在役高压管式反应器残余应力松弛试验研究(英文)

Experimental Study on Relaxation of Residual Stresses in Tubular Reactor of High Pressure Polyethylene in Service

自增强反应器管壁残余应力因交变压力及温度、温差的作用随时间而减小。在操作状态下 ,残余应力的松弛规律及其计算对反应管安全分析是十分重要的。用和反应管相同材料及相同截面尺寸的试件模拟反应管在设计温度、温差作用下 ,以及开停工引起的压力变化的作用下反应管内壁残余应力的松弛。温度和温差引起的管内壁残余应力的松弛率(或剩余率)随时间的变化可用自然对数函数来描述 ,压力变动导致的管内壁残余应力松弛率(或剩余率)随压力循环次数的变化为指数函数。给出了温度、压力循环作用下反应管内壁剩余残余应力计算式。该式计算结果不但和本文试验结果符合很好 ,而且和其他作者报道的实验数据相吻合。预测了一根服务了九年的反应管(4340钢) ,其剩余残余应力误差在10 %以内。因此 ,该方法不但适用于30CrNiMo8材料的反应器也适用于4340钢制的聚乙烯反应器。

The residual stresses in autofrettaged reactors will decrease in the temperature field and under the pressure fluctuation in service.It is important for reactor safety analysis to know the remnant residual stresses in the reactor after a period of operation.In order to determinie the relaxation of residual stresses of the reactor under the operating temperature and temperature gradient,and the pressure fluctuation,speciˉmens with the same material and same cross section of the reactor were tested separately.The experimental results showthat the relaxation rate of residual stresses at the inner surface of the reactor varies with the serˉvice time in operation temperature field and it can be fitted to an natural logarithm function.The relaxation rate of the residual stresses with the number of pressure fluctuation can be fitted to an exponential funcˉtion.By superimposing these two functions,an empirical formula for calculating the remnant residual stresses in the inner surface of the reactors is established.The predicted results by this formula are not only in well agreement with this paper’s test data(30CrNiMo8),but also with those(AISI4340)tested by other auˉthors.A procedure simulating the relaxation of residual stresses of the tubular reactors in service under the operation condition is described.A prediction of a practical HP reactor of9years service history is also made and the result is proved to be quite accurate.Therefore,the empirical formula developed in this paper is able to predict remnant residual stresses in HP reactor made of30CrNiMo8,AISI4340and the equivalent materials under operation conditions.