Application of Damage Detection of Metal Structure Lamb Wave Modal Superposition Imaging Based on Scanning Laser Vibration Measurement

Round 1

Reviewer 1 Report

The article "Application of Damage Detection of Steel Structure Lamb Wave Modal Superposition Imaging Based on Scanning Laser
Vibration Measurement" by Wang et al. is a well-written methodology paper.
The introduction summarizes previous studies quite concisely.
However, I suggest some minor improvements regarding experimental and computational details that the authors should consider before this article is accepted for publication:

1) Lines 145 and subsequent: "For the purpose of excitation, a distinctive five-peak waveform signal, characterized by its center frequency of 250 kHz, is as-
tutely selected."
Please give a more detailed description of the exciting signal, it could be a graphical representation.

Experimental part:
2) What is the thickness of the metal plate? For now, only 800 x 800 mm are given as dimensions.

3) Regarding the excitation signal, please confirm that you are using the same "five-peak waveform signal, characterized by its center frequency of 250 kHz" as mentioned in line 145 previously for the simulation, or otherwise specify the real signal.

4) Indicate the approximate power of the amplified excitation signal applied across the PZT.

5) Experimental results:
The authors start section 3.3 (= experimental results) with the following sentences:
"The experiment was conducted using an aluminum plate with dimensions of 700mm ×700 mm×1 mm. The center position of the plate was considered as the origin of coordinates (0mm, 0mm), and PZT were attached to the plate. Two flat bottom holes were intentionally created at the coordinates (90mm, 90mm) and (100mm, 50mm) respectively."

This information should be removed from the results and instead appear in the experimental part only.
Please note that the dimensions given here 700x700 mm are different from what was previously given in the experimental part.
(See my comment 2).
Please revise carefully all dimensions.

Author Response

Thank you for your letter and for the reviewer’ comments concerning our manuscript entitled “Application of Damage Detection of Steel Structure Lamb Wave Modal Superposition Imaging Based on Scanning Laser Vibration Measurement”. Those comments are all valuable and very helpful to revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in the paper. The main corrections in the paper and response to the reviewer’s comments are as following:

To reviewer 1:

1. Figure 2 adds the signal waveform.
2. Page 7, line 225: the thickness of the metal plate is 1 mm.
3. Page 7, line 225: The excitation signal is a five-peak wave signal with a center frequency of 250kHz.
4. Page 7, line 223: The excitation signal is generated by a signal generator with an amplitude of 5V, a five-peak wave signal with a center frequency of 250kHz, which is amplified by a power amplifier 20 times and then output by a PZT.
5. Different boards were used to test the validity of the method.

Reviewer 2 Report

This paper addresses the detection of damage in a simple isotropic material structure using the 3-dimensional superposition imaging process excited by different Lamb waves (A0, S0). We validated this approach through an analysis of a finite element model and experimental results. While this topic may be of interest to readers, there are several issues that have been raised:

[1] The highlighted method is based on previous studies [21-23], and it is important to clarify in the introduction how our work builds upon and advances the findings of these references.

[2] We claim the originality of our study lies in the sensitivity analysis of different modal responses of an isotropic structure to local deformations. However, there appears to be limited sensitivity analysis conducted during the validation steps.

[3] You mentioned that using two different modal data (A0, S0) leads to more visible damage detection results compared to single modal cases. It's essential to explain why this is the case and provide a clear physical explanation for the enhanced damage detection with the superposition of multiple modal data. Furthermore, if more than two modal response data were used, would it still increase the detection sensitivity?

I am negative on this version. 

Minor editing of English language required. 

Author Response

Thank you for your letter and for the reviewer’ comments concerning our manuscript entitled “Application of Damage Detection of Steel Structure Lamb Wave Modal Superposition Imaging Based on Scanning Laser Vibration Measurement”. Those comments are all valuable and very helpful to revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in the paper. The main corrections in the paper and response to the reviewer’s comments are as following:

To reviewer 2:

1. To verify that the method can be used on different materials this practicality ah conducted the following experiments.
2. Sensitivity analysis is valid to a certain extent.
3. The A₀ and S₀ modes have different sensitivities to different forms of damage such as cracks and through holes, and the damage location will be made more accurate by superposition of the two modes, and the superposition of more than two modes will be analyzed in the subsequent study.

Reviewer 3 Report

The paper shows an approach for damage detection in steel plates using Lamb wave propagation. Finite element models are developed and experimental tests are conducted. The topic is interesting and the presence of numerical and experimental studies makes the methodology robust. However, some clarifications and changes are necessary.

Major issues

Section 1

- “In this paper, the analysis primarily focuses on the S0 and A0 modes as they are typically the predominant modes observed in ultrasonic Lamb waves at low frequencies”. Explain what S0 and A0 are.

Section 1.2

- Provide more information about the window used to disentangle the signal.

Section 2.1

- “The coordinates of this flaw are precisely located at (60 mm, 40 mm), ensuring accuracy in subsequent analyses. The significance of this positioning lies in its representation of real-world scenarios where structural anomalies tend to emerge at specific vulnerable points”. Please provide further explanation.

- Improve the description of the created FE model (material properties, mesh…). Include an image of the FE model showing the loading and boundary conditions and other applied properties.

Section 2.2

- Provide additional comments on Figure 4e. There are two relative maximum points.

References

- The most recent references are one from 2021 and two from 2022. Add more recent references.

General comment

- How would the damage location influence the results?

Minor issues

- It is not common to use the personal form in the scientific papers ( “position of my country’s steel production).

- Check Figure 4b. Why is the maximum value greater than 1?

Author Response

Thank you for your letter and for the reviewer’ comments concerning our manuscript entitled “Application of Damage Detection of Steel Structure Lamb Wave Modal Superposition Imaging Based on Scanning Laser Vibration Measurement”. Those comments are all valuable and very helpful to revising and improving our paper, as well as the important guiding significance to our research. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked in the paper. The main corrections in the paper and response to the reviewer’s comments are as following:

To reviewer 3:

1. Page 2, line 90: in this paper, the analysis primarily focuses on the symmetric modal S0 and antisymmetrical mode A0 mode as they are typically the predominant modes observed in ultrasonic Lamb waves at low frequencies.
2. Page 2, line 93: the window width of the 3D window function is chosen to be 200(1/m), and the window is added to the 3D Fourier transformed signal matrix to realize the separation of the single S₀ and A₀ modes。
3. Page 4, line 138: the coordinates of this flaw are precisely located at (60 mm, 40 mm).
4. Page 4, line 149: considering the efficiency of the computer and the correctness of the results, the meshing size is set to 0.2 mm in this paper.
5. Page 5, line 200: the top left is the real damage, and the bottom right is the artifacts produced by the scattering of the wave near the damage.
6. Damage close to the scanning area is more easily detected; if it is near the edge of the plate, the reflected wave from the damage mixes with the reflected wave from the edge of the plate, resulting in increased error.

Round 2

Reviewer 2 Report

No conflict issues were found in the revised version. 

Minor English editing maybe required before publishing it.