Volume 32, Issue 4 (July 2004)
On the Possibility of Avoiding the Use of a Clip Gage When Testing Precracked Charpy-V Specimens in the Ductile-to-Brittle Transition Region
Fracture toughness testing using bend-type samples, such as precracked Charpy specimens, requires using a clip gage for measuring crack mouth opening displacement (CMOD). This paper demonstrates that it is possible to avoid using a clip gage and use instead machine crosshead displacement (MCD) as an approximation of load-line displacement; this simplifies considerably the test procedure, both in terms of mechanical operations and specimen instrumentation. This is particularly desirable for irradiated materials and when testing subsize specimens. Results obtained in the ductile-to-brittle transition regime from the analysis of 151 toughness tests show that reference temperatures calculated using the Master Curve methodology with CMOD and MCD are fully equivalent within a few degrees. The investigation has been conducted on different materials, test machines, full-size, and subsize specimens.