Helical buckling is very common in slender structures and it is characterized by the development of helical deformation patterns along their length. This phenomenon is particularly acute in very slender drill-strings as associated high stresses decrease drilling efficiency and shorten life expectancy of expensive drilling assemblies. Hence, understanding and predicting buckling behaviour is of paramount importance. In this paper, we investigated buckling phenomena of slender flexible shafts in forms of stranded wire ropes mimicking drill-strings, by experimental and numerical means. From experiments we obtained the loading curves for the flexible shafts and developed governing buckling equations using dimensional analysis. Based on these equations, we calculated the effective material properties of the stranded ropes and carried out FE modelling and analysis in Abaqus. Finally, we developed a robust method to predict the helical buckling behaviour, which matches well with experiment results.

中文翻译：

---

各向异性细长轴螺旋屈曲的实验校准有限元模型

螺旋屈曲在细长结构中非常常见，其特征是沿其长度发展螺旋变形模式。这种现象在非常细长的钻柱中尤其严重，因为相关的高应力降低了钻井效率并缩短了昂贵的钻井组件的预期寿命。因此，理解和预测屈曲行为至关重要。在本文中，我们通过实验和数值方法研究了模仿钻柱的绞线钢丝绳形式的细长柔性轴的屈曲现象。通过实验，我们获得了柔性轴的载荷曲线，并使用尺寸分析开发了屈曲控制方程。基于这些方程，我们计算了绞绳的有效材料特性，并在 Abaqus 中进行了有限元建模和分析。最后，我们开发了一种稳健的方法来预测螺旋屈曲行为，该方法与实验结果非常吻合。