Double Optimization Design of the Formula Racing Car Frame Based on the Variable Density Method and the Joint Variable Method
Round 1
Reviewer 1 Report
This is an interesting paper with respectable structural analysis and optimization procedure. My comment is that list of references could be completed, for example concerning variable density method. From my point of view following book should be cited. I mean chapter 4 in the book describes the method, applied in the paper at automotive (formula student) structure as an object.
Introduction to Structural Optimization and Its Potential for Development of Vehicle Safety Structures
Jesper Christensen, Christophe Bastien, in Nonlinear Optimization of Vehicle Safety Structures, 2016
Another observation from my side is concerning free modal analysis of the frame. In the chapter 1.5 is shown that the lowest first order frequency obtained is about 36Hz, while the general road excitation is around 20Hz. Here is concluded that this result avoiding the natural frequency of the frame and preventing resonance?!
My question is do those natural frequency analysis is valid for the starting or for the optimized frame (with lower mass)? Authors could add this explanation in chapter of modal analysis or may be at the end in the conclusions, aimed to comment these frequencies, watching from the optimized solution point of view (if it changes natural frequencies)?!
So, please, could you do these minor corrections, means to add comments aimed to make higher quality of the paper, that is anyway almost ready for the publishing!
Authors present clearly terms explaining their ideas and research results. From my point of view expressed language is adequate and very clear for the Journal readership, just may be check a pair of sentences.
Author Response
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Reviewer 2 Report
This work deals with the topology optimisation of car frame in the context of Formula Student Racing Car. The proposed approach relies on a density-based topology optimisation algorithm available in the OptiStruct Module by Altair HyperWorks.
The topic could be of interest for the audience of Applied Sciences (APPSCI). Unfortunately, this work is characterised by a significant number of weaknesses, which make it not suitable for publication in the current form. Rejection is then recommended according to the comments listed here below.
1) The form. English should be improved throughout the manuscript. The form is often too colloquial. The style is often too verbose. Several typographical errors can be found in each section of the paper. Moreover, the English should be revised by an expert, native speaking. In the current form the manuscript is unreadable.
-The punctuation must be revised throughout the paper, especially for equations.
-The notation is not rigorous at all. Italic font should be used only for unknown scalar quantities. Vector and matrices should be indicated by means of lowercase and uppercase bold symbols and/or letters, respectively (not italic). Constant scalar parameters must be indicated without using italic font.
- A list of Acronyms should be provided for the sake of clarity, according to APPSCI format.
- Please, avoid the use of acronyms in the title of the paper as well in the title of sections and subsections.
- Please, add the paper outline at the end of Introduction by concisely describe the content of each section (one/two sentences per section).
- There are numerous typos in the manuscript. A careful proofreading is needed to weed out typos.
2) Introduction, page 2: "Among them... materials". All the sentences related to the homogenisation method used for topology optimisation are incorrect and must be revised. The authors are invited to revise the fundamentals at the basis of the homogenisation method for topology optimisation.
3) Introduction, page 2: "... isotropic penalty microstructure model (SIMP) method...". This reviewer believes that the authors need to revise the fundamentals of topology optimisation. The acronym SIMP stands for "solid isotropic material with penalisation" and is a penalisation scheme used in density-based topology optimisation algorithms (not a method). Moreover, the description provided for density-based topology optimisation methods (and the related state of the art) is really superficial and needs to be improved. Please, revise the introduction accordingly.
4) Introduction, pages 2-3: "Design sensitivity.... more design variables". The description provided for the different techniques used to calculate the gradient of the structural responses is misleading and not adequate for a scientific paper. Authors are invited to revise the fundamentals of sensitivity analysis, especially for automatic differentiation, finite differences and the adjoint method since most of the fundamental concepts at the basis of these techniques have not been correctly described in the introduction. Please, revise this section accordingly.
5) Introduction. The literature survey on topology optimisation algorithms is outdated because modern CAD-compatible density-based topology optimisation methods, like the one based on non-uniform rational basis spline entities (see [R1] for example), or other CAD-compatible approaches, such as geometric projection, moving morphable voids and moving morphable components are completely missing. Authors should agree that such modern methods represent the state of the art of topology optimisation algorithms since the optimised topologies resulting from these methods can be directly integrated into CAD software, without the need of a time-consuming post-processing phase to recover the boundary of the optimised topology. Authors are invited to cite and add some comments on the main works related to these methods within the introduction (this task is not mandatory but essential to provide a complete literature survey).
