Modal Identification of Train Passenger Seats Based on Dynamic Tests and Output-Only Techniques
Round 1
Reviewer 1 Report
Modal identification of train passenger seats based on dynamic tests and output-only techniques
Manuscript Number: applsci-2192029
Comments:
1) This manuscript needs careful proofreading to address several writing bugs. For example:
· “The last method allows to clearly distinguish the seat structural movements” An edited form: The last method allows us to clearly distinguish the seat structural movements
· Please fix the following error in line 382: “Error! Reference source not found”
· Please double-check the number of equations. For example, page 6.
· Please remove the red underline from Yn (t) in Figure 2.
· Please adjust the text between lines 152 to 155.
· Please mention Figure 11 in the text.
· Please remove duplicate lines (273 through 278).
2) Please double-check the references section and provide accessibility (DOI or URL) to support some references, such as Ref. [28].
3) The overall quality of several figures should be increased. For example, 7, 8, 11, 19, 21.
4) Please support the following statement with at least some review papers in the field of structural health monitoring: “Vibration measurements have been intensively applied to structural health monitoring applications in civil and transportation engineering.” For example, https://doi.org/10.3390/sym13111998 , https://doi.org/10.3221/IGF-ESIS.62.32 ,
https://doi.org/10.1007/s11831-021-09665-9 , A review of the application of the simulated annealing algorithm in structural health monitoring (1995-2021).
5) Please support the following description with some references regarding the range of MAC value: “MAC parameter is a scalar, varying between 0 and 1, whose unit value indicates that the modes are coincident or linearly dependent.” For example, https://doi.org/10.1016/j.proeng.2012.09.551 , https://doi.org/10.1002/tal.1967
6) Modal characteristics are sensitive to temperature variations. Therefore, please mention the temperature degree.
7) The authors are encouraged to compare natural frequencies obtained by the transmissibility functions and EFDD method using a single table.
8) Please mention the number of experiment repetitions and calculate the mean value and standard deviation for natural frequencies. The authors could compare the variations in natural frequencies when using transmissibility functions and EFDD method.
Author Response
We would like to start by expressing our gratitude to the Reviewers for the relevant remarks addressed in their reports about the manuscript referenced above. These comments and suggestions helped us to improve the manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper describes the experimental study, especially on vibration modal identification, of train seats based on the dynamic tests performed on Alfa Pendular and Intercity trains. First, the output-only modal identification techniques are introduced; one is the transmissibility functions and the other is the Enhanced Frequency Domain Decomposition (EFDD) method. Then, the case studies of Alfa Pendular and Intercity trains are depicted, and the correctness of the natural frequencies and mode shapes were validated by comparing the results of the transmissibility functions and EFDD method. Moreover, the EFDD method can clearly be used to distinguish the seat structural movements, particularly the ones related to torsion and bending of the seat frame, from the local vertical foam vibrations. Finally, the relevance of the identified modal parameters and the characteristics of the vibration transmissibility provided by the foams (local transmissibility) and the vibration transmissibility derived from the metallic seat frame (global transmissibility) are discussed.
Overall, the manuscript is good, in the meantime, it’s well-written and -presented. The study aims to experimentally connect the identified vibration modes with seat comfort, yet the content isn’t very detailed and rigorous in some aspects. Therefore, some revisions are needed before it is accepted for publication in the journal. The followings are the comments or issues existing in this version.
1. In line 146 and line 147, the input and output acceleration should be acceleration spectrum because they are functions of frequency.
2. The indentation should be removed if there is no new sentence in the paragraph, such as line 146, line 181, line 210, and so on.
3. From line 152 to line 155, some words are mixed with Equation (1). Please revise it for a better reading experience.
4. The authors state that the resonances of typical seat transmissibility are comprehended between 4–6 Hz in line 158; however, the resonances seem to locate around 3 Hz in Figure 1.
5. In line 162, the figure number isn’t specified.
6. In line 183, the authors mention that EFDD method works under the assumption of white noise excitations. The authors are encouraged to describe that the dynamic tests are under the same assumption.
7. In line 186, the word ‘decomposition’ can be removed because SVD stands for singular value ‘decomposition.’
8. The abbreviation, EFDD, has been defined in line 127, but the full name still appears in multiple locations, such as line 191 and line 498.
9. The authors mention that the natural frequencies and damping coefficients are derived from the time domain autocorrelation function in line 196 and line 197. It’s better to give a detailed description of the derivation.
10. Similarly, the authors mention that the selection of the SVD points is based on the similarity between their singular vectors calculated through the Model Assurance Criterion (MAC) parameter in line 199 and line 200. It’s better to give a detailed description of the selection.
11. In page 6, Equation (1) should be Equation (3).
12. In line 253, some words seem to be lost before the word ‘Table 1.’
13. In Section 3.1, why the data is first sampled with 2048 Hz and then down-sampled to 100 Hz? The Nyquist frequency of the 2048 Hz sampling rate, 1024 Hz, is far larger than 100 Hz.
14. From line 273 to line 278, this paragraph is reduplicated from line 267 to line 272. Please remove it.
15. It’s unclear where is sensor 2 in Figure 6.
16. In Section 3.2, which two sensors are used for calculating transmissibility curves?
17. In Figure 7, Figure 8, and Figure 11, there are local peaks around 3 Hz. What are the peaks?
18. In Figure 9, there are 6 blue dots but 7 red dots in mode 1. Should they have the same number? And, Figure 9 seems to be identical to Figure 12. Please check.
19. The sentence ‘Error! Reference source not found’ shouldn’t appear in line 382.
20. In line 491, the word ‘Seat back’ should be ‘Seatback.’
Author Response
We would like to start by expressing our gratitude to the Reviewers for the relevant remarks addressed in their reports about the manuscript referenced above. These comments and suggestions helped us to improve the manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The paper is acceptable.
