Kinematic analysis of plastic instabilities occurring in microhardness tests

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Characteristics of plastic instabilities occurring during dynamic microhardness testing of Al-3.3 wt%Mg alloy samples have been investigated. During the experiments the load, F is increased at a constant loading rate, μ, and the indentation depth, d is detected. The measurements were carried out at room temperature. It was found that quasi-periodic motion of the indenter head sets in after a critical load, FC, has been attained. The time period, ΔTP, of the oscillations and the depth increase in one period, ΔDP, have been investigated as a function of time while the loading rate was varied between 1.4 and 70 mN/s. The dependence of FC on the loading rate has also been investigated. The dynamic Vickers microhardness, HV ∼ (F/d2) shows small amplitude oscillations around a nearly constant value. These small amplitude oscillations were found to change with the penetration rate of the indenter tip which is related to an N-shaped hardness-indentation velocity characteristic.

Original languageEnglish
Pages (from-to)2029-2037
Number of pages9
JournalActa Materialia
Issue number6
Publication statusPublished - Mar 23 1998


ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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