simulation, just only a certain consistency in the movement trend for bearing position due to the practical experimental conditions.”



    Cite this author response
  • pre-publication peer review (ROUND 2)
    Decision Letter
    2020/08/21

    21-Aug-2020

    Dear Mr. Wang:

    Manuscript ID ilt-05-2020-0189.R1 entitled "Effect of a transverse crack on the dynamic behaviours of a 3D rod-fastening rotor bearing system" which you submitted to the Industrial Lubrication and Tribology, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.

    The reviewer(s) have recommended major revisions to the submitted manuscript, before it can be considered for publication. Therefore, I invite you to respond to the reviewer(s)' comments and revise your manuscript.

    To revise your manuscript, log into https://mc.manuscriptcentral.com/ilt and enter your Author Centre, where you will find your manuscript title listed under "Manuscripts with Decisions." Under "Actions," click on "Create a Revision." Your manuscript number has been appended to denote a revision.

    You will be unable to make your revisions on the originally submitted version of the manuscript. Instead, revise your manuscript using a word processing program and save it on your computer. Please also highlight the changes to your manuscript within the document by using the track changes mode in MS Word or by using bold or coloured text.

    Once the revised manuscript is prepared, you can upload it and submit it through your Author Centre. The deadline for uploading a revised manuscript is 19-Nov-2020 from receiving this email. If it is not possible for you to resubmit your revision within this timeframe, we may have to consider your paper as a new submission.

    When submitting your revised manuscript, you will be able to respond to the comments made by the reviewer(s) in the space provided. You can use this space to document any changes you make to the original manuscript. In order to expedite the processing of the revised manuscript, please be as specific as possible in your response to the reviewer(s).

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    Please note that Emerald requires you to clear permission to re-use any material not created by you. If there are permissions outstanding, please send these to Emerald as soon as possible. Emerald is unable to publish your paper with permissions outstanding.

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    If your article has been rejected or revisions have been requested, you may benefit from Editage’s services. For a full list of services, visit: authorservices.emeraldpublishing.com/
    Please note that there is no obligation to use Editage and using this service does not guarantee publication.

    Once again, thank you for submitting your manuscript to the Industrial Lubrication and Tribology and I look forward to receiving your revision.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Reviewer(s)' Comments to Author:
    Reviewer: 1

    Comments to the Author
    (There are no comments.)

    Reviewer: 2

    Comments to the Author
    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption.
    Authors have resolved most of the queries in the revised manuscript.
    Reviewer would like to give following suggestions:
    • In the final manuscript, it is suggested that the specification of rotor system (length of the shaft, mass of the disc, distance between the bearings, length to width ratio of the bearings, unbalance mass) should be included.
    • Number of time steps used in the transient analysis should be mentioned.
    • Initial conditions used in the analysis should be mentioned.
    • Flow chart of the numerical solution may be included.
    • In the conclusions section it is reported that, “The experiments of dynamic behaviours agree well with the numerical simulations.”
    However, from Fig. 10, it seems that numerical results are have large deviation as compared to experimental measurements.
    Reviewer: 1

    Recommendation: Accept

    Comments:
    (There are no comments.)

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: I am not an expert in this field, so I leave this field open

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: yes

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: very likely

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?:

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: No, I would not like my name to appear with my report on Publons

    Reviewer: 2

    Recommendation: Minor Revision

    Comments:
    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption.
    Authors have resolved most of the queries in the revised manuscript.
    Reviewer would like to give following suggestions:
    • In the final manuscript, it is suggested that the specification of rotor system (length of the shaft, mass of the disc, distance between the bearings, length to width ratio of the bearings, unbalance mass) should be included.
    • Number of time steps used in the transient analysis should be mentioned.
    • Initial conditions used in the analysis should be mentioned.
    • Flow chart of the numerical solution may be included.
    • In the conclusions section it is reported that, “The experiments of dynamic behaviours agree well with the numerical simulations.”
    However, from Fig. 10, it seems that numerical results are have large deviation as compared to experimental measurements.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: yes.
    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption.

