The J-integral resistance curve (or J-R curve) has been widely used as material property in fracture mechanics methods for structural integrity assessment. ASTM E1820 provides the standard fracture toughness test methods to measure JIc and J-R curves. The conventional J-R curve utilizes the J-integral parameter proposed by Rice  based on the deformation theory of plasticity. Due to crack-tip constraint effect, J-R curves of a material depend on specimen size, geometry type and crack length. In order to obtain size-independent resistance curves, Ernst  introduced a modified J-integral or Jm to minimize the size dependence and to characterize the resistance curve for large crack extensions beyond the limitation of deformation J-R curves. In the late 1980s and in the early 1990s, different experimental results showed the modified Jm-R curves were still size-dependent and may even behave worse than the deformation J-R curves. However, to date, the Jm-R curves are still regarded as “size-independent” in fracture mechanics analysis. To clarify this, the present paper gives a brief historical review of ductile resistance curves in terms of deformation J-integral and the modified Jm-integral, and evaluates the size dependence using experimental results for various steels and specimens, including A285 carbon steel and SENB specimens. A suggestion how to use the resistance curves is made accordingly.
- Pressure Vessels and Piping Division
Deformation Versus Modified J-Integral Resistance Curves for Ductile Materials
Zhu, X, & Lam, P. "Deformation Versus Modified J-Integral Resistance Curves for Ductile Materials." Proceedings of the ASME 2012 Pressure Vessels and Piping Conference. Volume 6: Materials and Fabrication, Parts A and B. Toronto, Ontario, Canada. July 15–19, 2012. pp. 97-107. ASME. https://doi.org/10.1115/PVP2012-78729
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