The ability to non-destructively map the residual strain field inside an engineering component is important for predicting its fatigue life or developing processing methods to prevent failure or enhance performance. In this paper, we describe a new residual strain mapping program at the Advanced Photon Source, Argonne National Laboratory. The new program is based on energy dispersive x-ray diffraction (EDXRD). It is capable of non-destructively penetrating a several-cm thick polycrystalline sample fabricated from engineering alloys using high-energy x-rays and measuring the residual strain field with mm or better spatial resolution and approximately $$\pm 1 \times 10^{-4}$$ strain resolution. A multi-element detector array is employed to measure multiple strain components simultaneously. The residual strain mapping setup is augmented with a high-energy tomography capability, allowing precise alignment of the material volume of interest for residual strain mapping and providing a complementary view of the structure to understand the measured strain field. These measurement capabilities are demonstrated using several strain mapping examples ranging from polycrystalline structural alloys to biological materials. We also provide some guidance for the future users of the program for a successful residual strain mapping experiment. We are expanding the capabilities of the new setup with various in situ capabilities including thermo-mechanical loading.

Tomography using diffracted x-rays produces reconstructions mapping quantities including crystal lattice parameter(s), crystallite size and crystallographic texture; this information is quite different from that obtained with absorption contrast or phase contrast. Diffraction tomography can be performed using energy dispersive diffraction (EDD) and polychromatic synchrotron x-radiation. In EDD, different, properly-oriented Bragg planes diffract different x-ray energies; these intensities are measured by an energy sensitive detector. A pencil beam defines the irradiated volume, and a collimator before the energy sensitive detector selects which portion of the irradiated column is sampled at any one time. A 3D map is assembled by translating the specimen along X, Y and Z axes. This paper reports results of 3D mapping of the integrated intensity of several reflections from the bioapatite in the mineralized cartilage centrum of a blue shark. The multiple detector EDD system at 6-BM-B, the Advanced Photon Source was used to map an entire blue shark centrum. The shark centrum consists of a double cone structure (corpora calcerea) supported by the intermedialia consisting of four wedges. The integrated intensities of the c-axis reflection and of a reflection with no c-axis component reveals the bioapatite within the cone wall is oriented with its c-axes lateral, i.e., perpendicular to the axis of the backbone, whereas the bioapatite within the wedges is oriented with its c-axes axial. Results of absorption microCT (laboratory and synchrotron) and x-ray excited x-ray fluorescence mapping are included to provide higher resolution data of the structures underlying the EDD maps. Application of EDD tomography to 3D mapping of large specimens promises to add to the understanding of other mineralized tissue samples which cannot be sectioned.