Analysis of Dynamic Characteristics of Low-Floor Train Passing Switch in Facing Direction with Bad Alignment Irregularity Ahead of the Turnout
Round 1
Reviewer 1 Report
Dear Authors,
The section 2.2. Coupling dynamic model of low-floor train and turnout switch is a mix of the field experiments with simulation ones. It should be clearly separated. The parameters of the rail vehicle are unfortunately unknown. What kind of simulation software was used in the research? The paper should introduce more information on the vehicle model and contact forces algorithm.
What wheel profile was used in the study? Are the profiles the same in the trailing and motor bogies?
Another issue is related with the plots in Fig. 9, 10, 11, 12, 13. Do they depict maximal or average values of the measured values? I was not able to find this information in the text, or it should be more apparent.
Model validation is poor. It relies only on the qualitative similarities, without exploiting any mathematical measure.
Section 4.3. The alignment optimization shows no otpimization at all. It does not introduce any objective function, nor the method of optimization. I recommend changing the title of that section.
Author Response
Dear Reviewer:
Thanks for your reviews of our manuscript. Your comments are insightful for us to improve the reported research. We have done our best to respond to your comments as clearly and concisely as possible. The revised part has been marked with the blue colore in the original manuscript. Please check the detailed point-by-point response in the following. We hope that the reviewers will find our responses to their comments satisfactory, and we are willing to finish the revised version of the manuscript including any further suggestions that the referees may have.
Point 1: The section 2.2. Coupling dynamic model of low-floor train and turnout switch is a mix of the field experiments with simulation ones. It should be clearly separated. The parameters of the rail vehicle are unfortunately unknown. What kind of simulation software was used in the research? The paper should introduce more information on the vehicle model and contact forces algorithm.
Response 1: Thank you for your suggestion, the relevant content has been added in the article below 2.2 (Blue font include Table 1).
Point 2: What wheel profile was used in the study? Are the profiles the same in the trailing and motor bogies?
Response 2: Thank you for your suggestion, the treads of all the wheels are measured by the WS2016-3W-LFT wheel tread measuring instrument. The motor and trailing bogies have the same wheel profiles. The relevant content has been added in the article below 2.2 (Blue font).
Point 3: Another issue is related with the plots in Fig. 9, 10, 11, 12, 13. Do they depict maximal or average values of the measured values? I was not able to find this information in the text, or it should be more apparent.
Response 3: Thank you for your suggestion, mechanical indexs in Fig. 9, 10, 11, 12, 13 are root mean square values. It is explained at the beginning of Part 4.
Point 4: Model validation is poor. It relies only on the qualitative similarities, without exploiting any mathematical measure.
Response 4: Thank you for your suggestion, the maximum relative error between simulated and measured values has been added in model validation (Blue font include Table 2).
Point 5: Section 4.3. The alignment optimization shows no otpimization at all. It does not introduce any objective function, nor the method of optimization. I recommend changing the title of that section.
Response 5: Thank you for your suggestion, due to the incomplete design parameters of the geometric shape and position of the track in front of the turnout, based on the measured data and the coordinates of the key control points for the geometric irregularity of the track, a commonly used optimization algorithm for the geometric shape and position of the track in China's railways is used to calculate the adjustment amount of the railway track configuration, and the optimized geometry of the turnout front line is obtained. the title of that section has been changed as ‘Alignment adjustment’.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript “ Analysis of Dynamic Characteristics of Low-Floor Trains Passing Switch in Facing Direction with Bad Alignment Irregularity before Turnout” presents theoretical studies in the field of mechanical engineering. The paper presents a development of a model for investigation of the mechanical response of train in turnouts. The model is aimed to compare the different vehicle types. It is important both for operational safety and the maintenance. However, the study is not novel. The novelty of the research should be highlighted, the difference to the conventional approach should be mentioned. The aim of the research is not clearly fulfilled.
The paper could be published in MDPI Applied Sciences after the major improvement that takes into account the following remarks:
1) It is not clear where is the Test section 1-2 in the Figure 7(a). – Please show the zone directly in the plot together with the other elements of the switch from Figure 1.
2) Figure 7(b) – please present additionally difference between the measured and the project (ideal) position as well as the horizontal curvature together with admissible values.
3) Please describe how the lateral loading was derived from the strain gauge sensors.
4) The train and track model parameters should be described.
5) The specific conclusions should be presented, not only the study steps done.
6) The turnout zones are characterised by different failures, especially in case of sleeper voids or unsupported sleepers. Please note in discussion and the literature review by referring the corresponding papers on void interaction in MDPI Journals (Geometry variation of ballasted railway tracks due to weather conditions, Evolution of Rail Contact Fatigue on Crossing Nose Rail Based on Long Short-Term Memory Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers, Identification of Sleeper Support Conditions Using Mechanical Model Supported Data-Driven Approach etc.)