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: yes

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?: few suggestion are given in the attached file.

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/08/21

    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption.
    Authors have resolved most of the queries in the revised manuscript.
    Reviewer would like to give following suggestions:
    • In the final manuscript, it is suggested that the specification of rotor system (length of the shaft, mass of the disc, distance between the bearings, length to width ratio of the bearings, unbalance mass) should be included.
    • Number of time steps used in the transient analysis should be mentioned.
    • Initial conditions used in the analysis should be mentioned.
    • Flow chart of the numerical solution may be included.
    • In the conclusions section it is reported that, “The experiments of dynamic behaviours agree well with the numerical simulations.”
    However, from Fig. 10, it seems that numerical results are have large deviation as compared to experimental measurements.

    Reviewed by
    Cite this review
    Author Response
    2020/07/24

    Response to Reviewer: 1’ Comments:
    (The corresponding corrections for Reviewer: 1’ Comments are marked with red colour in revised manuscript)
    1. All through the manuscript: there should always be a space between number and unit
    A1: There are many mistakes of this type in our manuscript. We have made corresponding corrections as marked with red colour in the text. Meanwhile, the same mistakes in Figures 3 and 5-7 have been modified.

    1. pg.1-50: Mayes, 1984 there is no reference given
      A2: This reference has been supplemented in the Reference section as follows.
      Mayes, I.W. and Davies, W.G.R. (1984), “Analysis of the response of a multi-rotor-bearing system containing a transverse crack in a rotor”, Journal of Vibration Acoustics Stress and Reliability in Design, Vol. 106 No. 1, pp.139-145.

    2. pg.1-45: ... crack will reduce increase the local ...
      A3: This should be “... crack will increase the local ...” and we have corrected it.

    3. pg.1-54: RBS - should be RFBS?
      A4: This should be RBS. Because it refers to the general bearing rotor system mentioned in the references (Sinou and Lees, 2007;AL-Shudeifat, 2013; Fu et al, 2019), referred to as RBS for short, rather than rod-fastening rotor bearing system (RFBS) in our manuscript. Meanwhile, a necessary supplementary description of RBS is given in the text as follows
      “... cracked rotor bearing system (RBS) are obtained ...”

    4. pg.1-54: FEM - when using abbreviations, first define them
      A5: A necessary supplementary description of RBS is given in the text as follows.
      “... developed and the finite element method (FEM) dynamic models ...”

    5. pg.1-54: Sinou and lees (Lees)
      A6: We have make corresponding correction as follows
      “... Sinou and Lees, 2007 ...”

    6. pg.2-2: researches (better: research)
      A7: We are pleasure to adopt this good expression.

    7. pg.2-Fig 1: when using abbreviations define them: Ll, Ld, Lr, ds ... but anyway: are these values of any importance throughout the manuscript? If not, remove them.
      A8: The unnecessary abbreviations (Ll, Ld, Lr, ds) defined in Figure 1 has removed.

    8. pg.3-4: it is to note ...
      pg.6-44: it is to note ...
      A9: The two incorrect expressions in the original text should be “…it is worth to note that…” and the corresponding corrections have been made.

    9. pg.3 Fig.3: the authors show Fig. 3b but do not explain the impact of this finding at all. Is
      A10: In the Last paragraph of section “2.3 Stress analysis of cracked RFBS” in original text, we have discussed the initial bending phenomenon due to the appearance of crack as follows
      “Besides, as shown in Figure 3(b), when the influence of gravity is excluded, the rotor system will appear the initial bending due to presence of the crack and the initial bending will gradually increase with the increment of the crack depth. The initial bending caused by the crack will introduce additional unbalance besides the mass unbalance from system, which will further affect the dynamic characteristics of the system. It is worth noting that 3D static analysis is one of the key steps before dynamic analysis for cracked RFBS.”

