Vol 89, No 4 (2022)

BACKGROUND: The study is focused on improvement of basic machines and development of new machines for digging of holes for young fruit trees in firm soils.

AIMS: Expansion of technological abilities and decrease of energy resource intensity of an earth auger with the rotary working body for the sake of replacement of technically obsolete pothole diggers.

METHODS: For working bodies parameters substantiation, the vineyard rotary earth auger, which design includes a bulk, a frame, a rod and a beam, forming the hinged forebody mechanism, whereas the bulk and the frame are linked to the attachment system of the power source, is investigated.

RESULTS: The most widespread actuators of working bodies of universal hole diggers are analyzed. Principles of shock-and-vibrational digging of a drill tool make it possible to obtain significant improvement of digging performance. The design and technological layout of an earth auger and the theoretical substantiation of working bodies parameters under the vibration effect are proposed. The amplitude of the bar reciprocating motion along the splines is not less than washer teeth height in order to transform the rotation into the reciprocating motion in the vibrational operation mode of an auger. For the vibrational operation mode of an earth auger, the simulation model, considering physical and mechanical properties of soils, geometry parameters of the working body for the sake of substantiation the number of teeth of working body drive washers are proposed. It is found that for the auger diameter increases from 0.15 to 0.35 m the number of teeth of working body vibratory drive washers, ensuring demanded vibration frequency for soil layer breaking-off by auger shares, increase from 7 to 16 pieces in accordance to technical properties of the auger and physical and mechanical properties of considered firm soils. The proposed design parameters for reducing gear box fixed to the frame and auger offset from the tractor longitudinal axis corresponding to frame rotation angle β = 33°20’ is ensured by a hydraulic cylinder, the beam length L₁ is 800 mm, for pivot fixing of the frame with the length L₂ of 1300 mm, the offset value up to 1500 mm.

CONCLUSIONS: The obtained results of the earth auger simulation for operation at firm soils in the case of planting perennials are given. The study is targeted to the expansion of technological abilities, the substantiation of design and technological parameters of an earth auger and the decrease of energy resource intensity of hole digging.

BACKGROUND: The Federal Scientific and Technical Program for the Development of Agriculture on 2017–2025 deals with the creation and implementation of competitive domestic technologies based on the scientific achievements. Therefore, the development and investigation of parallel driving systems for a machine-tractor unit with information and navigation equipment in the direction of increasing their accuracy of coordinates determination are relevant.

AIMS: Improving the accuracy of coordinates determination of the software and hardware complex for the parallel driving system based on algorithms for correcting and filtering information data of navigation equipment.

METHODS: The simulation of the machine-tractor unit (MTU) is carried out in MATLAB/Simulink and contains the models of physical modules of coordinates correction for cases of tilt, geographic coordinates transformation into plane coordinates, orientation and velocity of the machine-tractor unit and the Kalman filter.

RESULTS: Using the proposed mathematical model, a simulation of a machine-tractor unit operation with a parallel driving system is carried out. The adequacy of theoretical studies is confirmed by large-scale bench and field tests. The scientific novelty of the study lies in the proposed algorithms for correction of datas obtained from GPS/GLONASS receivers (computer program registration certificate No. 2019617131), the implementation of the 3D visualization of the machine unit on a tablet screen with the Android operating system (computer program registration certificate Nos. 2018613106 and 2020613458).

CONCLUSIONS: The practical meaning of the present study lies in usability of the proposed algorithms for corrections and filtration of navigation equipment data under creating modern hardware and software systems for parallel driving of a machine-tractor unit.

BACKGROUND: For transport accessibility in areas with an undeveloped road network, the use of tracked trains that provide low ground pressure is a rational solution. To ensure the mobility of a semi-trailed, unmanned caterpillar train, which can be controlled remotely by a driver-operator or by an automatic unmanned driving system, traffic control laws are needed.

AIMS: Ensuring energy efficiency in curve control of a unmanned semi-trailer tracked train for off-road freight transport.

METHODS: The methods of simulation mathematical modelling and analytical methods based on the consideration of the quasi-stationary motion of the caterpillar train links are used to derive energy-efficient control laws and determine the mobility performance that can be achieved.

