Controlled Creation of Contact Cracks in Additive Manufactured Components

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work presents a method to create a controllable contact crack in additive manufactured components using a combination of tensile load and resonance excitation. The crack dimensions are tracked by monitoring the resonance frequencies. The topic under investigation is interesting and may potentially facilitate the development of NDT techniques through the use of cracked samples. The paper is generally well written and structured. I can recommend this work to be published subjecting to addressing the following issues:

 

1.     It is not clear how the resonance drift metric and nonlinear metric 2 are defined in Fig. 11.  11. The authors mentioned in the manuscript that details of the nonlinear metric 2 are in a potential patent. If the details can not be presented in the paper, I suggest simply removing the relevant discussions. Otherwise, there is no way to judge the results. Having said this, the is a clear correlation between the exposure level and the resonance drift metric, which confirms the feasibility of the method to create a controllable crack. By the same token, the definition of resonance drift metric should be provided.

2.     Different symbols might be used for different specimens in the figures instead of different colors.

3.     The method shows its ability to create a controllable crack in the present structure. How can it be applied to large and complex structures in practice like plates or cylindrical shells? Please comment.

4.     Please provide more details about Figure 3. How is that obtained? What does each line mean in the diagram?

 

5.     Please correct the references which are not properly shown. (Lines 282, 289 and 360)

Comments on the Quality of English Language

The English language is fine. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please provide more details about the AM process of the specimens. Their  final microstructure is highly dependent on the adopted manufacturing parameters (laser speed, layer thickness, hatch distance, etc)

The specimen in Figure 4 is not totally vertical.

There is a concern about the way specimens are attached to the “bobs’ via bolts as some damage may be concentrated there.

Please provide more references regarding the use of ‘bobs’. Is this method standardized? If not, may the measurements be generally usable?

Please provide more details about the FEM model. What is the utilized density for each component? What kind of support conditions were utilized? Note that the existence of a true crack contact phenomenon (under friction between crack faces) under cycling loading is very important, but not discussed at all (see for example 10.1016/j.jsv.2014.09.037).

Correct ref. in line 289.

The conclusions are not very helpful. I strongly believe that the authors should provide a figure characterizing the damage evolution versus the frequency (or other loading parameters).

Has the adopted AM technique led to enough readability of the experimental outcome?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is now appropriate for publication.