大型回转窑支承系统的力学行为分析

对操作工况下大型回转窑支承系统的力学行为规律进行理论分析和接触非线性有限元仿真.根据轮带结构和运行特点,解析导出轮带内壁受简体的压力分布公式,修正了长期以来前人轮带压力公式的不妥之处.基于Ansys及其APDL( Ansys parametric design language)编程,实现对支承系统的多体接触模型在分布压力、摩擦转矩和预紧配合作用下的复杂加载及其边界非线性有限元模拟,获得回转窑支承系统的变形与应力分布规律.结果表明,轮带与托轮之间是循环挤压过程；每回转一周,轮带内外表面的等效应力经历五次脉冲循环,在与托轮接触处的峰值应力达最大.托轮外表面也存在较高接触应力.循环应力集中是使轮带与托轮发生表面疲劳失效的根本原因.过盈配合与支承载荷的双重作用,导致轮孔在与轮轴的配合端面成为托轮强度的最薄弱部位,可解释轮孔开裂或喇叭口失效现象.摩擦转矩使载荷偏置,导致支承系统应力分布非对称,故左右对称模型只适用于停工状态,对操作工况是不准确的.这些认识对回转窑支承系统的设计、检修和窑线调整具有参考价值.

ANALYSIS OF THE MECHANICAL BEHAVIOR OF THE SUPPORTING SYSTEM OF A LARGE ROTARY KILN

Theoretical analysis and numerical simulations of contact nonlinear finite elements are presented on the mechanical behavior of the supporting system of a large rotary kiln in the working condition.According to the structural and running characteristics of the kiln tyres,the pressure load on the inner surface of the tyre brought by the kiln shell was analytically educed,which modified the tyre pressure load formula being used in the literature for a long time.Based on the APDL(Ansys parametric design language) programming in Ansys,a 3D multi-body contact nonlinear FE(finite element) model for the supporting system of the rotary kiln with complex loading of distribution pressure,interference fit,contact and friction effects was developed.The deformation and stress distribution characteristics of the supporting system of the large rotary kiln were simulated via the above model.Numerical results show that there is a serious periodic extrusion process between the tyre and the rollers in each round,and there are five pulse cycles of the equivalent stress on the external and internal surfaces of the tyre,in addition,the maximum peak of the equivalent stress occurs in the contact areas of the tyre and the rollers.The periodic stress concentration plays an important role in the surface failure of the kiln tyres and rollers.High stress concentration also occurs on the conjugate faces between the roller and its axle due to the load addition caused by both the interference fit and supporting loads,which interprets the bugle shape deformation or fracture failure of the roller hole.The stress distribution of the supporting system is unsymmetrical about the lengthways vertical section because of the friction moment on the surface of the tyre and rollers,which indicates that the left-to-right symmetrical FE model only applys to the static condition,not accurate for the working condition.These findings can apply as instructions for the design and repair of the supporting system,and also the axis alignment of the kiln shell.