Experimental,Numerical And Theoretical Studies On The Dynamic Response Of Plates With Initial Cracks Under Repeated Impact Loadings

In recent years,due to the irreversible greenhouse effect,the arctic is valued by many countries for its rich natural resources and potential shipping routes.As the ship is the key equipment for polar resource development and freight transport,its structural performance in the polar environment has been attracted more and more attention from scholars,and a lot of research work has been carried out successively,involving the impact simulation of floating ice in low temperature environment and the prediction of ice load.During the long service period time of ships,the surface of hull structure will inevitably produce cracks,pitting corrosion and other forms of damage due to the action of marine environmental load.At low temperature,the possibility of brittle fracture of the structure with initial cracks caused by repeated collision of floating ice increases tremendously,which threatens the safety of the whole ship.Therefore,it is of great theoretical significance and engineering practical value to study the bearing capacity of cracked structures under repeated impact loads at low temperatures.However,there is little research on the bearing capacity of structures with initial defects at low temperature at present.In this paper,a series of studies have been carried out on the repeated impact of cracked plates with different crack lengths at room temperature and low temperature.The effects of crack length on the load carrying capacity and deformation failure mode of plates are obtained,the influence mechanism of low temperature on the repeated impact performance of plates is revealed.Firstly,repeated impact tests were carried out on intact plates and plates with an initial crack of different lengths at room and low temperatures.The difference of dynamic response characteristics between intact plates and cracked plates under repeated impact was analyzed,the influence of crack geometry parameters on impact damage mode and bearing capacity was discussed,and the influence of environmental temperature on repeated impact performance of cracked plate was studied.Then,the numerical simulation model of plates subjected to repeated impacts was established in order to gain further insight into the effects of crack length and low temperature on the repeated impact behavior of plates.The numerical model was verified by the experimental results.The damage process of plates under repeated impacts was analyzed,the effects of crack geometry size and environmental temperature on energy absorption,stress distribution and load carrying capacity of the plates were studied.At last,the approximate analytical formula of plastic deformation of circular plate under repeated impact load was derived,and the accuracy of the theoretical formula was verified by experiments of repeated impact on intact plates.In this paper,the effect of initial crack on the plastic deformation of circular plate is characterized by the Reduction Factor of plate thickness.