基于特征值和弧长法计算套管抗挤强度

Calculation of Casing Collapse Resistance Based on Eigenvalue and Arc Length Method

文章基于ABAQUS软件特征值和弧长法研究套管可承受的外挤临界值。ABAQUS特征值用于确定套管弹性挤毁的外挤临界值;而弧长法克服了Newton-Raphson方法极值点发散、无法跟踪极值点以后的位移—载荷路径的缺点,全程跟踪后屈曲载荷位移路径,并给出准确的外挤临界解值。通过弧长法分析还发现弯曲度对套管抗挤毁能力产生的影响较为显著,随着弯曲度增大,套管抗挤毁能力逐渐降低;随着缺欠模态的增加套管的抗挤毁性能也逐渐降低。文章以TP140V钢级不同规格的套管做模型,在单轴载荷条件下得到套管极限挤毁值,结果表明:有限元计算套管挤毁值与实物试验检测值基本一致,误差在3%左右,且模拟的挤毁形貌与实物挤毁形貌相同。随着国内非标管材用量不断增加,对于受压溃设备能力限制而无法获得极限挤毁值的套管,该方法具有借鉴和参考意义,并且相较于API5C3算法,弧长法具有计算准确及适用产品范围广特点。

Based on ABAQUS software eigenvalue and Arc length method, the critical value of casing extrusion is studied. The ABAQUS software eigenvalue is used to determine the external squeeze critical value of casing elastic squeeze. However, by overcoming the shortcomings of Newton-Raphson method such as divergence of extreme points and inability to track the displacement-load path after the extreme points, the Arc length method can track the displacement path of post-buckling load in the whole process and give an accurate solution. It is found that the bending degree has a significant impact on the collapse resistance of casing. With the increase of bending degree, the collapse resistance of casing decreases gradually. With the increase of missing modes, the anti-collapse performance of casing also decreases gradually. Taking TP140 V steel casing with different dimensions as an example, the casing ultimate collapse value is calculated under uniaxial load. The results show that the casing collapse value calculated by finite element method is consistent with the actual test value, the error is about 3%, the collapse morphology is the same as the actual collapse morphology. With the increasing consumption of non-standard pipes in China, this method has reference significance for casing with limited capacity of pressure equipment and unable to obtain the limit collapse value. Compared with API15 C3 algorithm, Arc length method has the characteristics of accurate calculation.