X-ray investigation of stress states in materials .4.

X-ray stress analyses of crystalline or partially crystalline materials are based on the determination of elastic lattice strains which are converted to stresses by means of theory of elasticity. The development of the sin(2) psi-method of X-ray stress analysis and of diffractometers substituting film chambers during the 1960s initiated an enormous progress in X-ray stress analysis during the following three decades both in respect of the knowledge of the underlying principles and in respect of the practical application. This report sketches the historical development of X-ray stress analyses and describes the actual state of the art of this important tool for materials science and engineering. Besides some important elements of X-ray physics and theory of elasticity, experimental aspects of practical applications are outlined. Standard measuring procedures and special measuring problems are described and hints for practical solutions are given. In particular, examples of destructive and non-destructive depth profiling of residual stresses of residual stress analyses in thin coatings, in multilayer structures of thin coatings and in chemically graded coatings, of residual stress analyses in presence of textures, of residual and loading stress analyses in heterogeneous materials, in coarse grained, and in single crystalline materials are presented. The methods established up to now are explained and possible future developments are pointed out.