Use of KLST-type Miniature Charpy Specimens for Measuring Dynamic Fracture Toughness under Impact Loading Rates

The knowlegde of dynamic mechanical properties is useful in all cases where the strain rate sensitivity of metallic materials is an issue, and whenever the actual loading conditions for a structure (either in normal operation or under accidental circumstances) are different from static. Furthermore, in some investigations increasing the loading rate in a mechanical test is used to simulate other embrittling mechanisms such as thermal aging or neutron exposure. This paper addresses the applicability of fatigue precracked miniature Charpy specimens of KLST type (PKLST - B = 3 mm, W = 4 mm and L = 27 mm) for impact toughness measurements in the ductile-to-brittle transition regime and in fully ductile (upper shelf) conditions. In the transition region, tests have been analyzed using the Master Curve approach; the multiple-specimen (low-blow) method has been applied in the upper shelf regime. A well-known and fully characterized RPV steel of the A533B Cl.1 type (JRQ) has been used; the results obtained have been compared with data previously obtained from standard-size precracked Charpy specimens. It has been found that under impact loading conditions PKLST specimens suffer significant loss of constraint when compared to conventional PCCv samples, in both transition and upper shelf conditions.