| Summary: | 碩士 === 逢甲大學 === 機械工程學所 === 100 === The main beam of an aerofoil(box beam) is a hollow structure. The beam is tightly fixed with the aerofoil structure by screw bolts. During the flight the loads to the aerofoil are aerodynamic buoyance lift and resistance. The distortion and internal forces caused by resistance are relatively much smaller than buoyance lift. That is, the main aerodynamic load is buoyance lift. In the flight the aerofoil can bend upward caused by buoyance lift, gravity and inertia. It can generate torque and stress inside the structure. In this thesis the Nonlinear finite element method is applied to discuss the impact caused by the contact stress of bolt holes and stud under the torque of the box beam. In addition, the comparison of elasticity and plasticity of the material is presented. From the analysis result it is concluded that under the load to the box beam the bolt holes on the contact surface between the beam and the structure are more seriously stressed by the stud. The bolt holes on the other side closer to the nuts are less stressed by the stud.
Since the box beam has a hollow structure, after given pre-load on bolts, the surrounding surface of the bolt holes which contacts the nuts has stress concentration under the pressure. The increase of the pre-load caused the rigidity of the bolts on the box beam increased and the stress of the bolt hole by the stud decreased. It is also proven that the increase of the distance between the hole and edge causes the increase of
the stress limit of the bolt holes.
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