Evaluation and interpretation of ductile crack extension in SENT specimens using unloading compliance technique

• Unloading compliance technique for evaluation of ductile crack extension in SENT specimens.
• Minimum of compliance curve coincides with moment of crack initiation.
• Use of elastic compliances remains approximation.

Resistance curves obtained from Single Edge Notch Tensile (SENT) specimens gain interest for defect assessment in pipelines. To determine these resistance curves, the unloading compliance technique is a commonly applied single specimen technique. A frequently reported problem is the occurrence of an initial decrease in the compliance, resulting in an apparent negative crack growth. To overcome this problem an offset in combination with a blunting correction is proposed. This approach is evaluated by finite element simulations. Then the proposed approach is validated experimentally. The presented approach is simple in use and provides an acceptable estimation error when it comes to constructing resistance curves.