【摘要】 文章系统讨论了套管有限元计算中容易被忽视的一些问题 ,如加载步长、单元划分和载荷的非均匀性等因素对计算结果的影响。分析结果表明 :①加载步长对计算结果有重要影响 ,尤其是进入塑性阶段后 ,不够精细的步长会导致错误的结果。②由于套管的形状比较简单 ,使人们容易忽视单元划分对计算结果的影响 ,事实上 ,即使是最简单的平面问题的应力计算 ,单元数量也不能太少。尤其是计算套管的变形 ,沿壁厚方向只划分一层单元是不够的。③载荷的非均匀性对套管损坏影响极大 ,体现在两个方面 ,一是载荷的非均匀性增大时 ,套管能承受的最大载荷急剧减小 ,二是在非均匀载荷作用下 ,套管出现一定程度的局部屈服后 ,即使载荷不再增大 ,套管的变形量仍会不断增加。这些分析和结论不但澄清了套管有限元计算中长期存在的一些问题 ,还使我们对套管变形损坏的机理有了新的认识更多还原

【Abstract】 In this paper,Some easy to be ignored problems in casing calculation by finite element method,such as the influence of the factors of load carrying step length,unit division and heterogeneity,etc.,on the calculation results,are systematically discussed.The analysis results show that ①The load carrying step length has an important influence on the calculation results,especially,after having entered into the plastic stage,the insufficiently precise step length will lead to wrong results;②Because the casing form is relatively simple,the influence of the unit division on the calculation results is easy to be ignored.In fact,even for the stress calculation of the most simple plane problem,the unit quantity should not be too few,especially,for the casing deformation calculation,only one unit divided along the wall thickness direction is not enough and ③The influence of hterogeneous load on casing damage is very great,which are reflected in two aspects as follows:①When the heterogeneity of load increases,the maxium load the casing bear will rapidly decrease and ②Under the action of heterogeneous load and after a certain local yield appears on the casing,even the load does not increase any more,the casing deformation capacity will still continuously increase.These analyses and conclusions not only clarify some problems existed over a long period of time in the casing calculation by finite element method,but also make us have a new knowledge of the mechanism of casing deformation.更多还原