Assessment And Optimization Research On Strength Of Flare Ship Bow Slamming

When ships sailing in rough sea conditions,because the motion between hull and wave is coMParatively violent,it is easily slammed that the hull structure is out of the water then into the water again.Slamming of the instantaneous hydrodynamic will cause transient elastic vibration of ship hull girder,namely,flutter.On the one hand,hull is under enormous pressure of slamming in the wave collision area,which may lead to a devastating effect on the strength of the local structure.On the other hand,it will also cause the entire hull flutter violently and produce large vibration of the bending moment.When induced by the low FRequency wave,the longitudinal strength of hull will be lost.Which has certain influence on the safety of hull structure.Therefore,in terms of hull structure safety,the structural response under the action of slamming load is worthy of our attention.The author uses quasi static analysis,dynamic response analysis and transient response analysis based on the finite element software MSC.PATRAN,MSC.DYTRAN and MSC.NASTRAN.The main content of this text is as follows:(1)This chapter mainly makes a quasi static analysis on the strength of 3800 parking Spaces car carrier(PCTC)in first outside which under the action of wave slamming by using MSC.PATRAN.The main content includes three parts: a.Calculating the first flare structure of wave slamming load according to Lloyd's(LR)specification;b.Checking the thickness of 3800 PCTC bow plate,the secondary structure and section modulus whether meet the standardized requirements according to Lloyd's(LR);c.establishing a finite element model of 3800 PCTC bow structure,calculating the stress level of the first structure under slamming load and checking the shear strength of its main supported Components(Primary Structures)whether meet the standardized requirements.(2)Using the nonlinear software with finite elements MSC.DYTRAN to repeatedly simulate and study the slugging problem of three-dimensional elastic-plastic flat-bottomed cylinder structure,coMPared it with the experimental results in reference [54],which proves that in the stimulated calculation of wave-making,how to control Lagrangian and Euler grids can make the calculating results more accurately.Finally,the author investigated the stress response of the wave-making process in the prelude segmental structure of 3800-stalls car carrier(PCTC)and analyzed the limit of yielding,the speed of entering into the water,the shape of the bow and the angles of the entering into the water of the bowing structural material to investigate the effects of stress response in wave-making process.(3)The author conducted “the direct transient response analysis” on the external floating structure of the 3800-stall car carrier(PCTC)by using the software with finite elements MSC.NASTRAN.Firstly,the velocity of ship hull is forecasted based on SESAM software.According to the forecast speed,combined with the standard formula of the slamming pressure in Chapter 2,the author obtained the slamming load on the outer structure of the 3800-stall car carrier(PCTC).Finally,the author conducted a direct transient response analysis on the outer floating regional structure by the software with finite elements MSC.NASTRAN.(4)The results of quasi-static analysis,dynamic response analysis and transient response analysis are coMPared and analyzed,Found: The results of quasi-static analysis is too siMPle to display a slamming process and instantaneous change process of the structure stress response.Although dynamics analysis could present a perfect process of ship bow structures into the water,the results of the simulation calculation error is relatively large,and it has certain limitation.The amount of calculation of transient response analysis is far less than of dynamics analysis.Moreover,the results of the stress response is instantaneous process of change over time,which is more conducive to ship stem partial and the overall strength assessment.Therefore,the direct transient response analysis is the best ship stem wave simulation calculation method of structural response.Direct transient response analysis is the best optimal simulated calculation method respond to bow-and-bow floating structures.The results show that the stress level of the multi-structure of the 3800-stall car carrier(PCTC)is higher than that of the outer structure of the PCTC,so the optimized structure should be simulated and analyzed.By the way,there should be a stimulated calculation analysis on the optimized structure by using “the direct transient response analysis”.The direct method of stress transient response analysis is used to optimize the structural stress area.