Effect Of Cumulative Damage On Damping Ratio Of Domestic Aluminum Alloy For Structural Use

Aluminum alloy material has the advantages of light weight,high strength and good corrosion resistance,so more and more aluminum alloy material is applied in the main structure of the building.Because aluminum alloy material has the disadvantage of fatigue resistance is not as good as structural steel,it is easy to suffer the impact of fatigue load.With the growth of service life,The accumulated fatigue damage will affect the mechanical properties and damping properties of aluminum alloy materials,cause a series of hidden dangers to the building and affect its service life.In order to study the influence of cumulative damage on the damping ratio of domestic aluminum alloy used in structure,firstly,the research method of damping ratio and the research of this paper are analyzed by determining the energy dissipation coefficient and equivalent viscous damping coefficient of components.Secondly,the fatigue load spectrum is prepared to determine the cumulative damage amount and the degradation of material mechanical properties in 50 years.Finally,the influence of cumulative damage on damping ratio of aluminum alloy under different working conditions was studied through parametric analysis.The main research contents of this paper are as follows:(1)In this paper,6061-T6 aluminum alloy hollow cylinder as the research object;Based on the hysteretic curve,skeleton curve and energy dissipation coefficient obtained from pseudo-static tests,the rationality of the finite element model in this paper is verified.(2)The daily wind speed of the city where the project background is located is statistically studied,and the probability of each wind speed grade occurring throughout the year is obtained;Based on MATLAB,AR linear filter method was used to simulate the fluctuating wind,and the wind load time history spectrum at the measuring point was compiled.The time-history spectrum of fatigue stress at the sensitive point of the model was obtained by transient analysis.Combined with the rain flow counting method,Goodman stress amplitude correction,and Miner’s linear cumulative damage theory,the cumulative damage degree of 50 years at the most dangerous point was calculated to be 0.21.Combined with damage mechanics theory and fracture mechanics theory,the time-varying function of mechanical properties degradation of aluminum alloy materials under the action of cumulative damage was studied,and the mechanical properties degradation of aluminum alloy materials after 50 years of use in natural environment was obtained.(3)Using Abaqus finite element software,the influence of different axial pressure ratio and different slenderness ratio on the damping ratio of aluminum alloy hollow cylinder under the same condition is studied.The results show that under the same condition,the damping ratio of aluminum alloy decreases with the increase of axial compression ratio,and under the same condition,with the increase of slenderness ratio,The energy dissipation and damping ratio of aluminum alloy hollow cylinder decrease due to the decrease of hysteresis curve.The influence of cumulative damage on the damping ratio of aluminum alloy hollow cylinder is studied when axial compression ratio and slenderness ratio are constant.The results show that when axial compression ratio and slenderness ratio are constant,the hysteretic curves of the initial aluminum alloy hollow cylinder completely surround the hysteretic curves affected by cumulative damage under the same loading displacement,which indicates that cumulative damage will affect the energy dissipation capacity of aluminum alloy.As a result,the damping ratio of aluminum alloy decreases.