The fracture and fatigue properties of cast irons used for trunk mains in the water industry
In order to assess the remaining life of cast iron assets in the water sector, an understanding of their fracture and fatigue characteristics is necessary. The present work is concerned with the toughness and Paris crack growth behaviour of cast iron materials with a range of micro-structures, taken from trunk mains currently in service. When considered with other data from the literature, the results from the present study enable the range of fatigue crack growth behaviour likely to be seen in service to be quantified. The role of microstructure in fracture and fatigue behaviour is discussed. Calculations of fatigue life based on integration of the Paris law are then carried out and compared with previously published data for samples from cast iron distribution mains. The results from these investigations support the development of asset management tools for use in the water industry.
Fracture toughness and fatigue crack growth of grey cast irons
The fracture behaviour of alloys with a pearlitic matrix and lamellar and spherulitic graphite has been compared. Fatigue crack growth functions were measured and various critical stress intensities obtained from load-displacement curves. An analysis of microstructure in the uncracked and cracked state served as the base for a discussion of quantitative models for the relation between microstructure and bulk fracture mechanical properties. In addition to volume fraction and shape of graphite, crack branching (and eventually transformation of residual austenite) are required to explain the resistance of grey cast irons against stable and unstable crack growth. It is concluded that the standard methods for the evaluation of fracture mechanical properties are not satisfactory especially for cast irons with lamellar graphite.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.