New technological solutions for restoring the inner surface of hydraulic cylinders

Relevance. Agricultural machines widely use hydraulic cylinders for various auxiliary and working movements. Operation in harsh field conditions leads to the failure of the hydraulic cylinder mirror and, as a result, to the loss of force on the cylinder rod. The development of technological solutions for the restoration of the inner surface as a more appropriate solution in repair production is relevant.Methods. Studies of the heat flow using the “Fluke Ti32” thermal imager and ofthe influence of gas-dynamic spraying (GDS) modes on the adhesive and cohesive strength when using a new design of the nozzle part of the GDS equipment were carried out.Results. The suitability of usage of new nozzle design for GDS in order to restore the inner surface of the hydraulic cylinder body has been established. The elongated and curved nozzle for installations of the “Dimet” type practically does not change the temperature regime of spraying. The adhesive and cohesive strength of the coatings obtained with the new nozzle design is sufficient to operate under conditions characteristic of the inner surface of the hydraulic cylinder body.

The failure behavior of buckling pin valve: Theoretical, numerical, and experimental study

At present, buckling pin in the bypass of piping as pressure relief valve has been gradually utilized in the low-concentration coal-bed methane (CBM), which bends to release pressure when the main valve fails leading to pipeline blockage. However, current researches mainly focused on the buckling behavior of hydraulic cylinder rod or rod string, and less consideration was given to the operational reliability of buckling pin valves. This paper deduced the calculation formula of the critical failure load based on Euler formula in the buckling pin under buckling load. Besides, three finite element models (FEM) based on Johnson−Cook constitutive model were compared to predict failure strength of buckling pin which were verified by experiment. In addition, the defect sensitivity analysis of the buckling pin under different initial geometric defects rate was carried out. The results showed that a) the experimental value of the critical failure load in the buckling pin was 206.04 N and the bending position was in the middle of the buckling pin; b) the analysis result adopting explicit dynamic method was in best agreement with the experimental results within deviation of 0.24%; and c) the initial geometric defect of buckling pin should be controlled within 1%. This study provides an important reference to predict the critical failure load of the buckling pin valve and achieve safe transportation of low-concentration CBM.

Application of computer systems for modeling dynamic processes of lifting machines

The main task of mechanical engineering is to organize the production of a range of machines to meet the needs of all industries. These are power, transport, lifting and transport units, agricultural machinery, construction industry, etc. Among them, one can single out devices in which the relative movement of their parts is assigned, that is, kinematic pairs are included in the calculation models. The real operating conditions of machines are varied, but most often they are associated with periodic starts-stops, which determines the relevance of the study of unsteady modes. The analysis of the operation of such models becomes more complicated. For successful design results, mathematical modeling of individual processes in mechanisms is carried out. One of the first calculations is dynamic. Modern, available CAD / CAE systems for modeling and analysis provide automation capabilities, building more realistic design models. The paper discusses the approbation of the use of CAD for modeling the dynamics of a jib crane with a set of four units: platform, boom, sleeve and rod. The developed model is combined: the platform and the sleeve correspond to the kinetostatic model, and the boom and rod are elastic. The crane is designed to perform lifting operations in a vertical plane, with the possibility of relative movement in 3 rotational and one translational kinematic pairs. The performed calculations of the static, modal and dynamic analyzes of the links of the mechanism confirm the adequacy of their models. Among them is the task of instantaneous load application, which is typical for the "lifting and picking" operating mode of crane lifting mechanisms. The deformation of the entire structure in one of the boom positions is also considered. The determination of the reaction forces in the hydraulic cylinder provides important information for the selection of the power unit.

