13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- coupled analysis is 593.548MPa located in the blade root trailing edge. In the aerodynamics load, the maximum stress is 43.016 MPa, which is much less than the value, 552.697MPa, under the centrifugal load condition. From magnitude, the displacement and the stress in the coupled calculation is equivalent to the total effect of the centrifugal load and the aerodynamics load. Table.2 Contrast of the maximum displacement and stress under different load condition Load type Max Von Mises stress（MPa） Max displacement（mm） blade shroud blade shroud Centrifugal load 552.697 433.24 1.348 1.5348 Aerodynamics load（A） 43.016 —— 0.09335 0.09916 Centrifugal load +（A） 593.548 435.944 1.411 1.613 4.3. Optimization Model of Turbine Blade Based on CO Strategy The turbine blade adopts the DZ125 materials. The material requires that the equivalent stress is not more than 75% 0.1 σ , the maximum stress of the joint is not more than 60% 0.1 σ , and the contact stress is less than the allowable pressure stress. The temperature of the material is restricted to 1273.5K and the mass flow (mf ) limited in range [ ] 1 102.5,112.5 ( . ) kg s− . Additionally the radial tip elongation is not more than 0.01m. Those are constraint condition, definited 1 2 { , } Y Y Y = , where Y is the system response value, 1Y the response value of the structure strength discipline, 2Y the fluid discipline response value, as formula (12). The object function adopts the weighted sum of the isentropic efficiency and the total mass in the formula (13): 1 2 { , , , , } { , } tip shroud chamfer blade contact Y dx Y mf T σ σ σ σ = = （12） 1 2 0 1 2 0 10 20 ( ) ( ) * ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) F X W X W m X m X m X m X m X m X m X m X η = + = + = + （13） Where ( ) Xη is the isentropic aerodynamics efficiency function, ( ) m X the quality function of the shrouded blade, 0( ) m X the initial model quality of the shrouded blade. The subscript 1 is the blade and the subscript 2 is shroud. 1W and 2W is the weighted factor, respectively taking 0.7 and 0.3. The MDO model of the turbine shrouded blade can be wrote as formula (14). [ ] 1 2 0 1 5 tan 2 6 3 7 4 : min ( ) ( ) * ( ) . . 0.01 0 173.0 0 (14) 645.5 0 78.5,80.5 516.4 0 1273.5 0 697.0 0 X [ , ] tip con ct shroud chamfer l u blade find X F X W X W m X m s t g dx g g g mf g g T g X X η σ σ σ σ = + = − ≤ = − ≤ = − ≤ = ∈ = − ≤ = − ≤ = − ≤ ∈
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