What is the effect of elevated ('dynamic') loading rate on the fracture toughness transition temperature of ferritic steel?

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A predictive framework has been developed by Wallin (1997). The predicted fracture toughness transition temperature shift, ΔT _o (in °K) depends on loading rate, Κ (expressed as the rate of increase of the applied stress intensity factor in MPa √m/s), static fracture toughness transition temperature, T _o ^stat (in °K for a loading rate, of Κ = 1MPa √m/s) and the static yield strength, σ _ys (in MPa), as follows:

For a ratio of dynamic to static loading rate of 10⁴, the predicted shifts are as shown in Fig.1. It can be seen that the shifts are a function of yield strength (with lower predicted shifts for higher yield strength), but also depend strongly on the absolute value of static fracture toughness transition temperature, with markedly lower predicted shifts for higher transition temperatures.

Fig.1 Predictions of fracture toughness transition temperature shifts for a ratio of dynamic to static loading rate of 10,000 according to the method proposed by Wallin

Reference