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- Autors
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Chayun I. M., Vovk P. E.
- Issue
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Hoisting and transport equipment, 2020, №2(63)
- Pages
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81-93
- DOI
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10.15276/pidtt.2.63.2020.07
- Abstract
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A technique has been developed for the theoretical determination of the strength P_e and deformation characteristics of the limiting elastic state of ropes for four loading schemes in the initial state, and also with taking into account the operational breakage of the wires. Two schemes are stretching with winding onto the drum with free suspension of the load and with the load in the guides, the other two schemes are stretching the straight rope without bending. As the ultimate elastic, is taken the state of the rope, in which one of the wires (or a group) reaches deformation of the limit of elasticity (yield). Tensile force P_e of the ultimate elastic state significantly depends on the loading scheme, rope design and the presence of wire breaks. For the studied loading schemes and various rope designs, the forces are presented in relative measurement ¯P_e=P_e⁄(P_C ), where P_C is the total breaking strength of the wire ropes. When stretching with a freely suspended load ¯P_eis 0,22 – 0,31 (lower values when stretched with a winding on the drum); when loaded in guides ¯P_e is 0,61 – 0,72. The main reason for the low values of ¯P_e characteristics is the unevenness of the tensile strains of the wires in the rope. This is primarily due to the torsional deformation θ of the rope, to the second due to bending deformation χ.
The values of the average conditional stress σ show that their level in the ultimate elastic state of the ropes is higher than this parameter at working (operational) loads. This is useful to consider when analyzing standard safety factors for specific rope loading schemes.
The presence of wire breaks leads to the formation of stiffness effects: longitudinally bending G_13,G_14; torsionally bending G_23,G_24, as well as bending-bending G_34. When the ropes are stretched in a state with these stiffnesses, additional bending and torsion deformations of the rope occur, and, therefore, deformations of the wires both in the direction of increase compared to the nominal state, and in the direction of decrease. The characteristics of ¯P_e in states with wire breaks under tension in the guides decrease, and with a freely suspended load they remain almost unchanged, because torsional strains of the ropes change insignificantly.
- Keywords
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rope, yield strength, elastic state, stress, strain, friction.
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