    10. pg.4-48: Ho et al.
      A11: This mistake have been corrected in revised manuscript.

    11. pg.8-36: Bachschmid et al. ... should be Vol.9
      pg.8- 43: should be: Fu, C., Xu, Y., Yang, Y., Lu, K., Gu, F. and Ball, A. (2020) ....
      pg.8-44: Nonlinear Science and
      pg.8-59: Liu et al.: should it be: April 2013Journal of Vibration and Acoustics 135(3):031017, DOI: 10.1115/1.4023843 ??
      pg.8-60: Mayes .... "The vibrational behavior ....
      pg.9-7: Pinkus, ... Theory of hydrodynamic ....
      pg.9-15: should be: E. L. B. Van De Vorst, R. H. B. Fey, A. De Kraker & D. H. Van Campen - and 295-313
      A12: Due to our carelessness, the format of the relevant literature is not standardized. We have revised them one by one based on the reviewers' comments (please see the revised manuscript). Besides the journal title and book title should be Italics, we have updated them (please see the revised manuscript).

    Response to Reviewer: 2’ Comments:
    (The corresponding corrections for Reviewer: 2’ Comments are marked with green colour in revised manuscript)

    1. In the present work, rather simple infinite long bearing assumption is used to account the bearing forces. Is this infinite long bearing theory applicable in the present circumstances? Otherwise, it seems there is no new contribution from present work as far as tribology study is concerned.
      A1: Firstly, the RFBS is a very complex rotor system compared with other rotor bearing system with no fastening rods and multi-contact rough interfaces, and we hope that even a simple nonlinear oil film force model can reflect the dynamic characteristics of such complex systems, especially the influence of cracks on the vibration characteristics of the system from the qualitative point of view. Secondly, when the oil film force is obtained by numerical solution of two-dimensional Reynolds equation and then it is tried to be used in this complex combined system, the convergence of the calculation is not very good. We hope that we can find more suitable models for present complex combined rotor system in later research.

    2. What is the motivation in selecting the location of crack on the fastening rod.
      A2: For rod-fastening rotor bearing system (RFBS), there are three places which are easy to fatigue damage or fracture. They are the end of the fastening rod (closing to the end of the thread), the transition position between disc and rotor shaft (i.e. the root of the disc), and the position of rod hole on the disc (the region compressed by the nut), respectively. These locations are mainly affected by the alternating stress during the actual working process, and it is also the position where the stress is relatively concentrated. In the revised manuscript, the stress distribution of fastening rod for intact RFBS has been supplemented as shown in Figure 2 (c) (please see Figure 2 (c) in the revised manuscript ). It can be found from the Figure 2(c), the largest stress is mainly located between the end of the per rod and nut as marked with red circles, i.e. these locations are more likely to appear fatigue crack or fracture which results from the alternating stress. Meanwhile the text description has been explained further and modified accordingly in section “2.2 3D FEM crack model”.

    3. How does the preload in the fasting rod and location of crack on the fastening rod, affects the dynamic behavior of the rotor system.
      A3: RFBS is a very kind of typical complex combined machine structure. Multiple disks are fastened by several circumferentially distributed fastening rods. The system is combined by pre-tightening the nut at the end of per rod. This connection forms contact interfaces among disks as well as between rods and disks. Firstly, only when the preload reaches a certain degree, the rotor system can be formed and has corresponding system stiffness. Secondly, the contact stiffness of interface is an important part of the system stiffness, and the preload directly affects the contact interface stiffness. After then the dynamic characteristics of the system is affected by system stiffness. Last but not least, the non-uniform preload will also directly affect the dynamic characteristics of the system.
      Besides, the motivation in selecting the location of crack on the fastening rod has been stated in the last question. Generally, the different location of crack may result in different local flexibility and initial bending shape changes of the rotor. But the influence of different crack position on the dynamic characteristics of the system is not the main focus of this paper.

