Structures are designed to withstand extreme loads, but when subjected to repeated applications of load, they can suffer from fatigue failure, under loads which are significantly lower than the extreme loads.
Fatigue cracks usually initiate on the surface of a component, where there is a stress concentration. Local geometric features are particularly important with regard to fatigue life, as they can cause high localised stresses to occur.
In addition, welded joints can be particularly prone to fatigue failures and will often limit the fatigue life of a component, as they will exhibit high tensile residual stresses if post-welding heat treatment is not undertaken.
Eatec Engineering Analysis has extensive experience of fatigue analysis. Generally, a fatigue analysis involves performing a finite element analysis (FEA) to determine the stresses for each loading condition. From these results, the stress ranges and mean stresses can be obtained for the fatigue life calculation. Depending upon the complexity of the loadings, the fatigue life is calculated using the appropriate standard or the fatigue analysis post-processing package fe-safe.
Some of the benefits of performing a finite element analysis (FEA) based fatigue life calculation over physical testing are:
- The fatigue life can be calculated before any components are made, avoiding the investment and time involved with prototype tooling.
- Physical testing can be relatively slow and expensive, particularly where there are a number of load combinations to be considered. Using an FEA model, a fatigue analysis can be performed for multiple load combinations in an efficient and timely manner.
- A fatigue life calculation based on finite element analysis (FEA) can provide information for all regions where the life is relatively short, and these can be redesigned in one iteration. With physical testing, the life to the first fatigue failure will be determined, but other locations, where the fatigue life may be only slightly longer, may not be identified in the initial testing.
- The effects of design changes on the fatigue life can be assessed quickly and efficiently using the techniques based on finite element analysis.
Eatec Engineering Analysis has experience of performing fatigue life calculations against a number of standards, including Eurocode 3, Eurocode 9, BS 7608 and various ASME standards.
Eatec Engineering Analysis has over 30 years’ experience of providing finite element analysis (FEA) consultancy services to a wide range of national and international clients in industries which include oil & gas, power, marine, processing, defence, transport and industrial.