圆柱壳大开孔接管连接处弯曲应力性质和评定准则的探讨及论证

Investigation and Discussion of Bending Stress in Connection of Large Diameter Nozzle and Cylindrical Shell and Its Evaluation Criteria

基于有限元软件对某一系列开孔率的圆柱壳大开孔接管结构进行了计算,通过应力云图、线性化后的应力变化规律、极限载荷计算结果并结合理论分析对其连接处弯曲应力的性质和评定准则进行了探讨及论证,并给出若干结论和建议:开孔边缘处存在两个正交的弯矩并引起显著的一次弯曲应力,且开孔率越大,总弯曲应力中一次成分占比越大并起主导作用,故将连接处的弯曲应力归类为一次弯曲应力进行评定更为合理;圆柱壳大开孔接管结构存在两个应力重分布过程,整体承载能力较大,若采用S_(Ⅲ)<1.5 S_(m)评定,会造成过于保守的评定结果,建议可将系数1.5调整为2.2,按S_(Ⅲ)<2.2 S_(m)作为进一步的辅助评定准则,以便设计出更为安全、合理、经济的结构。

In this paper,finite element method was used to calculate a series of structures with large opening on cylindrical shell.The properties of bending stress at the joint and the evaluation criteria were investigated and discussed by means of comparative analysis on the stress distribution graph,the stress variation rule after linearization,and the limit load calculation result combining with theoretical analysis.Several conclusions and recommendations are then given as follows:There are two orthogonal bending moments exist at the edge of the opening,which cause significant primary bending stress.The larger the opening rate is,the greater the proportion of the primary component in the total bending stress,and it may play a leading role.Therefore,it is more reasonable to classify the bending stress at the joint as primary bending stress for evaluation.There are two stress redistribution processes in cylindrical shell-large opening structure,and the overall bearing capacity is larger.If S_(Ⅲ)<1.5 S_(m) is used for evaluation,it will lead to overly conservative results.Thus,in order to result with a safer,more reasonable and more economical structure,it is recommended to adjust the coefficient from 1.5 to 2.2 and then take S_(Ⅲ)≤2.2 S_(m) as the evaluation criterion.