Impression Plasticity and Creep in Hard Crystals

  • E. Jill Brookes
  • Chris A. Brookes

Abstract

In 1973, Brookes and Green1 first introduced the principles of the’ soft’ impressor technique by using copper cones to deform (001) surfaces of single crystal magnesium oxide (MgO). They employed an etch pit technique2 to show that, for otherwise identical experimental conditions, the mean contact pressure (Pm) due to the blunted copper cone (i. e. about 0.53 GPa) did not form a visible impression but, nevertheless, produced a dislocated volume in the bulk of the crystal which was about the same size as that due to a diamond (Knoop) indenter where the mean contact pressure was about 6 GPa. Thus, it was established that hard crystalline solids could be plastically deformed by contact with softer materials at pressures of at least one order of magnitude less than the relevant measured hardness value. In addition, they suggested that cumulative deformation, as in repeated sliding over the same track, could lead to the mechanical wear of hard materials by softer ones. Those earlier suggestions have been investigated and verified for magnesium oxide and a wider range of crystals at room temperature3–10 and for diamond at elevated temperatures11–16.

Keywords

Zinc Fatigue Titanium Anisotropy Graphite 

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Copyright information

© Springer Science+Business Media New York 1995

Authors and Affiliations

  • E. Jill Brookes
    • 1
  • Chris A. Brookes
    • 1
  1. 1.Department of Engineering Design and ManufactureUniversity of HullHullUK

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