SEDL / STP / STP982-EB / STP27229S

Correlation of Fatigue Crack Growth Data Obtained at Different Stress Ratios

Booth, GS
Head of Environmental Fatigue Section and head of Fatigue Department, The Welding Institute, Abington Hall, Abington, Cambridge,

Maddox, SJ
Head of Environmental Fatigue Section and head of Fatigue Department, The Welding Institute, Abington Hall, Abington, Cambridge,

Pages: 12    Published: Jan 1988

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Abstract

Fatigue crack propagation tests have been carried out on three C-Mn structural steels at stress ratios between 0.67 and −4. Surface strain gage techniques have been used to determine crack-tip closure stress and an expression proposed to relate the proportion of the stress cycle for which the crack tip is actually open U to stress ratio. Satisfactory correlation of the crack propagation results for this range of stress ratios has been achieved by defining an effective stress intensity factor range as the proportion U of the total stress intensity range. In addition, reasonable correlation of the results was obtained on the basis of the tensile portion of the stress intensity factor range.