[R1] https://doi.org/10.1007/s10957-019-01622-8
6) Section 1. The authors are invited to revise the fundamentals of the finite element method and density-based algorithms for topology optimisation. In particular, it is quite surprising to read a paper on topology optimisation in which the authors use a density-based topology optimisation algorithm based on the SIMP scheme and to find no information about the penalisation scheme when writing the relationship between generalised displacements and generalised forces of the element (equation 3). The authors should agree that the stiffness matrix of the element should be penalised according to the SIMP formula. Why is this relationship omitted here?
7) Section 2, Eqs. (11)-(14). In the reviewer's opinion the authors need to revise the fundamentals at the basis of the adjoint method. The strategy to obtain the gradient of the generalised displacement at a given node according to the adjoint method requires different logical steps and passages as described in [R1] (or in other similar works available in the literature).
Moreover, it is rather strange to see a paper whose title is "Double optimisation design of FSAC frame based on variable density method and joint variable method" and then to discover that the authors use a commercial software (OptiStruct by Altair HyperWorks) where they have no access to the calculation of the gradient of the structural responses (and especially to the coding of the adjoint variables).
In summary, this work seems to be more of an exercise carried out by an undergraduate student than a research paper. The manuscript lacks originality (no new formulations and/or algorithms and/or methods are proposed) and scientific rigour. In this paper, the authors only apply known concepts implemented in commercial software to a relatively simple problem that has already been addressed in the literature. For all of the above reasons, I recommend rejection. This paper is not suitable for publication in an international journal.
Please, see my review report for more details.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
Comments for author File: Comments.docx
Author Response
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Reviewer 4 Report
The paper presents a study regarding the optimization of Formula SAE car frame based on global topology optimization. The paper fits the journal's scope.
The introduction section needs major improvements. The novelty and main objective of the current paper are not clear. The authors need to clearly mention the main contribution of the current paper. The state-of-the-art description should be improved with more references. The majority of the cited studies should be papers recently published by high-relevance journals, in order to clearly show that the current approach is novel as compared to the most relevant studies in the field.
The authors need to discuss in detail the main achievements and limitations of the mentioned studies, in order to establish the literature gap that should be fulfilled by the current study. The authors need to provide a clear comparison between the current paper and the mentioned studies, to show the main novelty of the presented method as compared to the cited studies.
Another good method to highlight the main contribution of the current paper as compared to the literature state of the art is including a table at the end of the introduction which summarizes the main difference between the proposed study as compared to similar published papers.
Please uniformize the citation style applied in the manuscript
Please include the missing space between numbers and their respective units. Check the whole manuscript regarding such typos. Except for the % symbol, which does not require a space before the numbers. Check the whole manuscript regarding these typos.
Please do not use the * symbol to indicate multiplication in the equations and the main text.
“7.8510 g/cm3” in section “1.2.2 Establishment process”. Please correct the unit superscript.
Figure 1 is too small and presents poor resolution. Please note that the embedded figure text font size should be similar to the main text font size.
Please do not split numbers and their respective units between lines.
Figures 13 and 14 can be improved regarding resolution.
Please do not split tables between pages (e.g. Table 2)
Data presented in Figures 21 and 22 can be presented in the main text or a table. There is no need to show in on printed images of the software.
The paper has shown some interesting results. However, the conclusion section needs major improvements. The conclusion should summarize the main achievement of the developed study but also mentions the simplifications applied in the models and their limitations.
The paper present typos, but regarding grammar is it fine in my opinion.
Author Response
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Round 2
Reviewer 2 Report
Although the authors have attempted to enhance the paper quality, the document remains unoriginal. Furthermore, the authors appear to concur with this statement as expressed in their response to my preceding comment (regarding the absence of original contents): "Thank you for your opinion, I also agree with you. However, the application of sensitivity analysis to the racing frame still has certain novelty. In addition, the variable density method is used to optimize the global topology of the frame, which is more accurate than the previous local topology optimization. I will try to find new ways".
This paper simply applies a commercial software to a straightforward problem. As there is no element of originality, I advise against publishing it.
Although the English language has been improved from the original version, there are still a few mistakes. This reviewer kindly requests that the authors thoroughly check the manuscript for any typographical errors.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
No Comments Added
Author Response
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Reviewer 4 Report
The authors have made significant improvements to the paper, and all of my questions have been thoroughly addressed. I am pleased to see that my suggestions have been incorporated into the current version, and after conducting a detailed review, I did not identify any major issues that need to be addressed.
Author Response
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Round 3
Reviewer 2 Report
Considering the authors' response and their viewpoint, I believe that this paper can be considered for publication only as a technical paper, not as a research paper.
Authors are invited to check English grammar because there are still some typos in the revised version of the paper.
Author Response
Thank you for your comments. I have modified the English and improved the readability of the article.
