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2 International Journal of Applied Mechanics and Engineering

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Shear crack formatlon in cold drawing of magnesium and cobalt wires

Eickemeyer J., Falter M., Guth A.

International Journal of Applied Mechanics and Engineering

2007

Vol. 12, no 4

1173-1179

The process of surface roughness development on cold drawn magnesium and cobalt wires inside the conical drawing hole was analysed using a wire stick preparation. It is shown that the hep-metals cobalt and magnesium are prone to be roughened in the conical part of the drawing hole. This roughening, including shear localization, leads to shear cracking. Shear cracks grow from the surface into the peripheral material of the wire in the die exit zone.

Near surface shear cracks in dawn cobalt and magnesium wires

Eickemeyer J., Falter M., Opitz R., Güth A.

International Journal of Applied Mechanics and Engineering

2002

Vol. 7, no 3

771-782

Wire drawing experiments were performed under laboratory conditions using the hexagonal close packed metals cobalt and magnesium. It was experimentally shown that the material flow in the peripheral region controls the drawability of both metals at ambient temperature. Further, it became apparent that the roughness peak parameter Rz(DIN) was a reasonable measure to characterise the wire surface with regard to the drawability. Rz(DIN) < 2 micro m resulted in a successful drawing process. On the other hand, Rz(DIN) > 4 micro m led to shear crack formation and failure of the cobalt wires. Magnesium was less susceptible to surface roughness effects on shear crack formation than cobalt. Thicker lubricant films were tolerated and even needed.