Establishment and Analysis of Load Spectrum for Bogie Frame of High-Speed Train at 400 km/h Speed Level
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study investigated the actual loads on the bogie frame of the CRAF400 high-speed train through line testing and analyzes the impact of speed on loads. It then established a load spectrum for bogie frames operating at 450 km/h. This research provides useful information for developing load specifications for bogie frames operating at 450 km/h or higher speeds.
Overall, the manuscript presents an important study with potential to advance our understanding of high-speed train dynamics. However, there are some areas that could be strengthened:
- The introduction lacks a summary of gaps in existing research that this study aims to address.
- The font in Figures 6, 12 is inconsistent with other figures.
- The analysis of experimental results on the impact of speed on loads in Sections 3.1-3.2 needs to be more detailed to better support the subsequent research.
- Tables should use a consistent format.
- More discussion is needed on how to evaluate the effectiveness and feasibility of the established discrete load spectrum for bogie frames operating at 450 km/h.
- CONCLUSIONS needs more in it. The authors are suggested to highlight important findings and include afterthoughts of this work.
Author Response
1. The introduction lacks a summary of gaps in existing research that this study aims to address.
Response: We have added some summary in introduction part, such as” At present, the research on the load characteristics of bogie frame focused on the high-speed EMUs with operating speeds below 400 km/h, and there is no research lacking studies on the measured load characteristics of bogie frame for EMUs operating at even higher speeds.”, “At current stage, the method for establishing the load spectrum of the bogie frame at the speed class of 400 km/h and above is not involved in the relevant research.”, and “In the above load spectrum fitting and extrapolating study, there is no extrapolation method with speed as variable. Therefore, the load spectrum of bogie frame with higher speed level cannot be obtained based on the existing study.”.
2. The font in Figures 6, 12 is inconsistent with other figures.
Response: We have adjusted the font of Figure 6.
3. The analysis of experimental results on the impact of speed on loads in Sections 3.1-3.2 needs to be more detailed to better support the subsequent research.
Response: We have combined the Sections 3.1-3.2 as “3.1 Time-domain characteristics of typical loads” to more clearly express the research process and result. At the same time, we highlight the results corresponding to speed, such as “By combining the speed and shaking angle velocity signals on Figure 6, the train is in acceleration condition within 0 - 450 s and the overall amplitude of bouncing load is positively correlated with the speed.”.
4. Tables should use a consistent format.
Response: We have adjusted the layout of all tables.
5. More discussion is needed on how to evaluate the effectiveness and feasibility of the established discrete load spectrum for bogie frames operating at 450 km/h.
Response: As we highlighted in the introduction section, “At the current stage, the loads recommended in the current international standard (EN 13749 [1], UIC 615-4 [2], and JIS E 4207 [3], etc.) are generally adopted for the structural design and reliability assessment of the bogie frame. It is worth noting that the current international standards do not provide a clear definition of the operating speeds of high-speed EMU. With the increasing operation speed of high-speed EMUs, especially when the design and operational speeds exceed 400 km/h or even higher, the applicability of current international standards is uncertain.”. The load spectrum established based on the measured load in this study provides a more realistic load condition for accurately evaluating the fatigue strength of bogie frames at higher speed levels.
6. CONCLUSIONS needs more in it. The authors are suggested to highlight important findings and include afterthoughts of this work.
Response: We have rewritten the conclusions to more clearly express the research process and results.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript presents and discusses a set of experimental data concerning the "Bogie Frame Load Spectrum" at different high viteses. The subject sounds inciting and I hope the manuscript will find more readers. But, at the same time, the conclusion " ..which provides useful information for the future studies...." it appears rather vague, without some clear recommendations.
Moreover, all final data which are either presented as tables or bi-plots that lack of uncertainties, which could raise doubts about the measurement accuracy.
Also, I would suggest a more diversified list of references.
For these reasons I do not recommend the publication of the manuscript in its present form, but after a thorough revision, by evidencing the possible implications for the future 450 km/h trains.
More remarks can be found in the attached annotated manuscript.
Comments for author File: Comments.pdf
Author Response
As we highlighted in the introduction section, “At the current stage, the loads recommended in the current international standard (EN 13749 [1], UIC 615-4 [2], and JIS E 4207 [3], etc.) are generally adopted for the structural design and reliability assessment of the bogie frame. It is worth noting that the current international standards do not provide a clear definition of the operating speeds of high-speed EMU. With the increasing operation speed of high-speed EMUs, especially when the design and operational speeds exceed 400 km/h or even higher, the applicability of current international standards is uncertain.”. The load spectrum established based on the measured load in this study provides a more realistic load condition for accurately evaluating the fatigue strength of bogie frames at higher speed levels.
