Finite Element Strength Calculation And Fatigue Strength Analysis Of Deep-towed System On Mother Ship With Large Open-hatch

In order to realize the operation function of a deep-towed system on mother ship,a large open structure of moon pool is set up in the midship of the ship,and the size of the opening is relatively large compared with the length of the ship.The structural characteristics will seriously weaken the overall longitudinal strength and bending and torsional strength of the whole ship.Therefore,it is not accurate to use the simplified calculation method applicable to the conventional ship type to evaluate the strength of the ship.In order to get the main hull of the ship It is necessary to use the finite element analysis method of the global ship structure to calculate the structural strength in order to obtain the detailed stress and deformation results of the components,especially the stress level in the large opening area of the midship,and the results are evaluated and checked..Based on the design wave method,the whole ship’s structural strength is calculated by the direct finite element method.Based on the SESAM software system,the finite element structural model of the whole ship is established,the wave induced motion and load long-term prediction under the condition of large opening and closing are calculated,the design wave group parameters are determined,the structural stress and deformation results of the whole ship structural model under the action of each equivalent design wave are calculated,and the stress characteristics of the open-hatch ship type are obtained,which can be used for the structural optimization of the same type of ship Significance.Due to the special structure of the deep-towed system on mother ship,the structure in the midship area has sudden change and does not have continuity.In order to ensure that its structure has sufficient safety margin,it is necessary to check its fatigue strength.The direct calculation method with finite element based on Spectral analysis method is used to evaluate the fatigue strength of the deep-towed system on mother ship.According to the strength calculation results of the global ship,select the thermal stress points to refine the model grid,apply the corresponding load,calculate the stress response transfer function of each thermal stress point under each working condition,calculate the total fatigue damage degree of each thermal stress point of the deep-towed system on mother ship according to Miner’s linear accumulation damage theory,and then calculate the fatigue life of each thermal stress point to complete the fatigue strength assessment of the deep-towed system on mother ship.According to the finite element calculation results of the global ship structure of the target ship and the fatigue strength analysis of the opening area,it can be concluded that the structural design of the large opening of the target ship meets the use requirements of the structural strength of the ship.