    4. Description of the symbols used in equation 4 should be mentioned.
      A4: The missing description of the symbols have been supplemented as follows
      “Theσis Sommerfeld number which is directly related to bearing width, radius, clearance, and oil viscosity, ω is rotating speed, φ is the angle of the rotor centroid relative to the vertical direction, and the symbolτequals ωt.” .

    5. For numerical solution whether commercial software is used or in-house computer code is developed?
      A5: In-house Fortran code is developed for the numerical solution for dynamics.

    6. From Fig 5., it is shown that collision occurs beyond 5120 rpm and 5040 rpm for intact and cracked RFBS, respectively. Description about this collision should be given.
      A6: In the pg. 6-9 and pg. 6-9 in original manuscript, the corresponding description of the collision has been given as follows:
      “With the increment of speeds, the cracked RFBS will encounter collision at 5040 rpm while this phenomenon will not occur until rotating speeds reach 5120 rpm for intact RFBS.”
      To be more clear, we have given a clearer description in revised manuscript as follows
      “With the increment of speeds, the cracked RFBS will encounter collision at 5040 rpm while this phenomenon will not occur until rotating speeds reach 5120 rpm for intact RFBS as shown in the two rightmost figures in Figure 5.”

    7. Only phase plots are provided to understand the nonlinear behaviour. Further, Poincare plots, Lyapunov exponent, power spectrum, bifurcation plots should be included.
      A7: In this paper, the effect of crack on the vibration characteristics of RFBS is focused. The more nonlinear behaviour will be specifically discussed in subsequent studies.

    8. Figure 7 should be described in detail. In Fig. 7, to have a better understanding, phase information should also provided along with the amplitude.
      A8: In the revised manuscript, the necessary supplementary description of Figure 7 has been given, and the corresponding phase information has also been given as well as its description.

    9. With reference to Fig. 8, numerical solution is compare with the experimental results. It is not clear whether experimental work is the contribution of present authors. If so, details about experimental set-up, procedures, sensors utilized should be reported.
      A9: The experimental work is carried out by ourselves on our own test rig in our own laboratory. The essential details of experiment set up and corresponding description of test rig have been supplemented by Figure 8 in section “4.3 Experiment validation” in revised manuscript.

    10. In Figure 8, comparison between numerical solution and experimental results at the disc node are shown. However, as far as measurement is concerned, for the rotor system supported on fluid film bearings, proximity displacement sensors are used which are mounted close to the bearings. However, in Fig. 8 it seems that measured amplitude at disc is shown? Satisfactory justification should be given.
      A10: The numerical solution and experimental results at the bearing locations have been supplemented by Figure 10 in revised manuscript as well as the essential descriptions.



    Cite this author response
  • pre-publication peer review (ROUND 1)
    Decision Letter
    2020/07/19

    19-Jul-2020

    Dear Mr. Wang:

    Manuscript ID ilt-05-2020-0189 entitled "Effect of a transverse crack on the dynamic behaviours of a 3D rod-fastening rotor bearing system" which you submitted to the Industrial Lubrication and Tribology, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.

    The reviewer(s) have recommended major revisions to the submitted manuscript, before it can be considered for publication. Therefore, I invite you to respond to the reviewer(s)' comments and revise your manuscript.

    To revise your manuscript, log into https://mc.manuscriptcentral.com/ilt and enter your Author Centre, where you will find your manuscript title listed under "Manuscripts with Decisions." Under "Actions," click on "Create a Revision." Your manuscript number has been appended to denote a revision.

    You will be unable to make your revisions on the originally submitted version of the manuscript. Instead, revise your manuscript using a word processing program and save it on your computer. Please also highlight the changes to your manuscript within the document by using the track changes mode in MS Word or by using bold or coloured text.

    Once the revised manuscript is prepared, you can upload it and submit it through your Author Centre. The deadline for uploading a revised manuscript is 17-Oct-2020 from receiving this email. If it is not possible for you to resubmit your revision within this timeframe, we may have to consider your paper as a new submission.

