In present day, the compressed air tank for ships is made of a cylindrical pressure vessel with welding structure and a stress amplitude caused by a dynamic load and mean stress by a dead load is occurred.
By means of variable stress condition caused the concentration of stress on a welding area. In order to minimize the fatigue failure by concentrated stress, the limit and size of allowable damage factor and the shape of welding type must be determined at the designs.
At this research, the property of safety for the compressed air tank evaluated in accordance with test and the established method related to the same kind of pressure vessel and the main result are followed as :
1. The compressed air tank for T.S. HANNARA of Korea Maritime University is selected for the testing model and calculated the operating hours of the air compressor for charging the tank. By means of the statistical analysis, it can estimate the cycle of dynamic load on the tank during the estimated design life.
2. The chemical and physical characteristics of the material for the pressure vessel are researched and collected data and other results. By those results, it is proposed that the formula of the fracture strength with 90% probability of fatigue failure with the stress concentration factor and stress ratio influenced on the fatigue strength.
3. At this research, the cumulative damage factor based on Miner-Palmgren hypothesis is used for the practical procedure of fatigue life prediction. Also, the quantitative analysis of the safety of fatigue fracture for the compressed air tank can be estimated and then the results are reflected on the optimization of design.
4. To review the theoretical calculation, the simulation test is conducted for stress concentration and stress ratio generated on the testing model by uses of finite element analysis program.