A model for determining the time of pointing a grip-cutting device of feller buncher machines on a growing tree

Исследование посвящено нахождению аналитической математической модели по определению времени наведения захватно-срезающего устройства на растущее дерево. В качестве известных параметров используются конструктивные размеры технологического оборудования, снятые с компоновочно-кинематических схем валочно-пакетирующих машин, требуемая высота пня и среднее расстояние между деревьями пасики. Поиск требуемой модели кратко можно разделить на несколько последовательных этапов: нахождение пути, который пройдет шток гидроцилиндра привода стрелы, и по известной формуле скорости перемещения поршня гидроцилиндра находится время на подвод стрелы к дереву; нахождение пути, который пройдет шток гидроцилиндра привода рукояти; нахождение пути, который пройдет шток гидроцилиндра привода наклона захватно-срезающего устройства; нахождение пути, который пройдет шток гидроцилиндра привода рычагов захвата в процессе раскрытия. Сумма времени на подвод каждого из элементов технологического оборудования и есть время на наведение, присущее неопытному оператору, в случае опытного оператора время на наведение захватно-срезающего устройства к дереву определяется максимальным временем одного из компонентов. The research is devoted to finding an analytical mathematical model for determining the aiming time of a feller head on a growing tree. As the known parameters are used. The design dimensions of the technological equipment, taken from layout and kinematic diagrams of feller-buncher machines, the required stump height and the average distance between the trees of the windrow. The search for the required model can be briefly divided into several successive steps: finding the path that the hydraulic cylinder rod of the boom drive will take and by the known formula of speed of movement of the hydraulic cylinder piston is time to bring the boom to the tree; finding the way which the rod of the hydraulic cylinder of the arm drive; to find the path which the hydraulic cylinder rod of the tilt of the feller head; finding the path which the hydraulic cylinder rod for the arm actuator will take during the opening. The sum of the time for supplying each of the elements of technological equipment is the time required for the orientation, which is characteristic for a nonexperienced operator. In case of an experienced operator the time for setting the feller head to the tree is determined by the maximum time of one of the components.

DESIGN AND TEST EVALUATION OF THE SUBSOILER EQUIPPED WITH TILLAGE DEPTH MONITORING AND CONTROL SUBSOILING ASSEMBLIES

Aiming at solving problems that the variation of tillage depth between rows and within rows caused by the surface undulation was great, the lateral stability of tillage depth obtained by the method of adjusting at the three-point suspension was poor, and lack of subsoilers with the function of accurate detection and adjustment of single row tillage depth, a method of independent control of single row tillage depth based on ultrasonic sensor detection and hydraulic adjustment was proposed. And the tillage depth monitoring and control subsoiling assembly and the subsoiler equipped with subsoiling assemblies were designed. The key structural parameters of the hydraulic cylinder and the model of the three-position four-way magnetic exchange valve were determined. The subsoiling quality and performance comparison tests were conducted, and the results showed that the mean value of the variable coefficient of soil hardness, looseness of soil and coefficient of soil disturbance were 52.23%, 32.55% and 62.15%, respectively, and the stability coefficient of tillage depth was 92.43%, which all met the subsoiling operation requirements. The standard deviation of tillage depth belonged to the method of independent adjustment of single row and unified adjustment of each row were 38.315mm and 51.521mm, respectively. The subsoiler equipped with tillage depth monitoring and control subsoiling assemblies designed in this paper was capable of significantly improving the stability of tillage depth between rows and within rows.

Research and Experimental Analysis of Hydraulic Cylinder Position Control Mechanism Based on Pressure Detection

This paper studies the precise position control of the hydraulic cylinder in the hydraulic support. The aim of this paper is to develop a method of hydraulic cylinder position control based on pressure and flow coupling, which takes the coupling feedback of load and flow into account, especially in the scene of cooperative control under the condition of multiple actuators and variable load. This method solves the problems of slow movement and sliding effect of hydraulic support in the traditional time-dependent hydraulic position control, as well as better realizes the intelligent and unmanned development of the fully mechanized mining face. First, based on the flow continuity equation and Newton Euler dynamic equation, the flow and stroke control model with the input and output pressure of hydraulic cylinder is established. Then, the effectiveness and correctness of the control model are verified by the comparison between the hydraulic system simulation software, AMESim, and the experiment. Finally, a test system is built. When the system pressure is large than 10 MPa, the error between the data determined by the fitting algorithm and the actual detection data is within 5%, which verifies the effectiveness of the theory and simulation model.

