Particle Impact Damage Research Articles

The interaction between corrosion and erosion during simulated sea salt compressor shedding in marine gas turbines

The erosion-corrosion behaviour of IN738C has been examined under conditions simulating compressor shedding of sea salt particles in a marine gas turbine. It is shown that under conditions for which thin surface oxide scales are expected to show good erosion resistance, deterioration by chloriderich deposits may occur. Rapid sulphation of sea salt deposits results in reduced damage because chloride-induced disruption of surface oxide scales is not observed. The protection afforded to the substrate by the oxide scale will then be a function of its resistance to particle impact damage.

Particle impact damage in silicon nitride at 1400� C

Impacts of tungsten carbide spheres on Si3N4 produced elastic fracture behaviour (ring and cone cracks) at room temperature, but elastic-plastic fracture behaviour (plastic impressions and radial cracks) at 1400° C. In contrast, no change in fracture pattern at the two temperatures was produced by impact with steel spheres. These results may be explained by the relative abilities of the impacting spheres to cause plastic flow at the impact site and hence to alter the stress distribution in the Si3N4 specimens. The type and extent of damage produced by hard particle impact at 1400° C appears to be more deleterious to structural integrity than that produced at 20° C under equivalent particle impact loading conditions.

Single particle impact damage of fused silica

Single particle impact damage of fused silica

Single particle impact damage of fused silica

Single-impact damage of fused silica by spherical and conical tungsten carbide (WC) projectiles of velocities up to 200 m sec−1 has been investigated with a high-speed framing camera photographing at a rate of up to 1.7×106 frames per second. For spherical particles the Hertzian cone cracks, which for higher impact velocities are accompanied by median and radial cracks, form during the loading part of the impact; some growth of all these cracks also occurs during unloading. With the conical particles the Hertzian cone cracks do not form; only radial and median cracks form during the loading; in this case both radial and median cracks grow during the unloading. In both cases “lateral” cracks form during unloading. From these experiments values of the static equivalent of the dynamic stress-intensity factor for high-velocity cracks are also obtained; these are found to be considerably lower than those obtained from quasi-static indentation experiments. Finally, the extent of the damage produced by a single impact has been discussed.

Refractory Metal Air Vane Leading Edge for Ballistic Missile Defense Interceptor

A research study has been performed to select, through a combined experimental and analytical effort, a refractory metal material and an air vane leading edge configuration capable of surviving the high-performance advanced ballistic missile defense (HMD) interceptor environments. Five candidate tungsten alloy materials and a tungsten-copper material have been screened for use on the basis of mechanical properties, thermal performance, and resistance to particle impact damage. Only those material fabrication processes which had potential to yield full-scale air vane leading edge hardware were considered. Tensile and coefficient of thermal expansion data were obtained for each material from room temperature to 5000°F. Tests conducted in 5-MW and 50-MW plasma arc facilities evaluated surface recession characteristics over a wide range of pressures and enthalpies. Particle impact damage tests on heated and unheated specimens were conducted in a light gas gun facility using /g-in. glass spheres traveling at 10,000 fps. Using the properties obtained, a leading edge design study and thermal stress analysis of several configurations yielded an acceptable design concept which exhibited significantly lower thermal stresses than others considered. The tungsten-hafnium carbide (arc cast) material was the superior candidate in every category.