Comparison Of Mechanical Characteristics Research Articles

INCREASING THE ENERGY EFFICIENCY OF ELECTRIC DRIVES OF SUBWAY CARS

The article proposes the use of a frequency-controlled drive for regulating asynchronous electric motors used on subway cars. The proposed solution creates all the grounds for increasing the energy efficiency of electric cars and, in general, the entire metro. Taking into account that the subway is one of the most used types of urban transport in large cities of Ukraine and at the same time consumes a significant part of electricity, therefore, in the conditions of rising prices for energy resources, these issues become the most urgent. It is shown that the methods of regulation of subway engines are not covered widely enough in scientific research, but the methods of increasing the energy efficiency of drives generally accepted in industrial spheres are a developed direction. This reveals the possibilities of integrating the developed methods for application on subway cars. The use of a frequency converter, which changes the frequency of rotation of the motor rotor by changing the frequency and amplitude of the supply voltage using vector and scalar control, is a generally accepted method of motor regulation. There are a number of conflicting findings in research regarding the use of scalar or vector control, with some favoring the induction vector control system. However, a clear regulation is not required to regulate the operation of metro engines. Therefore, the article considers scalar control, which has not lost its importance due to the ease of implementation and adjustment and is used in various areas of industry and transport. The parameters of the STDa 280-4B-UK type STDa 280-4B-UK traction asynchronous traction motor with a capacity of 180 kW, manufactured by the EMIT Cantoni Motors company, which are installed on subway cars of the 81-7036/7037 series, were used for the study. The parameters of the T-substitution scheme of the asynchronous electric drive and the numerical values of the vectors of the asynchronous motor were calculated. To analyze the operation of an asynchronous motor, the article uses the mechanical characteristic of the dependence of the motor torque on slippage at certain frequency values. It has been established that an asynchronous motor can operate stably only in a limited slip range, when the moment reaches its maximum value and the motor stops, as it has a load limit. The main reason for this is the increase in the influence of the active resistance of the stator winding when the supply voltage frequency decreases. The solution to this problem is the introduction of IR-compensation into the control system of the electric drive, which provides positive feedback on the stator current acting in the voltage channel. To demonstrate the effect of IR compensation, a comparison of mechanical characteristics was made before and after its introduction into the control system. Therefore, it was proved that the application of IR compensation is a promising direction of work, as the value of the electromagnetic moment increases significantly in the case of a low control frequency. Keywords: energy efficiency, asynchronous electric motor, subway, electric drive, scalar control, IR compensation.

Compensation for the Shock Absorbing Function of Low Arch Foot Based on a Comparison of Mechanical Characteristics

Compensation for the Shock Absorbing Function of Low Arch Foot Based on a Comparison of Mechanical Characteristics

Finite Element Analysis of Composite Soil-Nail Retaining Structure in Foundation Pit Engineering

Base on general three dimension nonlinear numerical simulation software, mechanism of composite soil-nail retaining structures in foundation-pit engineering are analyzed in this paper. Research contents include construction process simulation of excavation by steps, soil nailing installation and panel manufacture etc. Tension distribution range of soil layer, bottom heaving in the pit and axial force distribution along nail etc. are analyzed through the comparison of mechanical characteristics between computational results and field test data in the case of micro pile composite soil-nail support engineering. The action mechanism and working performance of composite soil-nail retaining support are also systematically studied and theoretical basis can be provided in optimal design, popularization and application.

Optimization Simulations of Support System by Composite Soil-Nail Retaining Structure

Mechanism of composite pre-reinforced micro pile soil-nail and pure soil-nail retaining structure in foundation-pit engineering are analyzed in this paper through general three dimension nonlinear numerical simulation software. Research contents include whole construction process simulation of construction such as excavation by steps, piles and soil-nail installation and panel manufacture etc. By the comparison of mechanical characteristics between the pure soil-nail and composite soil-nail retaining structures in the same slope engineering example, differences of tension distribution range of soil layer, deformation features, mechanical characteristics of support and axial force distribution along nails etc. are analyzed. Research results are verified by in-site projects and measured data. The action mechanism and working performance of composite soil-nail retaining support are also systematically studied and theoretical basis can be provided in the similar application.

Comparison of mechanical characteristics between semi-liquid state and semi-solid state in Al–Mg alloys

In our previous works, tensile test devices for both semi-liquid and semi-solid aluminum alloys were developed. In this report, comparison of mechanical properties such as ultimate tensile strength (UTS) and fracture strain between semi-liquid and semi-solid Al–Mg alloy was examined. Difference of the mechanical properties will be caused by the microstructural change during heating process in the tensile test of semi-liquid alloy. By constant load creep test to the semi-liquid alloy, about 90% deformation of permanent and 10% of elastic deformation were found. Thus, in the thermal-stress analysis, solid–liquid co-existence aluminum alloy should be dealt as visco–elastic or viscoelasto–plastic material rather than elasto-plastic material.

Comparison of Mechanical Characteristics of Deployment for Expandable vs. Fixed Interbody Cages: Implications for Premature Clinical Failures

Comparison of Mechanical Characteristics of Deployment for Expandable vs. Fixed Interbody Cages: Implications for Premature Clinical Failures

Comparison of mechanical characteristics between segments and whole excited cardiac muscle by means of new servo-control system

Comparison of mechanical characteristics between segments and whole excited cardiac muscle by means of new servo-control system