【作者】 王旭；

【导师】 李风； 李忠；

【作者基本信息】 吉林大学 ， 机械工程， 2005， 硕士

【摘要】 三通作为重要的压力管道元件广泛用于石油化工、电力和油气输送等行业中,由于其几何形状复杂和数学分析上的困难,至今仍没有成熟简便的应力计算方法。鉴于管道三通的破坏常表现为塑性失效,因此,管道三通的塑性极限载荷成为工程中重要的设计参数。本文采用有限元分析的方法,在对纯弯矩作用下无缺陷三通进行研究的基础上,详细地研究了单一弯矩及不同比例内压弯矩联合作用时对三通塑性极限载荷的影响。主要研究内容和结论如下: (1)建立了无缺陷焊制管道三通的三维有限元计算模型,编制出适合本课题需要的有限元前处理程序。(2)建立了无缺陷三通塑性极限弯矩有限元解数据库,研究了不同几何尺寸对三通塑性极限弯矩的影响规律。更多还原

【Abstract】 The pressure piping is the special pressure equipment at the risk of explosion in industrial production, widely used in petrochemical engineering, steel making, power plant, pharmaceutical industries and other fields such as urban gas and heat supply system, shouldering main duty of transportation of inflammable, explosive, high-temperature, corrosion and poisonous media. Piping tee plays a common role in the piping system, not only served as an important structure to change direction of piping and separate materials, but also used as a kind of flexible components that are able to effectively relieve stress of the piping system caused by temperature difference and installation dimension variation. Compared to the straight portion of piping system, piping tee belongs to big-holed structure with discontinuous geometry, so stress concentration shall be produced on the corner of the intersection lines, even work under normal conditions, where yield shall still be possible to reach. In most cases, piping tee is appeared at the support points where piping directions are changed or materials are separated. It becomes the concentrated position of piping system load, not only standing against internal pressure, but also against moment, twisting torque and axial force. In the meantime, in the piping in service, bottom-thinning due to eroding by high speed media and pits due to corrosion media both increase the chance of fatigue cracks being produced, local expanded, leakage and broken. At present, solution for limit load of defect-free piping tee attracts full attention of the engineering circles both home and oversea and much has been done on investigation work, but most still remains in the experimental or theoretical interference phases and not convenient for engineering use. In the light of this fact, it is necessary to further study of the estimating formula of the plastic limit load of the piping tee under the combination load of moment and pressing-bending. The study on defected piping tee is only limited to the cracked piping tee, but nobody had yet investigated on the bottom-thinned piping tee occurred in theproduction practice. Although a lot of work had been done on the study of limit load of piping tee by the predecessors, there still remain not less problems. In order to perfect the safety evaluation of piping tee, this paper carries out the following study on the basis of the predecessor’s work. 1. Establish the finite element models of defect-free piping tee, use the parameter design language of ANASYS, makes preprocess and solution program for defect-free finite element suitable for this subject, possible to change parameters within a wider range including OD & ID, wall thickness, load and lattice size. 2. Study the calculation method of defect-free plastic limit load on piping tee under only bending moment. By use of the pre-made program to calculate the piping tee of different geometry parameters, establish the database of defect-free plastic limit load under only moment and make a comparison of the calculated results with the relevant formula stated in the information.Based on analysis of plastic limit moment of defect-free piping tee, conclusion is made as follows: 1.Under the function of moment of branch piping end, the plastic failure modes of welded piping tee including 3 cases: branch piping collapse failure, tee shoulder or abdomen collapse failure and intersected section entire plastic collapse failure. 2.As for piping tees with identical geometric dimensions, limit moment under load of outer surface moment is lower than limit bending under load of inner surface moment. Furthermore, the thinner the thickness of main piping goes and the bigger the diameter ratio of main piping to branch piping become, the more evident the difference value of the above-said bending grows. 3.Under inner surface loading, a piping tee of specific size of main piping shall have an increasing inner surface plastic limit moment with the increase of outer diameter and wall thickness of branch, and the change of outer diameter will play a predominant role. In case of piping tee with K 1 ≥1.2, it is unable to improve its limit loading capacity if only increase of wall thickness of mainpiping. 4. Under outer surface loading, the wall thickness of main pipe and outer diameter of branch pipe are the main factors to exert influence on the limit moment of outer surface, limit load increased with increase of the said two factors. If the wall thickness of main pipe is thinner, even increase of branch pipe, it fails to raise its limit load, this moment the load enduring capacity of piping tee is controlled by main pipe. All in all, this paper, under the situation of promotion use of natural gas and in order to improve safety of industrial piping tee and prevent plastic failure, made an elastic & plastic finite element analysis of piping tee’s geometric deformation effect by use of ANSYS. Main achievements and conclusions are summarized as follows: 1.Determine the of finite element calculation models of defect-free tee, make the suitable preprocess program for the subject piping tee plastic limit load analysis, realize to change parameters setting within a wide range including tee OD and ID,wall thickness and loading means (load ratio). 2. Through finite element analysis of piping tee under only loading of bending, comparison is made on the finite element solution of piping tee plastic limit bending between 1/4 model and 1/2 model. Taking the geometric deformation of piping tee, conclusion is drawn that 1/2 model is comparatively reasonable. 3. The plastic limit moment database about piping tee are built on the basis of a great amount of finite element analysis, and law effect and its failure modes of the different geometric dimensions on the plastic limit moment of defect free piping tee.更多还原