Structural and Vibro-Acoustics Optimization of a Car Body Rear Part

Round 1

Reviewer 1 Report (New Reviewer)

Although the manuscript was interesting to read, it is presented more as an internal report than a research article. In particular, the study seems to be confined to a single model car, with very little discussion on the applicability of the method to other models and situations. If this work is to be published, it needs to be completely reframed. My suggestion to the authors is to rewrite several sections to answer the following questions: How can this work be applied to other vehicles? Is there any particular innovation that will result in a change to vehicle design going forward? Certain car models have evolved substantially in the past decade. Is this work still valid for modern vehicles? How can others duplicate this work on an arbitrary car model? What is the main innovation with this work? Raising the frequency of the first torsional mode by 2 Hz in a single car model isn't innovative enough. The innovation needs to be generalized.

There are other concerning issues with the manuscript. The English needs substantial work as certain sections are difficult to read. The introduction needs to state up front (and be explicit) what the benefits are to increasing the frequency of the first torsional mode. The manuscript dances around this point for far too long. The number of self-citations versus outside citations is inappropriate. Most of the graphs in this manuscript are very low quality and have a myriad of issues, including missing labels, inconsistent style, usage of internal data labels, cutoff labels, units missing, etc. These problems exist in nearly every graph, so I suggest a complete pass over all of the graphs to make sure that the above issues are rectified. The resolution of several other figures is too low. The text on figure 18 is far too small. Other issues, such as inadequate explanation of methods also exists (such as how the nodes are selected in figure 7).

 

There are some good research results here, but the manuscript needs to be refined before publication. Focusing on the innovation and how it can be applied to other problems instead of reporting on results will greatly improve the manuscript and move it towards publication.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

The paper deals with an important task. It has great practical value and logical structure. The paper is technically sound. The proposed approach is logical. The results are clear.

Positive sides:

1.     The article is well organized and the material is presented sequentially with a logical conclusion.

2.     A modal and sensitivity analysis of the studied models was carried out.

3.     Topological optimization was carried out, the obtained results were analyzed and appropriate conclusions were drawn.

4.     The work contains a significant amount of illustrative material.

Suggestions:

1.     Introduction section should be extended using more clearly the motivation of this paper.

2.     It would be good to add the remainder of this paper.

3.     The authors indicated what types of finite element decomposition will be used in the work. However, it would be advisable to specify the characteristics of the finite element mesh for a specific experiment.

4.     It is necessary to formulate optimization criteria and parameters on which they depend more clearly.

5.     The constructed models used isotropic or anisotropic materials. Justify this choice.

 

6.     Conclusion section should be extended using prospects for future research.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 3 Report (New Reviewer)

 ---Please refer to the attachment---

Comments for author File: Comments.docx

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report (New Reviewer)

The manuscript has been greatly improved and the overall objective of the research is now clear. This is a great example of collaborative research between academia and industry that can result in tangible outcomes for end users. I appreciate the author's efforts in addressing the concerns of the previous review round. Just a couple small changes remain before publication:

Figure 8a - Change Nodo to Node and add a label to the y-axis.

Figure 36 - Add tick mark labels to both axes. Fix the blank space in the top right quadrant of the graph.

Author Response

done both requests. 

Reviewer 3 Report (New Reviewer)

--NA--

Author Response

no requests

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

Answers

2. A vehicle with high torsion rigidity will give the driver and passenger a more “solid” feel when the car is running, especially when the road is bumpy and has lots of potholes on it. The cabin will have less rattling and popping noises because the car body has less twist and flex when there are forces transmitted from the suspension. When considering the torsional modes clearly the 1^st is the most important because more easily excited and with higher amplitude.
3. Further references have been added from literature which better explain the vibroacoustic issue.
4. Some figure captions where enriched and some more explanations were provided.
5. More details on fe model cannot be added because of a non-disclosure agreeement imposed by stellantis. The modal analysis is carried out following nastran manual.
6. The only purpose of the modal analysis is to identify the first torsional mode of biw and tb model so there is no need to provide much details on other modes. With reference to the torsional modes some more explanations are provided.
7. Figure 7, 8 and the sensitivity analysis were better explained.
8. Screws are added to glue in those areas with a need for a stiffer connection. Further information cannot be added because of a non disclosure agreeement imposed by stellantis.
9. Some comments were added
10. Such information cannot be added because of a non disclosure agreeement imposed by stellantis. The provided results specify the percentage variation with respect to the original model and are sufficient to prove the significant benefits obtained with the implemented procedure.
11. A flow chart has been added. The exposed work relies completely on numerical analyses (no experiments).
12. The forced analysis helps in identifing the first torsional mode for the tb model, because, as written in the text “the presence of the fittings makes more complicate the identification of the first torsional mode’’. As a matter of fact, the presence of local modes at frequencies close to the global torsional frequency, e.g. Those involving the seats, may hide the global mode.
13. The outcome of this section is the new topological design, whose related improvements are detailed in the section no 5. Anyway some more comments are added to section 4.3.
14. The section 5 has been broaden with more details and figure explanations
15. The choice was done based on past company experience. The stiffness values cannot be provided due to the non disclosure agreement.
16. The vibro-acoustic transfer function are evaluated numerically as explained in section 6. A unitary force is applied at some points (engine and suspension mounts) in x, y, z direction; then the ratio between the cabin sound pressure at mic2 and mic5 and the applied external unitary force is calculated.

