Удосконалення методики визначення довговічності канату

Abstract

Current technologies require more and more new standards for the reliability and durability o f hoisting ropes. W hen choosing the design o f the steel wire rope it is necessary to consider the conditions in which they will be operated and make calculations based on these conditions. The cur­rent standard-based method o f calculating the steel wire ropes does not reflect actual steel wire rope operating conditions and does not ensure the required durability. The calculations provided in the course books and reference guides underestimate the impact o f the geometric and elastic parameters o f the rope sheaves on the durability o f the steel wire rope. The rope is selected only based on the conditions on extension, while it has been experimentally proved that the wire breakage occurs pre­cisely in most cases when the rope passes through the sheave.Considering the forces that arise when a steel wire rope is rolled on a pulley, the dependence o f the tension o f the rope wire on the transition point is determined, depending on the radius o f the pulley, and the angle o f the wire twist. W hen the rope runs on a pulley, the elongation o f the wire on the convex side o f the rope, depending on the friction forces, will be distributed to the compres­sion, side on the concave side o f the rope. This elongation changes the axial force in the wire.To ensure the absence o f w ear o f the rope and the sheave, at the point o f the rope coming off the sheave, a mathematical relationship has been obtained for the maximum allowable deflection angle o f a rope coming off the sheave. The maximum allowable rotation angle o f the rope at the point o f its detachment from the surface o f the sheave has been determined based on the contact o f the rope with the sheave rim and prevention o f the rope fracture along the edge o f the groove rim.The expansion angle o f the sheave groove is determined considering the reduction the tor­sion o f the rope when it is deviated, and its amount has a very significant effect on the durability o f the steel wire rope. The thesis contains the analysis o f the influence o f the expansion angle o f the sheave groove on the allowable deflection angle o f the rope coming off the sheave.Due to the inflexibility o f the steel wire rope and the fact that its curvature in the zone o f winding on the sheave does not change instantly, but with a certain terminal speed, when the rope winds on the sheave, the contact o f the rope does not occur along the entire length o f the groove. By applying the law o f changing the load o f a bent rope, taking into account the frictional force b e­tween the sheave and the rope, a formula has been obtained to determine the angle at which the steel wire rope comes o ff the sheave. This provides a more truthful overview o f the load o f the rope when bent on the sheave.