Fatigue and vibration

Fatigue is by far the most common failure mechanism of mechanical structures. However, the underlying mechanisms are extraordinarily complex, and often hidden for the designer. This is because the fatigue process is strongly affected by local properties and conditions at the micro level, such as the grain structure of the material, undesired inclusions, welding defects or scratches.

 

Due to the complexity of the physical mechanisms involved, fatigue research at SP is carried out on several levels:

 

  • At the overall design and dimensioning level, investigating operating conditions together with the expected lifetime characteristics, and seeking an optimum design in terms of safety, economic life and environmental impact.

  • At the material - and component level, developing empirical models with the help of spectrum tests, numerical calculations and stochastic modelling.  This also includes analysis of the accuracy of the experimental methods.
  • At the local level, in terms of local stress and bending behaviour in three axes. Although numerical calculation methods nowadays can provide information on local stress and strain fields, there are still no good fatigue models for local loads. The objective of this research is to develop new criteria based on numerical methods in combination with experimental results, and so to bring life length calculation to the same level as stress calculations.

  • At the micro level, in order to understand and model the damage mechanisms.

Research within fatigue is firmly concentrated on solving real problems encountered by industry when dimensioning structures and products. An important part of this is therefore continuous contact with industry's own experts in the field. This is organised through the Swedish Fatigue Network - UTMIS, of which SP holds the chair. The network arranges extensive activities, in the form of seminars, courses and projects.

The problem of fatigue involves many disciplines. SP has a joint research group together with FCC and Chalmers University of Technology.

 



www.utmis.org

 

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Erland Johnson

Phone: +46 10 516 56 22

Gunnar Kjell

Phone: +46 10 516 52 23

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