Experimental and analytical research on erosion of 1100-0 aluminum, 316 stainless steel, commercially pure annealed nickel, and 6A1-4V titanium (annealed) is summarized. The erosion is caused by the multiple impacts of a water jet in a rotating disk facility. The relationship between the velocity of impact and the number of impacts at which visible indentations were observed is compared with the high-frequency fatigue strength of these materials. The experimentally observed rates of erosion are compared with a recently developed theory of erosion. The fatigue life distribution curves also are included. The peak rate of erosion varies approximately as the fifth power of the velocity, whereas the time at which the peak rate is observed varies as the one-fifth power. The cavitation erosion strength and liquid impact erosion strengths of these materials also are compared.

The latest results from a study of the dynamic behavior of rain erosion-resistant coating and substrate materials are described. The correlations between rocket sled erosion data and fracture stresses determined from single-impact tests with a split Hopkinson pressure bar facility have been extended to include polyurethane. The results of tests within a small-scale erosion facility, and analyses of large whirling-arm studies, have shown that a fatigue type of behavior, already found to be applicable for an acrylic plastic, may also be used to describe the rain erosion resistance of elastomeric coatings such as polyurethane, and the glass fiber-reinforced epoxy composite substrates which are frequently utilized for radome construction. The importance of the “dynamic recovery rate” or relaxation time, and stress wave interactions, in understanding the rain erosion phenomenon is described in this paper. The applicability of the elastic-plastic, uniaxial stress wave theory for making rain erosion predictions is also discussed.

Laboratory coal-cutting experiments with CAVIJET cavitating waterjets have demonstrated the feasibility of this technology for hydraulic coal mining applications. The objective of the first phase of a developmental program, as described in this paper, was to determine the system and operating parameters required to cut coal with CAVIJETS, and to compare the results with those observed for noncavitating jets. Comparable coal cutting was achieved with the CAVIJET, relative to high-pressure, noncavitating jets, using one-fifth the pressure and one-half the specific energy. These results suggest that CAVIJET-augmented mining devices can be developed with compact, low-pressure pumps. Thus, CAVIJET should be capable of operating with safer, lighter, more suitable support equipment, while providing all of the advantages (reduction of dust and sparks; decreased damage to cutters) of conventional hydraulic mining methods.

Hot rolled plate steel is heat treatable steel made in Indonesia for commercially developed to Quenched and Tempered Steel. This steels made by PT. Krakatau Steel (Persero) Cilegon, Banten, Indonesia. The aim of this study to improve the hardness and energy impact through heat treatment of double quench + temper. The method used is heating up to 900°C (maintained for 30 minutes and cooled by water) for fives specimen hot rolled plate steel and produce the quenched 900 steel (Q900 Steel). Four Q900 steel specimens were heated at 750°C, 800°C, 850°C, and 900°C (maintained for 30 minutes) each. Then five specimens (include Q900 Steel) are tempered at 150°C (maintained for 30 minutes) and produced Q900 & T Steel, Q900+750 & T Steel, Q900+800 & T Steel, Q900+850 & T Steel, Q900+900 & T Steel. Results of the study were changes in microstructure, hardness and impact energy. Hardness and impact energy absorbed of Q900+750&T Steel higher than Q900 &T Steel.