Small-size specimen with hard zones near crack tip for fracture toughness evaluation of pressure vessel in service (part 1: constraint effect of laser welds on K{sub}IC-toughness measurement)

摘要

This paper presents a small-size fracture toughness specimen with hard zones for evaluation of pressure vessels in service. Key idea is elevation of plastic constraint near the crack lip by hard zones. Test piece was sampled from a long-termused pressure vessel and welded with dummy material by CO{sub}2 laser welding. Laser welding created a couple of hard zone sandwiching the sample. Welding condition was selected to yield no change in material properties of the test region. Fracturetoughness obtained with the small-size specimen was almost the same as K{sub}c-value for full-thick specimen. Sample size of test region in the small-size specimen was minimized to l.6×2.5×5.0mm.