Comparison of Fatigue Performances Based on Shape Change of Rail Fastening Spring

Round 1

Reviewer 1 Report

The work is interesting, but I have the following concerns.

1. The novelty of the current work may be included in the abstract.

2. The fastening force was set at 9KN what is the reason for that? Was the study limited to type C railway systems only, kindly clarify.

3. What was the reason for choosing the "partially fixed" boundary condition?

4. Line 150 and 173 -speculative terms like"This  might be due to the fact " or may also be attributed to similar internal forces" avoid using such sentences and little more explanation is required about the mechanism.

5. Critical things are missing in the study like the assumptions and limitations and most important, the validation of the study is missing.

6. In the conclusions, quantify the results in terms of % or numbers.

Some other observations-

Instead of train running "running of train" may be used. Sentence in line 20-23 is too long and may be cut into 2 or more sentences. Line 142 , it can be written as " Plots in figure 6 depicts".

Line 162"We investigated"-avoid using first person line I, we, our.

Line 183- fasting spring-is it fastening spring?

If possible better to put the location of the figures near to the text so that the continuity is better maintained in the paper. Introduction can be improved and the English grammar should be thoroughly checked before submitting again.

Author Response

Please see the attached file for our responses to the reviewer comments.

Author Response File: Author Response.docx

Reviewer 2 Report

In this paper, fatigue performances based on shape change of rail fastening springe are investigated by using FEM. My questions are as follows.

 

1. Finite element analysis modeling is unclear. Where is the fixed area in Fig. 2(a)? What are the loading conditions of Step 1 and 2? Figure 2(a) has the x-y-z coordinate axis. You should use it for the explanation.

 

2. I cannot understand where the output area is. Where are the “rail to spring” and “guide plate to spring”?

 

3. Step 1 shows stress states for the fastening force = 9KN. Step 2 shows stress states for the vertical displacement = 1mm. In section 3.4, the spring diameter is evaluated.

The stress decreased as the diameter increased in loading control. The stress range increased as the diameter increased in displacement control.  It’s a natural result.

I think that the comparison with displacement control lacks validity for changes in diameter.

 

Author Response

Please see the attached file for our responses to the reviewer comments.

Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript presents the fatigue performance of rail fastening spring with varying heights of the spring end, heights of the spring arm, spring widths and spring diameters. However, the spring widths and diameters were the factors that profoundly influenced the fatigue performance. This work is interesting and can be a valuable addition to the literature. I recommend the acceptance of the manuscript after a minor revision.

1. In the abstract, please add some quantitative results.

2. In the introduction, I can understand well the significance of the study. However, the novelty is not found in the introduction. Please emphasize the novelty in the last paragraph of the introduction.

3. On page 5; lines 162 – 163, please rephrase ‘We investigated the effect of the spring…..’. Generally, a research article should be expressed in third-person.

4. On page 8; line 244, ‘Figure 17(b)’ should be ‘Figure 16(b)’.

5. Please refer to and add a few more recently published articles as reference sources.

Comments for author File: Comments.pdf

Author Response

Please see the attached file for our responses to the reviewer comments.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments on the manuscript ‘Comparison of Fatigue Performances Based on Shape Change of Rail Fastening Spring’ (Ref: applsci_2151719)

 In this work, the authors have calculated the stress in a rail fastener spring and used the data for calculating the safety margins based on modified Godman’s diagram. The reviewer has the following comments.

 1.      The title should be modified by specifying the type of cyclic load considered in this analysis in order to be more specific. This aspect is further elaborated in point no. 18 also.

 2.      The abstract should be modified by mentioning the type of mean and cyclic loads that are used in this analysis. The material grade of the spring should also be mentioned in the abstract.

 3.      Geometry of fastening spring should be provided with the dimensions in Fig. 2(a).

 4.      Fig. 2(b): Stress-strain curve upto 2% is only is provided. What about the data after this strain? Local plastic strain can reach the order of 30 to 40%. Data of true stress vs plastic strain should be provided.

