Simulation and Verification of Involute Spline Tooth Surface Wear before and after Carburizing Based on Energy Dissipation Method
Round 1
Reviewer 1 Report
Dear authors,
To my point of view, this is an interesting and nicely written work that fits well with the scope of this journal. However, this article can further improv if the following points are addressed:
1. In the introduction you mention the relevant research articles, but you only focus on your work at the last paragraph, where you describe what you did. However, what is missing is an analysis of the added value and novelty of this work. You should make clear what is new (considering that you already have published similar articles e.g. lubricants 2022, 10, 270) and how it would help the research in this field. In this way the impact of this work will be better highlighted.
2. You mention that ‘According to the wear theory and process analysis’, please add reference(s).
3. Please add Annex describing all symbols used.
4. One of the main keywords that is highlighted in this work are the ‘wear mechanisms’. Indeed, different mechanisms can occur by changing the contact conditions or even during a test. However, no images of how these mechanisms change or evolve (as mentioned in section 1.1) are shown. There are two Figures 20 and 21 showing a part of a worn spline without and with carburizing, but the mechanisms are not clearly shown/explained. For example, indicate transfer film, where is the area of fretting, is there oxidative wear due to fretting etc. To my point of view, the wear mechanisms should be better explained and illustrated.
5. From your test procedure several graphs showing the fluctuation of the wear depth at the axial distance. I understand that wear is highly unrepeatable, so you should mention or comment on the repeatability of these measurements. This is important to know if there is significant difference between them or if it falls within experimental error.
6. Having the above in mind, please add error bars (if multiple tests were performed) on the actual measured points.
7. Finally, in the experimental part (Section 5) more information should be given on the how you measured the wear, how you studied the wear mechanisms etc.
Author Response
We have responded carefully to each comment and made the appropriate changes in the article.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Manuscript interestingly describes the use of involute spline couplings in the aviation drive system and their wear. The reviewer presents his comments on the text below:
I. General remarks:
1. In eq. (1) authors use energy wear coefficient α=k/μ. Could You please explain what is "k" in this equation?
II. Editoral remarks:
1. Shouldn't Introduction starts from number 1., etc.??
2. There are a few punctation marks mismatch in the text - there is e.g "," in place of "." etc.
3. In eq. (2) authors use markings for the auxiliary loss volume V: "I", "II", "III" and then in the text below there are markings "1", "2" and "3". Should be better to unificate the markings in the text.
4. Eq. (1-13) shouldn't be marked as (13)
5. Could be the charts description better visible on Figs. 2-13 ??
6. According to the reviewer, there are many mistakes and editorial shortcomings in the text, e.g. in the formatting of references, formatting of the list of article's authors, lack of a detailed description of the research stand, the correct engineering drawing presented in Fig. 15 and Fig. 16 - in technical drawing it is assumed to be made in one color (black) for different line thicknesses depending on the drawn contour.
III. Factual remarks
1. Fig. 15 and Fig. 16 show the geometrical tolerances of internal and external spline shaft. The authors never mention dimensional tolerances especially for A-A cross-sections. What dimensional tolerances were obtained for the test samples? Were geometrical and dimensional tolerances included in the simulation?
2. Are the experiment (test) and test stand made according to standards?? If so, what is the standard??
3. How was the acting torque measured during the experiment? Or has it been calculated? Have been included in the calculations, e.g. efficiency of the clutch, gear box, etc.??
4. What equipment was used to measure wear depth?
Author Response
We have responded carefully to each comment and made the appropriate changes in the article.
Author Response File: Author Response.pdf
Reviewer 3 Report
The article submitted for review unfortunately contains many deficiencies and should be corrected and supplemented. Only the modified version should be submitted for re-evaluation.
Below are the errors and omissions that need to be corrected, supplemented, or discussed in more detail.
(Unfortunately, the article lines are not numbered, so please read the location of the notes from the description)
1. The all analysis concerns axial inaccuracies, and no mention is made of the much more dangerous for couplings life radial displacements and angular inaccuracies.
