Fatigue Life Improvement Techniques
The use of fatigue life improvement techniques and specifically ultrasonic peening treatment to extend the service life of offshore structures has become an accepted practice during the last five years. The understanding of the process as well as equipment’s upgrading for treatment in-situ including quality control and assurance have been developed up to a level that it has become a current practice in many parts of the world. However, the maximum benefit of the ultrasonic peening treatment can only be achieved if it is applied on the welded connections of structural integrity concern and on the precise extend.
FE model and sub-model technique
Therefore if a welded joint playing a significant role in the structural integrity in any offshore installation is treated by ultrasonic peening the enhancement of this specific weld detail will contribute towards the structural integrity of the entire installation. However, the main challenge is to find these specific welded details of structural integrity concern and more precisely the extension of the high stressed area in them. Currently most FEA software’s support sub-modeling techniques where highly stressed areas as for example weld connections could be analyzed with very fine mesh based on results from global models with coarse mesh.
LETS Global Ultrasonic Peening Procedure
LETS Global Ultrasonic Peening procedure extends the fatigue life and/or the service life of welded attachments four times. The high stressed weld connections, selected with the help of fine mesh FE modeling and spectral fatigue analysis subsequently verified by offshore inspections are where the LETS Global Ultrasonic Peening Procedure will be applied. Once the fatigue hot-spots have been located the Ultrasonic Peening treatment is applied to these locations. By treating the fatigue hot-spots with this procedure, the fatigue strength of treated areas is increased fourfold.