油气输送管典型应力状态下的屈服行为研究

准确计算油气输送管的实际屈服强度对合理确定输送压力有重要影响。该文分析了4种应力状态下对屈服强度有明显影响的钢管轴向应力，发现管材横向小试样试验时，轴向应力为零，工厂静水压试验时，轴向应力小于零，裸露钢管静水压试验时，轴向应力为环向应力的一半，埋地服役状态时，轴向应力为0.3倍环向应力。并从理论和试验两方面分析了实物钢管屈服强度与管材小试样屈服强度的差别。理论计算表明，4种应力状态下，屈服时vonMises理论计算的钢管环向应力值大于或等于Tresca理论计算值，其中裸露钢管受内压状态下，vonMises理论计算的管道屈服环向应力为1.15倍管材屈服强度，Tresca理论计算值为1.0倍，6根钢管爆破试验及小试样拉伸试验表明，该值为1.18倍。vonMises理论比Tresca理论更适合油气输送管的屈服计算。

STUDY ON THE YIELD BEHAVIOR OF OIL AND GAS PIPE IN TYPICAL STRESS STATES

The yield strength of oil and gas pipe has significant influence on pipeline design pressure. The axial stress which has a noticeable impact on the yield strength was studied in four typical stress states, including small specimen tensile test, mill test, hydrostatic burst test and buried in service state. It is shown that the axial stress is below zero in mill test, one half of hoop stress in hydrostatic burst test, 30 percent of hoop stress in service state, and zero in small specimen tensile test. The differences between specimen yield strength and true yield strength of pipe body were also studied by both theoretical research and experiments. The theoretical research shows that among the four stress states, on basis of von Mises criterion,the hoop stress is larger than that of Tresca criterion. And in hydrostatic burst test,the yield hoop stress of von Mises criterion is 1.15 times of specimen yield strength while 1 time of Tresca criterion. The results of six hydrostatic burst tests and specimen tensile tests show the hoop stress at yielding is 1.18 times of the specimen yield strength. This shows von Mises criterion is more suitable for oil and gas pipe design than Tresca criterion.