Page 38 - Biaxial Multiaxial Fatigue and Fracture

BiaxiaVMultiaxial Fatigue and Fracture
Andrea Carpinteri, Manuel de Freitas and Andrea Spagnoli (Eds.)
0 Elsevier Science Ltd. and ESIS. All rights reserved. 23

EVALUATION OF FATIGUE OF FILLET WELDED JOINTS IN
VEHICLE COMPONENTS UNDER MULTIAXIAL SERVICE LOADS

Georgios SAVAIDIS', Alexander SAVAIDIS', Robert SCHLIEBNER'
and Michael VORMWALD3
'MAN Nutzfahrzeuge AG, Dept. for Fatigue and Testing of Materials and Components,
Dachauer Str. 667, 80995 Munich, Germany
2National Technical University of Athens, Dept. of Mechanics, Zografou Campus,
Theocaris Bld., 15773 Athens, Greece
'Bauhaus-University of Weimar, Institute of Structural Mechanics, Marienstr. 15 ,
99423 Weimar, Germany

ABSTRACT

The mechanical behaviour and fatigue life of a thin-walled tube joined to a forged component
by fillet welding is investigated theoretically and experimentally. The component is loaded by
nonproportional random sequences of bending and torsion as measured during operation. The
stresses in the welded structure are calculated using finite element analysis. The structure has
been meshed following the IIW guideline for application of the hot spot stress approach. The
fatigue lifetime of the welded structure is evaluated using the hot spot stresses in conjunction
with the critical plane approach to account for multiaxial fatigue. Additionally, a model has
been created to calculate fatigue lifetime based on local elastic stresses. The accuracy of the
calculations is discussed using corresponding experimental fatigue life results.
KEYWORDS

Multiaxial fatigue, hot spot stress approach, local stress approach, fillet welds, submodelling

INTRODUCTION
Methods for calculating the fatigue behaviour of components are gaining increasing
importance even in areas of application which have to date been dominated by experimental
methods. For welded joints, various calculation procedures are available, which differ
fundamentally in their type of evaluation (nominal, structural or local stress/strain).
Summarising overview and detailed description of the several procedures are given in [ 1, 2, 3,
41.
In the automotive sector there is a need for computer-aided methods to shorten
development time of products. In the last years, significant developments on theoretical
assessment of welded automotive components have been achieved in connection with the hot