Abstract

PurposeThis paper aims to investigate the fretting wear mechanism of an Al-Li alloy at room temperature, the tangential fretting wear tests were carried out.Design/methodology/approachThe effects of displacement amplitude and fretting frequency on the tangential fretting wear characteristics were mainly investigated. The experimental data obtained are analyzed and compared.FindingsThe results indicated that the fretting friction coefficient increased with the increase of displacement amplitude. As the displacement amplitude increased, the wear scar morphology changed significantly, mainly in terms of delamination debris and furrow scratches. The wear mechanism changed from initial mild wear to more severe oxidative wear, adhesive wear and abrasive wear.Originality/valueThis paper extends the knowledge into mechanical tight connections. The conclusions can provide theoretical guidance for the fretting of mechanical tight connections in the field of automotive lightweight and aerospace.Peer reviewThe peer review history for this article is available at:


Authors

Xiao, Teng;  Wen, Daosheng;  Wang, Shouren;  Zhang, Mingyuan;  Kong, Beibei;  Yu, Qiqi

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  • 1 reviewer
  • pre-publication peer review (FINAL ROUND)
    Decision Letter
    2020/03/04

    04-Mar-2020

    Dear Xiao, Teng; Wen, Daosheng; wang, shouren; Zhang, Mingyuan; Kong, Beibei; Yu, Qiqi

    It is a pleasure to accept your manuscript ilt-11-2019-0490.R2, entitled "Investigation on fretting wear of Al - Li alloy" 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.

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

    Decision letter by
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    Reviewer report
    2020/03/04

    No further comments.

    Reviewed by
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    Author Response
    2020/03/01

    Dear reviewer,
    Thank you very much again. We have carefully revised the manuscript based on your comments. The revisions have been highlighted in red in the marked manuscript.

    • Added error bars on Figs. 3, 7 and 10 are the same for all displacements. Most probably this is accidental mistake. Nevertheless, it needs to be corrected prior to publication.
    response: Thank you for the useful comments. We are sorry for the accidental mistake. It has been revised in Fig. 3, 7 and 10, respectively.

    • The authors corrected statement that the delamination wear, adhesive wear and abrasive wear are not wear mechanisms, but did not cite the appropriate reference which defines wear mechanisms in tribosystems (see the previous review). In addition, new confusion arises, since authors added word “fretting” in “The predominant fretting wear types of the AZ91D is the adhesive wear, abrasive wear and delamination wear” (page 2, line 54). Word “fretting” should be deleted.
    response: Thank you for your comments. We have accordingly added the appropriate reference. And the word “fretting” has been deleted in the new manuscript.



    Cite this author response
  • pre-publication peer review (ROUND 2)
    Decision Letter
    2020/02/27

    27-Feb-2020

    Dear Dr. Wen:

    Manuscript ID ilt-11-2019-0490.R1 entitled "Investigation on fretting wear of Al - Li alloy" 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 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.

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    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 28-Mar-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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    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
    Authors mostly corrected the paper as per reviewer comment, but some new issues appear.
    • Added error bars on Figs. 3, 7 and 10 are the same for all displacements. Most probably this is accidental mistake. Nevertheless, it needs to be corrected prior to publication.
    • The authors corrected statement that the delamination wear, adhesive wear and abrasive wear are not wear mechanisms, but did not cite the appropriate reference which defines wear mechanisms in tribosystems (see the previous review). In addition, new confusion arises, since authors added word “fretting” in “The predominant fretting wear types of the AZ91D is the adhesive wear, abrasive wear and delamination wear” (page 2, line 54). Word “fretting” should be deleted.

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

    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 it does.

    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, the paper arguments are built on an appropriate concepts and ideas, and the theoretical base is appropriate.

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

    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.: The English is acceptable and the style of presentation is adequate.

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

    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: No, I would not like my name to appear with my report on Publons

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/02/26

    Authors mostly corrected the paper as per reviewer comment, but some new issues appear.
    • Added error bars on Figs. 3, 7 and 10 are the same for all displacements. Most probably this is accidental mistake. Nevertheless, it needs to be corrected prior to publication.
    • The authors corrected statement that the delamination wear, adhesive wear and abrasive wear are not wear mechanisms, but did not cite the appropriate reference which defines wear mechanisms in tribosystems (see the previous review). In addition, new confusion arises, since authors added word “fretting” in “The predominant fretting wear types of the AZ91D is the adhesive wear, abrasive wear and delamination wear” (page 2, line 54). Word “fretting” should be deleted.

