Browsing by Author "Hädrich, Helmut"

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    Entwicklung eines Verfahrens zur zerstörungsfreien Eingangsprüfung schmelzgegossener Steine für Glasschmelzöfen
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1985) Hädrich, Helmut; Röpke, Helmut
    Die Grobstruktur schmelzgegossener Steine kann mit Hilfe von Ultraschall überprüft werden. Es wurde eine Meßapparatur entwickelt, bei der die Durchschallungstechnik angewendet wird. Die Steine werden nach einem Raster-Scan-Verfahren untersucht. Meßwerterfassung und -speicherung sowie die Motorsteuerung des Rasterantriebs sind automatisch und werden von einem Computer übernommen. Das Meßergebnis wird als C-Bild in Grauwertdarstellung ausgedruckt.
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    Non-destructive testing of ceramically bonded refractories - Application of ultrasound and microwaves
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Ulizka, Stanislav; Hädrich, Helmut; Gebhardt, Franz
    Quality control on refractory bricks is either mostly destructive or methods are used which require samples with a certain geometry. In a joint project between the University of Erlangen and industry the applicability of non-destructive testing methods for sintered refractory bricks was tested. Various materials with artificial flaws were measured in transmission with ultrasound (500 kc/s) as well as with microwaves (24 to 40 Gc/s) and the results were compared. Despite of good results, the testing with ultrasound proved to be unsuitable for the measurements of greater lots, because the open-pore blocks have to be coupled in water. An excellent alternative is the transmission measurement with microwaves. With both methods structural inhomogeneities as well as density differences or inclusions can be detected.
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    Quality assurance of sintered refractories through nondestructive testing with microwaves
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Dannheim, Henning; Hädrich, Helmut
    For quality assurance of refractories for the glass industry an early nondestructive testing is required. A possibility for nondestructive testing, especially in the green product, is given by the transidon of microwaves, as this requires no coupling medium like water. In this work, some basic physical characteristics were measured which determine microwave absorption through refractories and flaw detection. For different refractories the dielectric constant, specific attenuation coefficient as well as dependence of the attenuation on the frequency were determined. It is shown that a high dielectric constant improves the detection of flaws. In order to improve flaw detection and resolution, lenses and frequency modulation were used successfully. Best results for the refractories investigated were achieved with a lens with a focal length of 86 mm. Measurements were then extended to other types of refractories, i.e. chromalumina, zirconmuUite and zirconsilica, as well as to unfired bricks. Here, especially one isostatic-pressed zirconsilica brick has shown the lowest specific attenuation coefficient due to low porosity and high dielectric constant. Furthermore, a test device for complete C-scans of large refractory samples was developed and tested successfully. A number of refractories without or with natural and artificial flaws, respectively, were checked. Nondestructive testing with microwaves has now been sufficiently developed to be transferred to industrial use.
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    Zerstörungsfreie Prüfung von gesinterten Feuerfeststeinen mit Mikrowellen
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1993) Hädrich, Helmut; Ulitzka, Stanislav
    [no abstract available]