Filtern
Erscheinungsjahr
- 2015 (2) (entfernen)
Dokumenttyp
- Beitrag zu einem Tagungsband (2) (entfernen)
Sprache
- Englisch (2)
Schlagworte
- Aluminium alloy (1)
- Analyser based imaging (1)
- CT (1)
- Computed tomography (CT) (1)
- Hydrogen assisted cracking (HAC) (1)
- Hydrogen embrittlement (HE) (1)
- Röntgenrefraktion (1)
- Synchrotron radiation (1)
- Wasserstoffunterstützte Rissbildung (1)
- Wasserstoffversprödung (1)
- X-ray refraction (1)
- cold neutrons (1)
- iron embrittlement (1)
- neutron imaging (1)
- neutron instrumentation (1)
Hydrogen in metals can cause a degradation of the mechanical properties with possible subsequent hydrogen assisted cracking (HAC). Though, the mechanism of HAC is not completely understood yet and thus suitable methods for in situ investigations to characterise the crack formation are needed. X-ray computed tomography (CT) is a well-known tool for analysing these properties. However, the effective resolution of the detector system limits the detection of small defects by CT. Analyser based imaging (ABI) takes advantage of x-ray refraction at interfaces between volumes of different density, i.e. of cracks, pores, inclusions, etc., within the sample to detect defects smaller than the resolution of the detector system. In this study, measurements on an aluminium alloy weld showed that ABI allows us to resolve the 3D structure of cracks undetected by absorption based CT. Prospective investigations will analyse HAC in steels.
CONRAD-2 is an imaging instrument using low-energy (cold) neutrons. The instrument is installed at the end of a curved neutron guide which avoids the direct line of sight towards the reactor core. This ensures a very low background of high-energy neutrons and. photons at the sample position. The cold neutron beam provides a wavelength range which is suitable for phase-and diffraction-contrast imaging such as grating interferometry and Bragg edge mapping. The instrument is well suited for high resolution imaging due to the high efficiency of the very thin scintillators that can be used for the detection of cold neutrons. An instrument upgrade was performed recently as a part of an upgrade program for the cold neutron instrumentation at HZB. The parameters of the instrument as well as some research highlights will be presented.