Refinement of the accuracy of residual life assessment based on the generation and growth behavior of creep voids for boiler welded zone

Hidetaka Nishida, Hiroshi Yamaguchi, Isamu Nonaka, Fumio Takemasa

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)1657-1665
Number of pages9
JournalNihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A
Volume66
Issue number649
DOIs
Publication statusPublished - 2000

Keywords

  • Coarse grain section in heat affected zone
  • Creep
  • Damage position
  • Fine grain section in heat affected zone
  • Life prediction
  • Master curve
  • Welded joint

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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