SENSITIVITY OF STRENGTH, RIGID AND DYNAMIC CHARACTERISTICS OF THE CONSOLE ROTOR TO VARIATION OF DESIGN PARAMETERS

The analysis sensitivity of strength, rigid and dynamic characteristics of the console rotor to variation of design parameters in paper describes The speed of rotation of the shaft, the material of the impeller vary. The dependences of radial and axial displacements on the angular velocities of rotation and the modulus of elasticity of the impeller material are established. For objects of the type of rotary systems with a cantilever arrangement of the impeller, not one, but a set of criteria has been introduced into consideration, which should be taken into account in the research of this type of objects. The tendencies of change of the first and second critical rotational speeds from the modulus of elasticity, rotor rotational frequencies and density of the impeller material are also determined. On this basis, recommendations have been developed for determining the design parameters of the rotor part of the air blower with a cantilevered impeller. Keywords: air blower; critical rotation speed; natural vibration frequency; rotary system; stress-strain state

ANALYSIS THE REACTION OF LIGHTARMOR MACHINES ON THE ACTION OF POLYPULSES FORCES

In modern conditions, lightarmored vehicles with powerful weapon modules are widely used in the armies of different countries. These modules are equipped with small-caliber automatic cannons, which have a rate of fire of several hundred rounds per minute and a high level of recoil forces. Moreover, there are tendencies towards an increase in the rate of fire and the caliber of weapons (and, accordingly, recoil forces). Considering that weapon modules rely on the lightarmored vehicles skeleton, which has higher responsiveness characteristics than heavy combat vehicles in terms of weight, the problem of determining the reaction of the «weapon module - armored hull - suspension» system to the action of recoil forces in order to ensure on the one hand, the strength of armored hulls, and on the other hand, reducing the load on the guidance and stabilization system of weapons during firing.To study the response of elements of lightly armored vehicles to the action of recoil forces when firing a burst of combat modules, numerous models have been built with a small number of degrees of freedom. Using these models, the reaction of a dynamic system to the action of a number of impulses was investigated.These impulses caused by the action of recoil forces when firing shots from combat modules. Keywords: lightlyarmored vehicle; weapon module; small-bore automatic cannon; recoil force targeting and weapon stabilization system; dynamic system; numerical modeling; method of finite elements; natural vibration frequency

An Indirect Method for the Quantitative Identification of Unstable Rock

Under the influence of continuous external factors (rainfall, earthquake, construction, etc.), the slope rock mass in a stable state gradually transited to an unstable rock, and then the unstable rock collapsed. However, a safety factor can identify the occurrence of failure but cannot identify the transition of stable rock to unstable rock; thus, it cannot realise the quantitative identification of unstable rocks. In this study, safety factor of adhesion (SFA ) and a relatively objective analysis method are proposed to effectively identify unstable rocks. SFA can be calculated by natural vibration frequency and applied as a mechanical index to judge unstable rock. When SFA is less than 1, the rock is defined as an unstable rock. Compared with the traditional method, the new method has the merits of simple operation, low cost and higher efficiency, and provides a relatively complete quantitative evaluation index and judgment criteria for quantitative identification of unstable rocks for engineers who are engaged in early warning and prevention of rock collapse.

Application of Elastic Fastenings of Equipment to Increase Vibration Frequency of the Wagon Body

Improving dynamic performance is a priority when designing new rolling stock. The frequency of natural bending vibrations of the body is one of the most important standardised indicators, a preliminary assessment of which allows obtaining optimal body designs.The objective of the work is to assess the prospects for the use of elastic fastenings of equipment to increase the natural vibration frequency of wagon bodies of suburban electric trains. Calculations were based on the finite element method and block Lanczos method. It is shown that it is advisable to use the rigid area tool and linearly elastic finite elements to calculate the frequencies in the simulation. The main ranges of fastening stiffness are highlighted, where the effect of using elastic supports is different. It is proposed to determine the stiffness of fastenings according to a given vibration frequency of the equipment. When the equipment is rigidly attached, the relative mass of the equipment does not affect the body bending vibration frequency. With elastic fastening, a greater effect can be achieved with a larger relative weight of the equipment. The effect of using resilient mounts increases with heavier equipment located closer to the centre of the body.It is shown that the effect of shear admittance of fastenings on the body vibration frequency is within 1 % and may not be considered in the simulation. In the considered example of a wagon body of a suburban electric train, the use of elastic supports allows an increase in the frequency of oscillations of the body by 3–10 %.

Increase of Technical Condition Control Efficiency of Marine Railways

The paper presents the result of solving a relevant scientific and practical problem, which consists in the development of methods and diagnostic tools and improving the efficiency of monitoring the technical condition of transport equipment, in particular elements and units of marine railways, through the introduction of an automated system for diagnostics and monitoring of technical condition, which provides an increase in the reliability of diagnosis, reducing the time and cost of diagnostics. The analysis showed that the existing methods for determining the main parameters of the technical condition of elements and units of slips, which are the basis for reliable diagnostics of the technical condition, need to be improved. A method has been developed for monitoring the integrity of the main elements of marine railways based on the analysis of the temperature and natural vibration frequency of the main elements, which, in contrast to the existing methods, gives an error in measuring the signal frequency of less than 0.05%, which makes it possible to determine defects at early stages of their development.

On the question of finding a universal mechanism for the transmission of sound wave energy in iron during heating and deformation

The paper presents a theoretical analysis of the experimental data on the ultrasound speed change in iron during heating and elastic deformation. The mathematical models proposed for assessing the change in the ultrasound speed based on the “adiabatic approximation” method do not explain, using one model, the change in the ultrasound speed in iron during heating and elastic deformation. During theoretical analysis, a new model of ultrasound wave transmission has been proposed, in which the wave energy propagates in the volume of the interatomic bond, namely in the loop, which is formed by the “collectivization” of valence electrons located in the outer orbit of atoms. The new model explains why with an increase in the interatomic distance a, the crystal lattice parameter, and an increase in the natural vibration frequency of atoms Vat during heating and elastic deformation, in one case (heating), the speed of the sound wave decreases, but in the other case (elastic deformation), the speed of the wave increases with a general decrease in the temperature of the rod.

Amplification Effect of Ground Motion in Offshore Meandering Sedimentary Valley

A sedimentary valley has a visible amplification effect on a seismic response, and the current 2D topographies cannot truthfully reflect the twists and turns of a large-scale river valley. Taking a sinusoidal curved valley site as a model, the dynamic finite element analysis method and the introduction of a viscoelastic artificial boundary were developed to study the 3D seismic response of the dimensional topographies in the homogeneous curved valley to vertical incident P, SV, and SH waves. The results showed that the bending sedimentary valley site earthquake presented significant features simultaneously, depending on the number of valley bends, the frequency of the excitations, the shear wave velocity of sedimentary soil, and the depth of the river valley. The surface displacement amplitudes of three-dimensional meandering sedimentary valleys are significantly different from those of sedimentary basins. The amplification area of the meandering valley is related to the angle between the valley axis and wave vibration direction, and the amplification effect is significant when the angle is small. The movement in the main direction showed a center focus, and the secondary y-direction displacement showed both a central focus and an edge effect. When the frequency of the incident wave was close to the natural vibration frequency in a specific direction, the movement in this direction significantly increased because of the resonance effect. The displacement amplitude of the surface was proportional to the depth of the river valley, and the surface displacement was presented in different forms based on the frequency of the excitations. The results provided some guidance for the earthquake resistance of the curved valley site.