Goals and challenges

90% of mechanical failures result from fatigue problems


Fatigue evaluation from combinations of static loads, random vibratory loads (PSD), or temporal loads makes it possible to predict the sensitive areas and to highlight the risk of crack initiation. The use of S-N curves with a high number of cycles, E-N curves with a low number of cycles, Haigh diagrams, Rainflow methods therefore constitutes an essential step for any development of a mobile or on-board system.

Numerical simulation allows this validation throughout the development process. The identification of areas with high damage will make it possible to optimise the product and increase the life of the structure.

Our simulation teams have over 30 years of expertise in the field of structural fatigue. Thanks to the experience acquired during the various projects that have been entrusted to us, our teams are able to estimate reliably the in-service behaviour of the products under various stresses in order to propose optimisation solutions.

Our developments have resulted in new computation methods that are much more successful on the risk of crack initiation and enable the prediction of crack propagation.

During the life cycle calculation, the simulation allows the cracking zone to be identified. However, when the crack is initiated, the stress distribution changes in the analysis zone. Two possibilities therefore exist:

  • The load constraints in the area are reduced. The crack does not develop.
    The load constraints in the area are the same or increase. It is then necessary to understand how the crack propagates in order to establish a maintenance plan and ultimately repair it

The testing capacities available to our teams make it possible to compare numerical analyses with physical results, and to effectively design and apprehend a multitude of complex vibration phenomena.


Fissuration - Crack initiation and propagation            Crack initiation and propagation             Crack initiation and propagation           

CIMES services

  • Performance and characterisation of CTOD (Crack Tip Opening Displacement) tests 
  • Advanced modelling of the cracking phenomenon 
  • Calculations of the stress levels for each cracking level as a function of the number of cycles seen by the structure
  • Proposal of predictive maintenance, repair, or redesign operations
  •  On-site verification of proposed repairs
  • Application of connected measures (monitoring, development of cracking behaviour, life profile, etc.)


Logo Altair                Logo Ansys


Keywords: fatigue, structure, cracking, Paris law, CTOD, numerical simulation, 3D calculation, mechanics, stresses, Von Mises, repair, Rainflow, Haigh diagram, DSP, Wöhler curves, SN curves, Rainflow, propagation.

Tools: ALTAIR Hyperworks, Ansys