Flat surfaces machining by the magneto-abrasive method with permanent magnet end-type heads 3. The influence of the types of the working heads on the effectiveness of the magneto-abrasive machining

Investigations of the magneto-abrasive machining (MAM) process of ferromagnetic flat surfaces by three types of end heads were carried out. The nature of the change in the magnitude of the magnetic induction in the working zones was determined. The influence of technological parameters of the machining process was investigated, such as the feed rate of the working heads, the frequency of their rotation about their axis, the size of the working gaps on the change in the parameters of the microroughness of the machined surfaces - Sa, Sp, Sv, the frequency distribution of heights microroughness and size of the supporting surface of the profile. It was shown that the level of roughness achieved after MAM is practically the same and does not exceed, under rational conditions of the MAM process, the values Sa = 0.05-0.07 μm, Sp = 0.2 μm and Sv = 0.39 μm with the only difference that the MAM process by the heads of the "brush-half of torus" type are being realized with increased productivity, especially in terms of reducing waviness and individual elements of the heredity of machining, determined by such factors as depth and feed rate during milling. The kinetics of the formation of a microprofile of surfaces is shown under various technological conditions of the MAM process.

Kramers nodal line metals

Recently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) can be Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta. In this work, we show that all achiral non-centrosymmetric materials with SOC can be a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting time-reversal invariant momenta. The KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type. Interestingly, all the electrons on octdong Fermi surfaces are described by two-dimensional massless Dirac Hamiltonians. These materials support quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they can be either KWSs or KNLMs.