平板封头与筒体连接应力释放槽结构分析与优化

Structure analysis and optimization of stress relief groove for the connection of flat head and cylinder

对平板封头与筒体连接应力释放槽结构进行了有限元分析,根据压力容器分析设计观点对结构的安定性进行了评价,发现有些情况下需开设一定尺寸的应力释放槽才能使结构满足安定性要求,而有些情况下仅需做结构对接开槽即可满足安定性要求,据此可确定是否开设应力释放槽的分界线.此外,分析表明,有些情况下即使开设应力释放槽也不能使结构满足安定性要求,此时需首先加强筒体,据此可确定是否需要加强筒体的分界线.通过参数化计算,得到了需开设应力释放槽及需加强筒体的结构参数区域.对需要开设应力释放槽的结构,探讨了应力释放槽圆弧半径以及开槽深度对薄膜加弯曲应力强度以及最大应力强度值的影响,提出应力释放槽横截面积最小、薄膜加弯曲应力强度水平系数最小以及应力强度幅水平系数最小3种优化方案.利用ANSYS的APDL及OPT模块,采用参数扫描及函数逼近法,以应力释放槽横截面积最小为优化目标,以薄膜加弯曲应力强度水平系数及应力强度幅水平系数小于1为约束条件,对应力释放槽的圆弧半径及深度进行了优化计算,给出了最优开槽尺寸,可供此类结构的设计参考.

Stress of flat head and cylinder connection with stress relief groove was analyzed with FEM, in which the shakedown property was evaluated from the viewpoint of design by analysis. It is found that structures with some configuration need stress relief groove （SRG） to meet the shakedown requirement, while butt connection groove is sufficient for shakedown requirement of other configuration. Partition line for stress relief groove may be accordingly determined. In addition, stress relief groove is not enough to meet the shakedown requirement for some configurations, in which the connected cylinder must be integrally reinforced. Partition line for cylinder reinforcement may be accordingly determined. The Partition lines for both the stress relief groove and the cylinder reinforcement worked out by parametric study. For structures in need of stress relief groove, effect of the groove radius and depth on the membrane plus bending stress intensity and maximum stress intensity was investigated. And three optimization schemes were suggested, namely minimum of the stress relief groove cross section area, minimum of the membrane plus bending stress intensity and minimum of the maximum stress intensity. With the aid of APDL and OPT, the design variable sweep and function approximation method was used to optimize the stress relief groove, in which the stress relief groove cross section area was taken as objective, the membrane plus bending stress intensity and the maximum stress intensity smaller than 1 as constraints. The optimal groove radius and depth were worked out, which may be referenced for reasonable design of such kind of structures.