The Fatigue Characteristics Research Of The Cross-Structures Of Trimaran

Cross-structures is the main part of the trimaran which is weak in strength, endured great force and large deformation. Especially in beam sea condition, the cycle of transverse wave dynamic load not only in the external shape of the hull of the ship and transverse bulkhead has the alternate stresses frequently, but also the stress concentration question is prominent, without doubt made these structure exist hidden danger.Base on the basic tenets and approach of fatigue evaluation, the main content of this paper is using the finite element method focuses on the fatigue characteristics of cross-structures of trimaran, and typical of a cross-structures node structure, major research are as follows:(1) Described the structure of the ship fatigue analysis of the theoretical basis and the basic method, the discussion focused on s-n curve method based on the finite element analysis method of whole-life principle of steps and the corresponding characteristics.(2) Established finite element model of the trimaran, its transverse wave conditions in the transient kinetic analysis to arrive at a node in the model of the overall dynamic response results, based on this extract cross-structures, and use the shell cell to re-establishment and refining the finite element model for applicable to fatigue analysis , then the entire basis of the dynamic response of nodes results of the use of fully cross-structures transient kinetic analysis, finite element model cross-structures nodes with time changes in the stress curves.(3) Under the cross-structures finite element model of transient kinetic analysis results, select the structure of the three bridges connecting nodes typical in the software were fatigue of three typical nodes fatigue life analysis, and to improve fatigue life of the three objectives typical node optimization method:1) Bracket against Cross-Structures plate by plate curved bracket, bracket board by changing the radius webs in the same load, selected 13 kinds of materials under different curvature of the arc contrast toggle plate fatigue life, and that when Radius and bracket-plate appearance, etc., toggle plate fatigue good performance conclusion.2) Used for connecting bridge profiles, angle profile asymmetry, as a result of its anti-fatigue is poor, and not because T profiles of asymmetric profile arising from the panel twisted, has strong anti-fatigue capacity. On this basis, using Fortran programming search and angle equal to the cross-sectional area of the largest section modulus T profiles, in the absence of structural weight increase under the premise of raising profiles used by the Cross-Structures the fatigue life.3) For cross-structures deck and the wet side of the main hull plate transition regions, use arc transition and the transition bracket board added two respective programmes in the region compared the impact of fatigue life obtained by the transition board is better bracket optimization of the structure of fatigue way.(4) Through ANSYS and finite element software MSC.Fatigue two mutual cooperation between the verified these two software on the static structural analysis -transient kinetic analysis - fatigue life analysis of the feasibility of this technology line.