Study of the Dynamics and Strength of the Detachable Module for Long Cargoes under Asymmetric Loading Diagrams

Round 1

Reviewer 1 Report

After review of the suggested manuscript, I can say that the research subject is very relevant. Overall, the research is interesting, and it is worth to present it.

However, there are several issues with this study that should be improved.

1. The authors indicated that tetrahedrons were used for creation of the finite element model. However, they did not explain why this particular element type was used.

2. What is the essence of the graphical analytical method that the authors used to create the finite element model?

3. It is necessary to explain how this module will be installed on the vehicle.

4. Were welding seams taken into account when performing strength calculations? This also needs to be indicated.

5. It is necessary to explain why, when calculating the strength, the permissible stresses were taken equal to 310.5 MPa?

Author Response

Dear Reviewer, we thank you for your recommendations and comments, which certainly improved our work. All corrections are highlighted in green in the text of the article. Regarding these comments, we would like to note the following:

1. The authors indicated that tetrahedrons were used for creation of the finite element model. However, they did not explain why this particular element type was used.

This element type was chosen due to the fact that the mesh was formed on a solid body.

2. What is the essence of the graphical analytical method that the authors used to create the finite element model?

The optimal number of grid elements is determined by the graphoanalytical method. The method is based on graphical (geometric) representation of admissible solutions and the objective function of the problem. The essence of the method for solving this problem is to construct the dependence of the maximum equivalent stresses on the number of finite elements. When this dependence begins to be described by a horizontal line, this is the optimum number of finite elements.

3. It is necessary to explain how this module will be installed on the vehicle.

Fitting stops are provided in the corner parts of the detachable module for mounting it on vehicles.

4. Were welding seams taken into account when performing strength calculations? This also needs to be indicated.

When conducting calculations, welding seams between individual components of the removable module were not taken into account, i.e. the design was considered as monolitic.

5. It is necessary to explain why, when calculating the strength, the permissible stresses were taken equal to 310.5 MPa?

These stresses are accepted as permissible, since at mode I, the permissible stresses in accordance with the regulatory document [25] are taken as equal to 0.9σy, where σy is the yield strength of the material. For steel grade 09G2S, it is 345 MPa.

We have added additional information to the text of the article. We ask you to look at the manuscript again.

Best regards,

Authors' team

Author Response File: Author Response.pdf

Reviewer 2 Report

I really like the article, but I have a few questions:

How is the loading of long items planned?

How was the computational mesh optimized?

In line 202 says: “It is taken into account that a longitudinal force of 3.5 MN acts on the rear stop of the flat car.” What is the nature of this force - constant or impulsive?

Line 362 says: “Traffic safety is assessed by the first oscillation frequency which, in accordance with [23] should be at least 8 Hz.” – you are referring to the Ukrainian standard, but how does it compare to EU standards?

The article lacks the results of the modal analysis regarding the damping values for individual modes.

It would be worth emphasizing the scientific aspect of the described content.

Author Response

Dear Reviewer, we thank you for your recommendations and comments, which certainly improved our work. All corrections are highlighted in green in the text of the article. Regarding these comments, we would like to note the following:

1. How is the loading of long items planned?

Loading of the removable module with long cargo will be carried out from above with the help of handling and transport equipment, i.e. according to the existing technology of loading transport units of this type.

2. How was the computational mesh optimized?

The optimal number of grid elements is determined by the graphoanalytical method. The method is based on graphical (geometric) representation of admissible solutions and the objective function of the problem. The essence of the method for solving this problem is to construct the dependence of the maximum equivalent stresses on the number of finite elements. When this dependence begins to be described by a horizontal line, this is the optimum number of finite elements.

3. In line 202 says: “It is taken into account that a longitudinal force of 3.5 MN acts on the rear stop of the flat car.” What is the nature of this force - constant or impulsive?

This force acts as an impulse.

4. Line 362 says: “Traffic safety is assessed by the first oscillation frequency which, in accordance with [23] should be at least 8 Hz.” – you are referring to the Ukrainian standard, but how does it compare to EU standards?

It is important to note that the analogue of the regulatory document [25] is the European standard [42]. However, it regulates the specifics of the loading of wagons of the 1435 mm gauge and it has certain differences from the standard [25]. In connection with the fact that the calculation was carried out on the example of the transport of the removable module by a platform car with a gauge of 1520 mm, at this stage of the study, the authors limited themselves to the requirements specified in the standard [25]. In the subsequent stages of the research, the requirements regulated by the standard [42] will be taken into account. 

5. The article lacks the results of the modal analysis regarding the damping values for individual modes.

The purpose of the modal analysis was to determine the natural frequencies and forms of oscillations of the removable module. Therefore, the authors did not determine the damping for individual modes in this study. However, thanks for the valid remark. We will certainly pay attention to this in the following works.

6. It would be worth emphasizing the scientific aspect of the described content.

The scientific value of this study is the proposed procedure for creating a removable module for transporting long loads, which includes the selection of profiles for its implementation according to the moment of resistance of the structural components, determination of dynamic load, strength and natural frequencies and forms of oscilla-tions. At the same time, it should be emphasized that the determination of the dynamic load of the removable module was carried out according to the mathematical model formed by the authors of the study and verified in their previous works.

Patent applications have been submitted for the proposed design of the removable module.

Thank you for your comments.

Please review the manuscript again.

Best regards,

The author's team

Author Response File: Author Response.pdf