Service life based high-temperature container creep fatigue strength design method

Abstract

The invention discloses a service life based high-temperature container creep fatigue strength design method. The method comprises the steps of 1, performing structure preliminary design; 2 determining load and temperature conditions and the design service life requirement; 3, determining dangerous sections; 4, calculating the equivalent stress and strain range; 5, calculating reference stress; 6, determining whether plastic collapse occurs; 7 determining whether the plastic ratchet occur; 8, determining whether creep damage is important; 9, estimating fatigue damage of each cycle when the creep damage is not important; 10, determining whether the fatigue damage is important; 11, estimating the creep damage when the fatigue damage is not important; 12, estimating damage of each cycle when the creep damage and the fatigue damage are non-ignorable; 13, estimating creep-fatigue total damage; 14, performing result analysis and structural design improvement; 15, completing structural design. According to the method, the foundation is laid for national establishing of creep and fatigue failure mode based high-temperature pressure container design standards and achieving design and manufacture of high-temperature pressure containers according to the service life.

Description

technical field [0001] The invention relates to a life-based design method for creep fatigue strength of a high-temperature pressure vessel. Background technique [0002] In recent years, with the rapid changes in the world economic situation, the deterioration of resource quality and the adjustment of energy structure, pressure vessels in the process industry have gradually developed towards extremes such as high temperature and ultra-high temperature. The steam pipeline temperature of supercritical power plant boiler is as high as 650°C, the temperature of catalytic cracking regenerator is as high as 720°C, the temperature of reformer furnace of ammonia synthesis unit and hydrogen production unit is as high as 900°C, and the cracking furnace of ethylene cracking unit is as high as 1150°C. [0003] In addition to the usual failure modes of brittle fracture and plastic collapse, pressure vessels serving in high-temperature environments also have crack initiation and propagat...

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Problems solved by technology

[0005] However, the British R5 code is difficult to apply in the strength design of high-temperature pressure vessels in my country. The reasons are: first, the R5 code is mainly aimed at the damage assessment and life prediction of pressure vessels that have been put into use; second, the R5 analysis process is too cumbersome. The cyclic stress-strain curve constructs a cyclically stable hysteresis loop one by one, and then calculates the fatigue strain enhancement range and fatigue damage; if it is necessary to consider the influence of residual stress, estimate the stability reference stress of the structure; if it is necessary to consider the performance of the base metal and weld The third is that the R5 evaluation conclusion is too conservative, and it is mainly used in the nuclear power field where the failure probability is required to be controlled at a very low level. Various high temperature performance data for the area

[0006] At present, my country still lacks pressure vessel design criteria or strength verification methods specifically for high-temperature specific failure modes. The structural design only divides the high-temperature enduring strength by a certain safety factor to obtain the allowable stress of the material, and then limits the stress level of the structure. structural safety

The biggest shortcoming of this design criterion is that it only considers the failure mode of permanent fracture, but does not consider creep, fatigue and their interaction, so that life-based high-temperature structural design and strength check cannot be realized

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