Effect of Ultrasonic Surface Rolling on the Fretting Wear Property of 7075 Aluminum Alloy
Round 1
Reviewer 1 Report
The work is very interesting; it is worth correcting certain substantive shortcomings:
1. Figure 3: In Figure 3b, the surface roughness profile was incorrectly determined; according to the surface roughness standard, the profile should be determined perpendicular to the machining marks, not along them. Due to the strong amplification of the Z-signal on the three-dimensional surface, it is difficult to assess whether the same error was made in Figure 3a. This is a significant methodological error.
2. In the scientific paper, the authors use the Ra parameter to assess surface roughness. However, if the Ra parameter was determined from the profiles marked in Figure 3, it is an incorrect value. If the authors insist on analyzing surface roughness using the Ra parameter, the profile should be determined perpendicular to the machining marks. The authors have data on 3D surface roughness, and for a more comprehensive analysis, it may be more appropriate to calculate parameters such as Sa, which refer to the entire surface, rather than Ra, which describes only one profile. The surface contains 1024 such profiles, hence the use of the Sa parameter appears to be more reasonable.
3. From such a conducted experiment, it is valuable to draw more than three conclusions.
Good translation.
Author Response
Reviewer #1: The work is very interesting; it is worth correcting certain substantive shortcomings.
- Figure 3: In Figure 3b, the surface roughness profile was incorrectly determined; according to the surface roughness standard, the profile should be determined perpendicular to the machining marks, not along them. Due to the strong amplification of the Z-signal on the three-dimensional surface, it is difficult to assess whether the same error was made in Figure 3a. This is a significant methodological error.
Response: Thank you for your careful work. In the revised manuscript, we have redrawn the surface roughness profile so that it is perpendicular to the machining traces.
- In the scientific paper, the authors use the Ra parameter to assess surface roughness. However, if the Ra parameter was determined from the profiles marked in Figure 3, it is an incorrect value. If the authors insist on analyzing surface roughness using the Ra parameter, the profile should be determined perpendicular to the machining marks. The authors have data on 3D surface roughness, and for a more comprehensive analysis, it may be more appropriate to calculate parameters such as Sa, which refer to the entire surface, rather than Ra, which describes only one profile. The surface contains 1024 such profiles, hence the use of the Sa parameter appears to be more reasonable.
Response: This suggestion is very meaningful, and we have revised it in the manuscript to use Sa to represent roughness.
- From such a conducted experiment, it is valuable to draw more than three conclusions.
Response: Thank you for your advice. In the revised manuscript, we have modified and improved the conclusion part.
Reviewer 2 Report
1. Page 6, line 3 from the top. When you write that running period is very short, please, provide the exact value.
2. Page 8, line 4 from the top. You wrote “positively correlated”. If you calculated the correlation coefficient value, please, provide the value.
Author Response
Reviewer #2:
- Page 6, line 3 from the top. When you write that running period is very short, please, provide the exact value.
Response: Thank you for your advice. In the revised manuscript, we have provided the exact running period value.
- Page 8, line 4 from the top. You wrote “positively correlated”. If you calculated the correlation coefficient value, please, provide the value.
Response: Thank you for your careful work. In fact, our main objective is to convey that the degree of wear increases as the displacement amplitude increases. We did not calculate the correlation coefficient value. We have revised the description in the revised manuscript to reflect this clarification.
Reviewer 3 Report
1. References 25 and 26 are missing from the text
2. Should be explained the novelity of the manuscript
3. The conclusion section is too short, should be enriched
4. The resolution of fig. 33 should be increased
5. The types and manufacturers of the testing equipements should bedescribed (are missing especially from the micro Vickers hardness testing machine).
Author Response
Reviewer #3:
- References 25 and 26 are missing from the text
Response: we are sorry for our negligence. we have updated the citation in the revised manuscript.
- Should be explained the novelty of the manuscript
Response: Thank you for your careful work. The existing research on the tribological properties of USR surfaces primarily concentrates on sliding wear, with limited studies investigating fretting wear properties. Furthermore, there is a lack of research considering the influence of lubrication conditions on these properties. This paper explores the effect of USR on the fretting wear mechanism of 7075 aluminum alloy under altered lubrication conditions, and such a comparative study is of significance.
- The conclusion section is too short, should be enriched
Response: In the revised manuscript, we have enriched the conclusion part.
- The resolution of fig. 33 should be increased
Response: In the revised manuscript, Fig. 3 has been redrawn with a higher resolution.