RESULTS: Control laws are obtained for two variants of tracked trains: a tracked train with independent drive control of driving wheels and a tracked train with a differential drive scheme of a semi-trailer link. The control laws are designed to improve the energy efficiency of travel which is achieved by rational distribution of traction forces on the driving wheels of the tracked train and use of the regulator which ensures adjustment of the traction on the semi-trailer driving wheels accord-ing to the sign and magnitude of force in the fifth-wheel coupling of the tractor.

A block diagram of a governing system of a caterpillar train and a mathematical description of its basic structural components (blocks) are given. Using the developed control laws the theoretical research of curvilinear movement by simulation mathematical modelling is carried out; the comparative analysis of the considered control laws of the semitrailer caterpillar train movement with two transmission variants is given.

CONCLUSIONS: The application of the developed caterpillar train motion control laws will enable the vehicle to move unmanned or follow the lead vehicle along a set path with high accuracy of turning manoeuvres and, consequently, will improve the safety of freight transportation.

BACKGROUND: Researches in the field of engine oils sludging take its origin from 1955. Scientists from different countries were searching for the reasons, defining consequences, building a chain of cause-effect links. Researchers have found that sludge represents a complex of compounds with low aggregative stability, such as: the additives inserted into a basis during production, partially oxidised fuel fractions subjected to thermal destruction, products of thermo-oxidative transformations of oil hydrocarbons. A number of factors stimulate transient processes of products with low aggregative stability. One of these factors is presence of water. Water may penetrate through ambient air, during engine service (washing), and as a result of condensation processes during operation at low temperature mode. Strengthening intermolecular interactions of compounds, water initiates sludging.

AIMS: Verification of the hypothesis about the binding effect of water on the composite package of additives, the content of which is determined by their indicator elements.

MATERIALS AND METHODS: The experiment was carried out under laboratory conditions. Production engine oils were watered intentionally in order to obtain sludge. Mixes of engine oils with water were made in different proportions. The formed sludge was separated from the mixes for the further research.

The search of the elements-indicators of additives in the analytical sample of a watered oil sludge was carried out with the method of raster electron microscopy. The Japanese-manufactured labware was represented by the Jeol JCM-5700 raster electronic microscope, the JED-2300 Analys Station software package. A raster microscope is the device intended for acquisition of object images, increased in several thousand times and with the huge spatial resolution, definition of chemical elements and their compounds.

RESULTS: The experiment conclusions are formulated on the basis of visual investigations and the raster electron microscopy studies.

CONCLUSIONS: The practical importance lies in integrity of the approach to the engine oils state change under the influence of water, regarding transition of the dissolved additives to a firm (amorphous) state. Possible consequences of watering are blocking of oil pickup screens and filtering elements, unfairly active corrosion and wear processes of surfaces of the related details.

BACKGROUND: During periodic long-term tests of tractor diesel engines D-240T with a combustion chamber of the CNIDI after 4000 m-hour, a deterioration in the indicators of the working process was observed. After disassembling the diesels, it turned out that the reason for this is the development of cracks on the edge of the combustion chamber (CC), and the deterioration of indicators is detected when the crack has reached a critical length.

AIMS: The aim of study is concerned investigation of a methodology for predicting of a tractor diesel piston durability with the crack on the CC edge and development of a method for calculating the crack evolution to before the transition to the improper state.

METHODS: Both experimental and computational methods were used in the research. Experimental pistons was manufactured with some design changes: the radius of the edge rounding changed, which changed the thickness of the side wall of the CC.

RESULTS: Motor studies of diesel engines have shown that with a certain piston design, a crack either does not appear at all, or appears after a large number of cycles. Additional computational studies have shown that the crack development depends on the stress intensity coefficient at the crack tip. Using the data of experimental studies, a method has been developed for estimating the critical crack length in the edge of the CC, at which the intensity of stresses in the vicinity of its vertex exceeds the limits accepted for this material from which the piston is made.

CONCLUSIONS: A method for calculating the durability of the piston during the development of a crack on the edge of the combustion chamber is proposed. Verification of the calculated data obtained during the numerical implementation of the piston evaluation method using the example of the diesel piston D-240 showed that for a range of crack lengths up to 1 mm and operating time over 7000 m-hour, the calculation error com-pared to the operational test data does not exceed 11%.