On calculation of stress-strain state of steel closed ropes in extension and twisting. Part 2. Influence of torsion on the stress-strain state of closed rope

Abstract

Comparative analysis of the results of determination of stress-strain state in a closed lifting rope during extension and twisting was conducted via analytical calculation according to the linear static equations and computer-aided finite element modeling. Computer modeling allows to establish the features of variation of internal axial forces and torques in the layers that are laid with different directions. It makes possible to predict workability of a closed lifting rope during operation. The most intensive redistribution of internal forces and torques in the internal and subsurface layers during rope turns under the effect of external torque was found out in comparison with extension. Decrease of the torque and axial force values to zero in the deposited external layer during its untwisting testifies about switching this layer off the operation and possibility of rope lamination in the case of external pressure absence. Internal compression of subsurface layer from the side of external rope layer, in its turn, decreases possibility of stability loss (opening) of this layer during its twisting. Deviation from the common rule for variation features of relative elongation ε during joint extension and twisting was shown during modeling. So, external untwisting torque tries to extend the rope (increase of ε), while twisting torque tries to compress it (decrease of ε), what is connected with influence of gap values between the rope elements (wires and layers) on distribution of the contact stresses between them during twisting.