Effect of nonlinear slamming loads on the fatigue damage of a ship with large flare

Abstract

[Objectives] The traditional spectral fatigue analysis method only considers the effect of linear wave loads on fatigue life. For ships with large flare,how to reckon in the effect of nonlinear slamming loads is to be a difficulty in fatigue life calculation.[Methods] In this paper,a three dimensional nonlinear time domain method was used to analyze the time history distribution of global bending moment for a ship with big flare. Then the distribution of fatigue stress range of nodes of the hull were calculated by using the rain-flow counting method and the fatigue damage considering the effect of nonlinear slamming loads was obtained. After comparing this damage with those induced by linear wave loads, the amplification coefficient of nonlinear slamming bending moment for a ship with big flare was calculated.[Results] After calculation,within the effect of slamming loads,the fatigue damage is enlarged by about 40%.[Conclusions] The method described in this paper is of practical significance to the fatigue life calculation for the ship with serious slamming loads.

Keywords

• nonlinear hydroelasticity
• slamming loads
• rain-flow counting method
• fatigue damage