    17. In section 6 and 7 some comments on the obtained results were added

Reviewer 2 Report

This paper presents the results of the optimization of the car body from an NVH perspective. The authors have optimized the vibro-acoustic characteristics of the BIW and the trimmed body model.

Although the author described in detail the noise reduction process of the car body, it is not easy to find any novelty or insights academically or in engineering.

The reviewer believes that the method and series of processes described by the author are general development processes in the automotive industry. 

From the reviewer's point of view, this article is considered suitable for a development report rather than an academic article.

Therefore, the reviewer presents the opinion that it is difficult to approve this paper for publication as a journal article.

 

Author Response

Answers:

1. To the author’s knowledge, the proposed optimization of the car rear part, involving at the same time material and geometry changes, has been carried out for the first time. There are some similar work in the literature but none of them took advantage of 3d printing possibilities in combination with change of adopted material for the component under analysis.
2. The novelty comes from an optimization approach leveraging on 3d printing for a replacement of a costly material (steel) with a more economic one (alluminum), with a more sustainable manufacturing process, based on a significant reduction of welding points as enabled by the versatility of 3d printing.

Reviewer 3 Report

The paper deals with the topological optimization of vibro-acoustics characteristics of a car body. It is maybe useful for the design of an actual car. However, the present form of this manuscript is just an incomplete engineering report, major revisions must done by the authors. Then I will reconsider it.

 

Comments:

1. Number of references is too small and more references should be added in Introduction, especially high-quality journal papers. Authors should report the state-of-art in this research field.

2. More information about the FEM model should be given, such an the gird size, type of the mesh element, total number of girds, connection form between components.

3. Figure 3 is too small. I can see the frequency of the first-order mode.

4. Figure 5. The figure is too small, and there are no numbers in the horizontal and vertical coordinates.

5. Figure 6. There is no rainbow cloud scale, and the place with the largest vibration displacement can not be seen from this view angle.

6. Figure 8 a) should be redrawn to better read

7. Sections 4. The flow chart and theory of topology optimization should be given.

8. Figure 18. The figure is too small, and there are no numbers in the horizontal and vertical coordinates.

9. Figure 21 and 22. There are no numbers in the horizontal and vertical coordinates.

10. Figure 27. There are no numbers in the horizontal and vertical coordinates.

11. Figure 29. There is no rainbow cloud scale.

 

12. Figure 30, 31, 34 and 35. The figure is too small, and there are no numbers in the horizontal and vertical coordinates.

Author Response

Answers:

1. Further pertinent articles were added to the introduction
2. It is not possible to provide these type of information due to the non-dislosure agreement with stellantis spa.
3. The figure was enlarged
4. It is not possible to provide these type of information due to the non-dislosure agreement with stellantis spa. The figure was enlarged
5. The rainbow cloud scale was added but without magnitude values due to the non-disclosure agreeement with stellantis spa. Anyway the maximum vibration magnitude is not of interest, what is important is to identify the torsional mode.
6. It was redrawn and explained.
7. A flow chart of optimization process was added.
8. It is not possible to provide these type of information due to the non-dislosure agreement with stellantis spa. The figure was enlarged
9. It is not possible to provide these type of information due to the non-dislosure agreement with stellantis spa.
10. It is not possible to provide these type of information due to the non- dislosure agreement with stellantis spa.
11. The rainbow cloud scale was added but without magnitude values due to the non-disclosure agreeement with stellantis spa. Anyway the maximum vibration magnitude is not of interest, what is important is to identify the torsional mode.
12. It is not possible to provide these type of information due to the non dislosure agreement with stellantis spa. The figures were enlarged.

Round 2

Reviewer 2 Report

Thanks to the author for submitting a revised version. However, with all due respect, there is insufficient evidence to support the author's reply. Moreover, since the revised manuscript still hides or omits much information about the details and results, the reviewer thinks it is difficult to provide practical and valuable information or knowledge to the readers. For example, the values of the graph axes are all unmarked. The reviewer also guessed that the value of the graph was deleted for security reasons. The reviewer can fully understand that. However, it is considered that the author should present at least one piece of information, such as the spacing of each grid. Consequently, it is difficult to recommend the publication as a research article in Applied Sciences.

Reviewer 3 Report

In the revised paper, all research results do not give numbers in the horizontal and vertical coordinates, such as Figure 3,5, 6, 18, 19, 22, 23, 28, 30, 31, 32, 35, 36, 37. For a scientific paper, this is incomplete and unacceptable.