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Effect of Residual Stress Relaxation due to Sample Extraction on the Detectability of Hot Crack Networks in LTT Welds by means of µCT

  • Investigations on weldability often deal with hot cracking as one of the most prevalent failure mechanisms during weld fabrication. The modified varestraint transvarestraint hot cracking test (MVT) is well known to assess the hot cracking susceptibility of materials. The shortcoming of this approach is that the information is only from the very near surface region which inhibits access to the characteristic of the hot crack network in the bulk. Here, we report about an alternative approach to monitor the entire 3D hot crack network after welding by means of microfocus X-ray computer tomography (µCT). However, to provide sufficient high spatial resolution small samples must be sectioned from the MVT-welded joint. The sampling is accompanied by local relaxation of the residual stress distributions that are induced by welding, which can have an impact on the crack volumes prior to the sampling. The studies were carried out to investigate the hot cracking susceptibility of lowInvestigations on weldability often deal with hot cracking as one of the most prevalent failure mechanisms during weld fabrication. The modified varestraint transvarestraint hot cracking test (MVT) is well known to assess the hot cracking susceptibility of materials. The shortcoming of this approach is that the information is only from the very near surface region which inhibits access to the characteristic of the hot crack network in the bulk. Here, we report about an alternative approach to monitor the entire 3D hot crack network after welding by means of microfocus X-ray computer tomography (µCT). However, to provide sufficient high spatial resolution small samples must be sectioned from the MVT-welded joint. The sampling is accompanied by local relaxation of the residual stress distributions that are induced by welding, which can have an impact on the crack volumes prior to the sampling. The studies were carried out to investigate the hot cracking susceptibility of low transformation temperature filler materials (LTT). As high compression residual stresses up to -600 MPa in the area of the crack networks were determined by means of the contour method, stress relaxation caused by sectioning for µCT sample extraction can affect the detectability of the cracks later on. X-ray diffraction studies revealed surface residual stress relaxations up to about 400 MPa due to cutting. To investigate this effect, the specimens with hot cracks were subjected to a load test with known stress states. The results clearly show that local stress relaxations will have a strong impact on the volume images reconstructed from tomography analysis. This effect must be considered during hot crack assessment on basis of µCT data.zeige mehrzeige weniger

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Metadaten
Autor*innen:F. Vollert, Jonny Dixneit, J. Gibmeier
Persönliche Herausgeber*innen:D. Marais, T.M. Holden, A.M. Venter
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Mechanical stress evaluation by neutron and synchrotron radiation, , MECA SENS 2017
Jahr der Erstveröffentlichung:2018
Organisationseinheit der BAM:9 Komponentensicherheit
9 Komponentensicherheit / 9.4 Integrität von Schweißverbindungen
Veröffentlichende Institution:Bundesanstalt für Materialforschung und -prüfung (BAM)
Jahrgang/Band:4
Erste Seite:85
Letzte Seite:90
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Hot Cracks; LTT Weld Filler Materials; Welding; µCT-analysis
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen
Veranstaltung:9th International Conference on Mechanical Stress Evaluation by Neutron and Synchrotron Radiation (MECA SENS 2017)
Veranstaltungsort:Skukuza Rest Camp, South Africa
Beginndatum der Veranstaltung:19.09.2017
Enddatum der Veranstaltung:21.09.2017
DOI:10.21741/9781945291678-13
URN:urn:nbn:de:kobv:b43-456765
ISSN:2474-395X
ISBN:978-1-945291-66-1
Verfügbarkeit des Dokuments:Datei für die Öffentlichkeit verfügbar ("Open Access")
Lizenz (Deutsch):License LogoCreative Commons - Namensnennung
Datum der Freischaltung:09.08.2018
Referierte Publikation:Nein
Schriftenreihen ohne Nummerierung:Wissenschaftliche Artikel der BAM
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