Running quality assessment of a passenger car produced in the Republic of Uzbekistan

The article discusses a topical issue regarding the replenishment of the passenger car fleet with promising and comfortable passenger cars. To determine the quality assessment of the passenger carriage, a check was carried out for compliance with the standards for the smoothness of the carriage. Based on the main technical parameters of the new passenger carriage, the main calculated values were determined with and without taking into account the payload. Comparing the results obtained with the highest permissible values, it was found that the quality indicators of the passenger carriage model 61-920 manufactured in the Republic of Uzbekistan do not exceed the permissible values and meet the requirements.


Introduction
In railway transport, it is important to prepare coordinated measures for the development of new types of traction, renovation of the car fleet, improvement of the track superstructure, which will ensure high train speeds combined with traffic safety and convenience for passengers [1][2][3][4]. The rational use of these funds and the rational organization of transportation work constitute the main content of the operational activities of railway transport [5][6].
The passenger carriage park of Uzbekistan railways is one of the types of railway rolling stock [7][8]. The quality of service and the timeliness of passenger delivery, productivity, and economic performance of railways depend on its technical condition and ability to meet transportation needs [9][10][11].
To replenish the fleet with promising passenger cars, the designers of the Tashkent Plant for the Construction and Repair of Passenger Cars JSC have designed a new 61-920 model passenger car with a modern air conditioning system [12].
The passenger carriage is an integral part of the passenger railroad complex, providing the demand for railway transport services. Such indicators characterize the criteria for evaluating passenger service as the comfort and smoothness of the carriage [13][14][15].
When determining the quality assessment of a passenger carriage, it is necessary to check the compliance with the standards for the smoothness of the carriage, provided for by the standard and other normative and technical documentation for cars [16][17][18].
When designing this passenger car for the railways of Uzbekistan, young scientists of the department "Carriages and carriage facilities" of Tashkent Railway Engineering Institute(TREI), theoretical studies determined the quality indicators of the carriage.

Materials and Methods
Passenger compartment carriage model 61-920, manufactured following the design documentation 920.00.00.000 developed by Tashkent Plant for the Construction and Repair of Passenger Cars JSC. The main technical parameters of this car are shown in Table 1. Evaluation of the quality of the carriage following [16] is determined by the following indicators:  coefficients of vertical and horizontal dynamics;  vertical and horizontal body acceleration;  indicators of smoothness in the vertical and horizontal (transverse) directions;  coefficient of wheel stability against derailment;  coefficient of stability of a car against overturning in a curve under the action of lateral forces;  coefficient of stability of a car in a train from derailment in a curve under the action of longitudinal compressive and tensile forces.

Results and Discussion
The main of the listed indicators of the quality of the carriage running are the coefficients of vertical and horizontal dynamics.
The coefficient of vertical dynamics of the body К dv is determined by the formula: where av dv К is the average probable value of the coefficient of vertical dynamics; β is the distribution parameter, according to [16], is taken equal to1,0; Р(К dv ) is the confidence probability with which the coefficient of vertical dynamics is determined, according to [16], is 0.97.
In this case, the average probable value av dv К is determined by the formula: where a is coefficient, according to [16], equal to 0.05 for body elements; в is coefficient that takes into account the influence of the number of axles n in the bogie under one end of the carriage, equal for biaxial bogies in в = 1; f st is total static deflection of the bogie, m.
The total static deflection of the bogie is determined by the formula: , where f Ц is static deflection of the central suspension stage, m; f Б is static deflection of the axle-box stage of suspension, m; , The force acting on the bogie of the car P is determined by the formula: where Q p is mass of passengers with cargo (payload); taken according to [16] (2), we obtain the calculated values of the parameters, which are summarized in table 2.
The horizontal coefficient of body dynamics К dg is determined by the formula: where dg k is the average value of the coefficient of horizontal dynamics; P(k dg ) is the confidence probability with which the coefficient of horizontal dynamics is determined, according to [16], P(k dg ) = 0.97. In this case, the average value of the horizontal dynamics coefficient is determined by the formula: Where δ is the coefficient taking into account the type of running gear is taken according to [16] 0.002; V is constructional speed of running, m/s. Substituting data into formula (8), we get dg Substituting the data into formulas (1) and (7), we obtain the coefficients of the vertical and horizontal dynamics of the passenger car body, the results of which are summarized in table 3.  The rest of the quality indicators of the carriage running were determined in the same way.

Conclusions
According to the results of theoretical studies, it was found that the quality indicators of the passenger carriage model 61-920 do not exceed the permissible values and meet the requirements [16]. Based on the positive results of theoretical studies, a prototype of this car was built. Experimental studies were carried out according to the requirements [12][13][14][15] and to check the selected parameters of the passenger carriage. The comparative analysis of the results of theoretical and experimental studies showed their good convergence, based on which it can be concluded that the designed carriage has high-quality performance, which creates favorable comfortable conditions for passengers on the way.