Published: Jan 2000
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Fracture toughness is often estimated from the Charpy fracture energy by empirical correlation formulas, although the latter are known to be in general of poor accuracy and valid only with restrictions. In the present paper the relation between these two types of toughness parameters is considered from a theoretical point of view. Unexpectedly a mathematical relation was found to exist. As known from experimental data, this relation is not unique, but dependent on some material properties like tensile strength and uniform fracture strain. The derived relation can be used in the upper-shelf and upper ductile-to-brittle transition range. It is in good agreement with experimental data and the current empirical correlation formulas, giving theoretical support to the latter and confirming the present model. In the lower transition range, the use of the ASME lower-bound curve is suggested. The temperature shift due to loading velocity and notch sharpness requires additional experimental work.
impact testing, fracture energy, Charpy-V-notch test, J-resistance curve, fracture toughness, correlation, analytical relation
Senior research engineer, Swiss Federal Labs, for Materials Testing and Research (EMPA), Duebendorf,