An increase in the length of gas-turbine compressor blades for higher compression ratio and volume of gas passing through may cause fretting fatigue problems because of larger centrifugal force to blade and pressure at contact area between the blade and wheel dovetails. Titanium alloy is a suitable material for blade dovetail, instead of steel, in order to decrease the blade centrifugal force. In this study the fretting fatigue life of an airplane engine dovetail comprising Ti-6Al-4V alloy was investigated experimentally and analyzed using by stress singularity theory. The stress around a contact edge is represented by the stress singularity and the field-element method. The cyclic force corresponding to the gas-bending force of the compressor blade was then superimposed on the axial force. The crack initiation of fretting fatigue occurs at the corner on contact facet of blade dovetail between blade dovetail and wheel dovetail. The fretting fatigue in case of an titanium alloy can be evaluated by the parameters of stress singularity obtained from maximum principal stress distribution in finite element analysis. The intensity ratio of stress singularity between intensity range and critical intensity range is an effective parameter to predict the fretting fatigue occurrence of titanium alloy dovetails as well as steel.
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