Two-parameter characterization of constraint effect induced by specimen size on creep crack growth

• Effect of constraint induced by specimen size on creep crack growth was performed.
• Creep crack growth rate increased as specimen size increased at same C∗ values.
• C∗–Q two parameter approach was proposed to correlate constraint effect.
• Values of constraint level Q were increased with specimen size enlarging.
• Two parameter approach provided more accurately predicted crack growth rates.

Experimental and numerical investigations on the effect of constraint induced by different specimen sizes on creep crack growth had been conducted using compact tension specimen with P92 steel. The experimental results revealed that at the same C∗ values, creep crack growth rates increased as specimen size increased and the difference enlarged with increasing C∗ values. In addition, the variations of constraint level Q during creep were obtained and a modified C∗–Q approach incorporating constraint effect was proposed to predict creep crack growth. In comparison with conventional single C∗ parameter approach, two parameter approach could provide more accurate crack growth rates.