Abstract
KEYWORDS - Finite Elements, fatigue, welded joints, standards, S/N curve
Fatigue assessment based on finite element analysis is widely practiced in the automotive industry. But how to deal with the weldings in structures like car bodies and chassis components is still a research subject. This paper gives an overview and makes comparisons of different methods for fatigue assessment of weld joints.
- Fatigue assessment of welds according standards (EUROCODE 3, BS 7608, DS1612): Detail categories will be used to identify a S/N curves on basis of nominal stresses; mean stress influence is treated in different ways (MKJ-diagrams, reduction of the compressive part of the load cycles).
- Fatigue assessment of welds according the german FKM guideline: Detail categories for the S/N curves; all three stress components will be analysed separately; different Haigh diagrams will be used for different residual stress levels.
- Fatigue assessment of welds on the basis of structural stresses coming from Finite Element analysis: Simple shell models provide structural stresses, that will be used in combination with notch factors from a database to obtain the notch stresses.
- Fatigue assessment of welds on the basis of notch stresses coming from Finite Element analysis: Solid models with notch radius 1mm or 0.05mm will be used for notch stress analysis; notch stresses will be assessed using master S/N curves.
- Fatigue assessment of welds on the basis of nodal forces coming from Finite Element analysis: Line loads coming from nodal forces along the weld will be used in combination with analytical equations for calculation of the structural stresses; notch stresses were determined with the aid of analytical estimations of the notch factor; a masters S/N curve is used for damage analysis.
The principles of the different methods will be explained theoretically as well as an application example will be used to demonstrate the differences in practice.