The Research On Damage Tolerance Desgin Of Secondary Ageing Aluminum Alloy

7055 aluminum alloy is an ultra-high-strength aluminum alloy which has been applied.It has a very prominent property,making the alloy widely used in the aspects of aerospace,automotive,shipbuilding and many other fields.Many scholars have carried out a number of studies on 7055 aluminum alloy mainly about the effects of different heat treatment conditions on mechanical properties in China,but little about the effects of secondary ageing on mechanical,especially damage tolerance properties.Research on mechanical properties and damage tolerance properties of 7055 aluminum alloy base metal and secondary ageing metal with the methods of combining test observation and theory analysis together in this paper;build fatigue crack growth rate model of 7055 aluminum alloy base metal and secondary ageing metal.The main works of the paper are shown as following.Firstly,sizes of grains and distributions of precipitations of 7055 aluminum alloy in different states are analysed with metallographic structure and TEM structure photos;Secondly,static tests are carried out on 7055 aluminum alloy in different states including tensile test,compression test and planar fracture toughness test in the constant temperature condition in laboratory.The differences between 7055 aluminum alloy base metal and secondary ageing metal on tensile properties are analysed with metallographic structure and SEM morphology,the differences between 7055 aluminum alloy base metal and secondary ageing metal on planar fracture toughness are analysed with metallographic structure(TEM);Besides,crack growth rate on 7055 aluminum alloy in different states are tested in the constant temperature condition in laboratory,R=0.06?0.5,F=20Hz.The differences between 7055 aluminum alloy base metal and secondary ageing metal on damage tolerance properties are analysed with metallographic structure and fatigue fracture morphology(SEM).The effects of stress ratio on crack growth rate are analysed;Last,build crack growth rate formulas of 7055 aluminum alloy base metal and secondary ageing metal,the remaining life of 7055 aluminum alloy in different states with crack are predicted and the results are compared with the real life tests.