Crack Tip Fields Under Non‐steady Creep Conditions—i. Estimates of the Amplitude of the Fields

Under non‐steady creep conditions, the stress and strain rate fields near the tip of a stationary crack can be described by the singular fields of Hutchinson, Rice and Rosengren for power‐law creeping materials. Estimation formulae are presented for describing the amplitude of these fields under load and displacement controlled boundary conditions. For constant loading, the formulae reduce to the result of Riedel and Rice for short times after load application and to the steady state line integral C * for long times. At intermediate times, the estimate is validated by detailed finite‐element computation. For displacement‐controlled loading, the amplitude of the near‐tip fields is shown to fall rapidly, consistent with finite‐element analysis. The implications of the results for data collection and defect assessments are discussed in a companion paper.