Using an Internal State Variable Model Framework to Investigate the Influence of Microstructure and Mechanical Properties on Ballistic Performance of Steel Alloys

Round 1

Reviewer 1 Report

In this study, an Internal State Variable (ISV) based constitutive model has been used within a Lagrangian Finite Element Analysis (FEA) framework to simulate ballistic impact of monolithic Rolled Homogenous Armor (RHA) steel plates by RHA steel spheres and cylinders. The ISV model predictions demonstrate good agreement with experimental impact data for spherical projectiles. A simulation-based parametric sensitivity study was performed to determine the influence of a variety of microstructural and mechanical properties on ballistic performance. It is a topic of interest to the researchers in the related areas but the paper needs improvement before acceptance for publication. My detailed comments are as follows:

1)      The summary should provide specific data to be convincing.

2)      The conclusion should be brief. Please modify.

3)      The writing of the introduction part cannot let the reader grasp the main research background and research content of the article effectively.

4)      The full-text font needs to be unified. Please check.

5)      The clarity of the pictures in the article needs to be improved.

6)      There are some grammatical and writing errors in the article. Please check the full text and make corrections.

7)      Please refer to other paper in this journal to modify the format of the References.

8)      It is suggested to increase the theoretical analysis of the experimental results to improve the scientific nature of the article.

 

Therefore, I recommend major revision.

None

Author Response

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Reviewer 2 Report

In my opinion, the article can be published in its present form. The authors presented extensive research with both modeling and experimental validation. The level of presentation is high and all results were supported by scientific discussion. Obtained effects of materials properties on target ballistic performance is well-described and supported by conclusions. After reading the publication I would like to clarify one question. You have studied the influence of mostly static mechanical properties on ballistic performance, which is a dynamic property of the material. Why don’t you take into account such simple and recognized dynamic parameter as impact toughness? From your vision how it will influence the ballistic performance of the material?

Author Response

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Reviewer 3 Report

The simulation of the impact process is of great interest to specialists in the fields of military and space technology. Due to the constant development of weapons, the impact behavior of steel alloys has been extensively studied experimentally, analytically and numerically. However, this problem has not been completely solved so far. The article obtained results that are valuable for science and practice, but there are several questions:

1. In Equ. (9), d is the secondary phase particle size, f is secondary phase particle volume fraction, KIC is the fracture toughness...

d is most likely the equivalent diameter that can be used for rounded particles. With elongated particles and inclusions, which are typical for rolled sheets, this parameter is difficult to use.

Look, for example, the shape of the ductile dimples formed near the particles, their shape factor has a very large dispersion of parameter values: https://www.mdpi.com/1996-1944/12/3/491

KIC is the fracture toughness, but for quasi-static loading. The strain rate under quasi-static loading and under dynamic impact are incomparable. How informative will this parameter be?

2. For this study, average particle diameter (d) and average number density (η0) are treated as independent design variables and average particle area fraction (f) is calculated as the product of particle number density and cross-section area. But for what area? After all, it is known that the scale factor is very important: https://www.mdpi.com/1996-1944/12/13/2051. How did you justify the scale at which these parameters were determined?

 

3. In fig. 6 simulation was carried out at the macro level. How can these results be correlated with the micro-level data that have been studied earlier?

4. Known levels of research macro-, meso-, micro-. At the same time, it is important to find a relationship between the parameters of different levels and systematize the study. I propose to do this in the article.

Author Response

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Round 2

Reviewer 3 Report

Accept.