Study On Methods For The Safety Assessment Of Components Containing Defects Operating At High Temperature

The rupture of components containing defects in the petroleum and chemical equipment operating at high temperature is mainly caused by crack propagation under circumstance of creep, and the crack propagation in the creep range is different not only from fatigue crack propagation but also from fast crack propagation at normal temperature. So, we need methods for the assessment of creep rupture at high temperature. For the purpose, several aspects are studied as follows: 1. This paper analyzed the basic principles of rupture mechanics at normal temperature and high temperature, and studied the difference between the assessment for the two kind ruptures. When assessing the safety of components operating at normal temperature, first, we make sure whether the crack will propagate at present. If fatigue loading can be neglected, we should also consider the crack propagation caused by fatigue loading. When assessing the safety of components operating at high temperature, we should not only assess the safety of components at present, but also assess the safety of components in future, because the components operate in the creep range. With the increasement of time, creep strain become great, and the plastic strain near the crack tip become great too, then the crack maybe grow. If fatigue loading can be neglected, we should also consider the crack propagation caused by the interaction between creep and fatigue. 2. For common materials of petroleum and chemical equipment operating at high temperature, this paper collected lots of mechanics and rupture property data (a, a,, E K IcJ, c5 )at high temperatures parameters A and q used to derive creep crack propagation rates, creep strain versus time curves and stress to rupture versus time to rupture curves from inside and outside. Meanwhile, several experiments are made to validate the consistency of the measured and the standard values. 3. Having studied related methods for the safety assessment of components operating at high temperature, this paper put forward a method for the assessment of crack creep rupture at high temperature. This method is useful from creep temperature to the maximum temperature prescribed by rules. This method have considered the crack propagation caused by the interaction between creep and fatigue. Meanwhile, this paper put forward an optimized method used to solve how to divide the remnant life of components, which unite the astringency of calculated results with calculating workload. 4. According to this method for the safety assessment, this paper work out a calculating program(MACCR. 1), using C computer language, and it validated by calculating examples.