Study On The Damage Problem Of The Super-high Pressure Tubular Reactor In Safety Engineering

Super-high pressure tubular reactor is one of the most important equipments in the productive process of polyethylene. Its safety and reliability are vital to the production, profit and workers' life. Study on the damage problem of reactor safety engineering in theory and practice is necessary and urgent. The exploratory study in the field will provide a reliable theoretical basis for the safety study of reactor and reasonable project of overhaul.To the practical engineering issues, the author tries to show the damage mechanism of the reactor in view of damage mechanics. Combined with the tests, the author uses the damage mechanics theory to study the self-reinforced damage mechanism, reactor life of fatigue damage, and the decay of residual stress under thermal impact action.According to the practical working condition and operating record, a series of normal mechanics and fatigue damage tests are carried out with the reactor materials (30CrNiMo8), the test materials are obtained from the practical field. The results of fatigue test of reactor manifest the fatigue life of the reactor materials under different strain and stress condition. This provides the reliable data for examination and assessment of the reactor. Because the materials of the reactor are imported, there is no systematic study on the materials. Thus, the experimental results given in the paper will provide reliable data for reactor design and repair with the materials.On the basis of expounding the theory of the thermal inner variables, the constitutive equation of fatigue damage, and the coupling damage theory of the homogeneous isotropic materials, the author set up the theory model of constitutive equation of non-linear damage and so on. The self-reinforced damage mechanism was also studied. By the microscopic mechanics, the damage zone and the initial damage condition are given. The cause of self-reinforcement by using the damage technology was point out. that is due to the changes of inner microstructure of the materials. From the calculation results, it is feasible in theory to produce self-reinforced effect of reactor by adopting the damage mechanical principle.The producing time of crackle is very important parameter to judge the safe grade of the reactor. Fatigue tests and fatigue damage analysis are very important for study of the reactor safe and damage. Begin with the coupling relationship between the fatigue cycle and damage, based on low cycle fatigue test and combined fatigue test with high and low cycles, the model of fatigue damage fordetermined the crackle producing time was established in view of the macroscopic aspect, and the general formula with elastic solution, plastic solution and elastic-plastic solution for the reactor crackle life of elastic and plastic smooth work pieces are also given in the paper. The formula is a function /( ξ), effected by the structure shape and the boundary condition restriction, there ξ is related to the distribution of the instant cycle's strain and stress, and it considered not only the fatigue characteristic, but also, the real structure characteristic and the effect of the loading. Compared with Manson-Coffin equation, the formula is more accurate and applicable. It is not only providing a convenience to solve the practical problem, but also innovating in theory.By damage theory and test, and analysis the fatigue damage of the reactor in working state, the reactor life of crackle producing was determined. And the effective radium, influence factors and their function values were obtained. Therefore, the designed curve and calculative equation for reactor life of crackle were given in the paper. These are references of theory and test for safety assess of reactors.The paper put forward the concept of decrease coefficient (KD), and the actual calculation process of KD for forecasting the fatigue life of the structure. The research made it possible to forecast the fatigue life of damaged materials, and the prediction was based on the S-N curve from the fatigue test of th...