2. The literature review should be in “0. Introduction”, not in 1.2, in the second paragraph, on page 4 (lines 5÷29).
3. The description of the finite elements used is incomplete and incorrect. In the article is: "hexahedral grid element" should be "hexadedral finite elements" and also not” divided” should be “discretized”. Finite elements should be dscribed in more detail as in the Abaqus program. For example, for the element C3D8R (8-node linear), or for the C3D20R (20-node quadratic). What finite element was used? Linear or quadratic? (as described in 2.1, page 6). - Please describe in more detail the preparation of FEM calculations and the process of discretization of the model.
4. In 2.1 it is written: "Then the wear of the spline couplings under different working conditions is simulated, and the wear depth values under various working conditions obtained from the simulation are analyzed." So, how was "various working conditions" introduced in the FEM calculations? - Please describe.
5. How were contact surfaces defined, with or without friction (what friction?)? With lubrication? Which one? Parameters? Oil film thickness? - Whether these parameters were included in the FEM calculations. If so, please describe.
6. What input data for the calculation was defined for uncured and carburizing material?
7. In my opinion, blocking the possibility of moving the computational model in the radial direction or changing the angle of the Z axis is wrong. This does not present the real working conditions. This fixing results in erroneously high values for teeth 1÷3 in Figure 22. (The article does not explain why such values appeared. Similarly, there is no explanation for the point-high value for tooth 3 in Figure 9 and teeth 2 and 5 in Figure 11.)
The problems from points 3, 4, 5, 6 and 7 are critical for the correctness of the solution in the analyzed case of tooth surface wear.
8. Figure 1 would be clearer if the elements were on the same scale. It is also worth giving the coordinate system because the description they refer to the Z axis, and it is not marked anywhere.
9. The description of Table 1 contains: "Geometric dimensions...", which is not true, because it also includes strength (material) parameters.
10. There is no description of what t1, t2, etc. mean in Figures 2, 4, 6, etc.
11. Figures 15 and 16 do not comply with international standards (lines, dimensions, markings). Even the basic rule that the technical drawing is black and white has not been preserved!
12. In Table 4, be sure to indicate the hardness.
13. Why was the numerical analysis of FEM discussing results for e = 0.6 and not including this case in stand tests? How can the calculations for e=0.6 be verified?
14. The conclusions of the article are obvious before we even start reading it. Surface pressures depend on the strength and surface of action. Maintaining a constant force, the stresses will be higher for the case e=0.3 than for e=0. In proportion to this, the destruction of contact surfaces will occur. Please provide what is the real result of the realised work and in what this knowledge is new.
I think that if the article included "real working conditions" and not forced coaxial rotation, the results of the calculations would be more similar to the measurements obtained on models at bench tests.
The article presented for review is not detailed enough. The further proceeded is possible after completing the basic information by the authors.
Author Response
We have responded carefully to each comment and made the appropriate changes in the article.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear authors,
After reading the updated version of this aticle and your point-by-point reply to my comments, I now believe that this work is appropriate for publicaton.
Author Response
Thank you very much for your affirmation and support of this work.
Reviewer 3 Report
Many of the previous problems have been chenged, but still a few errors remain or the description is missing:
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1. In Figure 2 (previously Figure 1), the model in view (a) is on a different scale than the models in b) and c).
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2. Table 1 shows material parameters (physical for example Young's modulus) and not just geometric parameters for the “involute spline”, so please give the table a correct title.
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3. The authors reply that in order to distinguish the operating conditions they give two different modulus of elasticity. One value is given in the table for involute: Table 1. Where is second?
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4. Removing Figures 15 and 16 bypasses the problem. It was possible both to correct the drawings and to add tables for readability.
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5. The missing experiment results for e=0.6 have still not been resolved. If there are none, maybe you need to do it?
In general, the science value of the article did not change after the authors' corrections. Of course, changes have been made to the text, drawings and tables, and some descriptions have been expanded. However, nothing was added to the work. Responses to my comments, for example: "... In this article, we only temporarily investigated the effect of floating distance on spline clutch wear." or "... Thus, the test data is not organized in this study. " do not increase the value of the article. In this case, you should extend the calculations and perform complete research, and then write an article that explains something
Author Response
We have responded to your questions point by point.
Author Response File: Author Response.pdf
