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Computed tomography is a non-destructive testing technique based on X-ray absorption that permits the 3D-visualisation of materials at micron-range resolutions. In this article, computed tomography is used to investigate fibre orientation and fibre position in various fibre-reinforced materials such as ceramic matrix composites, glass fibre-reinforced plastics or reinforced concrete. The goal of this article is to determine the quantitative orientation of fibres in fibre-reinforced materials. For this purpose, a mathematical technique based on the structure tensor is used to determine the local orientation of fibres. The structure tensor is easy to implement and results in a fast algorithm relying solely on local properties of the given reconstruction. In addition, the local X-ray transform is used to denoise fibres and to segment them from the matrix

A new highly precise angle measuring table has been developed for the Physikalisch-Technische Bundesanstalt, which is to be used as a comparator to calibrate angle standards. First results of the determination of the comparator's errors of measurement obtained by two calibration methods are reported. Considering the results obtained, it is to be expected that the desired uncertainty of measurement of can be achieved.

No abstract

At the Physikalisch-Technische Bundesanstalt, autocollimators are calibrated with the aid of the WMT 220 angle comparator to ensure their direct traceability to the SI unit of plane angle, the radian (rad). It is shown that high-resolution electronic autocollimators can thus be calibrated with an uncertainty of 0.007 arcsec (k = 2) in reproducible measurement steps down to 0.005 arcsec. Calibrations in very small measurement steps close to the autocollimators' resolution can inform about possible short-period deviations and resulting aliasing effects in measurements with autocollimators.