Research On Improving The Bearing Capacity Of Marine Aluminum Alloy/Steel Composite Joint

The use of aluminum alloy superstructure in ships is the development trend of lightweight manufacturing of ship structure.The reliability of aluminum/steel composite structures connected to steel hulls of aluminum alloy superstructures depends mainly on aluminum-steel transition joints.However,due to the difference sirrationality of physical properties and metallurgical incompatibility between heterogeneous metals,the aluminum/steel composite structure currently in use is prone to major safety hazards of cracking of transition joints in the welding manufacturing and service process,which seriously affects the safety service performance of the ship composite structure.Relying solely on increasing the width of composite transition joints and regulating welding process parameters have not solved the problem of aluminum/steel composite structure cracking,which restricts the wide application of composite structure.First of all,this article is based on aluminum/steel composite transition joint shear strength,proposed the ship aluminum/steel composite connection structure double bearing model,the aluminum and steel transition joint bearing mode change from the traditional pattern of positive tensile load for tensile and shear interaction model,composite transition joint Angle by the tensile strength and shear strength of composite interface().Numerical simulation results show that the tensile load capacity of aluminum/steel composite structure can be increased by 27%,and the test shows that the tensile strength of aluminum/steel composite structure can be increased from 256 MPa to 306 MPa after the change of bearing mode,and the bearing capacity of aluminum/steel composite structure can be increased by 20% under the double bearing mode.Then,Through numerical simulation,it is found that the high temperature and uneven distribution of the temperature field at the aluminum/steel interface during the fillet welding of the composite joint structure lead to different degrees of reduction in the tensile strength of the interface,which affects the reliability of the aluminum/steel composite structure.For the first time,this paper proposes a method to determine the composite transition joint based on non-uniformity of mechanical properties,that is,to determine the characteristics of the composite interface partition of the non-uniform temperature distribution based on the relationship between tensile strength and temperature,so as to accurately calculate the width and size of the composite transition joint.When the thickness of the aluminum plate is 4 mm,the width of the transition joint should be 24 mm.The tensile test shows that the interface bearing capacity of the composite transition joint meets the requirements when it is stretched,and the fracture occurs at the fillet weld of the composite connection structure.Finally,by means of numerical simulation,the distribution characteristics of residual stress and external load stress in the composite joint structure and the dangerous area are determined.It is found that when the external load and residual stress are superimposed,the stress values at both ends of the aluminum-steel composite interface will be close to the bonding strength of the post-welding interface.Therefore,the design method of "weld-tenon" structure of stepped tenon in the dangerous area of composite interface between aluminum and steel transition joint is put forward,so as to improve the bearing capacity of composite interface between aluminum and steel transition joint.The numerical simulation shows that the "weld-tenon" structure can fully bear the external load and residual stress.