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 hardness of carefully prepared median plane sections through indentations. By comparing the hardness values thus determined with those of axial sections and flats of the annealed copper cylinders compressed to different 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 below the indentation surface and along the load axis, with its magnitude being more than twice the strain given by the empirical expression epsilon = 0.2a/R, where epsilon is the strain, and a and R are the radii 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 discussed in relation to determining the uniaxial stress-strain curve of a solid using the spherical indentation test.