Evaluation of creep damage in Ti60 alloys by nonlinear Lamb waves

Creep induced damages occur when metallic materials are operated in the condition of elevated temperature and high pressure. It has an important engineering value to make an early test and evaluation of material creep damage. The present paper performs an in-depth analysis on the evaluation of creep damage of titanium alloy by nonlinear Lamb waves, in which Lamb mode pairs of S₁-S₂ and A₄-S₈ are conducted on creep damaged Ti60 plates. The normalized acoustic nonlinear parameter is proposed to characterize the creep damage state. A "mountain-shape" change in the normalized acoustic nonlinearity of Lamb wave versus the level of creep degradation in the Ti60 specimens has been observed both for Lamb mode pairs of S₁-S₂ and A₄-S₈. The change rate of the normalized nonlinear parameter of Lamb mode pair A₄-S₈ is much greater than that of S₁-S₂, which means that Lamb mode pair A₄-S₈ is more sensitive to the creep damage of Ti60 alloys.