REGULARITIES OF DISTRIBUTION OF WIRE DEFORMATION IN MULTILAYERED STRAND AT CIRCULAR CALIBRATION COMPRESSION

The mechanism of plastic crimping of the strand has been identified and justified, as the process of formation of arches: a strong arch of wires, the appearance of each leads to a change in stressed state of the strand at reduction stages. It was established that before appearance of the first arch, wires of the outer layer and the central wire are the most priority to deformation, with the initial absence of side contacts. After appearance of each arch, stresses in wires of the arch layer become predominantly compressive, which temporarily prevents the given layer from actively deforming, up to the formation of arches in all other layers of the strand. After formation of all arches, wires of the upper layer again become the most priority to deformation. Central wire of the strand is overstrained in relation to all other wire strands at all stages of compression. The developed technique allows analyzing the degree of working out of each wire of a lock at a certain amount of reduction. It reflects the features of a multilayered strand deformation: sharp increase in width of the newly appeared contact at almost constant reduction; arches formation; non-simultaneous occurrence of new contacts in layers of strands due to the geometry of the strand and direction of the wires displacement. Application of the proposed technique allows to make rational designs of strands and ropes subjected to small and medium circular plastic crimping, as well as to determine the necessary amount of compression of strands and ropes of a particular design, proceeding from the conditions for retaining the flexibility of the rope and forming the required contact geometry of the wires. It was found that for strands with a diameter of 7.68 mm in the construction of 1 + 5 + 5/5 + 10, the most uniform development of the strand and the contacts is ensured during the reduction in the range of 3.74 < Q < 7.06 %. Intensive filling of the gaps in the strand begins at Q = 7.06 %, which determines the subsequent deformation as the limiting for the ropes working on bending both for performance characteristics and for the conditions of operation of the round caliber of a roller die.

Photoemission in Geiger-Müller counters

Nunn May (1) has developed the theory of the mode of action of the Geiger-Müller counter in terms of the photoemission produced in the electron avalanches constituting the discharge of the tube. An avalanche of electrons in the counter produces excitation and ionization of atoms and molecules in the neighbourhood of the positive central wire: the photons liberated by these in their turn release from the walls of the counter the photoelectrons which initate the following avalanche. Direct experimental evidence that such a sequence of events may occur is to be found in the work of Greiner (2).