Chemical and Petroleum Engineering, Vol. 54, Nos. 1–2, May, 2018 (Russian Original Nos. 1–2, Jan.–Feb., 2018)
Ural Federal University, Ekaterinburg, Russia; e-mail: Krasilnikov1951@yandex.ru. Translated from Khimicheskoe i Neftegazovoe Mashi-
nostroenie, No. 2, pp. 29–33, February, 2018.
COMPLEMENTARY PRODUCTS AND DEVICES
CALCULATION OF SHEAR FORCE OF THIN, HIGHLY
COERCIVE PERMANENT MAGNETS PRODUCED FROM
THE ALLOYS KS-25DTs AND Ch36R IN MAGNETIC
SYSTEMS AND MAGNETIC COUPLINGS
A. Ya. Krasil’nikov UDK 621.825.038
Use of a standard technique for calculating the shear force of highly coercive KS-25DTs and Ch36R thin
permanent magnets in magnetic systems and magnetic couplings is considered. Based on the results of the
study, correction factors may be introduced into the standard technique used to determine the shear force
in magnetic systems and magnetic couplings with thin magnets.
Keywords: magnetic coupling, magnetic system, permanent magnet.
Magnetic systems and magnetic couplings with highly coercive permanent magnets are used today in hermetically
sealed machines and different types of instruments (magnetically driven conveyor belts, pumps, vacuum cleaners, mixing
devices, and others). To achieve failure-free operation of such machines, the permanent magnets are produced in the form of
rectangular prisms with thickness of the magnet between the magnetic poles 8–10 mm. Permanent magnets 4 mm thick are
often used in hermetically sealed equipment produced abroad. This makes it possible to reduce the cost of manufacturing
equipment, though the operational reliability falls in this case (demagnetization of the magnet occurs once the magnetic sys-
tem or coupling has been heated above the stabilization temperature of the highly coercive permanent magnet, and the mag-
netic system or coupling fails). If a magnetic system or coupling that has failed is replaced, the tractive force (shear force)
between the different sections of the magnetic system or half-couplings of the magnetic coupling has to be calculated .
Previously developed techniques for calculating the shear force may be applied for highly coercive permanent magnets with
thickness in the range 8–10 mm .
Let us consider how to calculate the shear force for thin highly coercive permanent magnets produced from alloys of
rare metals, such as samarium–cobalt (KS-25DTs) and neodymium–iron–boron (Ch36R), and 4 mm in thickness. A diagram
illustrating the process of measuring shear forces is presented in Fig. 1.
The magnet has dimensions 20 × 40 × 4 mm (width A × length B × thickness H). The shear force F
is maximal when
the upper section of the magnetic system is shifted relative to the lower section by one-half the width of the magnet (A/2). In the
course of performing the measurements, the air gap δ between the sections of the magnetic system is varied from 2 to 10 mm.
The variation in the speciﬁ c shear force ƒ
as a function of the size of the air gap δ between the sections of the magnetic
system is illustrated in Fig. 2a, for four groups of permanent magnets produced from the alloy KS-25DTs (technical speciﬁ -
cations TU 48-4/0531-6–92) and for ﬁ ve groups of permanent magnets produced from the alloy Ch36R (TU 6391-002-
55177547–2005) in Fig. 2b.
The variations in the speciﬁ c shear force (cf. Fig. 3a, b) are linear in nature. The computed and experimental depen-
dences of the speciﬁ c shear force as functions of the air gap for the ﬁ rst group of permanent magnets produced from the alloy
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