Express method for the testing of tribotechnical properties of lubricants

The paper presents the results of experimental study of the tribotechnical properties of lubricants on a unit that simulates the geometric, kinematic and force similarity of well drilling conditions. Bearings with different radial clearances and the same chemical-thermal treatment were investigated. Data registration was carried out on cathode, loop oscilloscopes and electronic recorders. The load on the bearing, the moment of rolling resistance on the journal, and the angular speed of rotation of the outer race were recorded. The temperature was registered using artificial and semiartificial thermocouples. A strobotachometer was used to determine the portable speed of the rolling bodies. The external appearance of all rolling elements was investigated, metallographic analysis of thin surface layers of all rolling elements was carried out, mathematical processing of test results was carried out. It is shown that for the express assessment of the tribotechnical properties of lubricants, the amplitude value of the oscillation of the rolling resistance moment can be used. Keywords: friction; lubrication; tribotechnical Properties; drilling.

Study on the training model of football movement trajectory drop point based on fractional differential equation

To study the landing point of the curved football track, the dynamic differential equations of the football were derived in this paper. The air resistance moment was taken into account, and the rotation axis was no longer confined to the vertical direction. We compare various soccer movement regularity of different initial angular velocity 0, in turn, using standard numerical methods to solve differential equations, the selection of the initial angular velocity of three typical 0s has been carried on the detailed numerical study, and the results show that: in the same velocity V play football, corresponding to different initial angular velocity 0, the movement of football is an obvious difference. Conclusion: For the same V = 5 + 28 + 11 m/s, when no rotation Ω 0 = 0, the trajectory of the football is the usual trajectory of the projectile. When 0 = 2 − 2 + 16 rad/s, the trajectory of the football is a typical banana ball trajectory; When 0 = 13+0+0 rad/s, the trajectory of the football shows the phenomenon of left-right fluttering, similar to the fallen leaf ball.

Characteristics of Combined Motor of Separator Drive

The paper describes the characteristics of a combined motor of a separator drive. Simulation experiment provided the characteristics of a combined motor of a separator drive, which allow considering the impact of the line voltage parameters (the supply voltage amplitude and frequency) and the resistance moment created by the separated product on the electromagnetic torque of a combined motor of the separator drive and the rotation speed of the working body of the separator with a combined motor.

Evaluation Methods of Vertical Subgrade Reaction Modulus and Rotational Resistance Moment for Seismic Design of Embedded Foundations

In a seismic design of embedded foundations, the vertical Subgrade Reaction (SR) acting on a foundation bottom surface and the Rotational Resistance Moment (RRM) generated by the SR are calculated using an SR Modulus (SRM). The SRM and RRM depend on both ground rigidity and Foundation Width (FW). However, the SRM and RRM calculation methods adopted in design codes might not properly consider their FW dependency. In this study, SRM and RRM evaluation methods for embedded foundations subjected to a seismic load were examined by conducting a two-dimensional finite element analysis under the condition where ground rigidity and FW were changed considering the nonlinearity of the ground. The results show that when the seismic load is large and the nonlinearity of the ground appears, the SR distribution is different from the assumption in the design code. The FW dependency of the SRM was lower than the assumption of the design code. Furthermore, methods to calculate the SRM and RRM in accordance with the FW and ground rigidity are proposed.

Improvement of mooring tests of main engine running to fixed pitch propeller

The most important stage in vessel’s construction is acceptance tests. By testing the main power plant of the vessel the design solutions adopted to ensure stable operation of the main engine and the propeller are checked. Such a check of the main engine according to design characteristics at the quay wall can significantly reduce sea trials cost. In practice, the peculiarities of the propeller operation at zero free-flow velocity at the quay wall limit the operating modes of the main power plant and the possibilities of mooring tests. There are considered the traditional and innovative simulation methods and tools used in mooring tests. The methods allow unloading the engine in terms of torque bringing its operation mode closer to the design parameters. An urgent scientific and technical problem has been solved to reduce the mechanical stress of the main engine, which operates according to the mooring characteristic on a fixed pitch propeller. The factors influencing the value of the resistance moment of the propeller at a zero vector of the incident flow are determined. Possible directions for improving the acceptance tests of the main power plant by supplying an additional environment, i.e. air to the suction surface of the propeller blade, are substantiated. In the complex of computational fluid dynamics, a computational model of a fixed pitch propeller has been created. The amount of air required to change the propeller operating mode has been estimated. Resistance moment of the propeller for various methods of air supply to the propeller has been analyzed. Additional means of controlling the main engine operating mode at the stages of the ship's life cycle are proposed.