    Reviewed by
    Cite this review
    Author Response
    2020/02/24

    Dear reviewers,
    Thank you very much for your comments on our manuscript. We would like to express our sincere appreciation for your careful reading and invaluable comments. These comments are very valuable and helpful in improving the manuscript. We have carefully revised the manuscript based on your comments. The revisions have been highlighted in red in the marked manuscript.

    Reviewer: 1
    1) What was the initial contact pressure in the fretting experiments?
    According to the ball-plane model in Hertz contact theory, the initial stresses at 100N are 1463 MPa. The values of contact stresses are also supplemented on page 4, lines 14-16. The contact stress (q) is given by the below equation:
    q3=6F/(π3×R02×((1-μ12)/E1+(1-μ22)/E2)2) (1)
    where μ is Poisson's ratio of 1420 (μ1=0.28) and GCr15 (μ2=0.3) alloys, E is elastic modulus of 1420 (E1=76 GPa) and GCr15 (E2=208 GPa) alloys and R0 is radius of GCr15.

    2) How representative are the data presented in Figure 3? How many repetition was done? What was the experimental scattering?
    Fretting test under the same conditions was carried out at least for three times. Then, the representative data were presented in Figure 3.

    3) Was wear of samples calculated in any way? If yes, please provide obtained results. Figures 4 and 5 present only cross-sectional areas of wear scar without quantitative information about wear.
    Thank you for your comments. The original Fig. 4 and Fig. 5 have been changed to Fig. 5 and Fig. 6, respectively. Based on the two-dimensional contours of Fig. 5 and Fig. 6, the wear volume under different displacement amplitudes is calculated, as shown in Fig. 7.

    4) If possible, it would be useful to add EDS data to Figures 6 and 7.
    Thank you for your comments. The original Fig. 6 and Fig. 7 have been changed to Fig. 8 and Fig. 9, respectively. EDS data have been added to Figure 8 and 9.

    5) Axis values presented on Figures 4 and 5 are invisible. Please improve them.
    The original Fig. 4 and Fig. 5 have been changed to Fig. 5 and Fig. 6, respectively. These issues have been revised in the new manuscript.

    6) Error bars on Figure 8 should be provided.
    The original Fig. 8 have been changed to Fig. 10. Error bars have been added to Figure 10.

    Reviewer: 2
    First thing is connected with the presentation of the results and their discussion:
    • The authors should clarify how many times they repeated tests for each frequency-displacement combination; if it is only one time, it should be written as well.
    response: Fretting test for each frequency-displacement combination was repeated at least for three times. Accordingly, it is revised on page 4, lines 12 and 13: To ensure the repeatability of tests, a fretting test was carried out at least for three times.

    • Different displacement amplitudes on Fig 3. Should be denoted next to the curves, since now it is fussy and it is also a problem if it is not printed in colour.
    response: Thanks for your comments. It has been revised in Fig. 3.

    • It is necessary to show all tribological results (for each frequency, and not only for 2 and 5 Hz). This could be done in the form of bar graph where steady-state COF for all conditions should be presented.
    response: It has been accordingly revised in Fig. 4.

    • Wear intensity should be calculated form Figs. 4 and 5 and presented in the similar was as steady-state COF (for all conditions)
    response: Thank you for your comments. The wear volume of the sample under different displacement amplitudes is calculated. The wear intensity was quantitatively analyzed. The contents are also supplemented in section 3.3.

    Second thing is connected with the terminology:
    • The authors use terms that are not familiar in the tribological literature, like “stratification” (page 3, line 9), “frictional strength” (page 6, line 6), “grinding debris” (several times in the text), “tangential fretting”, “slight wear” (page 1, line 31) ; this terms should be harmonized with the literature.
    response: Thank you for your comments. Revisions are as follows:
    (1) Page 3, line 3: …delamination…
    (2) Page 6, line 5: …strength of friction…
    (3) Page 6, line 13, Page 7, line 7 and Page 9, line 18: …wear debris…
    (4) Page 1, line 14: …mild wear…
    (5) As for the word “tangential fretting”, many works show that it is adequate in the manuscript [1-3].

    References
    [1] M. H., Zhu, Z. R., Zhou, Kapsa, Ph and Vincent, L. (2001), “An experimental investigation on composite fretting mode,” Tribology International, Vol. 34 No. 11, pp. 733-738.
    [2] X. Y., Zhang, Z. B., Cai, J. F., Peng, J. H., Liu, M. H., Zhu, R., Du, X. L., Yuan and P. D., Ren. (2018), “Experimental study of the fretting wear behavior of Inconel 690 alloy under alternating load conditions,” Proceedings of the Institution of Mechanical Engineers, Vol. 232 No. 11, pp. 1343-1351.
    [3] Z. B., Cai, M. H., Zhu, H. M., Shen, Z. R., Zhou, X. S., Jin. (2009), “Torsional fretting wear behavior of 7075 aluminum alloy in various relative humidity environments,” Wear, Vol. 267 No. 1, pp. 330-339.

