Variation In Erosion Resistance Research Articles

WAVE OVERTOPPING SIMULATOR TESTS IN VIET NAM

Sea dikes in Viet Nam have been built up during a long history. Every year, about 4 to 6 storms attack the coast and cause severe damages of the sea dikes. Till now, little is known about strength and stability of the inner slope covered with grass under impacts of wave overtopping during storm surges. Destructive tests have been performed with the Wave Overtopping Simulator in Viet Nam revealing that grass slopes are able to withstand a certain amount of wave overtopping. In Hai Phong, a slope section covered by Vetiver grass could suffer a maximum wave overtopping discharge of up to 120 l/s per m. In Nam Dinh, three tested locations within a short dike section of 50 m show a large variation in erosion resistance of the Bermuda grass slope with maximum discharge of 20, 40 and 70 l/s per m.

Variation in erosion resistance of pseudoelastic TiNi alloy with respect to temperature

Near-equiatomic TiNi alloy exhibits excellent wear resistance, benefiting from its pseudoelasticity and other intrinsic mechanical properties. The pseudoelasticity helps to reduce plastic deformation and absorb impact energy, thus decreasing the material loss. Since the martensitic transformation is temperature dependent, research was conducted to investigate the performance of Ti–51at.%Ni alloy during erosion as a function of temperature and the erodent velocity. The erosion behavior of the TiNi alloy was evaluated using a high-temperature air-jet erosion tester. The worn surface was examined using scanning electron microscopy and the transformation temperature was determined using differential scanning calorimetry (DSC). It was demonstrated that there was a minimum erosion loss with respect to temperature and the velocity of erodent also influenced this minimum erosion loss. Possible mechanism responsible for the erosion behavior of TiNi alloy is discussed.

Water jet erosion behaviour of Ti-Ni binary alloys

The water jet erosion behaviour of Ti-Ni alloys has been studied. The variation in erosion resistance with chemical composition of alloys containing 54–60 wt.% nickel is described and discussed in terms of the microstructure of these alloys. Erosion tests were conducted using a high velocity (370 m s −1) water jet for 2–60 min. The erosion resistance of the Ti-Ni alloys was found to be strongly dependent on chemical composition and microstructure but not on hardness. The erosion resistance appeared to be at its best in alloys with a nickel content of approximately 55–56.5 wt.%; there was a sharp reduction in resistance when the nickel content of the alloys was reduced and a gradual reduction along a series with increasing nickel content. The differences in erosion resistance were due to differences in the incubation time for the erosion. The weaker erosion resistance observed at the low-nickel end of the series of alloys was a result of continuous brittle Ti 2Ni phase precipitation. The somewhat reduced erosion resistance in the nickel-rich alloys may be due to localization of the strain energy with precipitation of a hard secondary phase, presumably of TiNi 3. The extraordinarily good erosion resistance of the TiNi phase must be related to the thermoelasticity of its martensite, which can absorb energy elastically.