Research on Computer Aided Test System for Sealing Characteristics of Hydraulic Support Pure Water Hydraulic Cylinder

The sealing characteristics of the hydraulic cylinder in the hydraulic support will have an momentous implication on the safety and reliability of the whole system. The traditional test methods of the sealing characteristics of hydraulic support pure water hydraulic cylinder have many shortcomings, such as single means, complex process, poor accuracy and low efficiency. Based on this, this paper first analyzes the sealing principle and function of hydraulic support pure water hydraulic cylinder, then studies the CAT system of hydraulic support, and finally gives the design and utilization process of CAT system for sealing characteristics of hydraulic support pure water hydraulic cylinder.

Analysis of Platform Leveling Systems for Tracked Feller-Buncher Machines

The study was devoted to the analysis of feller buncher platform leveling systems. The widespread use of these systems in the design of modern feller-buncher machines makes the study relevant to assess operational efficiency. The analysis was conducted in five stages using analytical and stochastic mathematical modeling methods. In the first stage, the existing layouts of alignment systems were analyzed from the position of force on the hydraulic cylinder rods of the platform tilt drive. The three-cylinder layout scheme, where the force on the hydraulic cylinder rod was 50…60% less than that on the two-cylinder layout, appeared to be the most expedient. In the second stage, a mathematical model for determining changes in the position of the center of mass of the feller-buncher depending on the inclination angle of the platform was derived. In the third stage, a mathematical model was derived for determining the limiting angle of slope of the terrain when the feller buncher moved up the slope. For this purpose, two calculation schemes were considered when the machine moved up the slope without and with a tilted platform. Zero support reaction on the front roller was taken as the stability criterion. In the fourth stage, a mathematical model for determining the limiting angle of slope of the terrain during the roll of the feller-buncher machine was obtained. In the fifth stage, the efficiency of the application of leveling systems was evaluated. A graph of the dependence of changes in the terrain slope angle on the platform slope angle was plotted, and a regression dependence for an approximate estimate was obtained. A regression analysis was also carried out, and dependencies were obtained to determine the weight of a feller-buncher with a leveling system and the added pressure on the ground caused by the increase in the weight of the base machine. The analysis of platform leveling systems showed the effectiveness of their application in the designs of feller-buncher machines, as it allows the machines to work on slopes with an inclination of 50…60% more than without them.

Energy Efficiency and Limitations of the Methods of Controlling the Hydraulic Cylinder Piston Rod under Various Load Conditions

The article is an overview of various methods of braking and controlling the movement of the piston rod under various load conditions. The purpose of this review is to systematize the state of the art in terms of efficiency, energy consumption and limitations of each method. The article discusses systems with different types of hydraulic actuators, operating under passive, active and variable load during the duty cycle of the piston rod. The existing literature was analysed in terms of applicability, reduction of energy consumption of the systems and even the possibility of energy return. Attention was paid to the costs and the need for additional power sources, as well as the problems and limitations of the presented methods. Based on the simulation model, energy consumption tests were carried out in systems with an actuator loaded with a variable force. There is a comparison of all methods in terms of actuator type, load, energy consumption and the possibility of energy recovery.

Electro-Hydraulic Drive of the Variable Ratio Lifting Device under Active Load

Hydraulic systems fed by fixed displacement pumps driven by frequency-controlled electric motors can replace conventional throttling systems due to their ability to control the speed of hydraulic cylinders regardless of the value and direction of the load. These systems can improve the energy efficiency of the drive or even provide the possibility of energy recuperation during lowering. This paper presents experimental studies of the new drive system with volumetric control of the speed of the lifted/lowered payload using the example of a scissor lift. The system uses a reversible gear pump driven by an asynchronous motor fed by a frequency inverter operating in field-oriented control mode. Comparative studies of the mapping of the assumed speed of the hydraulic cylinder and platform are presented, as well as studies of the influence of the load change on the speed and positioning of the mechanism driven by the open-loop controlled system.