Berlin 2024 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Instrumentation and Methods for Micro- and Nanoanalysis

KFM 6.2: Talk

Monday, March 18, 2024, 11:00–11:20, TC 010

Planar Strain Tomography with X-ray Powder Diffraction — •Peter Modregger — Department Physik, Universität Siegen — Center for X-ray and Nano Science, DESY, Hamburg

The measurement of local strain and residual stress fields in polycrystalline engineering materials constitutes an essential tool of materials science engineering. In general, there are two types of methods available: X-ray diffraction with conical slits and energy dispersive X-ray diffraction - both featuring anisotropic gauge volumes with aspect ratios of 1:20 or worse. Here, we introduce planar strain tomography based on X-ray powder diffraction that utilizes a high energy pencil beam and iterative reconstruction. The gauge volume is defined by the size of the pencil beam with typical aspect ratios close to 1:1. We will demonstrate the feasibility with data collected in a pilot experiment at P21.2 at PETRA III. The sample was shot peened martensite and the measured strain and residual stress field distributions meet expectations. The results will be compared to energy dispersive X-ray diffraction collected with the high energy wiggler beamline P61A at PETRA III as well as laboratory measurements. We will further discuss limitations of the proposed approach in terms of stability of iterative tomographic reconstruction, suitable sample thicknesses (in the range of centimeters) and currently achieved strain sensitivity (in the order of 1e-4).

Keywords: X-ray stress analysis; Tomography; strain; powder diffraction; martensite