Contribution to the Characterization of Vibration Isolators Based on Metal Mesh

Round 1

Reviewer 1 Report

1. The keywords are not written.

2. There are no references in Ref. 15 and 24.

3. Line 115 mentions “turns of the wire” and “spirals”, which belong to “tangled” specimen, while “knitted” specimen does not have this structure. The author should modify it and should not confuse the meso structure of two different processes.

4. Section 3.3 the effect of cross-sectional area only gives the test results, but does not explain, the reader can not understand why this phenomenon occurs.

5. Section 3.4 describes the phenomenon of stacking effect, but the reason is not explained. The author should supplement the relevant mechanism explanation in the paper.

6. In the last paragraph of section 3.5, the explanation of this part is not accurate, and it is mainly explained by the meso-structural characteristics of helical turns, which is not consistent with the meso-structure of the studied samples, and does not combine the macro and meso-structural characteristics of the knitted structure.

7. Section 3.6 carries on the parameter modeling, according to the article description, mainly carries on the modeling by the way of polynomial fitting. What is the specific model expression? Is the model universal? Can the model predict the mechanical properties / behavior of metal rubber? The author should make a supplement in the article.

8. The title of section 4 is miswritten.

9. The references cited in this paper are not new enough, and there are no relevant research results in the past three years, so they should be supplemented.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

All the reviewer's comments are addressed in the file attached.

Comments for author File: Comments.pdf

 Extensive editing of the English language is required.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Summary:
The paper deals with vibration isolators made of metal wire and focusses on the experimental examination of quasi-static mechanical characteristics of a certain type of knitted metal cushions. Starting from a literature survey with references to a variety of applications the authors point out that there is only little work found on modelling this type of vibration damping damper. The goal is therefore to gather as much information as possible from experimental investigations of metal cushions to be able to predict their dynamic behaviour and enable engineers to design metal insulators as needed. The main challenge is the nonlinear force-displacement behaviour as well as different linear and nonlinear damping effects which need to be fully understood to be able to set up a model as the authors point out.
The paper is interesting and the topic is challenging. However, even though the authors perform nice experiments which give good insight into the rich mechanical behaviour they miss to give educated explanations for what the observe. Therefore, the paper is more like a description of the results and the explanations of the underlying physical relationships come up short.

Review:
page 1: You mention that dynamic test are necessary. This must be explained in more detail. You thus indicate that you expect a frequency dependence of the damper. Why do you think so? In rubber dampers we do see a change of stiffness and damping with vibration frequency which is typically covered by introducing a complex modulus. In metal mesh dampers based on friction between wires one would not expect a similar viscoelastic behaviour as with rubber material, but this must be confirmed. Another possible secondary effect might be a temperatur effect due to friction damping. Neglecting temperature changes however, the friction hysteresis should be independent of Omega. Later you show relaxation behaviour which is again more like rubber. So, if you say dynamic testing is necessary, you should give some detailed motivational thoughts.

page 1/line 14: it will be necessary also dynamic tests --> also dynamic tests will be required

page 2: you describe the manufacturing process of knitted metallic isolators. Here, a supporting image of the product or even the production steps would be very helpful for a better understanding. From more detailed manufacturing information, one could better estimate the chances of reproducibility and the challenges involved.

page 3/Fig. 1: labels should be in english and the figure resolution and font size are too low.

page 3/Fig. 2: all texts should be in english and the figure resolution and font size are too low.

page 4/line 136: "low strain rates were used to minimize the inertial effects of the mesh" --> with this statement you indicate that inertial effects might come into play when harmonic motion is applied. Can give references or did you experience such effects before? I would expect inertia effects need to be considered when you are close to an eigenmode of the damper which should be in a relatively high frequency range. Can you estimate at which frequency the damper dynamics start to obscure the measurements?  

page 4/Fig. 4: caption is copy pasted from fig. 3 --> please correct

page 5/line 174: and the density of the material (?_h) and. --> the sentence is not correct

page 5/eq.(2): there is something wrong with this equation: putting eq.(1) into eq.(2) would end up in ? = ?_?

page 6: Here, the MDPI header repeats and the page numbering starts over --> please fix

page 7/line 226: "the relationship between the force and the relative density does not have a regular 226
relationship" --> what do you mean with 'regular'?

page 7/line 231: "at least part of the damping is of the viscous type" --> here you talk about viscous damping, but what maybe the explanation for that? Did you take air flow into account? When you compress the metal cushion you squeeze out the air which may have an effect similar to viscoelasticity.

page 7/Fig. 8: resolution is quite low, quality should be improved

page 8/line 248: why would you arrange 8 of these insulators in the depicted way and not just 2 on top of each other? With the positioning of these 4 towers and probably deviating properties of the individual cushions you will only get an averaging of the mechanical behaviour, or is that what you intend?

page 9/Figs. 11 and 12: Please try to adjust the font sizes of each diagram to be at least close. This is unprofessional.

page 10/Fig. 13: the font size is to small

page 10/Fig. 14: again poor figure quality, please improve

page 11/line 319: from the fact that there is an exponential evolution you deduce that energy dissipation can be treated as viscous damping. There is no causal link since one is a conservative force-displacement relation and the other is about energy dissipation. Please revise!

page 11/Fig. 15: font size is too small. Furthermore, the modell seems to consist of a linear spring, a linear damper and a Coulomb element which cannot model the nonlinear exponential behaviour. Please show in the model which component is nonlinear if any.

page 11/Fig. 16: font sizes too small in (b) at least, quality is not good

Quality of English is good. Some minor grammatical mistakes. Please proofread thoroughly.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The paper and especially the figures are much better and the overall impression is improved. Furthermore, I would like to thank you for considering my comments and also for providing more information with additional figures about the manufacturing process.