Complete factor experiments on fifth-class rotary kinematic couples

. The article presents the analysis of the results of the multi-factor experiment conducted on the experimental tests conducted on the improved fifth-class rotary kinematic pair available in technological machines. Recommendations for the number of longitudinal grooves opened in the inner cylinder of the fifth-class rotary kinematic pair structure, their angle of inclination relative to the axis, and the use of lubricating oil are given. Test results and conclusions are presented.


Introduction
One of the main directions of the development of the field of mechanical engineering is the improvement of resource-saving technological machine units, mechanisms and devices and the creation of new ones [1][2][3][4].Due to the high speed of the rotating links of modern rotor machines, there is a need to develop resource-efficient rotating kinematic pairs of a new design.
Kinematic pairs are divided into 5 classes depending on the restrictions placed on the movement of the links relative to each other.If there are five restrictions on the six movements of the links forming a kinematic pair (a free link in space has 6 movements), such a kinematic pair belongs to the fifth class pair.The relative movement of the links in the fifth class kinematic pair can be rotational or forward.
It is known that the fifth class rotary kinematic pair consists of two cylinders in constant contact.In such a pair, the protrusion on the inner cylinder prevents the outer cylinder from moving along the axis, but the cylinders can rotate relative to each other [5].The main disadvantage of the rotating kinematic pair is the low work resource due to friction and wear of the kinematic pair elements.Especially in high-speed operation modes, friction and wear are high, and in turn, movement accuracy decreases and noise appears [6,7].
In order to increase the work resource and the accuracy of transmission of rotary motion, an improved design of the fifth class rotary kinematic pair was developed, and research was conducted to determine its parameters [8].
The number of longitudinal channels opening the inner cylinder of the newly improved fifth-class rotary kinematic pair, which save oil reserves and reduce the frictional contact surfaces, the angle of inclination of the longitudinal channels relative to the axis, and the viscosity coefficients of the driving oils used in the kinematic pairs meet the specified requirements.
It was aimed to determine the optimal values that ensure that the level of wear in the outer cylinder of the improved rotating kinematic pair is minimal.To achieve the set goal, full factorial experiments were conducted under the TOT 23 plan.
Based on the results of the conducted theoretical and one-factor experiments, the lower, main and upper levels of the factor were determined (Table 1).Table 1 shows the factors, their coded designations, levels and intervals of change.A laboratory device has been developed for researching and conducting experiments on the kinematic couple [9]. Figure 1 shows an overview of the device.
The experimental fifth-grade rotating kinematic couple research device works in an open circuit.
Experimental copies of the construction of the rotating kinematic pair of the fifth class with only rotational movement, used in technological machines, have been improved.
The geometric characteristics of the existing and improved fifth-class rotating kinematic pair construction were developed.For the developed structure, the fifth class rotating kinematic pairs, which differ from each other in terms of the number of longitudinal channels, geometric dimensions and material, were prepared.
The experimental device shown in Figure 1 consists of: electric motor 1, couplings 2, reducer 3, fifth-class rotating kinematic pairs (sliding bearings) 4, shaft 5, braking device 6, strain gauges 7, magnetic laser tachometer for determining the number of revolutions 8.The fifth class included in this device is implemented using the hand brake, which acts on the resistance forces acting on the rotating kinematic pair.The number of rotations coming out of the drive is changed in the ratio of 1÷40 with the help of a worm gear reducer, and with the help of an inverter, it is ensured that the number of revolutions on the shaft is divided between 15-30 rev/min due to the change in the rotation frequency of the drive.
It is possible to change the resistance torque on the kinematic pair shaft in the range of 10-200 N•m with the help of the hand brake.
BrO8S12 bronze and steel grade 45 with a carbon content of 0.45% were selected for the preparation of kinematic pair elements.Figures 2-3 show experimental copies of the elements of the construction of the fifth class rotating kinematic pair.Full factorial experiments were conducted in the experimental room of the Namangan Engineering and Construction Institute.
To reduce the level of wear in the outer cylinder of the kinematic pair (Fig. 2) and to determine the optimal parameters of the prepared inner cylinder (Fig. 3), a working matrix was created for conducting multifactorial experiments (Table 2).The experimental results and variance values of the outgoing factors are included in Table 3 to summarize the experimental results.
Experiments were carried out on the basis of the developed working matrix.The data obtained from full factorial experiments were processed according to the "Planexp" program, developed in the experimental testing department of the Scientific Research Institute of Agricultural Mechanization.In this case, Cochran's criterion is used to evaluate the uniformity of variance, Student's criterion is used to evaluate the value of regression coefficients, and Fisher's criterion is used to evaluate the adequacy of regression models.

Results
The experimental results were processed according to the specified program, and the following regression equation was obtained for the level of wear in the outer cylinder of the kinematic pair, which adequately represents the evaluation criteria.

Discussion
It can be seen from these graphs that the number of longitudinal grooves opened to the inner cylinder of the kinematic pair (shaft), the angle of inclination of the grooves relative to the axis, and the increase in the viscosity coefficients of the lubricating oils, in turn, lead to a decrease in the level of wear in the outer cylinder of the kinematic pair. .However, it can be seen from theoretical studies that the torsional strength of the inner cylinder of the kinematic pair decreases due to the increase of the total surface of these channels by 10-12%.

Conclusion
From the results of a large number of full-factor experiments, it can be concluded that the proposed kinematic pair design was applied to the G-24 oil press machine used for the production of vegetable oil.According to the results of studies, taking into account that the nominal value of the number of rotations of the working shaft of the technological machine is 24 rev/min and ensuring the conditions of strength of this working shaft, that is, ensuring that the grooves do not exceed 10% of the total surface of the inner cylinder surface.for this purpose, it is recommended to choose the number of longitudinal grooves opened to the inner cylinder of the kinematic pair as 9, and the angle of inclination of the longitudinal grooves to the axis as 10⁰.

Fig. 1 .
Fig. 1.Overview of the research device of the fifth grade rotary kinematic pair

Fig. 4 .
Fig. 4. Graphs of dependence on factors X1, X2, X3 when the number of longitudinal grooves opened to the inner cylinder of the outer cylinder of the kinematic pair varies.

Table 1 .
Table of factor levels in natural value.

Table 2 .
Work matrix for conducting experiments.

Table 3 .
Table summarizing the results of the experiment