Numerical And Experimental Study On Ultimate Strength Of Aluminum Alloy Ship Structures

In order to meet the requirements of modern ships for high speed and light weight,aluminum alloy has been widely used in the field of ships with its excellent specific strength property.However,as the low rigidity of aluminum alloy,the strength of aluminum alloy hull gradually attracts people's attention,especially in the stability and ultimate bearing capacity of the hull structrues.At present,the researches on the structure of the steel stiffened plate have been more mature,while the researches on the extruded aluminum sheet-with-ribs are few.Therefore,it is necessary to study the ultimate strength of the aluminum sheet-with-ribs so as to improve the accuracy of the numerical prediction and provide guidance for hull structure design.Based on a high-speed aluminum alloy trimaran,the ultimate strength study of aluminum sheet-with-ribs in two typical structural forms(the notched and the suspended sheet-with-ribs)were carried out by the finite element method and test method.This numerical method was validated first and then the further research of box girder and hull ultimate strength was carried out.The main contents are as follows:1)The research on nonlinear finite element analysis of ultimate strength of aluminum sheet-with-ribs was carried out.Combined with two common structural forms of sheets with ribs,the sensitivity analysis of ultimate strength of aluminum sheet-with-ribs under various influencing factors was carried out by using nonlinear finite element method.2)The research on ultimate strength test of aluminum sheet-with-ribs was carried out.The test device and the test program were designed,and the ultimate strength test of aluminum alloy ribbed plate was completed.The buckling and ultimate strength of two typical aluminum alloy ribbed plate structures under axial compression was obtained.Finally,the nonlinear finite element analysis method was validated through the comparison of the numerical prediction and the test results.3)Based on the nonlinear finite element method,the ultimate bending moment analysis of aluminum alloy box girder was carried out.The box girder model,used by Vahid Farajkhah,was selected and its ultimate bearing capacity was calculated by nonlinear finite element method.Compared with the results of the literature,the numerical analysis method was validated further.On this basis,the effects of residual stress and HAZ material softening on the ultimate bearing capacity were also carried out.4)Based on the nonlinear finite element method,the ultimate bearing capacity of the aluminum alloy trimaran was analyzed.According to Lloyd's trimaran rules for the total bending stress of hull girder,the ultimate strength evaluation method of the trimaran based on vertical bending moment was derived and established,and then applied to the ultimate strength evaluation of aluminum alloy trimaran.