Crack initiation and growth in the Charpy V-notch test are investigated for controlled deflections of the specimen applied both by slow bending and by impact. Charpy test specimens were deformed to various deflections, heat-tinted to mark the crack extensions, and broken apart at low temperature to allow measurement of the crack extensions. These measurements provide estimates of crack initiation as defined by various criteria. The loading point at which crack initiation occurs depends on the particular definition being used for ''initiation,'' but in all cases it is well before the maximum load is reached. When initiation is defined as the first observable micro-initiation away from the ductile blunting of the notch root, the experimental results are in good agreement with computer modeling predictions.

A two-phase turbine, using a low-quality steam-water mixture as a working fluid, was designed, built, and tested in the laboratory. Two-phase fluids are found naturally in most geothermal fields throughout the world and can also be used in the conversion of waste heat from industrial sources. The thermodynamic and fluid-dynamic properties of such fluid mixtures are reviewed, with specific reference to the selection and design of an appropriate expander. Various types of practically realizable expanders are considered, and the choice of a single-stage, axial-flow, impulse turbine is explained. Also the basic design parameters, including sizing and blade and nozzle geometry, are described.