磨损套管抗挤强度计算模型

套管磨损后其承载能力降低,因此对磨损套管进行抗挤毁能力预测或评估就显得尤为重要。采用数值模拟和实物试验相结合的方法,系统分析了磨损套管的挤毁失效机理、影响抗挤强度的因素及影响规律。分析得出,月牙形磨损套管的挤毁属"三铰"失稳,严重磨损处首先屈服进入塑性区并产生很大变形,从而导致整体结构发生弹塑性失稳。磨损套管的抗挤强度随剩余套管壁厚、磨损半径和轴向载荷分别呈指数、幂函数和线性函数式变化。以此为基础,从未磨损套管实际抗挤强度计算入手,建立了完整的磨损套管抗挤强度计算模型,并对模型进行了试验验证,试验结果表明,模型计算值与试验实测值的相对误差在5%以内。所建立的磨损套管抗挤强度计算模型可用于磨损套管和未磨损套管抗挤强度的预测和评估。

Model for Collapsing Strength Calculation of Worn Casing

Since bearing capacity of a casing will reduce when the casing is worn,it is very important to predict or evaluate the collapse capacity of the worn casing.To combination numerical simulation and actual tests,the collapsing failure mechanism of worn casing and the factors and rules impacting the collapse strength were studied.Collapse of crescent worn casing belongs to "three hinged" instability.The severely-worn position on the casing was yielded into plastic zone first and deformed greatly,which resulted in the plastic instability of the whole structure.The collapsing strength of the worn casing presented changes of exponent,power function,and linear trend with the residual casing wall thickness,wear radius and axial load respectively.Based on this study,the calculation model of collapsing strength for the whole worn casing were established and the model was verified by tests,which showed the relative error between calculated from the model and those tested was within 5%.