Welded Joints

Multi-FEAST© allows the Modified Wöhler Curve Method to be used to estimate fatigue damage in both steel and aluminium welded components subjected to constant as well as to variable amplitude uniaxial and multiaxial load histories. The above multiaxial fatigue criterion can be applied in terms of both nominal, hot-spot, and local quantities. Independently from the strategy adopted to perform stress analysis strategy, Multi-FEAST© estimates fatigue lifetime of welded joints by fully complying with the recommendations of the International Institute of Welding.

When the Modified Wöhler Curve Method is applied in terms of local stress quantities, the required linear-elastic stress fields/states can be either imported from commercial FE software packages or estimated through a number of closed form solutions which are directly implemented in Multi-FEAST©.

Finally, Multi-FEAST© can use as input files load histories either defined analytically (such as, for instance, a simple sinusoidal loading path), constructed from a combination of varying loads, or built through load signals gathered experimentally via standard transducers.

Nominal Stress based Analysis

This tool allows the user to perform the fatigue assessment of welded components by applying the Modified Wöhler Curve Method in terms of either nominal or hot-spot stresses. This means that weldments of steel as well as of aluminium can be designed against both constant and variable amplitude uniaxial/multiaxial fatigue by following a strategy fully complying with the recommendations of the available standard codes (in particular, Eurocode 3, Eurocode 9, and International Institute of Welding).

Reference Radius based Analysis

This tool allows the user to perform the fatigue assessment of steel and aluminium welded components by applying the Modified Wöhler Curve Method along with the reference radius concept. It is worth observing that the reference radius concept, which has been developed at the Fraunhofer-Institute for Structural Durability and System Reliability (LBF) in Darmstadt, Germany, represents the most modern concept which has been recently incorporated into the design recommendations of the International Institute of Welding. To our knowledge, Multi-FEAST© is the only tool allowing such a concept to be systematically used to perform the fatigue assessment of welded joints subjected to both constant and variable amplitude multiaxial loading paths. Finally, it is worth observing that the necessary stress states can be determined either by post-processing static linear-elastic finite element models or by using closed form solutions directly implemented in Multi-FEAST©.

Critical Distance based Analysis

This tool allows the user to perform the fatigue assessment of welded components by applying the Modified Wöhler Curve Method along with the Theory of Critical Distances. The peculiarity of this tool is that fatigue damage is estimated by directly post-processing the stress fields acting on the material in the vicinity of weld beads/roots, where such stress fields can be determined either by solving conventional static FE models, or by using closed form expressions. Such a tool can be employed to predict finite life as well as high-cycle fatigue strength under both constant and variable amplitude uniaxial/multiaxial fatigue loading. To conclude, it is worth observing that the method implemented in such a tool of Multi-FEAST© represents the research frontier in the weldment fatigue discipline.

The above peculiarities make Multi-FEAST© completely different to the available commercial software packages and this holds true not only in terms of modus operandi, but also in terms of design philosophy.

It is worth concluding by observing that the philosophy on which Multi-FEAST© is based is the one recommended in the most advanced research centres worldwide (like, for instance, at LBF in Germany).