Investigating the Fracture Process and Tensile Mechanical Behaviours of Brittle Materials under Concentrated and Distributed Boundary Conditions

Round 1

Reviewer 1 Report

The document presents a research about a particular issue on the concrete characterization.

So far, the Brazilian test has represented many weakness points on its set-up and data processing, expecially regarding its reliability.

For this reason, despite of the sufficient importance of this work, this research could represent a pretty good starting point to develop future improvement for this testing field.

 

Author Response

Dear Reviewer,

Thanks for your constructive suggestions.

We will develop future improvement for the Brazilian test method.

English language and styles have been improved by an paid editiing service.

All the best.

Author Response File: Author Response.pdf

Reviewer 2 Report

 

The manuscript entitled “Real-time Investigating the Fracture Process and Tensile Mechanical Behaviours of Brittle Materials under the Concentrated and Distributed Boundary Conditions” by

Haozhe Liang, Xiaozu Fang, Xinlu Yu, Yingqian Fu and Gangyi Zhou deals with the problem experimental analysis of the Braziliant test based on DIC.

 

The strength of the material is estimated using analytical laws that account for the loading conditions of the sample. These analytical laws assume perfectly rigid tools and idealized contact conditions. In order to plot the force vs. displacement curves, DIC is used in order to limit the impact of the stiffness of the machine and tools. In order to obtain valid results, the crack must nucleate at the center of the sample, but the heterogeneous nature of the material combined with the variability of the test leads to dispersion on the force measurements and the crack patterns observed. The main conclusion of the article is that the measured strength depend on the crack nucleation region and that in average the results obtained in Brazilian test with concentrated loading is similar to the average values obtained with a Brazilian test with distributed loading. Furthermore the authors claim that the proposed methodology is somehow new.

 

I think that the article does not present relevant novelties for the field. The use of DIC is now rather common in plenty of mechanical tests and the results of the Brazilian tests studied are also already well documented. The methods used are not described at all. DIC is not plug-and-play the parameters of the analysis windows can have significant impact on the results. The test carried could be analyzed by using finite elements simulations, especially since the material is brittle so it can be considered as elastic up to the onset of fracture. The analysis and post-treatment of the results are poor. The legends of the colormaps cannot be read and the analysis is almost limited to describe the raw data obtained.

 

Oftentimes, the term real-time is used to refer to computations/post-treatments that are carried out live during the experiment; In this case, the term real-time seems to be inappropriate and might be misleading.

There are plenty of writing problems that make it difficult to focus on the content of the article rather than the English errors. There is almost an error per paragraph… Regardless of the decision taken by the editor, I strongly recommend that the article is partially/completely rewritten in order to improve the English language and style.

Author Response

Thanks for your constructive comments. We have provided a point-by-point response to your comments in a word file.  

All the best.

Author Response File: Author Response.pdf

Reviewer 3 Report

The reviewed work deals with the fracture process and the mechanical tensile behavior of brittle materials in disc shape, which is well and clearly written.

However, can a brittle material in rectangular shape also be used for the investigations carried out in this work? If so, how might the results differ from those of the material studied?

The personal pronoun should be avoided throughout the manuscript.

Author Response

Thanks for your constructive commemts.

Using a rectangular shape to determin the tensile strenght of the brittle material is rarely adopted in main international or national standards nowdays.  The failure of this method is generally taken as caused by the stress concentration at  loading points. So, we did not carry out such investigations  in this work.

Additionally, the writting has been improved.

All the best.

Author Response File: Author Response.pdf

Reviewer 4 Report

Dear Authors,
thank you for your paper. My comments are:
- abstract: abbreviations such as BTC, BTD, and ISRM are mentioned for the first time in the abstract - at the first introduction, it is necessary to describe what the abbreviations mean,
- line 17, here is "[5-7]." - erase dot,
- line 28, here is "The compression induces tensile stresses normal to the direction of compressive force" - I think that it is "normal stresses perpendicular to the direction of compressive force",
- line 90, isn't it better to use the notation "tau xy" for shear stresses rather than "sigma xy"?
- general question - which method (BTC, BTD) do the authors recommend using for practice? So which one gives better results?
- is it possible to compare the mentioned methods with other methods? For example, using not cylindrical samples but using cube-shaped samples?

Best regards.

Comments for author File: Comments.pdf

Author Response

Thanks for your constructive commemts.

English language and style has been carefully checked and improved. Please seen the attachment file.

Using a cubic-shaped specimen to determin the tensile strenght of the brittle material is rarely adopted in main international or national standards nowdays.  The failure of this method is generally taken as caused by the stress concentration at  loading points. So, we did not carry out such investigations  in this work.

All the best.

Author Response File: Author Response.pdf