Page 40 - Biaxial Multiaxial Fatigue and Fracture

Eualuation of Fatigue of Fillet Welded Joints in Vehicle Components Under Multiaxial Service Loads 25

Fig. 2. Load configuration on the test rig Fig. 3. Load sequences, 1 block

LIFE CALCULATION IN ACCORDANCE WITH THE HOT SPOT STRESS APPROACH

Finite Element Modelling

Niemi [8, 91 presents a series of variants for realising the joint between two welded parts in a
finite element (FE) model but does not give a clear recommendation. Figure 4 [8] shows
various ways to model cover plate endings.
?I Is!L- Rigid bar
ell elements
: I , ?
a) double shells connected b) double shells connected c) double shells connected
bv a vertical shell by a vertical shell and by rigid bars
inclined shell elements
Rigid bar Solid element

d) Elfis3- single shells with offset, e) solid element modelling
connected by rigid bars

Fig. 4. Various modelling approaches for cover plate endings [8]

To take advantage of the experience from a previous investigation [7] on the applicability
of the hot spot stress approach, simple 4-node shell elements have been used to model the
tube, 8-node volume elements have been used for the forged arms. Both meshes are tied
together with constraint equations. The weld itself is modelled by increasing the shell
element’s thickness. In accordance with Niemi’s suggestions, the element length has been set
to 2.5 mm (=0.4’h, where h is the shell thickness). Figure 5 shows the finite element mesh
used together with the load configuration.