The Influence of Surface Texturing on the Frictional Behaviour in Starved Lubricated Parallel Sliding Contacts

Round 1

Reviewer 1 Report

The paper deals about the influence of the surface texture on the lubricated sliding contacts. The paper is interesting and well built even if, in my opinion, some concerns must be addressed before its publication.

1) The introduction presents an interesting scientific framework on the investigated topic. Even if most of the considered papers are "milestones", may be, the Authors should improve the introduction by considering more recent relevant papers and findings on the topic.

2) The first part of M&M could be joined to the introduction part;

3) The investigated model is based on the Greenwood and Williamson’s contact model and on the Johnson load sharing concept; even if both represents  classical models, in the conclusions the Authors should explain how their findings are connected with more recent and detailed models;

4) Al line 129 "The deformation of an asperity is defined as (see Figure 2)": unfortunately the figure is not so clear....

5) At line 158 is better to write "under classical hypothesis of the Reynolds isothermal equation;

6) With reference to lines 171 and 172, even if details on Eq 7 are referred to [44], is better to introduce shortly at least the fi cavitation index;

7) The used cavitation model must be clarified;

8) Figure 5 must be improved in its resolution;

9) The results are interesting but they have to be validated or experimentally or by considering other investigations in scientific literature;

10) The temperature was not considered in this investigation; has this parameter influence on the results? Please discuss it with reference to other recent scientific results...

11) Please underline in the conclusions the limitations of this investigation. 

Author Response

Dear reviewer,

Thanks for the corrections and requests, I revised the manuscript based on these corrections. The modified text is addressed in comment section of word file.

Best regards,

1- The introduction presents an interesting scientific framework on the investigated topic. Even if most of the considered papers are "milestones", may be, the Authors should improve the introduction by considering more recent relevant papers and findings on the topic.

Answer:

Introduction and literature review are modified based on this suggestion.

2- The first part of M&M could be joined to the introduction part;

Answer:

Introduction is revised based on this suggestion.

3- The investigated model is based on the Greenwood and Williamson’s contact model and on the Johnson load sharing concept; even if both represents classical models, in the conclusions the Authors should explain how their findings are connected with more recent and detailed models;

Answer:

Conclusion is changed based on this request.

2- At line 129 "The deformation of an asperity is defined as (see Figure 2)": unfortunately the figure is not so clear....

Answer:

Text and figure are changed based on this comment.

5- At line 158 is better to write "under classical hypothesis of the Reynolds isothermal equation;

Answer:

Text is modified based on this suggestion.

6- With reference to lines 171 and 172, even if details on Eq. 7 are referred to [44], is better to introduce shortly at least the fi cavitation index;

Answer:

Text is changed based on this request.

7- The used cavitation model must be clarified;

Answer:

Text is changed based on this request.

8- Figure 5 must be improved in its resolution;

Answer:

Resolution and contrast are changed based on this request.

9- The results are interesting but they have to be validated or experimentally or by considering other investigations in scientific literature;

Answer:

Validation result and text are added in the manuscript.

10- The temperature was not considered in this investigation; has this parameter influence on the results? Please discuss it with reference to other recent scientific results...

Answer:

Text is changed to add temperature influence on frictional behavior of sliding contacts from literature but temperature study is out of scope of this project. Therefore, there is no calculation based on temperature effect, just the literature study on temperature is addressed in introduction.

11- Please underline in the conclusions the limitations of this investigation.

Answer:

Text is changed based on this request.

Author Response File: Author Response.pdf

Reviewer 2 Report

This is an interesting and well written paper, with some minor errors:

Page 3, line 129: (see Figure 2) … should it be (see Figure 1)

Page 6, equation (12); please define the parameters E and Ri

Page 8, Table 1: Simulations were conducted only under one contact loading condition and one type of lubricant. Please explain why such single conditions were chosen and whether the results would be similar under other contact loading and lubricant conditions.

Figure 7 to 13: I think the results for no-texturing surface are missing from these figures, which also require some discussion in the paper.

Figures 7 to 13: please remove the top axis labels (Groove depth, Groove size, Groove pitch, etc). They are misleading.

Figure 7 caption: should hi be hoil?

Figures 10 and 11: The vertical axis scale is different in (a) and (b). Keep the same scale is good for comparison.

Figure 13: The caption should be more specific to reflect the figure contents.

Author Response

Dear reviewer,

Thanks for the constructive comments. Manuscript is modified based on these comments. The modified parts are addressed in comment section of word file.

Best regards,

1- Page 3, line 129: (see Figure 2) … should it be (see Figure 1):

Answer:

Text is corrected.

2- Page 6, equation (12); please define the parameters  and:

Answer:

Text is changed based on this suggestion.

3- Page 8, Table 1: Simulations were conducted only under one contact loading condition and one type of lubricant. Please explain why such single conditions were chosen and whether the results would be similar under other contact loading and lubricant conditions:

Answer:

This study is focused on the influence of surface texturing therefore the geometrical characteristics of surface texturing is considered as the subject of this article. Text is changed in conclusion to underline the limits of this study.

4- Figure 7 to 13: I think the results for no-texturing surface are missing from these figures, which also require some discussion in the paper:

Answer:

In case of non-textured parallel sliding contacts, because it is not possible to form a lubricant film in contact, lubrication regime stays in boundary lubrication region and Stribeck curve transforming into a constant/horizontal line. In addition, in this numerical study when, distance between two surfaces are also zero and algorithm cannot converge. Text is changed to mention this effect in section 2 of this article.

5- Figures 7 to 13: please remove the top axis labels (Groove depth, Groove size, Groove pitch, etc). They are misleading.

Answer:

Figures are changed based on this request.

6- Figure 7 caption: should hi be hoil?

Answer:

Caption is corrected.

7- Figures 10 and 11: The vertical axis scale is different in (a) and (b). Keep the same scale is good for comparison.

Answer:

Figures are changed based on this suggestion.

8- Figure 13: The caption should be more specific to reflect the figure contents.

Answer:

Caption is changed based on this comment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The Authors addressed correctly all my suggestions

Author Response

Thanks for your comments.