Experimental Study on In Situ Storage of Grease-Lubricated Ball Screws

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have examined the performance of an aged grease with a new one. The aged grease generally performed worse than the new grease. While quantification of the disparity between the two greases is interesting, it is not unexpected. My biggest issue with the paper is that the results are not presented with error bars, and thus it is difficult to be able to understand if the degradation of the grease is real or just a statistical aberration. In each figure presented (viscosity, temperature shear, friction, wear, efficiency, torque), please revise with error bars on the figures. Also, were repeat measurements taken for each of the grease samples to show the variability in the measurements. Finally, the outcome of this paper suggests that greases that are kept for long periods of time should not be used. This outcome seems obvious, but perhaps the authors may wish to explicitly write this statement and estimate the storage time/shelf life for greases based on their experiments, and possibly provide some information on how to improve the stability of the grease to increase it's shelf life.

Comments on the Quality of English Language

The quality of the writing was sufficient.

Author Response

Comments 1: " it is difficult to be able to understand if the degradation of the grease is real or just a statistical aberration "

Response 1: Thank you for pointing this out. All tests have been measured multiple times, and the results of the same test are relatively consistent. Therefore, one group of test results was taken as the final result for comparison. We have added an explanation in the "Test results and analysis" section of the re-submitted files.

Comments 2: " explicitly write this statement, " greases that are kept for long periods of time should not be used ", and estimate the storage time/shelf life for greases based on their experiments "

Response 2: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the third point of Chapter 4 of the re-submitted files.

Comments 3: " provide some information on how to improve the stability of the grease to increase it's shelf life "

Response 3: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the fourth point of Chapter 4 of the re-submitted files.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

 

The experimental study on in-situ storage of grease-lubricated ball screws provides valuable insights into the performance changes of lubricating grease over time and its impact on the transmission performance of ball screws. However, in the opinion of this reviewer there are some weaknesses in the work that could be addressed for further improvement:

·       While the storage conditions are described, additional details about the specific temperature and humidity variations during the eight-year storage period could offer a more nuanced analysis of the impact of environmental factors.

·       The article mentions significant changes in the appearance of the lubricating grease after storage but doesn't provide a detailed explanation or microscopic analysis of these changes. Further investigation into the microscopic morphology would enhance the understanding of appearance alterations.

·        The FTIR results show changes in characteristic peaks, indicating chemical changes in the lubricating grease. A more in-depth analysis and discussion of these changes and their implications would add clarity to the chemical degradation process.

·        The study must be more specific in the conditions of the experiments.

·        Friction tests of 70 seconds are very short. It is suggested to increase the time to be able to analyze the behavior after stability.

·        The SRV testing results indicate a need for improved anti-fretting wear performance. The article could provide more detailed insights into how this deficiency could impact real-world applications and potential solutions to address it.

·        While the study compares the performance of stored grease with fresh grease, a comparison with other common lubricating greases or industry benchmarks would help contextualize the findings and highlight areas for improvement.

·        The article mentions the guiding significance of the storage simulation test but provides limited details on the specific parameters for accelerated storage testing. Elaborating on the design considerations for such tests would be beneficial.

·        The study discusses physical and chemical degradation separately. Integrating the discussion on how these degradation modes might interact or contribute to overall lubricating grease failure would provide a more holistic view.

·        The article could provide more explicit practical implications of the findings for engineers and practitioners in terms of selecting, storing, and maintaining lubricating greases in real-world applications.

Addressing these deficiencies would contribute to the overall depth and applicability of the study, ensuring that the insights gained have broader relevance and are more readily applicable to real-world scenarios.

 

Comments on the Quality of English Language

 Minor editing of English language required

Author Response

Comments 1: " additional details about the specific temperature and humidity variations during the eight-year storage period could offer a more nuanced analysis of the impact of environmental factors "

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the first point of Chapter 4 of the re-submitted files.

Comments 2: " The article mentions significant changes in the appearance of the lubricating grease after storage but doesn't provide a detailed explanation or microscopic analysis of these changes "

Response 2: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the the " (1) Appearance " section of the re-submitted files.

Comments 3: " Further investigation into the microscopic morphology would enhance the understanding of appearance alterations "

Response 3: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the the " (2) SEM Testing " section of the re-submitted files.

Comments 4: " A more in-depth analysis and discussion of these changes, " chemical changes in the lubricating grease ", and their implications would add clarity to the chemical degradation process. "

Response 4: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was revised and highlighted in the the " (3) FTIR Testing " section of the re-submitted files.

