Page 68 - Biaxial Multiaxial Fatigue and Fracture

Multiaxial Fatigue Assessment of Welded Structures by Local Approach 53

1000

m
P AA A
2
Y
X
E
v)
AA
g!
tj test R=0.5
-calculation R=-I
100
I IE+O3 IE+M 1 E+05 1E+06 IE+O
cycles

Fig. 10. Comparison between predicted and experimental lives
of stress-relieved butt-welded steel

DEFINITION OF THE WELD QUALITY: THE GEOMETRICAL PARAMETERS

The quality of welded joints is defined from a design point of view by geometrical
parameters such as the width of the weld (denoted as Lpc and Lrc for the weld toe and the weld
root respectively), the height of the joints (S), the transition radii, the axial misalignment and
the angular distortion. Transition radii and geometrical defects (distortion and misalignment)
constitute in fact the main parameters of the quality of welds. Figures 11 and 12 show the
geometrical parameters of butt and fillet welded joints respectively.

R1 R2

Fig. 11. Geometrical and micro-geometrical parameters of butt welds

The mean values and standard deviations of the geometrical parameters measured on several
butt welded joints in 7020 aluminium alloy of 20 mm thickness, welded using the multi-layer
MIG process, are given in Table 3. The angular distortion and the axial misalignment measured
are respectively 0.7 f 0.9' and 0.5 mm.