Comparison of Lightweight Structures in Bearing Impact Loads during Ice–Hull Interaction

Round 1

Reviewer 1 Report

The paper as presented is well written and quite extensive in scope. 

The authors present an analysis of various types of structural panels that could be consider suitable for use in a ship to withstand ice impact. The study is based on FEA simulations for the different material types, using a rigid indenter and a model ice. There are a wide range of material types considered. 

In this reviewer's opinion, the challenges with the paper are that there is very little in the way of experimental validation (only the aluminum panel) and the FEA analysis does not discuss validation of the methods, mesh convergence or benchmarking to justify the selection of the material properties. Can we be assured that the material properties defined in the Ansys input are suitable for high speed impact loads from a deformable material? The authors should address why this information is missing, and what steps they plan to take to mitigate the lack of information. 

The potential interest in this paper is in the use of light weight materials and their resistance to ice impact loads, and the analysis shown is a good start, but it not fully convincing compared to the level of detail used in classical FEA analysis of steel ship structures impacting with ice. 

Author Response

Dear Reviewer,

We thank you for taking the time to review our paper thoroughly.

A. We acknowledge your concerns with respect to the lack of experimental validation. We agree this as a weakness of the study. To overcome this, we have taken the following measures.

1. 1. We limited our scope to low-velocity impact. In this speed range, we assume the strain-rate effects are negligible. Under this assumption, the material data provided by ANSYS Explicit material library is justified.
   2. We investigated relative structural performance instead of absolute structural performance. By doing so, the dependence on accurate solutions can be reduced. Relative structural performance allowed us to identify
      1. Parametric trends
      2. Significant parameters
      3. Comparison between structural concepts w.r.t. weight.

We really appreciate that you brought this point forward. It would be valuable to readers to be aware of this. We have now added these points clearly in the discussion section.

B. Mesh quality is an important aspect that we considered in the analysis. For this, we did the following.

1. 1. Have a minimum elemental quality of 0.25. Aspect ratios under 10 and Jacobian ratios under 3.
   2. A mesh convergence study with element edge lengths starting from 5 mm to 0.5 mm.

With regards to material models for different structural concepts, we referred to published literature. We have included these details in section 3.4.

The work done in this paper provides suitable parametric ranges for different structural concepts. This narrows the scope for experimental studies in the future. As an example of this approach, the best configuration for an aluminium grillage was investigated using an experimental validated ice impact model.

The study provides an informative start towards future experimental studies and new concept development. An upcoming paper is planned with respect to the development of an experimentally validated ice impact model for sandwich structures.

We thank you for reviewing our paper. We have added the points mentioned here in the manuscript. We would be happy to address any more concerns that you might have.

We wish you a pleasant day.

Kind Regards,

Harsha Cheemakurthy, Zuheir Barsoum, Magnus Burman, Karl Garme

Reviewer 2 Report

An interesting study on ice impact loads on various proposed lightweight structures is presented.

One concern is that the aluminum plate drop test validation presented in this manuscript is not enough to justify the ice impact simulations for those composite structures. I suggest the authors explicitly mention that in the paper. Also, the following few comments for authors' consideration:

1. Line 292, why the SSF is a more critical factor? It will be good to add a line to clarify.

2. It appears awkward to have a section named 'Discussion and Conclusion' and another following section named 'Conclusions'. I guess section 6 can be absorbed under section 5 with the section heading 'Results and Discussion'.

3. I found it a bit difficult to follow the writing of the manuscript smoothly in one go. I suggest revising the overall language and style of the paper to improve its readability.

Author Response

Dear Reviewer,

We thank you for taking the time to review our paper thoroughly. Please note our responses to your feedback in the following paragraphs in blue.

One concern is that the aluminum plate drop test validation presented in this manuscript is not enough to justify the ice impact simulations for those composite structures. I suggest the authors explicitly mention that in the paper. Also, the following few comments for authors' consideration:

Thank you for bringing this point to light. We agree with your comment. We have now clearly mentioned this point in section 5.4 and the discussion section.

1. Line 292, why the SSF is a more critical factor? It will be good to add a line to clarify.

Thank you for the suggestion. We have added a clarification now.

From the figure 7 and figure 8, the stress safety factor (SSF) lie within the range of 1-5 while the deformation safety factor (DSF) lies in the range of 1-25. This makes strength more critical in comparison to stiffness.

2. It appears awkward to have a section named 'Discussion and Conclusion' and another following section named 'Conclusions'. I guess section 6 can be absorbed under section 5 with the section heading 'Results and Discussion'.

Thank you for the suggestion. We have now changed the section 5 header to ‘Discussion’.

3. I found it a bit difficult to follow the writing of the manuscript smoothly in one go. I suggest revising the overall language and style of the paper to improve its readability.

Thank you for the feedback. We have read through the paper again and made changes in language in the introduction, results and discussion sections. We hope the readability has improved.

We thank you for reviewing our paper. We have added the points mentioned here in the manuscript, The important changes are marked in red in the updated manuscript.  We would be happy to address any more concerns that you might have.

We wish you a pleasant day.

Kind Regards,

Harsha Cheemakurthy, Zuheir Barsoum, Magnus Burman, Karl Garme

Round 2

Reviewer 1 Report

The authors have addressed the reviewers concerns.