Download (4Mb) - Etheses - Saurashtra University

Chapter VIII Micro-hardness studies…
time a measure of intrinsic bonding of the material [4]”. “There are clear
connections between chemical bonding, hardness and dislocation mobility
[5]”. The precise definition of hardness depends entirely on the method of
measurement [6]. Resistance to the movement of dislocations will determine
the hardness of the materials [7].The above quotes suggest a complexity in
defining the hardness.
For quite some time, only metallurgists and mineralogists were
interested in hardness. However, in the last several decades, physicists and
chemists also have involved themselves in studies of hardness. Discussion of
various aspects of hardness and data on a large number of materials are
found in books [3-6], compilations [7-13] and also in several articles strewn
over many scientific journals.
Several methods are available for the measurement of hardness. Shaw
[11] has listed various hardness tests and categorized them. Nevertheless,
the most commonly used form of measuring hardness of sample is the
indentation type. An elaborate description of these methods, with their relative
merits and demerits, is given in the books by Tabor [3] and Mott [6]. In order to
describe the ISE (Indentation Size Effect) and RISE (Reverse Indentation
Size Effect) behaviors of materials, several models for relation between
applied indentation test load and indentation diagonal length have been
reported in the literature [3] and in this chapter it has been explained with the
help of Meyer’s law [6] and Kick’s law [13], Hays and Kendall’s [14] approach
and Proportional Specimen Resistance (PSR) model proposed by Li and
Bradt [15].
284