During the compilation of load spectrum, the inaccuracy shall not be considered.
We have carefully revised the annotations in the article.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript under review delves into the analysis and establishment of the bogie frame load spectrum for high-speed trains at 400 km/h speed level. Reach to a decision in this stage is not possible for me unless to study the revised paper based on the following comments.
1- The authors should clarify the novelty of their paper, particularly in relation to the work conducted by other researchers. How can you ensure that the CRAF400 high-speed trainsets utilized in this study are comparable to other high-speed train models operating at similar speeds?
2- What are the implications of this study's findings for future high-speed train designs and modifications, particularly ones that move at or above 400 km/hour?
3- Can the findings on load characteristics and the stated discrete load spectrum be applied to high-speed train operations outside of China?
4- Can you elaborate on the calibration experiments mentioned? Specifically, how were they created to appropriately mirror real-world conditions?
5- How do the findings of this study help to improve the fatigue performance evaluation of high-speed train bogie frames?
6- The writing of this paper needs to be improved and polished. Some clumsy expressions and grammar issues can be found.
Comments on the Quality of English LanguageThe writing of this paper needs to be improved and polished. Some clumsy expressions and grammar issues can be found.
Author Response
1- The authors should clarify the novelty of their paper, particularly in relation to the work conducted by other researchers. How can you ensure that the CRAF400 high-speed trainsets utilized in this study are comparable to other high-speed train models operating at similar speeds?
Response: We have added some summary in introduction part, such as” At present, the research on the load characteristics of bogie frame focused on the high-speed EMUs with operating speeds below 400 km/h, and there is no research lacking studies on the measured load characteristics of bogie frame for EMUs operating at even higher speeds.”, “At current stage, the method for establishing the load spectrum of the bogie frame at the speed class of 400 km/h and above is not involved in the relevant research.”, and “In the above load spectrum fitting and extrapolating study, there is no extrapolation method with speed as variable. Therefore, the load spectrum of bogie frame with higher speed level cannot be obtained based on the existing study.”.
2- What are the implications of this study's findings for future high-speed train designs and modifications, particularly ones that move at or above 400 km/hour?
Response: The load spectrum established based on the measured load in this study provides a more realistic load condition for accurately evaluating the fatigue strength of bogie frames at higher speed levels.
3- Can the findings on load characteristics and the stated discrete load spectrum be applied to high-speed train operations outside of China?
Response: As shown in Section 3.1, the bogie frame load characteristics are closely related to the operating conditions. Under the same operating condition, the bogie frame shows the same load change rule, but the specific value of load depends on the line conditions. Therefore, the bogie frame load spectrum established in this paper is not suitable for direct application outside China. At present, we are carrying out research on the universality of load spectrum of bogie frame to reduce the relevance of load spectrum to line conditions and vehicle dynamic parameters. Although the current load spectrum results in this paper are not widely applicable, the load spectrum establishment method has a strong scalability.
4- Can you elaborate on the calibration experiments mentioned? Specifically, how were they created to appropriately mirror real-world conditions?
Response: We have rewritten the purpose and brief description of the calibration test and noted the references to the detailed calibration process.
5- How do the findings of this study help to improve the fatigue performance evaluation of high-speed train bogie frames?
Response: As we highlighted in the introduction section, “At the current stage, the loads recommended in the current international standard (EN 13749 [1], UIC 615-4 [2], and JIS E 4207 [3], etc.) are generally adopted for the structural design and reliability assessment of the bogie frame. It is worth noting that the current international standards do not provide a clear definition of the operating speeds of high-speed EMU. With the increasing operation speed of high-speed EMUs, especially when the design and operational speeds exceed 400 km/h or even higher, the applicability of current international standards is uncertain.”. The load spectrum established based on the measured load in this study provides a more realistic load condition for accurately evaluating the fatigue strength of bogie frames at higher speed levels.
6- The writing of this paper needs to be improved and polished. Some clumsy expressions and grammar issues can be found.
Response: We have corrected the expression and syntax problems in the entire paper.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThis article has been substantially improved and no additional content needs to be added.
Reviewer 2 Report
Comments and Suggestions for AuthorsI have no more observations.
At this moment, I consider the manuscript could be published
Reviewer 3 Report
Comments and Suggestions for AuthorsI think this manuscript could be accepted for publication because the authors carefully revised the manuscript based on the comments.
