Theoretical Study of the Wear of a Reduced-Diameter Wheel for Freight Wagons, Based on Its Diameter

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The comments will be presented in the order in which the article is read:

- Two important elements are missing from the pavement factors on page 2, namely stiffness and damping in the track - this is important in determining the vertical forces in the process of vehicle movement along the track.

- It is stated in the assumptions ((assumption s) - page 5) that the vehicle travels in a curved motion.  In this motion there are three accelerations and non-holonomic ties, which are not mentioned by the authors. I refer you to the mechanics.

- Assuming u) - page 5 - infrastructure parameters - there are also different magnitudes of stiffness and different nature of damping in the track. Viscous damping is most often assumed despite the fact that dry friction damping is actually present. 

- On page 6, in paragraph from 232, a number of elements that affect the movement of the vehicle on the track are listed and track parameters are missing.

- On page 8, in paragraph 2.4.2, the authors cite a number of papers that do not consider the three accelerations arising in curved motion. In addition, they do not consider non-holonomic bonds in curved motion. In the following section, the three parameters found on the railway line are considered, and no mention is made of the element that provides the largest values of the normal forces occurring between wheel and rail, namely the turnout. In addition, movement along a switch track in a turnout is quite different mechanics to movement along a curve.

- On page 9, formula 1 uses designations that are missing from Figure 5.

- On pages 13-14 there are considerations for loads which are treated only in static terms. This is a far-reaching simplification, as dynamic forces are generated in the movement along the track under various conditions, which in some cases can be up to twice the static load. This can be disregarded, but it should be mentioned.

- On page 17 a consideration of Kalker's theory is carried out. This is questionable news to say the least, because there are two areas in the contact ellipse determined from Kalker's theory: slip and adhesion. Furthermore, Kalker's theory takes into account the values present in the track (inequalities) which affects the size and shape of the contact ellipse.

- In section 2.4.8 - application of partial loads only - it is necessary to define these quantities in relation to the vertical forces, which is not taken into account by the Sauvage model.

- When practical measurements are taken into account, the vertical forces fluctuate widely by up to twice the static loads. In reality, the normal forces are variable as a function of time and distance, which would be fair to say that such quantities are neglected.

- Section 2.4.9 - not all methods from computational practice have been considered. I recommend referring to the wear results obtained from the work of Kalker, J.J.; Chudzikiewicz, A. Calculation of the evolution of the form of a railway wheel profile through wear. In International Series of Numerical Mathematics; Birkhauser Verlag: Basel, Switzerland, 1991; Volume 101, Available online: https://link.springer.com/chapter/10.1007/978-3-0348-7303-1_7. Calculations based on this method can be found in J. Kisilowski, R. Kowalik, 2021. ‘Mechanical Wear Contact between the Wheel and Rail on a Turnout with Variable Stiffness,’ Energies 2021, 14(22), 7520; https://doi.org/10.3390/en14227520. These calculations are for a wheel with a fixed radius. Wheels with different radii can be introduced in this method.

- On page 21 in section 2.5, knowing the structure of the Kalker program, I am sure that this program can be added to the proposed algorithm, or at least state that no such aspect is taken into account.

- On page 22 the Y-25 bogie has damping in the form of an active friction damper which very much influences the magnitude of the vertical forces generated when the rail vehicle moves along the track.

- On page 24 a fixed value for the track width is assumed, which is not true. You can see in international standards how the track gauge varies.

- In the citation of the paper (Pellicer and Larrode,2021) there is an obvious error, because an important element of the railway infrastructure is the turnout, where the vertical forces in the wheel-rail contact within the crossover increase by more than twice the static load. Furthermore, these considerations do not take into account that the movement of the vehicle along the circular curve and the switch track is loaded by non-holonomic bonds.

- The actual magnitudes in the track obtained by measurement can be found in J. Kisilowski, R. Kowalik, Method for Determining the Susceptibility of the Track, Appl. Sci. 2022, 12(24), 12534; https://doi.org/10.3390/app122412534.

- The conclusions presented are questionable due to the fact that the paper does not indicate that a number of important elements influencing vertical forces, and thus normal forces and wear processes, have been omitted. The authors should clearly define, correctly according to mechanics, what kind of research is presented in the article.

Author Response

Thank you for your review report. Please find our response to each and every point in the attached document. 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In this paper, the authors propose the development of a numerical analysis model which enables the calculation of the life of a reduced-diameter wheel used for freight wagons as a function of its operating factors. Manuscript subject is interesting for the railway industry and falls within the journal topic.

However, the following issues should be addressed:

1.      Abstract should provide concretely the main results.

2.      Punctuation used by the authors is useless: after two points an enumeration follows, not another phrase.  

3.      Authors cite their work as ‘(Pellicer & Larrodé, 2021)’, but this is missing in the References.

4.      List of hypotheses is exaggerated.

5.      Many hypotheses are based on ‘(Pellicer & Larrodé, 2021)’, but this is missing as above.

6.      Hypothesis r is questionable because the freight bogies are not usually equipped with brake disc and because of that the area of interest of the manuscript is limited.

7   7 .  There are many similarities between the present manuscript and preceding works of the authors.  Few examples: (a)  Figures 1, 2, 3, 4, 6(b) from the present manuscript are like the Figure 1, 2, 3, 4, and 5 from Pellicer, D., Larrodé, E., Sensitivity Analysis of Bogie Wheelbase and Axle Load for Low-Floor Freight Wagons, Based on Wheel Wear, Machines 12, 2024, 515; (b) Figure 15 with Figure 8; (c) Figure 16 with Figure 4 from Pellicer, D., Larrodé, E., Analysis of the Rolling Phenomenin if a Reduced-Diameter Wheel for Freight Wagons, as a Function of Operating Factors. Authors should clearly explain what is new in this manuscript in comparison to the preceding their works.

8   8.  Equations of the model: eqs (1)-(26) and (37) – (56) from the present manuscript are identic to eqs (1)- (26) and (27) – (46) from the Machines paper. Eqs (27) – (36) from the present manuscript are well known from the Hertz’s theory. One question arises: What is new in the model of the authors?  

9   9.  Eqs. (13), (14) etc, what means ‘sen’?

Author Response

Thank you for your review report. Please find our response to each and every point in the attached document. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

In the executive summary, it would have to be added that the considerations concern only quasi-static studies (analysis).  This would make the scope of the research carried out clear.

Author Response

Dear Reviewer #1,

Thank you for this new revision. We have added the following phrase to the executive summary (abstract) of our paper: “under quasi-static conditions“.    

Yours sincerely,

David S. Pellicer & Emilio Larrodé. 

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript should be published after revision.

Author Response

Dear Reviewer no. 2,

Thank you again for your revision, which helped us improve the article.

 Yours, sincerely,

David S. Pellicer & Emilio Larrodé.