Software structure

Multi-FEAST© is designed to perform fatigue assessments of plain, notched, and welded components. The underlying philosophy is to allow the user to choice a suitable approach from a wide range of options. The choice will depend on the type and quality of information available to the engineer and the following section highlights the nature of those choices.

To perform a fatigue assessment of structural components subjected to in-service time-variable loading, you can proceed as follows:

1) In the absence of any stress concentration, fatigue damage can be estimated from the known time-varying stress state at the known or postulated critical location where failure will start.

Multi-FEAST© tool: Unnotched Materials

2) If you have to design axisymmetric components with stress concentrating features subjected to combined tension, or bending, with torsion, you can perform the fatigue assessment in terms of nominal stress components, provided that the nominal stresses can be defined unambiguously.

Multi-FEAST© tool: Notched Components – Nominal Stress based Analysis

3) If the geometry of your component is complex or, the nominal stress quantities cannot be calculated unambiguously, you can perform the fatigue assessment in terms of local quantities. This is done by post-processing the stress field acting on the material in the vicinity of the assumed crack initiation sites. The stress field would normally be found from a finite element analysis, but an analytical solution, if known, would be just as suitable (a number of closed form solutions being already implemented in Multi-FEAST©).

Multi-FEAST© tools:

Notched Components – L based Analysis (high-cycle fatigue)

Notched Components – LM based Analysis (finite lifetime)

We recommend a different approach when performing a fatigue assessment of welded components subjected to in-service time-variable loading. In these cases, you can proceed as follows:

1) If the specific geometry of the welded detail being assessed is stated by the available standard codes, then the multiaxial fatigue assessment can directly be performed in terms of the nominal stresses.

Multi-FEAST© tool: Welded Components – Nominal Stress based Analysis

2) If the welded detail is not a standard one, then a multiaxial fatigue assessment can be performed in terms of hot-spot stresses.

Multi-FEAST© tool: Welded Components – Nominal Stress based Analysis

3) When either nominal stresses cannot be calculated or the standard fatigue curve for the specific geometry of the welded detail is not available, then local stress based approaches are recommended.

Multi-FEAST© tools:

Welded Components – Reference Radius based Analysis

Welded Components – Critical Distance based Analysis