Numerical investigation on stress concentration of surface notch on blades

Crack grinding process is the essential step in the remanufacturing pre-treatment for the compressor blade with fatigue crack. After crack grinding process, a notch will be generated on the surface of the blade. Stress concentration factor (SCF) of the surface notch is a basic parameter on remanufacturability assessment depending on fatigue behaviors. However, few equations can be employed directly to estimate SCF of surface notch in the current lecture. In the present study, stress concentration of surface notch with semi-elliptical sections on a plate with finite thickness and width has been investigated using finite element analysis. It was found that the depth and width of surface notch and the thickness of plate were the main factors that controlling the stress concentration. What is interesting in theoretical modeling is that SCF of surface notch with semi-elliptical sections with large thickness can be estimated by the simple modification of Inglis's equation. Following, based on the modified Inglis's equation, an empirical SCF equation of surface notch was proposed with the consideration of depth and width of the surface notch and the thickness. A reference value of SCF for the blade after crack grinding process can be provided using the equation.