A load cell employing foil strain gauges is described for measuring small uniaxial loads (5×104 to 2×106 dynes) applied magnetically to develop bending stresses in crystals under hydrostatic pressures up to 15 kbar. Two calibration methods of direct loading at pressure were used—a magnetically operated plunger and dead weight loading. It was established that the change in gauge output (the ``pressure effect'') during increase of pressure at no-load is in keeping with previous work. However, the gauge factor, as determined by the load cell response after balancing at pressure, decreases with increasing pressure. For the strain gauges used here, the decrease is approximately linear and at 10 kbar is as much as 20%.
The presence of machining damage (MD) in beryllium may be determined nondestructively in the acoustic microscope via the acoustic material signature (AMS). Rayleigh wave dispersion is attributed to substantial modification of the macroelastic properties in the surface region due to the machining process. Comparison of acoustic material signatures at 35 MHz obtained from chemically etched (undamaged) and machining-damaged (MD) specimens show substantial (3%) Rayleigh velocity reduction in the latter. Damage variation with depth may be ascertained via AMS mesurements over a wide frequency range.
Corrosion characteristics of high-purity polycrystalline beryllium as a function of pH and NaCl concentration were studied at 25°C, using cyclic polarization tests. Single crystal beryllium specimens oriented close to the (0001), (1010), and (1120) planes using Laue back reflection techniques were studied using cyclic polarization tests in 0.01M NaCl with a nominal pH of 7. Pit morphology of the polycrystalline and single crystals was studied using conventional scanning electron microscopy. On the polycrystalline specimens, passivity appears to be more a function of solution pH than of chloride concentration. Single crystal studies show dramatic differences in cyclic polarization plots and SEM micrographs. The two prism planes (1010) and (1120) behave similarly while the basal plane (0001) behaved in a substantially different manner.
IntroductionUnalloyed beryllium metal components are ordinarily of high value, and they are used in unique applications. Usually, the applications are such that the beryllium components are protected from adverse corrosive environments and, if this is not possible, coatings are applied to improve the corrosion resistance. In addition, the inherent corrosion resistance of beryllium is excellent. The thin oxide film on beryllium is strong, thin, and adherent; it provides good protection for the underlying metal. Unalloyed beryllium is not a commonly used metal, such as steel or perhaps aluminum, copper, or nickel based alloys. The net result of all these factors is that there is not a broad base knowledge of the corrosion behavior of beryllium. It is known that beryllium is sensitive to pitting corrosion in some moist environments. The pitting may be stimulated by the presence of other elements such as chloride ions. This is common for many metals. Also, it is well known that beryllium carbides, a common inclusion in some grades of beryllium, react with moisture in the air to form beryllium oxide and methane.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.