| Aluminum alloy has the advantages of light weight,beautiful appearance,easy processing,corrosion resistance and recyclability.It can not only be used in glass curtain wall,doors and Windows,etc.;but also can be used as the main force-bearing member of the structure.It has been widely used in the field of civil engineering in recent 50 years.As the transmission hub of the Aluminum alloy structure,the node plays a vital role in the bearing capacity of the overall structure.At present,there are few hysteresis studies on the mechanical properties of aluminum alloy welded joints under cyclic loading,which will inevitably limit its application.Therefore,this paper selects the H-section of 6061-T6 and 6061-T4 aluminum alloy profiles commonly used in engineering,and through experimental research and finite element analysis to research the hysteretic behavior of the beam-column welded joints.The main work is as follows:(1)A series of experimental studies were carried out,including testing the hysteretic behavior of four H-section 6061-T6 and two H-section 6061-T4 alloy frame beam-column joints.The study reveals the force mechanism of welded joints of aluminum alloy frames.The effects of different axial compression ratios and different types of joints on the failure modes,hysteretic curves,stiffness degradation,ductility,energy dissipation and damage of the welded joints of two types of alloy frame beam-column joints were investigated.(2)The material properties of the welded joints of 6061-T4 alloy and 6061-T6 alloy were tested.The specific contents include the tensile test of the butt weld in the direction of the vertical weld axis and the tensile test of the tensile weld in the axial direction of the parallel weld.So that the accurate material properties of the welded parts of the test piece are obtained.Analysis of the influence of welding heat influence on the strength of strong and weak hardening alloy.Based on the test results,using the Ramberg-osgood formula to fit the material relationship curves of the parent metal,the heat affected zone and the weld metal.The material static constitutive relationship model was determined.The material hysteretic constitutive model of 6061-T4 alloy and 6061-T6 alloy under cyclic load was studied based on the experimental results of welded joint of frame beam-column.It provides the material basis for the numerical analysis.(3)Established the finite element model of beam-column joint of aluminum alloy frame welded joint and described the modeling process of meshing,material properties,boundary conditions and load application is described.Compared the finite element calculation results with the experimental results to verify the rationality of the modeling method adopted in this paper.(4)Using the finite element method,the typical example specimens of 6061-t4 and 6061-t6 two different type of alloy welding H-type section aluminum alloy beam-column connection nodes are designed respectively.The influence of axial pressure ratio,joint zone thickness,welding strength and joint type on the hysteretic performance of welded joints of aluminum frames is considered.(5)Based on the results of the joint test,the whole process analysis of the stress mechanism of the component is carried out,and a simplified hysteretic curve model of this kind of joint is proposed. |
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