Self-loosening is one of the major failure reasons for bolted joints. Utilizing the finite element method, a 3-Dimension finite element model under dynamic shear loading is built to study the loosening of bolted fastener phenomenon. And the effect of increment step length, initial clamping force, amplitude of the shear load, thread tolerance, friction coefficients on the loosening process are studied.
For the fracture failure phenomena occurred in random vibration experiment of the isolation clamp cylinder on the aerospace vehicles, the NX NASTRAN was used to make the finite element modeling for the overall structure of cylinder and analyze the random vibration response. The simulation results show that the maximum RMS stress of the clamp was 96 MPa at the test load conditions. The position of the maximum RMS stress is consistent with the one where fracture happens during vibration test. According to finite element analysis results, the original structure has been modified. The maximum RMS stress of modified structure is only 21.8 MPa.
Considering the elastic-plastic and creep behavior of the material of bolted joint, and the nonlinear variation of its properties with temperature, this paper proposed a one-dimensional mathematical model for predicting clamp load variation with cyclic elevated-temperature. Then, relevant factors which may affect the process are studied, and some measures to enhance the threaded fitting reliability are proposed.
Reverse design and forward design have their strong points each other. The advantages of reverse design lie in the treatment of free-form complex modeling, while forward design is good in modeling in simpler feature. The car body often contains complex curved surface and some simple features. Through a single reverse or forward design can’t realize the efficient design. In order to combine advantages of reverse and forward design, using the hybrid design process design can improve the efficiency of the development of car body.
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