Ultimate Resilience Research Articles

Correlating Models and Prediction of Erosion Resistance to Cavitation and Drop Impact

Abstract Using venturi and rotating disk data, correlations are established between volume loss rates obtained from different stages of volume loss-time curves and various single and multiple material properties. The significance of correlations and relationships is judged from various statistical parameters computed. The analysis indicates that during the initial and development phases hardness and shock compression ratio play a predominant role, and once the erosion develops modified resilience and tensile strength significantly influence the erosion phenomenon. For the correlations involving volume loss taken from the initial and development phases the statistical parameters exhibit considerable variation, while in the developed phase their variation is insignificant. Analyses of extensive erosion data from the authors' laboratory and from other laboratories indicate that groupings of properties like ultimate resilience × hardness (UH) and tensile strength × hardness (T,H) or groupings such as UHE and UHT, exhibit best correlations. Several equations are proposed to predict erosion rates of various materials tested in different laboratories.

Cavitation Erosion Studies With Venturi and Rotating Disk in Water

A study of the cavitation erosion behind blunt bodies with varying hydrodynamic factors of flow, such as, the test time, length of cavity, velocity, and pressure; the geometrical parameters of the system, namely, the size and shape of the cavitating body, its aspect-ratio, and its surface roughness; and the mechanical properties of the materials, namely, the density, yield strength, tensile strength, engineering strain energy, hardness, ultimate resilience, percent elongation, percent reduction in area and elastic modulus are reported. The study of the volume eroded along with the hydrodynamic factors of the flow and the geometrical parameters of the system in general indicated that a critical zone of cavitation conditions exists in which the erosion caused is very severe. This critical zone is described by a range of values of V/l (α Strouhal frequency, f for detachment of cavities). Among the correlations studied for the inverse of rate of volume eroded as a function of individual and twin mechanical properties, the product of ultimate resilience and Brinell hardness showed the best correlation.

Cavitation Damage and Correlations With Material and Fluid Properties

A comprehensive set of cavitation damage data has been obtained in a vibratory facility using water, mercury, lithium, and lead-bismuth alloy as test fluids, and covering temperatures ranging from room temperature to 1500 deg F. Materials tested include a wide variety of metals and alloys. From this data a simple, reasonably precise, damage predicting equation has been derived, including only ultimate resilience as a material property, but also corrections for cavitation “thermodynamic effects” and NPSH. It has been found that of the conventional mechanical properties, ultimate resilience is the most successful in this regard. A direct comparison between venturi and vibratory cavitation damage shows that the relative rankings of materials remain about the same for mercury, and a good correlation is obtained between the mercury data from the venturi and ultimate resilience. Neither statement applies for the water venturi data, possibly because of the greater effects of corrosion in the low intensity cavitation field.