Abstract: For checking strength of airfoil spar structure, stress distribution is analyzed and the maximum stress and location are obtained by using software MSC NATRAN. Owing to machining deviation and design tolerance, the airfoil spar structure is always with some uncertainties such as material, loading and geometry. The thickness of strip, rib and web for the airfoil spar structure are expressed by base random variables. Due to the performance function of the strength reliability is an implicit one of the base random variables, finite element stress analysis is carried out by using software MSC NASTRAN and PANTRAN. Second order responds surface method is introduced to analyze the reliability of the structure. The parameter sensitivity is also analyzed, which shows that the thickness distribution parameters of web 3, web 4 and the blow strip have great influence on the reliability of structure strength.

Key words: Airfoil spar, Quadratic responds surface method, Reliability, Sensitivity