Improvement of agricultural machines reliability by means of controlled tightening

Abstract

One of the reasons leading to accidents is the formation of cracks in machine parts. Therefore, when designing it is quite relevant to solve a problem related to the control of internal forces, in order to create adaptive machines which automatically change the stress cycle amplitude in dangerous sections, so that their maximum values don’t exceed the endurance limit. The research objective is to develop the additional groups of elements united in one kinematic chain and fastened on the designed machine; they will change its stress-deformed state in operating time in a way necessary for engineer. The system of additional elements (parts), creating the internal forces which reduce or completely compensate the internal forces from rated external load in the stressed (main) structure at the set time point, can be called the controlled tightening. The paper describes the possibility of use of a three-disk six-rod almost instantly changeable system for creation of high controlled force, with the aim of change of stress-deformed state of the machine framework with a slight controlling torsion torque. According to the results of computer analysis of the stress state of proposed system, the diagrams are built; they show the change of internal forces in rods. The combination of angles is found, that provides the maximum force in each rod, with constant torsion torque and tilt angle of the control rod. The sizes of disks and lengths of rods are matched for the purpose of achievement of maximum controlled force. The conclusion is drawn that it is more preferable to change the controlling torsion torque synchronously with changing of stress level in the most loaded sections of the main machine structure, by transferring of torsion torque on controlled tightening from any rotating shaft of machine by means of checkblocks, or from an element of the machine framework under torsion, by system of torsion bars.