Material inertia and size effects in the Charpy V-notch test

The effect of material inertia on the size dependence of the absorbed energy in the Charpy V-notch test is investigated. The material response is characterized by an elastic-viscoplastic constitutive relation for a porous plastic solid, with adiabatic heating due to plastic dissipation and the resulting thermal softening accounted for. The onset of cleavage is taken to occur when a critical value of the maximum principal stress is attained over a critical volume. Plane strain dynamic analyses are carried out for geometrically similar specimens of various sizes with all parameters adjusted so that a quasi-static analysis would predict a size independent response. Sizes ranging from 1/4 to 16 times the ASTM standard size are analyzed and two sets of material properties are considered. No size effect is seen below a critical specimen size. Above this limit, a monotonic increase with specimen size is found for the normalized lower shelf energy (LSE) and the normalized upper shelf energy (USE) for both sets of material properties. The ductile-to-brittle transition temperature (DBTT) is found to increase monotonically with specimen size for one set of material properties, but a non-monotonic variation is found for the other set of material properties.