Study Of Stability Performance For 7A04-T6 Aluminium Alloy Square And Rectangular Tubes Under Compression And Bending

Aluminium alloy,as a mature metal material,has been widely used in the field of building structures.At present,6000 series aluminium alloys are often used in aluminium structure projects around the world,but their strength is generally low and gradually fails to meet the needs of large span structures.The domestic 7A04-T6 high-strength aluminium alloy,with a yield strength of 500MPa or more,can effectively reduce the cross-sectional size of members in practical engineering,but there is little research on the stability performance of 7A04-T6 aluminium alloy compression-bending members.Therefore,in this paper,the stability performance of 7A04-T6aluminium alloy square hollow section members and rectangular hollow section members is studied through a combination of experimental research,finite element analysis and theoretical analysis,and the main contents and conclusions are as follow:（1）The mechanical properties of 7A04-T6 aluminium alloy were determined by unidirectional tensile test.Initial bending of 7A04-T6 aluminium alloy members was measured to determine the overall initial geometric imperfection amplitude.Eccentric compression tests were also carried out to obtain the failure modes and stability bearing capacities of the members.7A04-T6 aluminium alloy square hollow section members occurred in overall flexural buckling and most of rectangular hollow section members occurred in combined overall flexural buckling and local buckling around the weak axis.As the normalized slenderness ratio（?）and eccentricity e increase,the stability bearing capacity and initial stiffness decrease,and the plastic deformation capacity increases with increasing（?）,while a change in e has no effect on the plastic deformation capacity.（2）The finite element model was established according to the parameters of the experimental study,and the feasibility of the finite element model was verified by comparing the experimental results with the finite element results.On this basis,the expanded parametric analysis of the overall geometric initial imperfection,the normalized slenderness ratio（?）and the eccentricity e.The effect of the initial imperfection on the stability carrying capacity is greatest at（?）=1.In the specimen axial force-end bending moment curve,the axial force decreases and the end bending moment increases as the member’s e increases;as the member’s（?）increases,the end bending moment gradually becomes the decisive factor affecting the instability of the member.（3）The calculation results were obtained by means of the calculation formulae for the stability carrying capacity of compression bending members provided by the aluminium alloy Chinese code GB 50429-2007,the European code BS EN 1999-1-1:2007,the American code AA-2015,the Australian/New Zealand code AS/NZS1664.1:1997,the direct strength method and the continuous strength method,and compared with the test values and finite element values.The calculation results of the four codes and the direct strength method are conservative,while the calculation values of the continuous strength method are more accurate.Based on the finite element values and the test values,the parameters（?）and η₁ of the Chinese code calculation equation were modified,with η₁ taking a value of-0.5.The modified equation was able to accurately calculate the stability bearing capacity of the 7A04-T6 aluminium alloy compression bending member.