Mechanism Of The Fatigue Crack Behavior Of 7N01-T6 Aluminum Alloy In Different Dust Environments

Because of the secrecy and suddenness of fatigue fracture,fatigue damage has always been the key problem affecting the service safety of aluminum alloy members.A large number of studies have shown that the service environment is an important factor affecting the fatigue damage of aluminum alloy.At present,domestic and foreign studies have mainly focused on aluminum alloys in terms of temperature,corrosive media,humidity and atmospheric environment,but there are few reports on the influence of dust environment on the fatigue damage behavior of aluminum alloys.Effect of dust on fatigue crack propagation behavior of 7 N01-T6 aluminum alloy was studied.The results show that:(1)Road-dust,coal-dust and mine-dust dust particles can reduce the fatigue crack growth rate of aluminum alloy at crack initiation stage and steady propagation stage.The fatigue crack growth rate of aluminum alloy in sand-dust environment is close to that in air environment.(2)The fatigue crack path under the action of road-dust and coal-dust particles is more tortuous than the air environment,and the crack deflection many times.Small particles entering the crack will promote the crack closure effect and lead to a large amount of slip at the crack tip,thus producing many microcracks and crack branches,greatly consuming extended energy.(3)The elastic modulus of the particles has a significant impact on the fatigue growth rate of the aluminum alloy.The graphite particles will accelerate the fatigue crack growth rate of the aluminum alloy,because the elastic modulus of the graphite is small and is crushed into small particles during the fatigue loading process.The crushed fine particles can effectively reduce the friction between the crack contact surface and weaken the crack closing effect.(4)Calcium oxide particles with the elastic modulus close to the aluminum matrix have little impact on the fatigue growth rate of the aluminum alloy,due to the interaction of reducing friction and early closing effect,making the fatigue crack growth rate close to the fatigue crack growth rate in the air environment.(5)Aluminum particles with elastic modulus greater than the aluminum base will slow the growth rate of the fatigue crack,while the particles will deposit on the crack surface and cause the crack closure of the advance,reducing the ?Keff value,so the fatigue crack growth rate is significantly slower than the fatigue crack growth rate in the air environment.(6)Manganese dioxide particles can significantly accelerate the crack growth rate.This is due to the very large elastic modulus of manganese dioxide,and these unbreakable particles enter the crack and cause a stress concentration at the crack tip,which plays a significant acceleration in the rate of the entire growth period of the aluminum alloy.