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分析了API屈服挤毁公式和ISO全管壁屈服挤毁压力公式,认为:API Bulletin 5C3屈服挤毁设计的基本原理是管内壁屈服即失效,实际上,内壁开始屈服时套管还有很大的抗挤余量,对于D/t<15的厚壁及特厚壁套管,若按API提供的这种最小屈服挤毁公式计算,会造成管材浪费或选择套管难的问题;而ISO全管壁屈服挤毁压力公式并非是全管壁屈服公式,可能并不适合所有壁厚段套管强度的计算。为此,根据弹塑性力学理论推导出了任意屈服半径处及全管壁屈服时的挤毁强度公式。通过计算对比可知,对于D/t≤15的厚壁管(API Bulletin5C3用屈服公式计算套管强度)用von Mises屈服准则计算的套管内壁起始屈服挤毁强度值,要比现行的API Bul-letin 5C3屈服挤毁值高15.45%,而全管壁屈服挤毁值至少要比API Bulletin 5C3屈服挤毁值高出32.78%。
The API yield collapse formula and the ISO total wall yielding collapse pressure formula are analyzed. It is considered that the basic principle of the API Bulletin 5C3 yield collapse design is that the inner wall of the tube will yield or fail. In fact, there is a large casing when the inner wall begins to yield Of the crush allowance. For thick-walled and thick-walled bushing with D / t <15, if calculated according to the minimum yield collapse formula provided by API, it will cause waste of tubing or difficult casing selection. ISO The total wall yielding collapse pressure formula is not a wall-yield formula and may not be suitable for all wall thickness section casing strength calculations. Therefore, according to the theory of elasto-plastic mechanics, the crushing strength formula at arbitrary yield radius and yielding of the whole pipe wall is deduced. Comparing the calculated results, the initial yield collapse strength value of the inner wall of the casing calculated by the von Mises yield criterion is larger than that of the current API Bul for thick-walled pipes with D / t≤15 (API Bulletin5C3 calculates the casing strength using the yield formula) -letin 5C3 The value of yield collapse is 15.45% higher, while the total wall yield collapse value is at least 32.78% higher than the API Bulletin 5C3 yield collapse value.