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在对大量的套管全尺寸挤毁试验结果分析的基础上,提出套管外压失稳机理:实际工程中的套管截面不是理想圆,在外压作用下的非圆套管圆周方向上环向应力分布不均匀,有附加弯矩效应;随外压增加,在最大压缩环向应力处达到屈服;当屈服达到一定程度时,材料由于强度承载力不足而失效,导致套管发生失稳挤毁。基于上述套管强度挤毁准则,分析了理想弹塑性套管在轴向载荷作用下的抗挤强度计算方法,得到较保守的套管挤毁压力计算公式。与试验结果对比表明:导出的计算公式偏差较小,计算精度满足工程要求,失稳强度准则是适用的。
Based on the analysis of a large number of casing collapse test results, the instability mechanism of casing external pressure is put forward. The casing section in actual engineering is not ideal, and the circumferential direction of the casing When the yield reaches a certain level, the material fails due to insufficient strength bearing capacity, resulting in the instability of casing extrusion. destroy. Based on the above criteria for collapse of casing strength, the calculation method of collapse resistance of ideal elastoplastic casing under axial load is analyzed, and a more conservative calculation formula of casing collapse pressure is obtained. The comparison with the experimental results shows that the derivation of the calculation formula has small deviation, the calculation accuracy meets the engineering requirements, and the instability criterion is applicable.