General Information on the Computer Aided Fatigue Life Prediction

Fatigue strength under variable stress amplitude is used to study the behaviour of components under dynamic load, with prediction of fatigue life being an important objective. In addition to the often very time-consuming experimental approach, computational fatigue life prediction is becoming increasingly important as a fast and cost-effective analysis is possible. Furthermore, parameter studies can be used to identify important influencing variables so that, if necessary, supplementary experimental investigations can be carried out in a more targeted manner and with a reduced scope. The analysis of the Fatigue strength under variable stress amplitude requires extensive knowledge of operational loads, manufacturing processes, materials, etc., so companies that only occasionally deal with this problem are happy to take advantage of the analysis of the fatigue strength under variable stress amplitude we offer.

A special case of the certification of fatigue strength under variable amplitude is the assessment of the fatigue limit. The characteristic point  of deflection of S-N curve (fatigue limit) is an important parameter which is often used for the dimensioning. The ratio between the maximum stress occurring during operation and the fatigue limit is expressed as the utilisation factor. It is not necessary to know detailed load-time-functions, only the maximum values of the loads and their form (alternating, growing, constant). Assuming a worst-case scenario, the utilisation factor is calculated. If the assessment of the fatigue limit shows only a low level of utilisation, the comparatively complex certification of fatigue strength under variable amplitude can often be omitted.

A number of guidelines are available to facilitate the process and help ensure that the dimensioning is state of the art. These include the FKM Guideline, the rules and regulations of Germanischer Lloyd (for shipbuilding and wind turbines) and the IIW-Guidelines (International Institute of Welding) guideline.

In addition to a deeper understanding of one's own product, the result of the endurance limit process is a more efficient component structure, reduced weight and often cost savings. Apart from the technical aspects, the issue of product liability is also an important motivation for the application.

Our software winLIFE has been developed to make the application of established methods as simple as possible. To be able to use winLIFE successfully, the user must have a solid basic knowledge of mechanics, which is taught in our seminars (two days, three times a year) and forms the basis for an in-depth introduction to the theory of Endurance Strength  and the application of our software. On request, we carry out initial projects with our customers to speed up the introduction to the methodology and provide confidence in the interpretation of results. The publications and winLIFE video examples give you a first impression of the application possibilities.