An Experimental Study to Evaluate Fatigue Damage Considering Springing and Whipping

초록

It is known that hull girder vibration fatigue resonating frequency of wave loading due to decreasing in natural vibration frequency of higher-speed and larger container ship and ore carrier. This hull girder vibration fatigue is usually defined as springing. Also, the hull girder vibration fatigue caused by bow slamming is defined as whipping. These vibration-induced wave responses cannot be used to expect the exact fatigue life through the current stochastic fatigue analysis methodology. As the stochastic fatigue analysis is only focused on the stress spectrum by wave and the resultant fatigue damage, the fatigue estimation of the vibration-induced wave has been depend on the simple summation method of each spectrum. And it is known that simple summation of damage from each spectrum provides unconservative rsults. In this paper, fatigue tests for simplified vibration-induced wave signal were conducted to find variables influencing fatigue damage of vibration-induced wave. Fundamentally, rain flow counting method and Palmgren-Miner's rule were used for calculating fatigue damage. And then, experimental fatigue damages are compared with each load cases to evaluate effect of vibration and to investigate tendencies of vibration-induced wave fatigue damage.