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抗挤能力的计算是套管设计的一项重要内容均匀壁厚的圆管,在弹性范围内的临界外压计算,已有比较成熟的理论但实际上,套管并不是理想的圆柱管壳。它往往存在初始椭圆度和壁厚不均度两种缺陷,这些缺陷对套管的抗外挤能力是有影响的。不同的临界外压计算方法,对这些缺陷的影响处理方法也是不一样的。本文用变分原理求出了变壁厚圆管临界外压的计算公式,并详细分析了《套管强度计算与设计》一书中用能量法推导临界外压公式过程中存在的问题这是由于用近似的屈曲形状函数,又不恰当地用位移的二阶导数来计算应变能造成的,若用位移表达式来计算应变能,就可得到与本文介绍的一样的公式了。
The calculation of anti-extrusion ability is an important part of casing design. The pipe with uniform wall thickness has more mature theory in the calculation of the critical external pressure in the elastic range. However, the casing is not an ideal cylindrical shell . It often has two defects, initial ovality and uneven wall thickness. These defects have an impact on the anti-extrusion ability of the casing. Different critical pressure calculation methods, the impact of these defects is not the same treatment approach. In this paper, the variation of the critical wall thickness of the pipe calculated the critical pressure formula and detailed analysis of the “Casing strength calculation and Design,” a book using the energy method to derive the critical pressure formula in the process of problems that are Since the approximate buckling function is used, and the second derivative of the displacement is not used properly to calculate the strain energy, the same formula described in this article can be obtained by using the displacement expression to calculate the strain energy.