—— Mr. David Chambers
—— Neil Renato
—— Fermin Lee
—— Dalius Skinulis
—— Sun Chull Kim
The hardness of the material immediately surrounding a previously made indentation will usually increase due to the induced residual stress and work hardening caused by the indentation process. If a new indentation is made in this affected material, the measured hardness value will likely be higher than the true hardness of the material as a whole.
Also, if an indentation is made too close to the edge of the material or very close to a previously made indentation, there may be insufficient material to constrain the deformation zone surrounding the indentation. This can result in an apparent lowering of the hardness value.
Both of these circumstances can be avoided by allowing appropriate spacing between indentations and from the edge of the material.
A, The distance between the centers of two adjacent indentations shall be at least three times the diameter d of the indentation.
B, The distance from the center of any indentation to an edge of the test piece shall be at least two and a half times the diameter of the indentation.
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