Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P372
Use of neutron diffraction method for residual stress analysis of laser welded
aluminium T-Joints for airframe applications
Funda Seniz Bayraktar 1 , Peter Staron 2 , Manfred Horstmann 3 , Mustafa
Kocak 4 , Andreas Schreyer 5
1 GKSS Research Centre Geesthacht GmbH
Abstract. Welded structures should provide optimum weld microstructure, sound mechanical
properties as well as control of residual stresses and distortions. Hence, in this
study residual stresses in a laser beam welded T-joint of aerospace grade aluminium alloy
were characterized using neutron diffraction. The figures 1 and 2 are schematically
showing the welded airframe section and idealized panel used in this study, respectively.
It is essential to understand the micro-mechanical properties of such new joint types
for successful applications in future aircrafts. Welding start (run-in) and end (run-out)
locations of the T-joints are generally considered as high risk areas with respect to
solidification cracking and crack initiations under external loadings. However, there is
lack of information both on residual stress and fatigue properties of such welds in open
literature. Therefore, detailed analysis of welding induced residual stresses and fatigue
crack propagation behaviours of such welds have to be conducted. These T-joints were
used for the determination of residual stresses and fatigue crack propagation properties.
Higher longitudinal tensile residual stresses are detected at the run-out locations than
at the run-in locations. Measurements in the clip showed that there is a longitudinal
tensile stress peak located about 8 mm from the weld seam. Fatigue crack propagation
tests have shown that the weld seam is not necessarily the preferred crack path if the
local design of the joints is optimised.
Fig. 1: Laser beam (LBW) welded airframe
section. Currently stringers are
welded in some part of the aircrafts.
Welded clips are yet to be used.
Fig. 2: Idealized welded panel to
conduct residual stress analysis on the
LBW of clips in this study.