Research On Strength Criterion Of Ship Structure Considering Dynamic Effect

Vessels are subjected to a variety of complex external loads throughout their operational navigation cycles,most of which are dynamic loads.The structural response under dynamic loads are greatly diffirent from static or quasi-static behavior.At present,for the ships and offshore structures that are subjected to dynamic loads,the assessment criteria used by the classification societies and abroad are mostly based on the quasi-static equivalent law.Although the quasi-static equivalent law has some inherent relationship with the plastic carrying capacity and permanent deformation of structures,it ignores the temporal characteristics of dynamic loads and the dynamic failure behavior of materials.If considering the dynamic effect,the quasi-static method to check the structural strength of ship can not fully reflect its real stress state and failure mode.In order to study the strength criterion of ship's structures considering the dynamic behavior of materials and the time characteristics of loads,the following research work was carried out in this paper:1)The theory of material mechanics and dynamics is generalized and sorted out,and the research status of the dynamic mechanical properties of steel materials and the method of evaluating the dynamic response of hull structures are summarized.2)For the ships and marine structures subjected to dynamic loads,the basic theories involved in the dynamic response analysis of structure were described.The process of contact,the theory of fluid-solid coupling analysis,the material of ship structure considering the strain rate effect and the phenomenon of hourglass were described.3)For the process of ship-ice collision,the nonlinear finite element simulation software LS-DYNA was used to solve the problem.The time history and structural response of the hull structure under the impact were obtained,and the structural response characteristic of the ship-ice collision was analyzed.4)According to the structural response characteristic of the ship-ice,a dynamic load model test was designed and carried out.Through the simulation and experiment,the response characteristic of the specimen structure was studied,and the specimen structure damage criterion was tentatively put forward.5)Based on the specimen structure damage criterion proposed by the test,the structure response under static load was investigated.Comparing the results of simulation and test under dynamic and static load,the structural strength criterion under dynamic effect is proposed.Aiming at the phenomena of ship-ice collision and slamming,the partial structure of a ship was taken as an example.According to the given criteria by the article and the criteria by the norms,the structural strength was checked and compared,which provides a reference for the structural strength criterion and structure design of ships considering the dynamic effect.