Comments 5: " The study must be more specific in the conditions of the experiments "

Response 5: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the the " 2.3. Performance testing of ball screw transmission " section of the re-submitted files.

Comments 6: " Friction tests of 70 seconds are very short. It is suggested to increase the time to be able to analyze the behavior after stability. "

Response 6: Thank you for pointing this out. Due to the poor lubrication performance of 7014 lubricating grease after storage, it can only be maintained for 70 seconds. After 70 seconds, the test results exceeded the testing range of SRV, so the experimental results were only retained for 70 seconds. We have added an explanation in the " (6) SRV Testing " section of the re-submitted files.

Comments 7: " The SRV testing results indicate a need for improved anti-fretting wear performance. The article could provide more detailed insights into how this deficiency could impact real-world applications and potential solutions to address it. "

Response 7: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the the " (6) SRV Testing " section of the re-submitted files.

Comments 8: " While the study compares the performance of stored grease with fresh grease, a comparison with other common lubricating greases or industry benchmarks would help contextualize the findings and highlight areas for improvement. "

Response 8: Thank you for pointing this out. At present, there is no relevant data available about other common lubricating greases or industry benchmarks. In our subsequent research, we have arranged for the in-situ storage of the other two types of lubricating greases, and comparative data can be obtained in the later stage.

Comments 9: " The article mentions the guiding significance of the storage simulation test but provides limited details on the specific parameters for accelerated storage testing. Elaborating on the design considerations for such tests would be beneficial. "

Response 9: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the fifth point of Chapter 4 of the re-submitted files.

Comments 10: " Integrating the discussion on how these degradation modes might interact or contribute to overall lubricating grease failure would provide a more holistic view. "

Response 10: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the first point of Chapter 4 of the re-submitted files.

Comments 11: " The article could provide more explicit practical implications of the findings for engineers and practitioners in terms of selecting, storing, and maintaining lubricating greases in real-world applications. "

Response 11: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the third point of Chapter 4 of the re-submitted files.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

   The paper deals with the problem of lubricating grease. The problem is of great importance in the field of aeronautics. The authors consider a batch of ball screw which is lying flat in a warehouse for a long period of time (approximately eight years). The lubrication grace is extracted from the raceways. Some properties are compared to those corresponding to the fresh grease (oxidation and friction performances and rheological properties). They also analysed the effect of grease degradation on the transmission performance of the ball screw. The tests are clear and the results are correct and pertinent and to the point. The paper leaves room for future research (for instance, ball screw lubrication schemas). Generally speaking, the paper is good.

     The aged grease leads to worse performance. There is no study concerning the errors of the results, and the viability and variability of the results. Generally speaking, the conclusion of the paper is that the aged grease is worse than a new one (this conclusion looks to be redundant). The authors must offer some additional information (e.g. the period of time in which the grease may be used, some ways in which the stability of grease may be increased etc.). The authors must highlight if Figs. 1, 2 and 3 are original or not. As they appear in the paper, they look as they were taken from elsewhere. In addition, which program(s) is(are) used and how (some explanations) for the diagrams?

Author Response

Comments 1: " The authors must offer some additional information (e.g. the period of time in which the grease may be used, some ways in which the stability of grease may be increased etc.). "

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, relevant information was added and highlighted in the third point of Chapter 4 of the re-submitted files.

Comments 2: " The authors must highlight if Figs. 1, 2 and 3 are original or not. "

Response 2: Thank you for pointing this out. Figs. 1, 2, and 3 are all sourced from our research team. Figure 3 is the original image. Figs. 1 and 2 have been appropriately annotated for the convenience of readers. The figures mentioned have been updated in the re-submitted files.

Comments 3: " which program(s) is(are) used and how (some explanations) for the diagrams? "

Response 3: Thank you for pointing this out. The diagrams were obtained through the data acquisition and processing platforms integrated with multiple programs that are compatible with the testing instruments’ interface.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have answered the questions and attended to the recommendations so the manuscript has been improved. However, there is only one more issue before acceptance of the work.

Revise carefully the captions of Figures, the majority are incorrect. For example, the caption of Figure 5 says " Infrared spectrogram of Grease 7014" but the figure corresponds to SEM micrographs.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

Comments: " Revise carefully the captions of Figures, the majority are incorrect. For example, the caption of Figure 5 says " Infrared spectrogram of Grease 7014" but the figure corresponds to SEM micrographs. "

Response: Thank you for pointing this out. We agree with this comment. The titles of Figure 4 and Figure 5 were modified in the resubmitted file.