    When submitting your revised manuscript, you will be able to respond to the comments made by the reviewer(s) in the space provided. You can use this space to document any changes you make to the original manuscript. In order to expedite the processing of the revised manuscript, please be as specific as possible in your response to the reviewer(s).

    IMPORTANT: Your original files are available to you when you upload your revised manuscript. Please delete any redundant files before completing the submission.

    Please note that Emerald requires you to clear permission to re-use any material not created by you. If there are permissions outstanding, please send these to Emerald as soon as possible. Emerald is unable to publish your paper with permissions outstanding.

    To help support you on your publishing journey we have partnered with Editage, a leading global science communication platform, to offer expert editorial support including language editing and translation.
    If your article has been rejected or revisions have been requested, you may benefit from Editage’s services. For a full list of services, visit: authorservices.emeraldpublishing.com/
    Please note that there is no obligation to use Editage and using this service does not guarantee publication.

    Once again, thank you for submitting your manuscript to the Industrial Lubrication and Tribology and I look forward to receiving your revision.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Reviewer(s)' Comments to Author:
    Reviewer: 1

    Comments to the Author
    Please check:
    all through the manuscript: there should always be a space between number and unit (https://physics.nist.gov/cuu/Units/rules.html)

    pg.1-50: Mayes, 1984 there is no reference given
    pg.1-45: ... crack will reduce increase the local ...
    pg.1-54: RBS - should be RFBS?
    pg.1-54: FEM - when using abbreviations, first define them
    pg.1-54: Sinou and lees (Lees)
    pg.2-2: researches (better: research)
    pg.2-Fig 1: when using abbreviations define them: Ll, Ld, Lr, ds ... but anyway: are these values of any importance throughout the manuscript? If not, remove them.
    pg.3-4: it is to note ...
    pg.3 Fig.3: the authors show Fig. 3b but do not explain the impact of this finding at all. Is
    pg.4-48: Ho et al.
    pg.6-44: it is to note ...
    pg.8-36: Bachschmid et al. ... should be Vol.9
    pg.8- 43: should be: Fu, C., Xu, Y., Yang, Y., Lu, K., Gu, F. and Ball, A. (2020) ....
    pg.8-44: Nonlinear Science and
    pg.8-59: Liu et al.: should it be: April 2013Journal of Vibration and Acoustics 135(3):031017, DOI: 10.1115/1.4023843 ??
    pg.8-60: Mayes .... "The vibrational behavior ....
    pg.9-7: Pinkus, ... Theory of hydrodynamic ....
    pg.9-15: should be: E. L. B. Van De Vorst, R. H. B. Fey, A. De Kraker & D. H. Van Campen - and 295-313

    Reviewer: 2

    Comments to the Author
    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption. Authors should address following queries,

    1. In the present work, rather simple infinite long bearing assumption is used to account the bearing forces. Is this infinite long bearing theory applicable in the present circumstances? Otherwise, it seems there is no new contribution from present work as far as tribology study is concerned.
    2. What is the motivation in selecting the location of crack on the fastening rod.
    3. How does the preload in the fasting rod and location of crack on the fastening rod, affects the dynamic behavior of the rotor system.
    4. Description of the symbols used in equation 4 should be mentioned.
    5. For numerical solution whether commercial software is used or in-house computer code is developed?
    6. From Fig 5., it is shown that collision occurs beyond 5120 rpm and 5040 rpm for intact and cracked RFBS, respectively. Description about this collision should be given.
    7. Only phase plots are provided to understand the nonlinear behaviour. Further, Poincare plots, Lyapunov exponent, power spectrum, bifurcation plots should be included.
    8. Figure 7 should be described in detail. In Fig. 7, to have a better understanding, phase information should also provided along with the amplitude.
    9. With reference to Fig. 8, numerical solution is compare with the experimental results. It is not clear whether experimental work is the contribution of present authors. If so, details about experimental set-up, procedures, sensors utilized should be reported.
    10. In Figure 8, comparison between numerical solution and experimental results at the disc node are shown. However, as far as measurement is concerned, for the rotor system supported on fluid film bearings, proximity displacement sensors are used which are mounted close to the bearings. However, in Fig. 8 it seems that measured amplitude at disc is shown? Satisfactory justification should be given.
      Reviewer: 1

