【作者】 陈孙艺；

【导师】 柳曾典；

【作者基本信息】 华东理工大学 ， 化工过程机械， 2006， 博士

【摘要】 异径管在受压管道系统中是常见的重要部件,但对异径管问题的研究基本还是空白。本文通过理论分析对内压以及面内弯矩、扭矩作用下同心异径管、偏心异径管、异径弯管的应力及极限载荷进行了研究,通过有限元数值分析和实验进行了验证。主要工作有:1推导了内压作用下异径弯管的环向应力公式和经向应力公式。在相应的结构参数条件下,异径弯管的环向应力公式可以转化为同心异径管、偏心异径管、或等径弯管的环向应力公式。在此基础上推导了异径管的极限压力式。异径管的极限内压由其大端截面控制。2推导了异径管的极限弯矩公式,异径管的极限弯矩由其小端截面控制。同心异径管、偏心异径管极限弯矩均相当于与小端口截面尺寸相同的直管的极限弯矩。异径弯管极限弯矩由与小端面尺寸相同的同心异径管、偏心异径管的极限弯矩作为基础项,再乘以弯矩系数。根据异径弯管弯曲系数的大小分为四个区间,弯矩系数分别按相应区间的回归式计算。3推导了异径管的极限扭限公式,异径管的极限扭矩均由其小端截面控制,相当于与小端口截面尺寸相同的直管的极限扭矩公式作为基础项,再乘以系数。同心异径管极限扭矩相对要比偏心异径管的极限扭矩略大一点,异径弯管大端面截面承受扭矩时的极限扭矩相对要比小端面截面承受扭矩时的极限扭矩小。在异径弯管承受端面扭矩作用上,还提出了一端的扭矩无法完全传递到另一端的概念,扭矩在传递中会逐渐转化为弯矩。90°弯管一个端面的弯矩既可由另一个端面的扭矩转化而来。4.提出了同心异径管、偏心异径管和异径弯管的有限元模型建模法。总结出应力分布或变形的特征:(1)内压作用下同心异径管大小端的面积压力差产生的弯矩引起大端相对张开、小端相对收缩的现象;(2)内压作用下偏心异径管偏心侧大端内表面及偏心侧中部外表面的环向应力最大。5.上述理论成果经过了有限元数值分析和实验验证。实验还表明,内压作用下环壳的弯曲半径和管截面半径均增大,而管壁厚变化很小。假设壁厚不变时弯曲系数随内压增大而减小。更多还原

【Abstract】 Reducer is one of ordinary and important components for pressure piping, but little study about it has been done. Stresses analysis and limit load of bend reducer, concentric reducer and eccentric reducer under internal pressure, bending moment in plane and torque have been studied separately. The results have been examined by finite element method and experiment. The main results were summarized as follows.i. The formulas used for calculating the circumferential stress and meridian stress of bend reducer under internal pressure were inferred. The circumferential stress formulas of bend reducer may be change into the circumferential stress formulas of concentric reducer and eccentric reducer or elbow under internal pressure. The formula used for calculating limit pressure that all of concentric reducer and eccentric reducer and bend reducer were inferred. The limit pressure is generally controlled by the cross section of larger end.ii. The formula used for calculating limit bending moment that all of concentric reducer and eccentric reducer and bend reducer were inferred. The limit bending moment is generally controlled by the cross section of smaller end. The limit bending moment for both of concentric reducer and eccentric reducer is equal to the limit bending moment of pipe that has the same dimension with the small end. The limit bending moment of bend reducer is equal to a basic bending moment multiplied by bending moment coefficient. The basic bending moment is the limit bending moment of concentric reducer or eccentric reducer that has the same dimension with the small end. The bending moment coefficient should be calculating by four different formula that according to bending coefficient.iii. The formula used for calculating limit torque that all of concentric reducer and eccentric reducer and bend reducer were inferred. The limit torque is generally controlled by the cross section of smaller end regardless the torque is acting on the larger end or on the smaller end. It is equal to a basic torque multiplied by a coefficient. The basic torque is the limit torque of pipe that has the same dimension with the small end of bend reducer. The limit torque on the larger end of bend reducer is some smaller than the limit torque on its small end. The torque on one end of 90°elbow can not transfer into the other end perfectly, and it would change into bending moment. The bend moment on one end of 90°elbow may change from the torque on the other end.iv. The methods set up corresponding finite element models of bend reducer and concentric reducer and eccentric reducer were provided. Some important features about stress distribution or deformation is as follows: (a) The bending moment tend to open the larger end and to close the small end relatively when concentric reducer is under internal pressure, which induced by the area difference between the diameter of transverse cross section at larger end and the diameter of transverse cross section at small end; (b) The largest stress is circumferential stress which occur at inside in the larger end or at outside on the middle of eccentric sides when eccentric reducer is under internal pressure.v. The academic analysis was identified with the FEM and experiments. The result of experiment also show that both bending radius of ring shell and radius of its cross section should augment as the increasing of internal pressure, but the bending coefficient of ring shell should reduce.更多还原