In this work, as reference for the BN measures, three different stress conditions were obtained through gentle, light abusive and heavy abusive grinding on distinct samples, that were completely characterized by means of X-ray diffraction (XRD) together with electrolytic polishing to remove layers for subsurface measurements. Nevertheless, to be used for quality control, XRD has some limitations because to perform it properly it must become a destructive technique, in fact, without polishing, it can investigate exclusively on the first 5 micrometer, and it can only be applied on purposely-prepared specimens or quite simpleshaped pieces. For real complex-shaped parts, therefore, the only possibility to keep under control the residual stress conditions goes through an accurate control of machining parameters. The inspection by BN technique, instead, can be carried out using contact probes, of small dimensions and adaptable to inspecting profiles, making the method interesting for application as a real NDT method on these topics. Barkhausen Noise measurements results obtained on both characterized samples and real complex-shaped parts are presented and compared to both the acid etch and XRD inspection results, proving the method to be already reliable for a qualitative evaluation of the residual stress state. However, because the XRD characterization has revealed very different stress distribution, due to abusive grinding, up to a depth of about 0.2 mm below the surface, this experience demonstrates the need to improve the BN technique by using a multifrequency driving alternate current to investigate at different depths.


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    Title :

    Experience on Barkhausen noise measurements for non destructive evaluation of residual stress in helicopter gears


    Additional title:

    Erfahrungen bei Messungen des Barkhausenrauschens für die zerstörungsfreie Bewertung der Eigenspannung in Hubschraubergetrieben


    Contributors:
    Merletti, L.G. (author) / Pezzoni, R. (author) / Buzetti, O. (author)


    Publication date :

    2002


    Size :

    8 Seiten, 9 Bilder, 7 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English