    Recommendation: Minor Revision

    Comments:
    Please check:
    all through the manuscript: there should always be a space between number and unit (https://physics.nist.gov/cuu/Units/rules.html)

    pg.1-50: Mayes, 1984 there is no reference given
    pg.1-45: ... crack will reduce increase the local ...
    pg.1-54: RBS - should be RFBS?
    pg.1-54: FEM - when using abbreviations, first define them
    pg.1-54: Sinou and lees (Lees)
    pg.2-2: researches (better: research)
    pg.2-Fig 1: when using abbreviations define them: Ll, Ld, Lr, ds ... but anyway: are these values of any importance throughout the manuscript? If not, remove them.
    pg.3-4: it is to note ...
    pg.3 Fig.3: the authors show Fig. 3b but do not explain the impact of this finding at all. Is
    pg.4-48: Ho et al.
    pg.6-44: it is to note ...
    pg.8-36: Bachschmid et al. ... should be Vol.9
    pg.8- 43: should be: Fu, C., Xu, Y., Yang, Y., Lu, K., Gu, F. and Ball, A. (2020) ....
    pg.8-44: Nonlinear Science and
    pg.8-59: Liu et al.: should it be: April 2013Journal of Vibration and Acoustics 135(3):031017, DOI: 10.1115/1.4023843 ??
    pg.8-60: Mayes .... "The vibrational behavior ....
    pg.9-7: Pinkus, ... Theory of hydrodynamic ....
    pg.9-15: should be: E. L. B. Van De Vorst, R. H. B. Fey, A. De Kraker & D. H. Van Campen - and 295-313

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: most likely

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: Yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: most likely

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: The FEM results seem to be conclusive. But there are data presented without further discussion, e.g. Fig. 1 (abbreviations), Fig. 3b (centroid offset)

    The authors mention 4.3 "Experiment validation" but do not describe the experimental setup.
    Were there any experiments conducted or are the findings in 4.3 just a conclusion from the FEM calculations?

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: Readability could be improved

    maybe the authors could ask a native english speaker to check the spelling

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?:

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: No, I would not like my name to appear with my report on Publons

    Reviewer: 2

    Recommendation: Major Revision

    Comments:
    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption. Authors should address following queries,

    1. In the present work, rather simple infinite long bearing assumption is used to account the bearing forces. Is this infinite long bearing theory applicable in the present circumstances? Otherwise, it seems there is no new contribution from present work as far as tribology study is concerned.
    2. What is the motivation in selecting the location of crack on the fastening rod.
    3. How does the preload in the fasting rod and location of crack on the fastening rod, affects the dynamic behavior of the rotor system.
    4. Description of the symbols used in equation 4 should be mentioned.
    5. For numerical solution whether commercial software is used or in-house computer code is developed?
    6. From Fig 5., it is shown that collision occurs beyond 5120 rpm and 5040 rpm for intact and cracked RFBS, respectively. Description about this collision should be given.
    7. Only phase plots are provided to understand the nonlinear behaviour. Further, Poincare plots, Lyapunov exponent, power spectrum, bifurcation plots should be included.
    8. Figure 7 should be described in detail. In Fig. 7, to have a better understanding, phase information should also provided along with the amplitude.
    9. With reference to Fig. 8, numerical solution is compare with the experimental results. It is not clear whether experimental work is the contribution of present authors. If so, details about experimental set-up, procedures, sensors utilized should be reported.
    10. In Figure 8, comparison between numerical solution and experimental results at the disc node are shown. However, as far as measurement is concerned, for the rotor system supported on fluid film bearings, proximity displacement sensors are used which are mounted close to the bearings. However, in Fig. 8 it seems that measured amplitude at disc is shown? Satisfactory justification should be given.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption. Authors should address following queries as mentioned in the comments.

