应用细观力学与扩展有限元法数值模拟钻柱损伤

Numerical simulation of drill string damage based on micromechanics and XFEM methods

钻井过程中,钻柱承受着拉扭等多种交变载荷的作用,其损伤机理一直是力学界深入研究的课题。笔者首先根据细观力学分析的基本原理,采用Abaqus软件的脚本语言Python建立细观尺度下晶粒分布模型,然后采用断裂力学算法——扩展有限元法对含有微裂纹的细观尺度下晶粒模型进行计算,分析裂纹的动态扩展过程以及相应的应力应变分布特征,最后根据细观力学中"均匀化"方法对不同时刻的应力应变进行处理,得到微裂纹扩展对钻杆材料宏观性能的影响。在宏观尺度下处于弹性阶段的钻杆材料,在细观尺度下仍会出现塑性区,且在微裂纹不扩展的情况下,弹性模量是恒定的。文章提出的思路为深入探索钻柱材料断裂机理提供了新的方法。

During the drilling process,the drill string subjects to various alternating loads.Therefore,mechanics community has always been deeply studying its damage mechanism.In this paper,we first used the Python scripting language to establish a grain-size distribution model at the meso-scale on Abaqus software platform based on the basic principle of mesomechanics analysis.Then,the fracture mechanics algorithm—extended finite element method（XFEM）was applied to calculate the meso-scale grain model which contains micro-cracks and analyze the crack dynamic simulation propagation and distributions characteristics of stress and strain in this process.At last,by using the mesomechanics homogenization method,we handled the stress and the strain at different time,and obtained the effect of micro-crack propagation on macro-properties of drill string material.For drill pipe in elastic deformation stage at macro-scale,plastic zone may also exist at meso-scale and elasticity modulus is constant when there is no microcracks propagation.The idea of this paper can provide a new method for deeply exploring damage mechanism of drill string.