Multidiscipline Design Optimization for Large-Scale Complex Nonlinear Dynamic System Based on Weak Coupling Interfaces

Round 1

Reviewer 1 Report

1. Overall assessment:

The large team of authors deal with a multi-criterial optimization of a railway wheel-set focusing to high speed operation of the bogie and the car. A strongly nonlinear MDOF dynamic model is considered. Numerical simulation as a core of analysis is used. Very large qualitative engineering analysis, results interpretation and operation consequences are presented.

Dynamics of railway systems namely their wheelset and bogies is followed already many decades on deterministic and stochastic platform. Despite of that, still large information gaps are obvious, which are to be fulfilled, provided a super high speed operation should be seriously substantiated from the viewpoint of a basic safety and acceptable wearing of the system car-track. Therefore, in general, the manuscript submitted is suitable to be published in the MDPI APPLIED SCIENCES Journal. 

On the other hand, no adequate relation with rational (analytical) dynamics based considerations are mentioned. Nevertheless, this way is an only way to confirm and validate results of simulations. Such a completion should not be any problem, as strong dynamic basics (ODE systems and their structure) of the system tackled are well documented in hundreds papers and readers are mostly familiar with the dynamics of railway bogies and their interaction with a rail road. Therefore, some complements (at least on a level of citations and brief commentaries) should be included, in order to keep the style of a well structured paper.

 

2. Some remarks:

Specific topics, where relation with earlier analytical results should be discussed on a level of relevant citation or brief commentary:

(a) nonlinear MDOF analysis considering interaction of a railway trac - car,

(b) local (Hopf) and global (Andronov, Neimark) dynamic stability,  limit cycles, critical speeds, internal viscosity and dry friction influence

(c) deformable track (including wave dynamics in layered subsoil),

(d) random non-homogeneity of the track and its neighborhood,

(e) air streaming and aerodynamic effects influencing stability of the car,

(f) interaction of electricity feeding devices (pantograph) with a car and with a catenary system, critical speeds and post-critical effects.

(g) Kalker effect and its influencing dynamic stability and wear of rails and discs.

      …….etc……..

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(h) Figures are well elaborated. However, some of them are in general illegible due very small characters used. Larger size of figures is highly recommended.

(i) English is good and can be understand. Nevertheless, a careful final reading is recommended, as some misprints and missing words have been observed.

 

3. Conclusion

Although there are not principal objections, adequate complements should be required, in order to provide a relevant embedding into a large context of the discipline as a whole. Thereafter the final approval to the acceptance and publication of the manuscript in the MDPI AS Journal can be delivered. Re-review is necessary.  

Author Response

Please refer to the attachment for details

Author Response File: Author Response.docx

Reviewer 2 Report

The paper suggests a new way of designing complex machines used in high-tech manufacturing based on MDO, such as trains that go fast. This new approach involves looking at how the entire machine stays stable and changes over time, making sure the different parts work well together, and checking for damage that could happen during welding. Engineers can create better and more reliable machines for these industries using these three methods.

Overall the manuscript is good. There are, however, a few concerns that must be addressed.

• The abstract needs to be simplified for better understanding.
• The findings part of the abstract needs to be simplified and clarified. "Comprehensive evaluations show that only under rational conditions of wheel-rail matching, i.e. 0.10 ≥ λeN > λemin and λemin= (0.03 – 0.06), can this low cast solution achieve three goals of low track conicity, optimal route planning and investment benefit maximization."
• The introduction quickly starts focusing heavily on mathematical formulations and does not establish an interest in the topic or provide necessary background information.
• The manuscript uses complex and jargon-heavy language, making it difficult for readers to follow.
• In L96, the term "extremely wrong" is not appropriate and should be replaced with a more suitable phrase like "inappropriate" or "impractical."
• The mathematical modeling in the paper may be challenging to follow, and readers may need to spend more time understanding it.
• The paper should explain the meaning of λe and λemin and how they relate to the rational condition of wheel-rail matching.
• The paper should elaborate on the safety evaluations that need to be carried out for the running gear of the next-generation HSRS, particularly regarding the load safety of the bogie frame and associated rubber joints of the rotary arm axle box.
• It needs to be clarified which architecture the manuscript uses to solve the MDO problem.
• It is difficult to understand the global and local variables of the problem. What is their mutual relation? An extended design matrix needs to be included. 
• The paper should discuss whether the study attempted to compare the cost-effectiveness of evolutionary algorithms with gradient-based algorithms to obtain a solution.
• While the conclusion is well-written and summarizes the main findings and contributions of the paper, it could be improved by simplifying the language and providing more context to make it accessible to a broader audience.
• The conclusion could also be strengthened by providing more actionable takeaways for readers, such as the practical implications of the findings for engineers or policymakers and how the research can improve the safety, efficiency, and sustainability of high-speed rail systems.

The figures and plots in the manuscript are attractive and well-explained.

Overall, the manuscript can be enhanced by implementing the suggestions provided.

Author Response

Please refer to the attachment for details

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you for addressing the concerns. One suggestion is to keep the response short, crisp, and to the point in future submissions.