Ball indentation test - uses different radii of curvature to determine elastic limit changes in depth

摘要

Internal stresses and changes of the elastic limit of workpieces as functions of the depth under the surface can be determined without having to destroy any part of the workpiece. A ram with a hemispherical contact face of a specific radius of curvature is pressed against the workpiece surface with successively increased force until the plastic limit is reached. The surface deformation is measured and the principal stresses are calculated and recorded. The same test is repeated with different radii of curvature (60mm, 150mm, 200mm). The envelope of the curves of the principal stresses versus the penetration indicates the elastic limit as a function of the depth.