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Although cavitation erosion in hydraulic systems is an old problem, the damage mechanism that culminates in material loss was not known with certainty until recently. An investigation is described that aimed at clarifying the damage mechanism in cavitation erosion and applying that knowledge to make hydraulic equipment more resistant to cavitation. Strong correlations were established between cyclic deformation (fatigue) parameters and cavitation-erosion rates. This identification facilitated the search for more resistant materials. Finite element modeling confirmed that localized impacts on metal surfaces produce fatiguelike deformations and damage accumulation. Among available materials, near-equiatomic alloys of nickel and titanium are anomalously resistant to low-cycle fatigue and thus should be very resistant to cavitation erosion. Experiments confirmed the expected erosion resistance. Building large machines entirely out of NiTi is impractical, however, and a way of selectively cladding common constructional materials is required. Because NiTi has not been fusion welded successfully to other alloys, explosive bonding of thin NiTi plates to structural steel was investigated. Excellent welds were achieved, and the erosion resistance of the resulting clads has been demonstrated. Comparisons are made to other erosion processes and to other erosion-resistant materials, and some applications to hydraulic devices are suggested. [ABSTRACT FROM AUTHOR]

Biological structural materials, although composed of unremarkable substances synthesized at low temperatures, often exhibit superior mechanical properties. In particular, the quality in which nearly all biologically derived materials excel is toughness. The advantageous mechanical properties are attributable to the hierarchical, composite, structural arrangements common to biological systems. Materials scientists and engineers have increasingly recognized that biological designs or processing approaches applied to man-made materials (biomimesis) may offer improvements in performance over conventional designs and fabrication methods. In this survey, the structures and processing routes of marine shells, avian eggshells, wood, bone, and insect cuticle are briefly reviewed, and biomimesis research inspired by these materials is discussed. In addition, this paper describes and summarizes the applications of biomineralization, self-assembly, and templating with proteins to the fabrication of thin ceramic films and nanostructure devices. [ABSTRACT FROM AUTHOR]