Author Response
Dear Reviewer:
Thanks for your reviews of our manuscript. Your comments are insightful for us to improve the reported research. We have done our best to respond to your comments as clearly and concisely as possible. The revised part has been marked with the blue colore in the original manuscript. Please check the detailed point-by-point response in the following. We hope that the reviewers will find our responses to their comments satisfactory, and we are willing to finish the revised version of the manuscript including any further suggestions that the referees may have.
Point 1: It is not clear where is the Test section 1-2 in the Figure 7(a). – Please show the zone directly in the plot together with the other elements of the switch from Figure 1.
Response 1: Thank you for your suggestion, the values of Section 1 and Section 2 in Figure 1 are the test points for dynamic indicators, while the test values mentioned in Figure 7(a) refer to the geometric shape and position tests of the longitudinal and vertical sections of the center line of the line in front of the turnout. The two expressions have different meanings. Added in detail in relevant sections.
Point 2: Figure 7(b) – please present additionally difference between the measured and the project (ideal) position as well as the horizontal curvature together with admissible values.
Response 2: Thank you for your suggestion, Figure 7 (b) shows a comparison between the theoretical design alignment of the front clamp straight line of the turnout and the measured values after deformation. The relative deviation value is also explained in the paper.
Point 3: Please describe how the lateral loading was derived from the strain gauge sensors.
Response 3: Thank you for your suggestion, the strain gauges for testing the lateral force shall be affixed to two cross sections 110mm from the center line of the sleeper box and 20mm from the bottom edge of the rail. Four strain gauges shall be affixed to the upper surface of the rail bottom, and the direction of the strain gauges shall be at a 45 ° angle to the longitudinal direction of the rail. Test the horizontal force to form two bridges according to the upper surface of the rail bottom. After the stress changes are affixed to the rail waist, it is necessary to calibrate it. The main method is to level the two strain gauge channels respectively, and apply equally spaced horizontal forces to the rail in the middle of the two patch sections (the center of the sleeper box) to convert the ratio, which has been added in Part 2.1. The basic principle of this method for testing lateral force is based on the strain symmetry method, which is relatively accurate for the test of section 1 in Figure 1. For the lateral force of section 2 in Figure 2, due to the influence of switch rails, there will be significant errors.
Point 4: The train and track model parameters should be described.
Response 4: Thank you for your suggestion, the train and track model parameters has been added in Table 1.
Point 5: The specific conclusions should be presented, not only the study steps done.
Response 5: Thank you for your suggestion,the conclusions include two parts. The first part is the study steps and the second part is main findings and results.
Point 6: The turnout zones are characterised by different failures, especially in case of sleeper voids or unsupported sleepers. Please note in discussion and the literature review by referring the corresponding papers on void interaction in MDPI Journals (Geometry variation of ballasted railway tracks due to weather conditions, Evolution of Rail Contact Fatigue on Crossing Nose Rail Based on Long Short-Term Memory Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers, Identification of Sleeper Support Conditions Using Mechanical Model Supported Data-Driven Approach etc.)
Response 6: Thank you for your suggestion, this paper mainly studies the influence of the deformation of the line in front of the turnout on the dynamic response of trains passing through the turnout. However, as experts have mentioned, the deformation of the line is related to factors such as empty sleepers, and some new methods can also be referenced. Due to the space limitations of the paper, relevant content will be mentioned in future research. The related references have been added in Section 1.
Unsupported sleepers or sleeper void zones in ballasted tracks are frequent track failures. Sysyn et al. carried out a series of studies on related issues including mechanism of sleeper–ballast dynamic impact in unsupported sleeper zone[1], sleeper support conditions identification[2], Evolution of Rail Contact Fatigue on Crossing Nose Rail[3], and dynamic characteristics of the railway ballast bed under various external environment [4].
- Sysyn, M.; Przybylowicz, M.; Nabochenko, O.; Liu, J.X. Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers. Sustainability 2021,13, 7740.
- Sysyn, M.; Przybylowicz, M.; Nabochenko, O.; Kou, L. Identification of Sleeper Support Conditions Using Mechanical Model Supported Data-Driven Approach. Sensors 2021,21:3609.
- Kou, L.; Sysyn, M.; Liu, J.X.; Nabochenko, O.; Han, Y.; Peng, D.; Fischer, S. Evolution of Rail Contact Fatigue on Crossing Nose Rail Based on Long Short-Term Memory. Sustainability 2022, 14, 16565.
