In Situ Elastic Strain Measurements—Diffraction and Spectroscopy

Understanding the mechanical properties of materials is crucial for their reliable application as bulk materials as well as in a miniaturized form. The deformation of materials is usually non-uniform and, hence, needs to be characterized on a local level. The following article focuses on the in-Situ determination of mechanical stresses in crystalline materials during deformation. This can be achieved by both diffraction as well as spectroscopical methods, where the elastic strain is the parameter measured, which is subsequently converted into stresses by the application of Hooke’s law. As in Situ measurements require rapid data acquisition in conjunction with reasonable penetration depths, we will focus on x-rays. However, the different techniques described can be applied to any other diffraction probe as well. The description of diffraction techniques, which span the range from averaging techniques to 2D and 3D strain mapping, is complemented by a section on Raman spectroscopy as an alternative method for stress determination for non-metallic materials. Local stresses also can be correlated to local defect densities.