Microanalysis of plastic strain

A technique for quantifying surface shear strains associated with plastic contact damage has been developed. A complete stereographic mapping of rotational transformations is determined using transmission electron microscopy from trace analysis of contours or convergent beam electron diffraction. A high resolution, quantitative surface mapping technique such as atomic force microscopy is then used to determine local declination. These measurements produce 5 of the 6 necessary relationships to determine completely the first order shear displacements; the sixth relationship must be determined using symmetry and continuity requirements. These techniques are applied to a model system, microindentation of AlN. Surface deformation associated with these indentations consists of a simple (engineering) shear, γ = 0.38, operating about axes coincident with the outer indentation edges and forming an inert layer or ‘dead metal cap’ immediately beneath the indenter tip.