The Use Of X-ray Diffraction To Determine The Triaxial Stress State In Cylindrical Specimens

A method of determining the axial, circumferential and
radial residual stress distributions in cylindrical
specimens is described. The axial and circumferential
residual stresses are measured directly by x-ray
diffraction at the free cylindrical surface exposed by
machining and electropolishing. The radial stress
component is then calculated from an integral of the
circumferential stress at the free surface as a function of
depth by the method of Moore and Evans.
The method is applicable only to cylindrical samples
with rotationally symmetrical stress distributions from
which complete cylindrical shells are removed for
subsurface measurement. The method does not require
prior knowledge of the stress-free lattice spacing, and
thus provides a means of verifying neutron and x-ray
diffraction methods of full tensor stress determination.
The stress-free lattice constant, do, is also calculated as
a function of depth from the sum of the principal
stresses.
Application of the method, to determine the triaxial
residual stress distribution in an induction hardened
1045 steel multi-axial fatigue specimen, is described.
The variation in the stress-free lattice spacing of the
(211) planes with depth is estimated through the
hardened case and into the core material.