    • There is confusion between wear types and wear mechanisms; Delamination wear, adhesive wear and abrasive wear are not wear mechanisms (page 2, line 53). They are different wear types (see. Fig. 1.10. Main wear mechanisms in tribosystems in Kandeva-Ivanova et al. “Advanced Tribological Coatings for Heavy-Duty Applications: Case Studies”, Sofia, 2016).
    response: Thank you for your comments. It is revised on page 2, line 19-20: …wear types…

    • Even the title is not adequate since the authors investigated fretting wear and not the mechanisms associated with tit, so maybe “Investigation on fretting wear of Al-Li alloy” is more adequate.
    response: Thank you for the useful comments. Accordingly, the title is replaced with “Investigation on fretting wear of Al-Li alloy”.



    Cite this author response
  • pre-publication peer review (ROUND 1)
    Decision Letter
    2020/02/09

    09-Feb-2020

    Dear Dr. Wen:

    Manuscript ID ilt-11-2019-0490 entitled "Investigation on fretting wear mechanism of a Al - Li alloy" 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 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 10-Mar-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.

    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
    Dear author’s, I think that your work is well organised, planned and presented according to the experimental work performed. Despite all these, the paper needs some revision:
    1) What was the initial contact pressure in the fretting experiments?
    2) How representative are the data presented in Figure 3? How many repetition was done? What was the experimental scattering?
    3) Was wear of samples calculated in any way? If yes, please provide obtained results.Figures 4 and 5 present only cross-sectional areas of wear scar without quantitative information about wear.
    4) If possible, it would be useful to add EDS data to Figures 6 and 7.
    5) Axis values presented on Figures 4 and 5 are invisible. Please improve them.
    6) Error bars on Figure 8 should be provided.

    Reviewer: 2

    Comments to the Author
    The paper is well written and the subject is interesting. The experiment in this paper is well designed and performed. The English is acceptable. Nevertheless, there are two major remarks that could/should be improved and revised.

    First thing is connected with the presentation of the results and their discussion:
    • The authors should clarify how many times they repeated tests for each frequency-displacement combination; if it is only one time, it should be written as well.
    • Different displacement amplitudes on Fig 3. should be denoted next to the curves, since now it is fussy and it is also a problem if it is not printed in colour.
    • It is necessary to show all tribological results (for each frequency, and not only for 2 and 5 Hz). This could be done in the form of bar graph where steady-state COF for all conditions should be presented.
    • Wear intensity should be calculated form Figs. 4 and 5 and presented in the similar was as steady-state COF (for all conditions)

    Second thing is connected with the terminology:
    • The authors use terms that are not familiar in the tribological literature, like “stratification” (page 3, line 9), “frictional strength” (page 6, line 6), “grinding debris” (several times in the text), “tangential fretting”, “slight wear” (page 1, line 31) ; this terms should be harmonized with the literature.
    • There is confusion between wear types and wear mechanisms; Delamination wear, adhesive wear and abrasive wear are not wear mechanisms (page 2, line 53). They are different wear types (see. Fig. 1.10. Main wear mechanisms in tribosystems in Kandeva-Ivanova et al. “Advanced Tribological Coatings for Heavy-Duty Applications: Case Studies”, Sofia, 2016).
    • Even the title is not adequate since the authors investigated fretting wear and not the mechanisms associated with tit, so maybe “Investigation on fretting wear of Al-Li alloy” is more adequate.
    Reviewer: 1

    Comments:
    Dear author’s, I think that your work is well organised, planned and presented according to the experimental work performed. Despite all these, the paper needs some revision:
    1) What was the initial contact pressure in the fretting experiments?
    2) How representative are the data presented in Figure 3? How many repetition was done? What was the experimental scattering?
    3) Was wear of samples calculated in any way? If yes, please provide obtained results.Figures 4 and 5 present only cross-sectional areas of wear scar without quantitative information about wear.
    4) If possible, it would be useful to add EDS data to Figures 6 and 7.
    5) Axis values presented on Figures 4 and 5 are invisible. Please improve them.
    6) Error bars on Figure 8 should be provided.

