ボイラ溶接部のクリープボイド発生・成長挙動に基づく余寿命評価の高精度化

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Currently, in order to evaluate the residual life of a welded area of an actual boiler, the Void Area Fraction is usually measured at the evaluation points. The residual life is calculated from the life fraction Master curve prepared in the laboratory. But since such Master curves are obtained from a series of partially completed creep tests and since the effects of temperature, stress, and weld-heat-affected-zone structure have not been satisfactorily examined, a lower limit of 99% of the data band has been adopted for safety. In order to achieve high-accuracy evaluations, differences in creep void generation and growth processes resulting from differences in heat, stress, and weld-heat-affected zone structure were observed in detail. As a result, the method described below is proposed as a high-accuracy method of Residual Life Asessment. (1) Clarification of damage evaluation position. a. Evaluate the coarse-grained areas of the circumferential joints of pipes subject to internal pressure. b. Evaluate the fine-grained areas of the longitudinal joints of pipes subject to internal pressure, longitudinal joints of elbows, and circumferential joints of pipes subject to system stress. (2) Use of Different Master curves for the evaluation positions. Use the different Master curves (which was conventionally a single curve) for the HAZ fine grain section and the coarse grain section. The Void Area Fraction method is appropriate for the HAZ fine grain section, and is not appropriate for the coarse grain section.
一般社団法人日本機械学会の論文
2000-09-25

ボイラ溶接部のクリープボイド発生・成長挙動に基づく余寿命評価の高精度化

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