Roman Kovalchuk

Intense oscillatory phenomena occur during start-up, changes in drive mode, or braking of a lifting boom crane. These cause a significant increase in forces in the elements of its structure. Dynamic loads determine the strength of structural elements and significantly reduce the accuracy and efficiency of the machine's operations. In addition, mechanical vibrations that occur during transient processes lead to the accumulation of fatigue damage in materials. They also reduce the service life of structural elements, and therefore, the technical object as a whole. The peculiarity of the analysis of the start-up processes of drive systems is the need to take into account in detail the inertial and elastic-dissipative characteristics of mechanical links, the dynamic properties of drive engines to ensure sufficient accuracy of calculations. Moreover, the development of mathematical models for these dynamic processes frequently entails the simultaneous analysis of oscillatory phenomena arising from diverse physical mechanisms. Non-stationary modes of operation of load-lifting jib cranes for both civilian and military purposes are studied in the article. The level of dynamic loads can be reduced by developing rational operating modes of the crane and making changes to the mechanism design (installation of elastic couplings, vibration dampers, etc.). A mathematical model of dynamic processes of lifting boom cranes system with four degrees of freedom is proposed in this work. The mathematical model includes differential equations of motion of the load, the rotary mechanism with the jib and the drum. It is built taking into account the simultaneous vertical and rotational movements of the load by winding the rope onto the drum. The results of mathematical modeling are analyzed. Graphical dependences of the angles of rotation and angular velocities in time of the considered moving elements of the crane and the load are constructed. Their analysis is carried out. The possibility of using mathematical modeling to increase the efficiency of operation of a jib crane is substantiated.

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