- Liu, J.X.; Liu, Z.Y.; Wang, P.; Kou, L.; Sysyn, M.. Dynamic Characteristics of the Railway Ballast Bed Under Water-Rich and Low-Temperature Environments. Asce-Asme Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering 2022, 252, 113605.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper is well done. I didn't find any serious flaws. Nevertheless, I still have a few comments:
1) Main findings and results are missing from the abstract.
2) In Figure 1, show the dimensions.
3) In the article, correct the display of km/h units to km.h-1
4) The paper lacks real discussion..
Author Response
Dear Reviewer:
Thanks for your reviews of our manuscript. Your comments are insightful for us to improve the reported research. We have done our best to respond to your comments as clearly and concisely as possible. The revised part has been marked with the blue colore in the original manuscript. Please check the detailed point-by-point response in the following. We hope that the reviewers will find our responses to their comments satisfactory, and we are willing to finish the revised version of the manuscript including any further suggestions that the referees may have.
Point 1: Main findings and results are missing from the abstract.
Response 1: Thank you for your suggestion,the main findings and results are added in the back of the abstract (Blue font).
Point 2: In Figure 1, show the dimensions.
Response 2: Thank you for your suggestion, Figure 1 shows only a schematic representation of a turnout structure, with specific dimensions varying depending on the type of turnout.
Point 3: In the article, correct the display of km/h units to km.h-1
Response 3: Thank you for your suggestion, vehicle speed units are unified into km/h.
Point 4: The paper lacks real discussion.
Response 4: Thank you for your suggestion, the paper discusses in detail the effects of vehicle speed, wheel/rail friction coefficient, and forward direction irregularities of switches on wheel/rail forces, safety indicators, etc., as added in Part 4.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors,
Thank you for your responses and taking my suggestions into consideration.
Best regards
Author Response
Dear Reviewer:
Thanks again for your reviews of our manuscript. We sincerely appreciate the reviewer for their approval of this article. In addition, we carefully considered the comments of other reviewers and made corresponding corrections. The revised part has been marked with the yellow in the original manuscript. We hope that the reviewers will find the revised manuscript satisfactory. We are willing to finish the revised version of the manuscript including any further suggestions that the reviewer may have.
Author Response File: Author Response.docx
Reviewer 2 Report
The manuscript has been somewhat improved and the Authors have responded to many remarks of the reviewer. However, Point 2. was not addressed. Fig.7 presents not the irregularity but the measured and ideal plane absolute positions. But the dynamic interaction is caused by relative position along the track. Thus, it is not possible to estimate the geometrical condition of the turnout in the plane. How bad is the irregularity? Is it a sufficient or severe state for the presented velocities? What is the admissible irregularity? Please additionally present:
1) plot of geometrical difference between the measured and ideal irregularity along the x-coord.
2) plot of the lateral curvature/versine for the cord 5 or 10m.
3) The direction of the curvature in Fig.7a for 65.8-67.0 is upwards and Fig.7b is downwards. Please make clear the discrepancy.
Author Response
Dear Reviewer,
Thanks again for your reviews of our manuscript. Your comments are insightful for us to improve the reported research. We have done our best to respond to your comments as clearly and concisely as possible. The revised part has been marked with the yellow in the original manuscript. Please check the detailed point-by-point response in the following. We hope that the reviewer will find our responses to their comments satisfactory, and we are willing to finish the revised version of the manuscript including any further suggestions that the referees may have.
Point 1: plot of geometrical difference between the measured and ideal irregularity along the x-coord.
Response 1: Thank you for your suggestion, plot of geometrical difference between the measured and ideal irregularity along the x-coord was added into Figure7(c).
Point 2: plot of the lateral curvature/versine for the cord 5 or 10m.
Response 2: Thank you for your suggestion, Figure 7: The horizontal alignment of the line is measured using a level gauge, while the vertical alignment is measured using a total station. Due to the complex alignment of the turnout area, the 5m chord and 10m chord measurement methods are not used to obtain the tangent.
Point 3: The direction of the curvature in Fig.7a for 65.8-67.0 is upwards and Fig.7b is downwards. Please make clear the discrepancy.
Response 3: Thank you for your suggestion, the expression in Figure 7a is the measured results of the horizontal and vertical alignment of the line in front of the switch rail. Compared to the measurement perspective in Figure 7b, the measurement perspective is larger. Figure 7b is an enlarged representation of local sections in Figure 7a. The curvature directions in the two figures are the same, but the places with large local deformation are not shown in Figure 7a. Figure 7b is represented by a red dashed frame in Figure 7a.
Author Response File: Author Response.docx
