Methods of Generating Dynamic Loading

Methods of generating well characterized dynamic loads for investigations of dynamic fracture phenomena are described in this chapter. Numerous methods have been used to generate reproducible loading for the purpose of examining dynamic crack growth, ranging from static or quasistatic loading of blunt cracks to impact with projectiles at speeds ranging from 5 to 100 m/s. Novel methods such as electromagnetic loading, pulse loading derived from a Hopkinson bar, and explosive loading have been developed to generate high-intensity, short-duration pulse loading on cracks. Of the many different loading schemes describedin the chapter, the electromagnetic loading provides two major advantages. First, it provides a very repeatable, electrically synchronized loading that makes experiments easy. Therefore, this loading method is well suited for studies of crack initiation as well as continued growth. However, specialized equipment is necessary for implementation of this loading and is not readily available commercially. Second, this scheme provides crack surface loads in a configuration that can be modelled as a pressurized semi-infinite crack in an unbounded medium, a configuration that is easily analyzed.