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Lebensdauervorhersage für Aluminiumschweißverbindungen unterschiedlicher Spannungskonzentrationen

Lifetime prediction of aluminium weldments by various stress concentration
 
: Brandt, U.; Sonsino, C.M.

Deutscher Verband für Materialforschung und -prüfung e.V. -DVM-, Arbeitskreis Bruchvorgänge -AKBV-:
Bruchmechanische Bewertungskonzepte im Leichtbau. Berichtsband der 31. Tagung, DVM-Arbeitskreis Bruchvorgänge
Berlin: DVM, 1999 (DVM-Bericht 231)
ISSN: 0943-3473
pp.41-51 : Ill., Lit.
Deutscher Verband für Materialforschung und -prüfung, Arbeitskreis Bruchvorgänge (Tagung) <31, 1999, Darmstadt>
English
Conference Paper
Fraunhofer LBF ()
aluminium alloy; Aluminiumlegierung; Anriß; Bauteil; crack; crack propagation behaviour; fatigue life estimation; Lebensdauerabschätzung; machine building; Maschinenbau; material property; mechanical property; mechanische Eigenschaft; number of load cycles; Probestab; reversed loading; Rißfortschrittsverhalten; rott split; Schweißverbindung; Schwingspielzahl; Spannungsdehnungsverhalten; Spannungsintensität; Spannungskonzentration; specimen; stress concentration; stress intensity; stress strain behavior; structural component; Wechselbeanspruchung; welded joint; Werkstoffeigenschaft; Wurzelspalt

Abstract
The fatigue behaviour of 25 mm aluminium-alloy full and partial penetration butt welds were investigated. Strain controlled fatigue tests of the 5083 aluminium-alloy base and 5183 weld metal were carried out to determine the monotonic and cyclic stress-strain properties. Crack propagation measurements were performed using center crack tension specimens. The weldments were tested under axial loading for R=0 and -1. For the full-penetration butt welds, the crack initiated at the weld toe, while for the partial penetration butt welds, the crack started at the weld root. The high stress concentration at the weld root decreases the fatigue strength of the welds with UP as compared to the full penetration butt welds. In presence of a tensile mean stress, the fatigue life is significantly shorter than under fully reversed loading. An analytical model was used to predict the lifetime of the weldments. The total lifetime is composed of crack initiation and crack propagation. Because of the high stress concentration at the weld root the period of crack initiation is negligible for the weldments with UP. The lifetime based on crack propagation can be simply described using the geometry factor of the center crack tension specimen. Considering of the extra material provided by the weld reinforcement is suggested. The model predictions agreed with the experimental results for the full penetration butt welds. While for R=0, the most lifetime was spent in crack initiation (and small crack growth), for R=-1 the relative amount of crack propagation is more dominant due to crack closure under compressive loading.

: http://publica.fraunhofer.de/documents/PX-21854.html