Design and Test of Auxiliary Steering System of High Clearance Sprayer Chassis Based on Self-steering Structure

A hydraulic assisted steering method was proposed to solve the problem of steering instability caused by insufficient reverse resistance moment of wheel hub motor in four-wheel independently electrically driven high clearance sprayer. Firstly, the principle of steering chassis structure of four-wheel independently electrically driven high clearance sprayer is briefly introduced. On this basis, hydraulic auxiliary steering system is designed. Then a simplified 2-DOF vehicle steering model is established to analyze the Angle control of the auxiliary steering system. Finally, simulation and road surface test are carried out respectively to verify the performance of steering and auxiliary steering coordination control. Under the working conditions of the steering system alone and the steering system and the auxiliary steering system together, the four-wheel electric drive sprayer carried out the obstacle crossing test and the downslope test with the slope of 15° respectively at the speed of 1 m/s on the smooth road surface. The test results show that in the downhill test, the maximum tracking deviation of the steering system alone is 6.1°, the maximum tracking deviation of the steering and auxiliary steering coordination is 0.9°, the maximum tracking deviation of the steering system alone is 12.0°, and the maximum tracking deviation of the steering and auxiliary steering coordination is 1.2° in the obstacle breaking test. The test results verify the feasibility and stability of the hydraulic steering system proposed in this paper. The system has good test performance and can meet the practical requirements.

Moment-less Arches for Reduced Stress State

This paper presents a study of two-pin arches of constant cross-section that are moment-less under statistically prevalent (permanent) load. The arches are defined by analytical form-finding previously reported in [1]. The work provides guidance regarding the solution process, and expressions for reactions and axial forces. New analytical results include the derivation of the arch length, and a method for finding co-ordinates of individual arch segments in pre-fabricated construction. The accuracy of the shape prediction for inextensible moment-less arches is good, compared to the results from elastic models. Case studies report on medium and large-span arches, with the latter resembling the iconic Hoover Dam arch. Comparative studies of the moment-less and conventional arch forms (mostly of parabolic configuration), are carried out using permanent and variable loads. Additionally, the Hoover Dam arch is analysed for a discrete load transfer from the deck. Circular arches are analysed for the permanent load only, and are shown to be extremely inefficient in load resistance. Moment-less arches are found to provide a minimal stress response to loading and require least amount of material – a feature observed in natural objects. These characteristics are important from a durability perspective – a key concern for our future infrastructure.

Experimental Research on Bending Bearing Capability of Grouted Double Mortise-Tenon Joint for Prefabricated Metro Station Structure

The grouted mortise-tenon joint, invented as the connection between the large prefabricated elements, is the most important component in the prefabricated underground structures. This paper conducts analysis of load-carrying capacity performance and failure mode with 1 : 1 prototype test in key working direction of different double mortise-tenon joint types for the prefabricated metro station. The resistance moment is developed and used to analyze the bending bearing characteristic curve, and the corresponding test results of each stage of the characteristic curve are described in detail. In addition, the bending bearing performance of different types of double-tenon joints under different load conditions is compared. The test results clarify the ultimate failure mode of double-tenon joint and the variable bearing capacity characteristics of the joint with the increase in axial load and explain the bearing performance of each stage. It is also found the auxiliary pretightening device is helpful to delay the appearance of cracks and improve the bearing capacity, especially when it is set on the tension side. The research results have important application value for the joint design of prefabricated metro station structures.

Adaptive Neural Network Control with Fuzzy Compensation for Upper Limb Exoskeleton in Active Spacesuit

In order to meet the maneuverability requirements of spacesuits for future manned planetary exploration, the concept of an active spacesuit based on the joint-assisted exoskeleton technology is presented. First, by studying the kinematic characteristics of the operator wearing the simulated spacesuit in different gravity environments, we developed a prototype of the upper limb exoskeleton. Then, the resistance moment of the simulated spacesuit was roughly obtained to match the operator’s motion range, being utilized to design the resistance moment model. Considering the unknown resistance moment effects in the active spacesuit and the uncertainties of the exoskeleton’s dynamics model, an adaptive neural network control with fuzzy compensation was developed to drive the upper limb exoskeleton’s tracking desired trajectories. Experimental studies were carried out using an upper limb exoskeleton to illustrate that the proposed method has excellent trajectory tracking performance and good adaptive ability to the gravity environment changes.

Dynamics of the hydraulic fluid power of rotation of the hose concrete pump

Purpose. Search for ways to improve the technical level of the hydraulic fluid power of a hose concrete pump by analyzing the hydraulic schematic diagram and dynamic characteristics depending on the moment of resistance, moment of inertia and properties of the working fluid. Method. The construction of a mathematical model of the dynamics of a hydraulic fluid power is based on Newton's laws of mechanics, Pascal's law and the continuity equation for fluids. The dynamics study was implemented using the VisSim package. The results of studies of the influence of variable parameters on the rotor speed and pressure in the discharge line of the hydraulic motor are presented in graphical form. Results. It was found that in a volumetric hydraulic fluid power of a concrete pump with rotor rotation from a gerotor hydraulic motor, there are significant fluctuations in pressure and speed, due to the kinematics of the pump, temporary factors of the increase in the moment of resistance and supply of the working fluid to the hydraulic motor with the throttle method of its regulation. The ratio of the maximum and steady-state pressure values is 1,9 times obtained for hydraulic motors of different displacement. The possibilities of reducing the dynamic loading of the hydraulic fluid power by improving its hydraulic schematic diagram and control algorithm are shown. Conclusion. Recommendations have been developed for reducing dynamic loads in a hydraulic fluid power by modernizing the hydraulic circuit diagram by introducing electrohydroautomatics devices and changing the algorithm for starting and stopping the pump.