主蒸汽管道弯管的金属监督

薄壳理论模型显示,弯管内弧位置有最大应力,但实际上弯制导致弯管外弧减薄,加之不圆度的存在,进一步加大了弯管外弧部位的应力集中.运行中的弯管受到管道内压与外载弯矩的共同作用,其不圆度既可能减小,也可能增大或不变,"复圆"不能视作弯管蠕变损伤发展的唯一趋势.已有的试验数据证明,弯管的材质老化速度并不比直管快.因此,不能认为弯管具有管道材质老化的典型意义而轻视对直管段的组织检验.

METAL SUPERVISION OF ELBOWS IN MAIN STEAM PIPELINE

The model of thin shell theory shows that the maximum stress value is located at intrados of the bended pipe,but the practical bending process makes the tube-wall thickness on the extrados to be thinned,and the existence of non-circularity enhances the stress concentration on extrados. Under joint effect of the internal pressure and the external bending moment,the non-circularity of elbow hasthree change trends, namely to reduce, to increase,or to keep unchanged. The "plural circles" can't be seen as the only development trend of creep damage on elbows. The data of previous tests show that the material of elbows isn't aging faster than that of straight pipes, thus, it can't be considered that the aging process of pipe metal at elbows has a typical significance for the whole pipeline, therefore, the metallograpphic examination of traight pipes can't be neglected.