冲压焊接多级离心泵叶轮的疲劳强度

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Fatigue strength on stamped and welded impeller in multistagecentrifugal pumpWang yn ，Wang Weun，Wang Hongyu，Ye Daoxing，Li Guidong(Research Center of Fluid Machinery Engineering and Technology，Jiangsu University，Zhenjiang，Jiangsu 212013，China)Abstract：In order to study the fatigue characteristics of an impeller under the pressure fluctuation in aflow field during its operation，the flow field in the first stage of the LVS 3-9 vertical multistage pumpwas simulated by software CFX on the multi--physics platform.Ansys Workbench according to the simi。

1arity of flow and structure among various stages，then the characteristics of pressure fluctuation in theimpeller and diffuser have been obtained.The fluid static pressure obtained by CFD was applied on thestructural model of impeler，and the stress and deformation of the structure were analyzed under sucha load based on the one.way coupling method for fluid-structure interaction(FSI)in Ansys.Conside。

ring the feature of pressure on bladed the fatigue limit of the welded impeller was estimated by best fit-ting the S-N curve of the impeller material obtained based on the least square method.Eventualy。

the fatigue strength of the impeller structure was assessed by means of the modified Goodman fatiguelimit diagram.The results show that the stress in the impeller structure decreases steadily from the inletto the outlet，the deformation，however，increases gradually and a peak one can be found at the impel-ler outlet.At the same radial position.the obvious stress concentration iS located at the welding zonesbetween the shroud and blades.The impeller structure exhibits a bending deformation.which iS to-wards to the impeller eye，all in the axial direction.The fatigue strength of the impeller with two wel-收稿日期：2012-03-16基金项目：国家自然科学基金资助项 目(51239005)；江苏省 自然科学基金资助项目(BK2009218)；江苏高校优势学科建设工程项 目作者简介：王洋(1955-)，男，河北定州人，研究员，博士生导师(pgwy###ujs.edu.CB)，主要从事流体机械及工程研究。

王维军(1987-)，男，甘肃陇西人，硕士研究生(wwjsdx###126.corn)，主要从事流体机械及工程研究。

材料0Crl8Ni9的强度极限为h520 MPa，屈服极限为soro 2 207 MPa。

r 1 ]由此绘制出叶轮焊接材料的 Goodman疲劳极 -限线图，即应力幅和平均应力之间的关系图，如图9所示。

% ，lVJra，、. Ⅷ [3]图9 叶轮材料的 Goodman图Fig.9 Goodman diagram of impeller material [4]4.2.3 叶轮疲劳强度评估对叶轮疲劳强度的校核以表 1中危险点主应力的计算结果为基础，乘以安全系数 1.72 j，危险点处的应力值均位于封闭折线内，文中两焊点形式下的叶轮在计算的各工况下均满足疲劳强度要求.同时计算结果表明，小流量工况下的应力及应力幅最大，为提高叶轮可靠性，应尽量避免叶轮在小流量工况下长时间运转。

5 结 论1)叶轮在流场中承受的载荷主要有离心惯性载荷和流场压力载荷，在相同半径上，盖板与叶片接合的焊接区域应力明显较大.叶轮的变形均表现为沿轴向的弯曲变形，变形方向指向叶轮进 口.随着半径的增大，叶轮的变形不断增大，在叶轮边缘达到最大值.较大等效应力均出现在叶轮轮毂和焊接区域，叶轮危险点为叶轮轮毂和焊点。

2)小流量工况下的应力及应力幅最大，为提高叶轮可靠性，应尽量避免叶轮在小流量工况下长时间运转.采用的Goodman疲劳极限线图可以准确确定叶轮各个危险点疲劳强度是否满足要求。