Relation between the reduced and unreduced hardness in nanomicroindentation tests |
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Authors: | S I Bulychev |
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Institution: | (1) Moscow State Industrial University, 109280 Moscow, Russia |
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Abstract: | Hooke’s law is generalized to the case of arbitrary elastic or plastic indentation
, where ɛ=q/E
r is the elastic strain, q is the average pressure over the contact area, E
r is the reduced elastic (Young’s) modulus, A is the projected area of the contact, w
1 is the deformation in elastic indentation by a flat punch. On this basis a relation is obtained between the reduced hardness
H and unreduced hardness H
h, which depends on the ratio w
s/w1=m
s; w
s is the elastic deformation along the perimeter of the indent, and m
s≅0.78. It is shown that the correction ΔE
r to the elastic modulus E
r determined from the condition of linearity of the initial part of the unloading diagram, is ΔE
r=0.27(ΔP/P
m), where ΔP is the value used in the calculation of E
r for the length of the linear part of the diagram, reckoned from the maximum load P
m. It is shown that for metallic construction materials of medium hardness one has q=HM, where HM is the Meyer hardness. With increasing HM and increasing angle ϕ at the tip of the indenter, the ratio HM/q grows by an exponential law.
Zh. Tekh. Fiz. 69, 42–48 (July 1999) |
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Keywords: | |
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