2 DEGREES OF FREEDOM MODELING OF PRECRACKED BEAMS UNDER IMPACT

Impact loading of three point bend specimens is modeled as a lumped ma ss-spring system with two degrees of freedom. The model gives all the forces involved in the impact process, viz. load measured by the tup i nstrumentation, contact force and the force experienced by the specime n. With a simplifying assumption of applicability of static crack-tip field solutions, the dynamic stress intensity factor (SIF) is computed from the beam force. Dynamic fracture toughness is obtained from the SIF at fracture initiation. The model explains the typical features of tup load and beam response records observed in instrumented Charpy te sting. The model predictions are compared with results of experiments conducted on aluminum 6061 T6 and polymethylmethacrylate (PMMA).