 5.      What is the material and grade of fastening spring? Some details regarding material and chemical composition should be provided in order to understand the reason for fatigue failure of the spring from microstructure point of view.

 6.      Boundary and loading conditions are not clear. Moreover, its interaction with the rail is not discussed. The spring is in contact with the rail and slipper at several points. How are these modeled?

 7.      Fig. 4: Two modes of failure are shown. How are these classified? Is there any basis for this classification except the location of failure?

 8.      What is the nature of fracture surface? Is it transgrannular or intergrannular type? Some micrographs of the fracture surface should be provided in order understand the failure mechanism.

 9.      Where is the origin of failure in these two locations of Fig. 4? Please check if these are originating from the surface. Again, what is the location? Is it the point with maximum stress? Please elaborate.

 10.  Eq. (1), Page-4: This limiting equation for frictional force may not be valid for this case. It is known that frictional force is self adjusting and hence, the value of frictional force can vary from 0 to mu*N. Its direction depends upon direction relative movement. It is not clear how the direction was chosen in this case?

 11.  Moreover, the magnitude must be calculated on the basis of equilibrium of all the forces acting on the spring including the forces due to movement of the wheel on the rail. The free-body diagram is not provided in this manuscript and hence, it is not possible to understand if the actual frictional force is same as given in Eq. (1). This aspect should be elaborated and clarified in the paper as the further calculations depend upon this data.

 12.  Eq. (2) and (3): In these equations, there is a mistake in the definition of sigma_E or S_E. It is not tensile strength. It should be endurance limit of the material of the spring based on fatigue test data. Unfortunately, no such data is provided in the paper. Hence, it should be modified and the data be analyzed again by changing this parameter. Similarly, Please check if S_U is the ultimate tensile strength of the material for modified Goodman’s diagram and Gerber’s parabola. It has been wrongly mentioned as yield strength of the material. Please correct it.

 13.  Fig. 5: Height should be mentioned as height difference between the free end and the support of the spring. It is mentioned as simply ‘height of spring’ in ‘Abstract’ as well in the texts. It is misleading and it should be modified accordingly.

 14.  Similarly, change legends of Fig. 6 as %age of initial height difference.

 15.  How is Fig. 7(b) obtained? The mean value of principal stress is obtained by applying some displacement. However, it is not clear how much cyclic component is applied. The cyclic components should be based on load of running train and not because of applied displacement. The constant loading comes from pre-load during fastening. The cyclic load is live load. These aspects of loading should be elaborated further as these data control the major outcome of your paper.

 16.  Fig. 15(a): What is value of D? D upto 18D is used. It is possible to use such a large diameter spring in practice. If the initial design has diameter of 12D, please mention it as D_0 and scale other diameters accordingly. It is very misleading right now.

 17.  Fig. 16(b): Why should range of stress increase with diameter? The overall mean and fluctuating components should decrease for a given applied mean and fluctuating force. Fig. 16(a) and (b) are contradictory.

 18.  Conclusions: The conclusions are very obvious regarding increase of margin of safety by increasing diameter of rod of spring and increase in spring. Moreover, the decrease of stress with increase of width of spring is possible only if displacement is applied instead of load. In actual practice, weight of train is the load and hence, the stresses will increase if we increase the width of arm of spring as the bending moment increases. So, this conclusion can be misleading. Please modify the conclusions by specifying that this is valid for certain applied displacement, not loads. However, I suggest that the calculations be repeated by using train dead weight and live loads as applied force instead of using displacement. For initial stress, applied displacement is okay as the spring is pre-loaded by applied a specific displacement.

Author Response

Please see the attached file for our responses to the reviewer comments.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you for your answer. 

Reviewer 4 Report

The authors have addressed all'the comments of the reviewers and hence, the revised manuscript may be accepted for publication in this journal.