Zhou, S; Turnbull, A (2005) Effect of stress transients on the crack propagation rate in steam disc steel. NPL Report. DEPC-MPE 017

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Abstract

An evaluation has been made of the effect of stress transients on the growth rate of long cracks in fracture mechanics specimens of a 3NiCrMoV steam turbine disc steel in deaerated 300 ppb Cl- + 300 ppb SO4 2- solution at 90 °C. Trapezoidal loading simulating two-shifting in service gave a high cyclic crack growth rate of about 10-6 m/cycle. With typically one cycle per day in service except weekends, and accounting for any stress corrosion cracking component at maximum load, a crack growth rate of 0.4 mm per year is estimated. Under constant load for the same environment no crack growth occurred at exposure times up to 9 months but an uncontrolled excursion in oxygen and chloride for just one hour was sufficient to induce crack growth with rates as high as 9.0 x 10-12 m/s.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	DEPC-MPE 017
Subjects:	Advanced Materials Advanced Materials > Corrosion
Last Modified:	02 Feb 2018 13:16
URI:	http://eprintspublications.npl.co.uk/id/eprint/3240

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