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

Field Test for a Base Isolation Structure on Condition of Horizontal and Initial Displacement

There are a few isolated structures that have been subjected to seismic testing. An isolated structure is incapable of tracking, adjusting, and controlling its dynamic characteristics. As a result, field evaluations of solitary structures’ dynamic characteristics are important. The horizontal initial displacement of a base isolation kindergarten made of 46 isolation bearings is 75 mm. The method for creating the horizontal initial displacement condition is illustrated, as are the primary test findings. Horizontal initial displacement is accomplished with the assistance of a reaction wall, rods, and hydraulic pump system. To begin, we removed the building using hydraulic jacks to produce horizontal displacement of the isolation layer and then attached rods to support the building. The rods were then shot and unloaded, causing the building to shake freely, and its dynamic response and other parameters were tested. The results indicate that the natural vibration period of an isolated structure is much greater than the natural vibration period of a seismic structure. The isolation layer’s hysteretic curve as completely filled; upon unloading, the isolation layer as promptly reset; the dynamic response control effect of each was visible, but the top floor’s acceleration was magnified by approximately 1.27 times.

Transport systems load-bearing structures state diagnistics and monitoring

Aim: To provide the study and control of the stress-strain state of load-bearing structures during the operation of magnetolevitation transport systems. Methods: Experimental and theoretical studies of dynamic parameters. Results: To assess the stress-strain state of the main load-bearing structures of magnetolevitation transport systems using string superstructure it is proposed to measure the natural vibration frequencies. Conclusion: The organization of diagnostics or monitoring of changes in the natural vibration frequencies of load-bearing structures ensures the operational reliability of load-bearing structures for Maglev.

Evaluation of seismic forces under modified structural schemes in the process of vibrations

The aim of the work - development of one of the possible methods for seismic analysis that considers the inelastic behavior of structures under seismic loads. This requires the development of seismic analysis methods that take into account the change (decrease) in the bearing capacity or the destruction of individual elements until the final loss of the bearing capacity of the structure. Methods. The dependences and algorithms include determining seismic forces using the method of normal forms, which until now is the main one in solving problems of the seismic resistance theory in seismic regions, calculation formulas to calculate seismic forces at each time step are presented in the form of expansions into natural vibration modes, which regard the changes in the design scheme. The calculation is repeated at each time step as a static calculation for the action of seismic forces determined at the previous stage, before the building collapses. Results. The developed dependencies and algorithms allow to consider changes in the design scheme during vibrations at each time step, changes in the dynamic properties of the building and, as a result, the values of seismic forces. The value of the coefficient of inelastic work of structures K 1, which are given in regulatory documents, do not give fully correspond to the actual behavior of the structure under seismic influences. The proposed calculation method allows to determine the estimated values of seismic forces and their distribution taking into account the influence of damage of elements and the appearance of inelastic zones in the design process of fluctuations at each time step and to assess the dynamic behavior of the building.

Modal analysis of a membrane structure with actuators

The aim of this paper is the analysis of the modal vibration of the membrane structure. Membranes are defined as structures of the lightweight architecture and they are currently very popular. They have a long history and development, in which they have reached a stage where we can complement them with action elements, also called actuators. These elements can change their length and thus affect a stress state of a membrane, which allows more efficient use. In addition to a static analysis, it is necessary to subject structures to a dynamic analysis, in this case we deal with the natural vibration. This modal analysis deals with the first 5 mode shapes and their dependence on the change in the length of the actuators. This initial calculation will be followed by a forced vibration analysis in the future.

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.