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

    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?: see below

    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?: see below

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

    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: No, I would not like my name to appear with my report on Publons

    Reviewer: 2

    Comments:
    The paper is well written and the subject is interesting. The experiment in this paper is well designed and performed. The English is acceptable. Nevertheless, there are two major remarks that could/should be improved and revised.

    First thing is connected with the presentation of the results and their discussion:
    • The authors should clarify how many times they repeated tests for each frequency-displacement combination; if it is only one time, it should be written as well.
    • Different displacement amplitudes on Fig 3. should be denoted next to the curves, since now it is fussy and it is also a problem if it is not printed in colour.
    • It is necessary to show all tribological results (for each frequency, and not only for 2 and 5 Hz). This could be done in the form of bar graph where steady-state COF for all conditions should be presented.
    • Wear intensity should be calculated form Figs. 4 and 5 and presented in the similar was as steady-state COF (for all conditions)

    Second thing is connected with the terminology:
    • The authors use terms that are not familiar in the tribological literature, like “stratification” (page 3, line 9), “frictional strength” (page 6, line 6), “grinding debris” (several times in the text), “tangential fretting”, “slight wear” (page 1, line 31) ; this terms should be harmonized with the literature.
    • There is confusion between wear types and wear mechanisms; Delamination wear, adhesive wear and abrasive wear are not wear mechanisms (page 2, line 53). They are different wear types (see. Fig. 1.10. Main wear mechanisms in tribosystems in Kandeva-Ivanova et al. “Advanced Tribological Coatings for Heavy-Duty Applications: Case Studies”, Sofia, 2016).
    • Even the title is not adequate since the authors investigated fretting wear and not the mechanisms associated with tit, so maybe “Investigation on fretting wear of Al-Li alloy” is more adequate.

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

    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 it does.

    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, the paper arguments are built on an appropriate concepts and ideas, and the theoretical base is appropriate.

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: The results are presented clearly and the conclusions adequately tie together other elements of the paper. Nevertheless some improvements in the presentation of the results are necessary (see Comments to the Authors).

    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.: The English is acceptable and the style of presentation is adequate.

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

    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: No, I would not like my name to appear with my report on Publons

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/01/23

    The paper is well written and the subject is interesting. The experiment in this paper is well designed and performed. The English is acceptable. Nevertheless, there are two major remarks that could/should be improved and revised.

    First thing is connected with the presentation of the results and their discussion:
    • The authors should clarify how many times they repeated tests for each frequency-displacement combination; if it is only one time, it should be written as well.
    • Different displacement amplitudes on Fig 3. should be denoted next to the curves, since now it is fussy and it is also a problem if it is not printed in colour.
    • It is necessary to show all tribological results (for each frequency, and not only for 2 and 5 Hz). This could be done in the form of bar graph where steady-state COF for all conditions should be presented.
    • Wear intensity should be calculated form Figs. 4 and 5 and presented in the similar was as steady-state COF (for all conditions)

    Second thing is connected with the terminology:
    • The authors use terms that are not familiar in the tribological literature, like “stratification” (page 3, line 9), “frictional strength” (page 6, line 6), “grinding debris” (several times in the text), “tangential fretting”, “slight wear” (page 1, line 31) ; this terms should be harmonized with the literature.
    • There is confusion between wear types and wear mechanisms; Delamination wear, adhesive wear and abrasive wear are not wear mechanisms (page 2, line 53). They are different wear types (see. Fig. 1.10. Main wear mechanisms in tribosystems in Kandeva-Ivanova et al. “Advanced Tribological Coatings for Heavy-Duty Applications: Case Studies”, Sofia, 2016).
    • Even the title is not adequate since the authors investigated fretting wear and not the mechanisms associated with tit, so maybe “Investigation on fretting wear of Al-Li alloy” is more adequate.

    Reviewed by
    Cite this review
    Reviewer report
    2019/12/15

    Dear author’s, I think that your work is well organised, planned and presented according to the experimental work performed. Despite all these, the paper needs some revision:
    1) What was the initial contact pressure in the fretting experiments?
    2) How representative are the data presented in Figure 3? How many repetition was done? What was the experimental scattering?
    3) Was wear of samples calculated in any way? If yes, please provide obtained results.Figures 4 and 5 present only cross-sectional areas of wear scar without quantitative information about wear.
    4) If possible, it would be useful to add EDS data to Figures 6 and 7.
    5) Axis values presented on Figures 4 and 5 are invisible. Please improve them.
    6) Error bars on Figure 8 should be provided.

    Reviewed by
    Cite this review
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