Experimental and Analytical Investigations on Multiple Liquid Impact Erosion
Abstract
This technical report summarizes the results of experimental and analytical investigations on multiple liquid (water) impact erosion of 1100-0 Aluminum and 316 stainless steel under contract No. NASW-1608. An existing rotating disk facility was modified so that six specimens might be simultaneously tested at three different velocities. High speed motion pictures as well as conventional movie films with stroboscopic illumination were taken to show the phenomenon of liquid jet impact with the test material in a qualitative manner. Using this facility, the threshold impact velocity at which visible erosion was observed after ten million impacts was determined. The threshold water hammer stress on the material corresponding to this threshold velocity, was correlated with the high frequency endurance limit corresponding to ten million fatigue cycles using the magnetostriction vibratory apparatus. The ratio between the fatigue endurance limit and the threshold water hammer stress is 1.7 for 1100-0 aluminum and 3.0 for 316 stainless steel. A mathematical theory of erosion has been recently developed to predict the rate of cavitation erosion as a function of exposure time. This theory was extended to multiple liquid impact erosion. In this theory, it is important to know the value of a parameter called the shape parameter, alpha. In the original theory it was assumed that the shape parameter was the same as that obtained in fatigue probability distribution (Weibull distribution). However, the present investigations show that the Weibull shape parameter as obtained from a high frequency fatigue test corresponding to ten million life cycles is about 0.5 whereas the shape parameter required to predict the erosion rates is 3.0 for aluminum and 5.0 for 316 stainless steel. The implications of this result on the erosion theory are fully discussed. The probable reasons for the variation in the shape parameter are also pointed out.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1969
- Accession Number
- ADA382444
Entities
People
- A. Thiruvengadam
- S. L. Rudy