| The hollow wide-chord fan blade has observably advantage of increasing the surge margin,resisting foreign object damage, improving engine thrust, decreasing the number of blade andreducing engine weight. It has become one of the pivotal techniques employed by highthrust-to-weight turbo-fan aero-engine. On summarizing and analyzing the structure characteristics ofhollow wide-chord fan blades at home and abroad, taking truss stiffened structure as a researchsubject, which is used to simulate the structural mechanics characteristics of the hollow fan blade, andcarrying out a study in the mechanical design, forming process and fatigue failure of the trussstiffened structure.For the manufacturing method and mechanical design of the truss stiffened structure, this paperhas designed two kinds construction of the structure. Superplastic forming/diffusion bonding processparameters and processing method have been studied.Stress versus fatigue life curve for diffusion bonded joints of TC4is obtained through fatiguetests of TC4diffusion bonded joints. A special self-made voltage gauge is used to measure the voltageof the weld area, which can be used to evaluate the fatigue damage evolution of TC4diffusion bondedjoints. By taking the voltage as a damage parameter, the evolution of fatigue damage of diffusionbonded joints is proposed based on the theory of damage mechanics. The micro surface morphologyof TC4diffusion bonded joints is analyzed with the help of scanning electron microscope.The paper also carries out the single wave test specimen fatigue tests and then fatigue life isobtained. The fatigue damage evolution is proposed base on change of strain amplitude in the processof fatigue. Through the analysis of macro and micro fracture surface, it is found that the fracture oftest specimen is belong to brittle fracture and most of fatigue sources at closed section internal angleof truss stiffened structure. |
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