In order to prevent the failure of X70 pipeline girth weld in plastic deformation, the single sample unloading flexibility method was taken for single edge tensile test of girth weld and heat affected zone for strain-based design of X70 pipeline, the resistance curve of crack ductile extension was obtained, and the test results of heat affected zone specimens were validated. The results showed that fracture resistance curve of girth weld and heat affected zone specimens were that δwas 1.34855(Δa)0.64334 and 1.60042(Δa)0.70999, fracture beginning of heat affected zone specimens were from the weld fusion line within 0.5 mm, and the test results could provide evidence for the strain-based design pipeline and engineering critical assessment.%为了预防X70管线环焊缝受塑性变形时的失效,采用单试样卸载柔度法对基于应变设计的X70管线环焊缝的焊缝金属及热影响区进行单边缺口拉伸试验,获得了裂纹延性扩展过程的断裂韧性阻力曲线,并对热影响区试样的试验结果进行了有效性验证.结果表明,焊缝金属和热影响区试样的断裂阻力曲线分别为δ=1.34855(Δa)0.64334和δ=1.60042(Δa)0.70999,热影响区试样的断裂始距焊缝熔合线0.5 mm以内,试验结果为管线基于应变设计和工程临界评价提供了依据.
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