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油气管道裂纹评价的理论基础是断裂力学。在线弹性断裂力学中,应力强度因子(SIF)是判断油气管道裂纹是否将进入失稳扩展状态的重要指标。油气管道为金属材料,发生严格线弹性断裂的可能性不大,但只要塑性区尺寸远小于裂纹尺寸,经过适当修正,应用线弹性理论分析产生的误差可以接受。当塑性区尺寸与裂纹尺寸处于同一量级时,需要应用弹塑性理论,包括裂尖张开位移(COD)判据和J积分。可以采用应力强度因子、失效评价图及有限元方法评价油气管道裂纹的状态,有限元方法能够在一定程度上弥补其它2种方法在适用性方面存在的不足,但同时存在建模和计算效率较低,难以进行预防性评估的缺点。
The theoretical basis of oil and gas pipeline crack evaluation is fracture mechanics. In the online elastic fracture mechanics, the stress intensity factor (SIF) is an important index to judge whether the oil and gas pipe crack will enter the state of instability expansion. Oil and gas pipelines are metal materials, and the possibility of strict linear elastic fracture is unlikely. However, as long as the size of the plastic zone is much smaller than the crack size, the error caused by the linear elastic theory analysis can be accepted if properly corrected. When plastic zone size and crack size are in the same order of magnitude, elastoplastic theory, including crack tip open displacement (COD) criteria and J-integral, needs to be applied. The stress intensity factor, failure evaluation diagram and finite element method can be used to evaluate the crack status of the oil and gas pipelines. The finite element method can make up for the deficiencies of the other two methods in terms of applicability to some extent. However, both the modeling and computational efficiency Low, it is difficult to carry out preventive evaluation of the shortcomings.