Introduction and Overview

Computational strength analysis is an essential part of the engineering design process. Favourable material utilisation, safe usage properties and often weight and cost reduction are important criteria. In addition to the technical aspects, product liability also plays a role, and manufacturers are increasingly striving to prove the fatigue life and reliability of their products mathematically, thus applying the state of the art.

The development of a component passes through several phases. The first step is dimensioning based on the (rarely) maximum static loads and, if necessary, a safety factor. The proof that the component will not fail under static loading is a prerequisite for all further verifications.

If the component is also subjected to dynamic loading, it must also be proven that this will not lead to failure. The fatigue strength is relatively easy to prove, as only a few details are required. If it can be shown that under worst-case assumptions the stresses are below the fatigue strength with sufficient certainty, this result is initially sufficient.

At a later stage, when the structure is to be optimised and more detailed information is available, the fatigue strength verification may be useful or even mandatory. The necessity depends strongly on the consequences that a failure of the component could have. A crack propagation calculation can also be useful, for example, in determining inspection intervals.

winLIFE offers suitable calculation options for all these development phases, from the compilation of a load to the printout of the report, and - if required - we also offer services in these areas.

The results of a fatigue life calculation have a comparatively large error, so the absolute fatigue life from a calculation can only be predicted with a large deviation. The reason for this is simple: fatigue life is logarithmically dependent on stress (stress amplitude). If this changes by 5%, the fatigue life changes by a factor of 5 to 10. This phenomenon, which is easy to understand from a calculation point of view, is also a physical reality! Nevertheless, a fatigue life calculation is extremely useful as it provides an accurate relative comparison of fatigue lives and identifies the critical point. This can significantly shorten the development process of a component.

However, for safety-related components, component testing is still required. The statistical nature of fatigue life requires a larger number of tests, which makes such tests very complex. Computational fatigue life prediction helps to identify the important influencing variables, reduce the number of tests required and also the test duration.

The combination of calculation, measurement and damage analysis leads to a solid knowledge base in the long term, which makes the tool of computational fatigue analysis increasingly powerful,  because the experimental verification and the factor determined between calculation and measurement also make quantitative predictions more accurate as the data base grows.

winLIFE offers programme modules for all common component types such as

  • Non-welded components
  • Welded components
  • Gearwheels and bearings

Different analysis methods such as

  • Calculation to crack
  • Crack propagation
  • Multi-axial problem definition
  • Stochastic analysis
  • Gearwheels and bearings

are supported by corresponding winLIFE modules.

Although winLIFE is easy to use, the user needs to have a good understanding of the theory, as a large number of input variables have to be selected that significantly influence the result. In addition, it is important that the user is aware of the possibilities and limitations of fatigue life prediction in order to be able to correctly interpret his calculation results and use them for a robust design. For this purpose, we offer training courses three times a year to familiarise winLIFE users with the theory and the product. Furthermore , we offer on-site training at the customer's premises.