The usual loading rate for impact testing is near 5 m/s. As it will be demonstrated, force-deflection diagrams show strong oscillations, at least at the beginning. Investigations on realistic loading rates showed, however, in most practical cases effective loading rates below 0.1 m/s. Because this is true in nearly every case, a loading rate of 0.1 m/s seems to be sufficient for precracked specimens.

If the loading rate is reduced from about 5 m/s to 0.1 m/s, the force-deflection-diagram can be evaluated without parasitic oscillations. Therefore measurement of fracture toughness, K_Id, J_d and the calculations of CTOD become easier.

Regarding fracture work and specific fracture work, the steel investigated shows no significant difference if 5 m/s and 0.1 m/s impact velocity is compared. Fracture toughness characteristics will become comparable when transition temperature shifts below 20°C are negligible.

If a transition temperature shift above 15°C is of importance, the experimental results have to be treated differently. A substitution will become not practicable without a function converting the 0.1 m/s results to 5 m/s results and vice versa.

If the steels tested are sufficiently brittle, an extrapolation to the fracture toughness of larger sections will become possible.