SUBSURFACE PLASTIC STRAIN DISTRIBUTION AROUND SPHERICAL INDENTATIONS IN METALS

Plastic strain distribution around spherical indentations in annealed blocks of copper has been investigated by exploring the Vickers hardne ss of carefully prepared median plane sections through indentations. B y comparing the hardness values thus determined with those of axial se ctions and flats of the annealed copper cylinders compressed to differ ent plastic natural strains of up to 0.97, it has been found that for an indentation of size a/R = 0.52 the strain is maximum immediately be low the indentation surface and along the load axis, with its magnitud e being more than twice the strain given by the empirical expression e psilon = 0.2a/R, where epsilon is the strain, and a and R are the radi i of the indentation and indenter respectively Our strain distribution results are also different from those determined theoretically using the finite-element method. The experimental findings have been discuss ed in relation to determining the uniaxial stress-strain curve of a so lid using the spherical indentation test.