Study on the application of spectral fatigue analysis

Abstract

Fatigue failure has long been an important issue for ships and offshore structures. Among the numerous methods for predicting fatigue life, the spectral method is accepted as the most reliable. Although the theory behind spectral analysis is straight-forward, the analysis itself is complicated and time-consuming because it is closely related to critical technical details such as the application of fatigue loading (wave pressures and the inertial forces due to cargoes), the extraction of the strees, and the calculation of stress RAO. Here, four key technical details-loading application, displacement boundary condition, the calculation of stress RAO, and the extraction of the fatigue stress-are discussed thoroughly. For each aspect, a resolution is presented based on the finite element pre-and post-processing software MSC/PATRAN or FE solver MSC/NASTRAN. The resolutions are effective and efficient, which can help engineers perform spectral fatigue analysis accurately and faster.

Keywords

spectral fatigue analysis / load application / BC / stress RAO / stress extraction

References

[1] Guoqing Feng. Study of the assessment of ship structural fatigue[D]. 2003, Harbin: Harbin Engineering University

[2] REN Huilong, FENG Guoqing, DAI Yuzhi. A PCL based automatic loading approach for wave pressures[A]. MSC. Software China Solution Forum 2002[C]. Beijing, 2002.

[3] Mansour A E, Ertekin R C. Proceedings of the 15^th international ship and offshore structures congress[M]. 2003, SAN DIEGO, USA: Elsevier