The Effects of the Punching Process Upon the Magnetic Properties of Steel Laminations

  • L.A. Walters

    Student thesis: Master's ThesisMaster of Science (by Research)


    The punching process used to stamp out iron laminations
    Causes a deterioration in the magnetic properties of the
    lamination material. This investigation is concerned with an
    experimental examination of the deterioration and finding the
    magnitude of the change in material properties due to punching.
    The punching effect is considered in terms of the ratio of
    total surface area of the lamination to the punched area, the material
    thickness and the punching tool clearance.

    Annular laminations of various sizes are punched out of sheet
    material and their magnetic properties measured under static and
    dynamic conditions. The material is then annealed and the tests
    repeated. A particular feature of the investigation is the
    equipment used for the dynamic tests. This consists of an
    electronic hysteresigraph, which maintains the rate of change of
    flux density constant for each hysteresis loop, used in conjunction
    with a specially designed test rig and an on-line digital

    A metallurgical analysis of the material is made so as to
    obtain the optimum temperature for annealing and also to assist in
    determining the extent of the plastic deformation. The deformation
    of the punched edge is also examined in terms of its micro-hardness
    and the Kerr optical method is used to investigate the reduction
    in permeability in the region of the punched edge.
    Date of Award1972
    Original languageEnglish


    • punching process
    • magnetic properties
    • magnetism
    • steel
    • steel laminations
    • electrical enginieering

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