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: Please see the comments below.

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: Please see the comments below.

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?: Please see the comments below.

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/07/19

    In the present work, the dynamic behaviours of a three-dimensional (3D) rod-fastening rotor bearing system with a crack in a fastening rod is studied using 3D finite element method. Bearing forces are incorporated using a simple infinite long bearing assumption. Authors should address following queries,

    1. In the present work, rather simple infinite long bearing assumption is used to account the bearing forces. Is this infinite long bearing theory applicable in the present circumstances? Otherwise, it seems there is no new contribution from present work as far as tribology study is concerned.
    2. What is the motivation in selecting the location of crack on the fastening rod.
    3. How does the preload in the fasting rod and location of crack on the fastening rod, affects the dynamic behavior of the rotor system.
    4. Description of the symbols used in equation 4 should be mentioned.
    5. For numerical solution whether commercial software is used or in-house computer code is developed?
    6. From Fig 5., it is shown that collision occurs beyond 5120 rpm and 5040 rpm for intact and cracked RFBS, respectively. Description about this collision should be given.
    7. Only phase plots are provided to understand the nonlinear behaviour. Further, Poincare plots, Lyapunov exponent, power spectrum, bifurcation plots should be included.
    8. Figure 7 should be described in detail. In Fig. 7, to have a better understanding, phase information should also provided along with the amplitude.
    9. With reference to Fig. 8, numerical solution is compare with the experimental results. It is not clear whether experimental work is the contribution of present authors. If so, details about experimental set-up, procedures, sensors utilized should be reported.
    10. In Figure 8, comparison between numerical solution and experimental results at the disc node are shown. However, as far as measurement is concerned, for the rotor system supported on fluid film bearings, proximity displacement sensors are used which are mounted close to the bearings. However, in Fig. 8 it seems that measured amplitude at disc is shown? Satisfactory justification should be given.

    Reviewed by
    Cite this review
    Reviewer report
    2020/06/26

    Please check:
    all through the manuscript: there should always be a space between number and unit (https://physics.nist.gov/cuu/Units/rules.html)

    pg.1-50: Mayes, 1984 there is no reference given
    pg.1-45: ... crack will reduce increase the local ...
    pg.1-54: RBS - should be RFBS?
    pg.1-54: FEM - when using abbreviations, first define them
    pg.1-54: Sinou and lees (Lees)
    pg.2-2: researches (better: research)
    pg.2-Fig 1: when using abbreviations define them: Ll, Ld, Lr, ds ... but anyway: are these values of any importance throughout the manuscript? If not, remove them.
    pg.3-4: it is to note ...
    pg.3 Fig.3: the authors show Fig. 3b but do not explain the impact of this finding at all. Is
    pg.4-48: Ho et al.
    pg.6-44: it is to note ...
    pg.8-36: Bachschmid et al. ... should be Vol.9
    pg.8- 43: should be: Fu, C., Xu, Y., Yang, Y., Lu, K., Gu, F. and Ball, A. (2020) ....
    pg.8-44: Nonlinear Science and
    pg.8-59: Liu et al.: should it be: April 2013Journal of Vibration and Acoustics 135(3):031017, DOI: 10.1115/1.4023843 ??
    pg.8-60: Mayes .... "The vibrational behavior ....
    pg.9-7: Pinkus, ... Theory of hydrodynamic ....
    pg.9-15: should be: E. L. B. Van De Vorst, R. H. B. Fey, A. De Kraker & D. H. Van Campen - and 295-313

    Reviewed by
    Cite this review
All peer review content displayed here is covered by a Creative Commons CC BY 4.0 license.