Experimental unit for determining the fracture-toughness characteristics of materials

An experimental unit is proposed for determining fracture-toughness characteristics in the starting, movement, and stopping of a crack under static, cyclic, and impact loading. A basically new method of securing and loading the specimen is employed in the unit. The method significantly reduces the amount of elastic energy accumulated in the machine-specimen system and improves the “purity” of the experiment by having the specimen acted upon only by a disjoining force. Also, the working element (wedge) provides only an initial impulse at the stage of crack initiation, stops in a predetermined position, and then functions as a transducer recording the force that develops in the specimen over time. Tests can be conducted on DCB (double cantilever beam), CT (compact), and CB (concentrated bending) specimens.