| Heavy-duty universal joints are key componets in main drive systems in rolling mills, which are also the weakest componets in main drive systems. Failure of the universal joint will cause the entire main drive system damaged, and halt the entire rolling production line. The failure will cause substantial econmical loss, thus, it is of great significance to establish the forward design method of universal joints in order to enhance the service life and reliability of universal joints. The forward design theory is established on the basis of kinematics analysis, dynamics analysis, structure analysis, which aims at avoiding motion interference and complying with the uniform-strength prerequisite. The main research content and archivements are as followings:(1) Motion equations are established by adoption of spatial projective geometry. Influence of phase angle and true shaft angle on instantaneous angular difference and instantaneous rotational velocity difference is analyzed, which supplies a theoretical basis for analysis of influence of elastic deformation, clearances and manufacturing tolerances on kinematics behaviors of universal joints. Kinematics equations of bearings in universal joints are established by adoption of spatial geometric projection method and space coordinate transformation method, and kinematics behaviors of bearings in universal joints are analyzed. Then unequality of rotational velocity of bearings in the driven yoke and driving yoke is proved, which provides the theoretical basis for analyzing and designing bearings in universal joints.(2) Torsional vibration equations are built by adoption of lumped-mass model, and the definition of application factor KA is given. Bending vibration equations are established by utlization of flexibility coeffient method, and influence of mass eccentricity and addtional load on bending vibration is analyzed. Hereafter, torsional-bending coupling vibration is analyzd, which occurs at biting and throwing stages of steel rollings. The addtional load factor KB is proposed in this paper, and the calculation method of KB is also given here. The software model for analyzing dynamic behaviors of main drive systems of rolling mills is established by using of object-oriented modeling method UML. Hybrid programming method which combines VB.NET and MATLAB is established, and the swift establishment method of the software is proposed in this paper.(4) The secondary-stress-relief method is proposed in this paper, by analyzing and deducing the relationship between local curvature of fillets and local stress concetration factors. By adopting of the second-stress-relief method, unconstant curvature fillets at roots of cross shafts are designed, and validity of unconstant curvature fillets is proved by using FEM. Furturemore, optimization software for designing dual-arc fillets of cross shafts is programmed with the complex method.(5) Design criteria are proposed according to analysis of failure modes of universal joints. Method for calculating load coefficient of universal joints is proposed by comprehensive analysis of universal joints togather with prime motors and loads. By taking detail structures of yokes and cross shafts into consideration, the forward design method is established, which aims at avoiding motion interference and complying with the uniform strength prerequisite. |
