Mechanical Deformation Analysis of a Flexible Finger in Terms of an Improved ANCF Plate Element
Round 1
Reviewer 1 Report
The paper focuses on the deformation of a flexible silicone finger. Different calculations and models are proposed and a comparison of the results with experimental data is given at the end of the paper. Before publication, some points need to be explained, clarified or corrected in the article.
It is difficult to understand what is really new in paragraph 2, the element is not new, the results come from previous studies, so the text can be shortened with good bibliographic references.
The remarks are similar for the hyperelastic part, what is presented is classical and could be shortened by citing the right bibliographic references. Moreover, the way of presenting is difficult to follow from a purely incompressible version to a quasi-incompressible version with penalty. The authors should present directly the invariants used and present Yeoh's constitutive equation only once, in the form that is used in the article.
Please replace "Cauchygreen" by "Cauchy-Green", the deformation tensor was created by two researchers.
“A reasonable value of k is usually selected to ensure the incompressibility of volume and set to 1000MPa” I do not agree with this sentence, it is not the value that ensures incompressibility but the ratio between the coefficient k and the equivalent elastic modulus of the material. This ratio should be large enough to ensure the quasi-incompressibility.
The identification of the parameters of the Yeoh model poses a problem mu30 cannot be negative to ensure the polyconvexity conditions of the constitutive equation! All simulations presented with this negative coefficient cannot be considered. The parameters must be re-identified and the simulations redone.
The first study is done with an elastic material having a Poisson's ratio of 0.3 while the second study with Yeoh is done in incompressible framework, it is difficult to follow what are the real assumptions of the authors about the materials of the study.
It seems that the numerical simulations are done with a time component since the results are presented at different times. How is time considered in the calculations? Shouldn't the viscous component of the material be considered?
The real aim of the article and in particular the purpose of the comparisons of the simulations should be clarified throughout the article to give the reader a better idea of what is going on.
Author Response
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Reviewer 2 Report
This manuscript treats a topic of interest and it proposes a more viable material model than the currently used model. However, the presentation of the results, establishing the story behind the topic can be improved and can be given in a leaner way. It would be better to re-consider the manuscript after implementing recommended changes.
1- After the literature review given in the introduction, the missing point of the literature /scientific gap can be underlined more in detail. The paragraph at the beginning of the 3rd page mentions about this subject. However, it can be re-constructed to transfer the scientific gap more evidently.
2- Cauchy- Green deformation tensor (above Eq.9)
3- Poisson’s ratio in Table 1 looks quite low for a hyperelastic material.
4- Silicone robber >> silicone rubber (under Section 5)
5- It is hard to follow the data on simulation. All data used to establish the model can be given in a table to facilitate the transfer of the information. The results should be scrutinized.
6- Conclusion is quite limited. It can be improved.
Author Response
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Reviewer 3 Report
Paper considers the mechanical behavior of silicone rubber flexible finger. It can be re-considered after some revision, namely:
1) Introduction, the first paragraph. The current state of formation and application of silicone rubber flexible fingers should be given in detail, including analysis of the literature data.
2) Section 5.2. The point is that ref [10] contains no experimental data given in the section. The source of the experimental data given in Figs. 9 and 10 should be given also in figure captions.
3) Section 6. The given data should be also compared with experiment.
4) References 1, 10, 12-16. Journal title is missed.
Author Response
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Reviewer 4 Report
Please find attached my comments to the manuscripts!
Comments for author File: Comments.pdf
Author Response
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Round 2
Reviewer 1 Report
I thank the authors for their work to improve the paper and for taking my comments into account. Nevertheless, I will remain obstinate on one of my comments C30 cannot be negative, even if the numbers come from an already published paper, it just means that an error is present in the already published paper. I invite you to look at the papers talking about the necessity of polyconvexity of hyperelastic laws. It is important to correct this point.
Author Response
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Reviewer 3 Report
Paper was revised and now it can be accepted in current state
Author Response
Thank you for the suggestion to accept our paper and the paper has been carefully proofread.
Reviewer 4 Report
The manuscript is revised according my comments and, therefore, I like to accept it in the present form.
Author Response
Thank you for the suggestion to accept our paper and the paper has been carefully proofread.
Round 3
Reviewer 1 Report
Various papers have been published on the criteria that the parameters of hyperelastic laws must satisfy, it is fairly well known that C10>0 and C30>0, the only parameter that can be negative is C20 (but to some extent). The polyconvexity of the laws was originally explained by Ball 1979 - Convexity Conditions and Existence Theorems in Nonlinear Elasticity and his demonstrations were later applied to the different laws in different papers.
I am sorry, but I cannot validate a paper with a negative C30 parameter.
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