连续油管(CT)的制造过程使其内、外表面产生了不同的表面形态。由于疲劳是一种表面现象,因此导致两个表面具有不同的疲劳特性。 表面形态 CT样品的疲劳试验所产生的破坏位置通常违背常规的工程直觉。在通常情况下,裂纹应在应力和应变最大处产生。对于弯曲状态的管材来说,这个位置应在其受拉伸一侧的外表面。然而CT管的大多数疲劳裂纹却产生在受压缩侧的内表面。人们使用塑性理论来 Coiled tubing (CT) manufacturing process to its inner and outer surfaces have different surface morphology. Since fatigue is a surface phenomenon, it results in different fatigue characteristics on both surfaces. Fatigue tests of surface morphology CT samples can often ruin the normal engineering intuition. Under normal circumstances, cracks should occur at the maximum stress and strain. For a bent tube, this position should be on its stretched side of the outer surface. However, the majority of fatigue cracks in the CT tube are produced on the compressed side of the inner surface. People use the theory of plasticity