Apparatus for measuring mechanical stress using white x-rays

Abstract

An apparatus for measuring mechanical stress in one direction (along the x-axis) in the surface of a sample, using white X-rays, wherein white X-rays are cast onto the surface of the sample from on one side of the plane (z-x plane) containing the white X-rays cast position on the surface of the sample, being perpendicular to the surface (x-y plane) of the sample and extending in the direction (along x-axis) along which the stress is measured; the energy of the X-rays diffracted by the lattice planes parallel to the surface of the sample, is detected at a predetermined Bragg angle while the energy of the X-rays diffracted by the lattice planes whose normals are contained in the z-x plane and which incline at an angle with respect to the surface of the sample, is detected also at the same Bragg angle; and the stress .sigma..sub.x in the x-axis direction in the sample surface is calculated on the basis of the difference between the two energies according to the expression ##EQU1## WHERE E.sub.n1 is the energy of the X-rays diffracted by the lattice planes parallel to the sample surface, E.sub.n2 the energy of the X-rays diffracted by the lattice planes including at an angle to the sample surface, .psi..sub.2 the angle which is made by the normal to the sample plane and the normal to the inclining lattice planes, and K is a constant given by the expression ##EQU2## WHERE E is the Young's modulus, .nu. the Poisson's ratio, and E.sub.n the energy of the X-rays diffracted by the sample when it has no strain therein.