As a simplified structural model, a semicircular frame is used to study the crashworthiness behavior of an aircraft fuselage. The quasi-static large elastic-plastic deformation of a semicircular frame in the process o...As a simplified structural model, a semicircular frame is used to study the crashworthiness behavior of an aircraft fuselage. The quasi-static large elastic-plastic deformation of a semicircular frame in the process of its being pressed against a rigid ground is analyzed. First, based on the linear elastic assumption, the quasi-static large deformation contact process of the frame can be divided into three phases, i.e., point contact, line contact and post-buckling. By means of a shooting method, the relations between the displacement and contact force as well as the distribution of bending moment in the three phases are obtained. Then, by assuming an elastic, perfectly-plastic moment-curvature relationship for the semi-circular frame, the contact process is analyzed in detail to reveal the plastic collapse mechanism, the traveling of plastic hinge and the force-displacement relationship. In order to verify the analysis, a preliminary experiment was conducted, in which two types of half rings with clamped ends were pressed by a rigid plate. In addition, a numerical simulation is also conducted by employing ABAQUS to analyze both rectangular cross-sectional beam and I-beam. Finally, the theoretical predictions are compared with the experimental results and numerical solutions, showing that the elastic-plastic analysis can predict the contact process very well.展开更多
Setting up a pair of moving frames on the two pitch circles, the instantaneous contact point being considered the attendant point of the frames, the equation of the trace of the contact points in the frame being p = p...Setting up a pair of moving frames on the two pitch circles, the instantaneous contact point being considered the attendant point of the frames, the equation of the trace of the contact points in the frame being p = p(t~), we can deduce that the basic rule for the gear profiles is dp / ds = - csos 0 where s is the are length of the pitch circles. Giving a known function of p = p (0), we can obtain the equations of the two conjugate gear profiles and the curvatures and inductive curvature of the profiles. The second order contact phenomenon that a given gear profile can contact with the mating gear at two points simultaneously is discussed by the method of moving frames.展开更多
基金the National Natural Science Foundation of China (10532020)
文摘As a simplified structural model, a semicircular frame is used to study the crashworthiness behavior of an aircraft fuselage. The quasi-static large elastic-plastic deformation of a semicircular frame in the process of its being pressed against a rigid ground is analyzed. First, based on the linear elastic assumption, the quasi-static large deformation contact process of the frame can be divided into three phases, i.e., point contact, line contact and post-buckling. By means of a shooting method, the relations between the displacement and contact force as well as the distribution of bending moment in the three phases are obtained. Then, by assuming an elastic, perfectly-plastic moment-curvature relationship for the semi-circular frame, the contact process is analyzed in detail to reveal the plastic collapse mechanism, the traveling of plastic hinge and the force-displacement relationship. In order to verify the analysis, a preliminary experiment was conducted, in which two types of half rings with clamped ends were pressed by a rigid plate. In addition, a numerical simulation is also conducted by employing ABAQUS to analyze both rectangular cross-sectional beam and I-beam. Finally, the theoretical predictions are compared with the experimental results and numerical solutions, showing that the elastic-plastic analysis can predict the contact process very well.
文摘Setting up a pair of moving frames on the two pitch circles, the instantaneous contact point being considered the attendant point of the frames, the equation of the trace of the contact points in the frame being p = p(t~), we can deduce that the basic rule for the gear profiles is dp / ds = - csos 0 where s is the are length of the pitch circles. Giving a known function of p = p (0), we can obtain the equations of the two conjugate gear profiles and the curvatures and inductive curvature of the profiles. The second order contact phenomenon that a given gear profile can contact with the mating gear at two points simultaneously is discussed by the method of moving frames.
