Nonlocal Free Vibrations of Metallic FGM Beams

Round 1

Reviewer 1 Report

The authors presented a study on free vibrations of metallic FGM beams using Eringen's nonlocal elasticity model.

1)However, in the introduction section, the novelty of the study is not given clearly. It is not possible to understand how this study is different from the ones in the literature. Is there a novelty in terms of the modeling approach? It seems that it is an application of the method to metallic FGM beams. 

2) The references given in the manuscript text should be corrected. The authors should check the journal's webpage on the format of the references in the text.

3) Figure 1-4 is not necessary. They are already clear from Equations 1 and 2.  Or they can be given in the appendix.

4) Material property Tables can be combined.

5) Each term in the equations should be clearly defined.

6) Model verification is only performed using linear elasticity theory. The verification should be performed including nonlocal effects. 

7) How is the nonlocal parameter is selected? But what is the real/realistic or logical value that researchers should use?

8) Figure labels should be corrected, they are not clear.

9) The authors performed many case studies, but based on the conclusions, the case studies can be redesigned to highlight all these conclusions. 

10) The writing of the paper is also not clear. The authors should carefully go over the manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments

This paper studied the nonlocal free vibration response of functionally graded beams with different gradient directions. The outcome is interesting for readers. However, there are several aspects that need to be improved. The reviewer can only recommend for publication if the author satisfactorily address the following comments in the revised version.

1. The introduction is very thorough, however, the novelty of the study should be highlighted at the end of introduction section. How this study is different from the published study in literature?
2. The in-text reference format is confusing and not in accordance with the journal requirement.
3. The parameters in equations have not been explained in the text, e.g. eqs.1-4.
4. Why the shear correction factor was set as 5/6? Need a justification.
5. Suggest to provide a schematic showing the x, y, z directions/planes and displacements for section 2.2.
6. What is new in section 2.2?
7. Suggest to provide a schematic diagram or flow chart for solving the equations.
8. Enlarge the front size in Fig. 7.
9. The difference of the developed model and the existing alternative solutions should be discussed more clearly.
10. How the outcome of this study will benefit researchers and end users? This need to be highlighted in introduction or end of conclusion.
11. The background study on the application of FGMs is insufficient. Recently, FGMs were used for industrial applications such as aerospace, automotive, electronic packaging, and so on. [10.1016/j.compstruct.2015.08.113; 10.1016/j.compositesb.2015.07.018]. Suggest to include them in introduction section with proper citations to improve the background study.

I would be happy to see the revised version to understand how these comments are being addressed.

Author Response

File included

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Based on the corrections and modifications done by authors, the paper is in acceptable form.