The J-integral resistance curve (or J-R curve) is an important fracture property of materials and has gained broad applications in assessing the fracture behavior of structural components. Because the J-integral concept was proposed based on the deformation theory of plasticity, the J-R curve is a deformation-based result. It has been known that the J-R curves of a material depend on specimen size and geometry; therefore, a modified J-integral or Jm was proposed to minimize the size dependence. Extensive experiments have shown that the Jm-R curves might remain size-dependent and could not behave better than the traditional deformation J-R curves. To date, however, it is noticed that the Jm-R curves were still used as “size-independent” results in some fracture mechanics analyses. It is necessary to revisit this topic for further clarification. This paper presents a brief review on the development of deformation and modified J-integral testing, and obtains a simple incremental Jm-integral equation. It is followed by typical experimental results with discussions on the issues of constraint or size dependence of J-R and Jm-R curves for different steels and specimens. Finally, a recommendation is made on properly selecting a resistance curve in the fracture analysis.
Deformation Versus Modified J-Integral Resistance Curves for Ductile Materials
Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received November 3, 2014; final manuscript received May 5, 2015; published online June 16, 2015. Assoc. Editor: Kunio Hasegawa.
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Zhu, X., and Lam, P. (October 1, 2015). "Deformation Versus Modified J-Integral Resistance Curves for Ductile Materials." ASME. J. Pressure Vessel Technol. October 2015; 137(5): 051407. https://doi.org/10.1115/1.4030593
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