Comparative Study on Durability and Damage Tolerance of TC4 and TC4-DT Titanium Alloys
As more and more structural parts of military aircraft utilized damage tolerance titanium alloy(TC4-DT),it is very urgent to compare the durability and damage tolerance of TC4-DT and TC4 titanium alloy.In order to compare the fatigue life characteristics of the two materials,a crack initiation life prediction model based on local stress-strain method and a crack propagation life pre-diction model based on Walker formula and Willenborg model were introduced.A fatigue test of double-hole coupon under random spectrum is carried out to verify the correctness of the method.By using the same method,the fatigue test of TC4 and TC4-DT titanium alloy under constant amplitude spectrum was analyzed.The percentage of weight gain required to increase the crack initiation life of TC4-DT material to the level of TC4 and the percentage of weight gain required to increase the crack propagation life of TC4-DT material to the level of TC4-DT at 300～400 MPa stress level under ran-dom spectrum were calculated.It is concluded that the superiority of TC4-DT material in crack growth life is not as obvious as that of TC4 material in crack initiation life.For the aircraft structure,both durability and damage tolerance design criteria should be taken into consideration to make a choice between TC4 and TC4-DT.
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