- The types and manufacturers of the testing equipment should be described (are missing especially from the micro Vickers hardness testing machine).
Response: In the revised manuscript, we have supplemented the types and manufacturer of the testing equipment.
Reviewer 4 Report
The overall paper is good, well written and well constructed until the conclusions.
The oil that is used, must be described, because 'oil' can have many different effects on the surfaces. Especially boundary lubrication and oxidative properties will play a role in a fretting mechanism.
It is concluded that the USR method increases the hardness from 170-183 HV.
1. With what HV method is this measured (weight ?).
2. What was the variation on measurements, in other words, is +13 HV significant ?
3. In the discussion and conclusion, this hardness increase is used as an explanation for different wear morphology and behavior. This is speculative, it seems a very small hardness increase to result in such different behavior. The grain size refinement can also play an important role in the differences of wear damage but are not considered in the discussion.
Conclusion number 3 is highly debatable. There can be other reasons why the USR surfaces wear more in dry testing and less in lubricated testing, than only the hardness of the surface. There can be different mechanisms, interactions with the lubricant, e.g. the FeS formation might be encouraged by the USR, whereas in dry testing there is no FeS and only the FeO and AlOxides are in play.
And in a fretting or reciprocating experiment, also the fatigue properties of the surface will play a major role. It is suggested to run similar experiments over a longer distance (gross slip, maybe 1 or 2 mm), or to consider similar experiments in an unidirectional motion (pin on disk ?) to confirm these trends ! Perhaps the subject of another paper ?
It is suggested to use the same scales in graphs and table, when comparing same conditions. E.G. figure 7 wear tracks in dry fretting : same scale !
The titles UT and USR in Table 2 are not well aligned with the columns
Author Response
Reviewer #4: The overall paper is good, well written and well constructed until the conclusions.
The oil that is used, must be described, because 'oil' can have many different effects on the surfaces. Especially boundary lubrication and oxidative properties will play a role in a fretting mechanism.
Response: The oil used in this study was gear oil, ISO VG 46. we have added the type in part 2.3.
It is concluded that the USR method increases the hardness from 170-183 HV.
- With what HV method is this measured (weight?).
Response: The surface microhardness before and after USR treatment was measured by micro-Vickers hardness tester (HV-1000A) under the load of 500g and dwell time of 10 s. These values are derived from the average of five separate measurements. We have incorporated testing methods into the revision manuscript.
- What was the variation on measurements, in other words, is +13 HV significant?
Response: Thank you for your careful work. 13HV does not change much, but under oil lubrication, small hardness changes will also affect its wear degree.
- In the discussion and conclusion, this hardness increase is used as an explanation for different wear morphology and behavior. This is speculative, it seems a very small hardness increase to result in such different behavior. The grain size refinement can also play an important role in the differences of wear damage but are not considered in the discussion.
Response: Thank you for your advice. Under oil lubricated conditions, the improvement in wear performance should be attributed to the synergistic effects of increased surface hardness and grain refinement. Under dry fretting, there may be little improvement in wear resistance due to the grain refinement layer being too thin, but instead harder abrasive grains are produced, which exacerbate wear. We will argue this in later experiments.
Conclusion number 3 is highly debatable. There can be other reasons why the USR surfaces wear more in dry testing and less in lubricated testing, than only the hardness of the surface. There can be different mechanisms, interactions with the lubricant, e.g. the FeS formation might be encouraged by the USR, whereas in dry testing there is no FeS and only the FeO and AlOxides are in play.
Response: Thank you very much for your comments. We have added an analysis of grain refinement and lubricant synergism to the results and discussion and modified the conclusions.
And in a fretting or reciprocating experiment, also the fatigue properties of the surface will play a major role. It is suggested to run similar experiments over a longer distance (gross slip, maybe 1 or 2 mm), or to consider similar experiments in an unidirectional motion (pin on disk ?) to confirm these trends ! Perhaps the subject of another paper?
Response: Thank you for your suggestion, this is a very important idea for us, and we will verify this idea in the later scientific research work.
It is suggested to use the same scales in graphs and table, when comparing same conditions. E.G. figure 7 wear tracks in dry fretting : same scale!
Response: In the revised manuscript, we adjusted the oil lubrication and dry fretting 2D profile scales to make our data more intuitive.
The titles UT and USR in Table 2 are not well aligned with the columns
Response: We have made correction according to the comments.
