Study Of Multi-axial Fatigue For The Connecting Bridge Of Multi-Hulls

Fatigue damage is a hot spot in the field of ship and ocean engineering for it is one of the main failure forms of ship and offshore structure.The current methods of fatigue assessment to hull structure have been very mature,but most of the important structural components in the actual engineering structures and equipment are served in a complex multi-axis load,as a result the research of more realistic multi-axial fatigue is paid a generally attention and it has been a hot issue in the intenational fatigue field in recent years .As the complex structure of the multihull,it is easy to bear multi-axial load and its connecting bridge is the key positions in fatigue analysis.Therefore,this paper analyze the multi-axial fatigue based on the methord of fatigue assessment in CCS Guidelines of Small Waterplane Area Twin Hull Craft.The main contents and conclusions are as follows:1)Fatigue assessment methods in Guidelines of Small Waterplane Area Twin Hull Craft were introduced and the designed load cases were analyzed.2)The finite element model was established according to designed requirements of Guidelines of Small Waterplane Area Twin Hull Craft. Load cases which are given in standard were carried on to the model and relevant data was extracted in order to analyze multi-axis status.3)Criteria for multi-axial fatigue life prediction was introduced and number of load cycles combined with practical examples was calculated as well as compared with the traditional method.4)Formular of multi-axial fatigue damage was deduced based on traditional S-N curve methord.Model instance was calculated with the new methord proposed in this paper and the result was compared with traditional methord in order to show the necessity of considering of multi-axial fatigue.