Introduction

Rail vehicles are complex mechanical systems made up of hundreds of moving components that interact with each other through friction forces, damping systems and unstable operating conditions. A company renewed its fleet of passenger cars by acquiring European-standard models, which it called "modern". As there were already other types in circulation, it was necessary for these modern vehicles to operate with cars from the classic fleet, as well as to determine the comfort level of this composition in operation.

In order to assess passenger comfort during rail journeys, an international standard establishes guidelines for evaluating the parameters to which passengers are subjected. These normatively defined criteria must be studied using the accelerometry method.

The passenger car comfort analysis included the evaluation of a complete journey cycle and a journey in the opposite direction under normal operating conditions. The first cycle took place with the classic fleet car in the last position and the modern passenger car, instrumented with accelerometers, in the penultimate position of the composition, as shown in Figure 1. At the end of the first cycle, the cars swapped positions, as can be seen in Figure 2.

Figure 1: Position of the passenger car in the first cycle.

Figure 2: Position of the passenger car in the second cycle.

The cars were instrumented using accelerometers in 3 directions, as shown in Figure 3.

Figure 3: Illustration of acceleration directions.

In order to correctly correlate the measured load and strain, the coupling was calibrated on a bench using hydraulic cylinders. Figure 4 shows where the sensors were installed and how the coupling was calibrated.

Figure 4: Extensometers installed in the coupling during calibration.

The acquisition system was connected to an on-board computer which recorded the data in text format, together with the GPS. The results were analyzed based on international standards. The results obtained during hitch calibration are shown in Figure 5.

Figure 5: Calibration results of the coupling deformations.

The results obtained during the two cycles are presented graphically. The X axis corresponds to the time domain, point by point on the railroad. Figure 6, in red, shows the NMV values of the first cycle for the modern passenger car, while the graph in black shows the NMV values for the classic car.

Figure 6: NMV results for the modern passenger car and the classic car, respectively, in the first measurement cycle.

Figure 7, in red, shows the NMV values of the second cycle for the modern passenger car, while the graph in black shows the NMV values for the classic car.

Figure 7: NMV results for the modern passenger car and the classic car, respectively, in the second measurement cycle.

It can be seen that the NMV values of the classic car are higher than those of the modern car in both cycles. By evaluating the results obtained in both cycles and taking the 95th percentile of these results as a reference, we obtain the comfort value, according to the international standard, as shown in Table 1.

Table 1: General comfort.

Conclusion

The comfort assessment of the passenger car enabled the NMV values to be obtained. The main accelerations that contribute to an increase in discomfort for the modern car are vertical accelerations. On the other hand, for the classic car, they are vertical and lateral accelerations. There was no considerable variation in both cycles evaluated, indicating that comfort levels do not change depending on the position of the cars.

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References:

[1] DYNAMIC BEHAVIOR OF THE EFVM PASSENGER TRAIN WITH DIFFERENT MODELS OF CARS IN THE COMPOSITION.