Lifetime evaluation of hot forged aerospace components by linking microstructural evolution and fatigue behaviour

AbstractThe present work aims at linking the local distribution of fatigue strength in a forged part to its manufacturing process. To this purpose, a predictive fatigue strength model for Inconel 718, also including the operating temperature, is derived from a reduced set of numerous microstructural parameters. The model is implemented, along with a microstructural evolution model from earlier work , into a finite element code in order to predict the local fatigue strength distribution in a component after being subjected to an arbitrary forging process

Among-individual diet variation within a lake trout ecotype: lack of stability of niche use

In a polyphenic species, differences in resource use are expected among ecotypes, and homogeneity in resource use is expected within an ecotype. Yet, using a broad resource spectrum has been identified as a strategy for fishes living in unproductive northern environments, where food is patchily distributed and ephemeral. We investigated whether specialization of trophic resources by individuals occurred within the generalist piscivore ecotype of lake trout from Great Bear Lake, Canada, reflective of a form of diversity. Four distinct dietary patterns of resource use within this lake trout ecotype were detected from fatty acid composition, with some variation linked to spatial patterns within Great Bear Lake. Feeding habits of different groups within the ecotype were not associated with detectable morphological or genetic differentiation, suggesting that behavioral plasticity caused the trophic differences. A low level of genetic differentiation was detected between exceptionally large‐sized individuals and other piscivore individuals. We demonstrated that individual trophic specialization can occur within an ecotype inhabiting a geologically young system (8,000–10,000 yr BP), a lake that sustains high levels of phenotypic diversity of lake trout overall. The characterization of niche use among individuals, as done in this study, is necessary to understand the role that individual variation can play at the beginning of differentiation processes

Assessment of traditional versus geometric morphometrics for discriminating populations of the Tropheus moorii species complex (Teleostei: Cichlidae), a Lake Tanganyika model for allopatric speciation

Abstract Lake Tanganyika harbours the oldest and ecologically, morphologically and behaviourally most diverse species flock of cichlid fishes. Its species are excellent subjects for the study of explosive speciation and adaptive radiation. Many species are subdivided into numerous genetically and phenotypically distinct populations, often classified as distinct geographical races or colour morphs, which mostly differ in colour and much less in terms of morphology. This study for the first time quantifies morphological differences among such morphs by studying three populations of Tropheus moorii. We compared Ôtraditional morphometricsÕ (TM) and Ôgeometric morphometricsÕ (GM) to explore their potential for discriminating populations. So far species description and population discrimination are almost solely based on TM in the form of standardized measurements, although specialists are aware of their lack of diagnostic power for discrimination of closely related entities. Moreover, comprehensive TM measurements are time consuming and can best be done on dead specimens which have to be preserved in the case re-measuring is necessary. In contrast, GM can also be based on photographs and computer scans of anaesthetized fish, so that the same individual can be repeatedly analysed during its ontogeny. Here, we show that GM is more flexible in data acquisition and more powerful in the discrimination of species and closely related populations. While TM is restricted to distances and ratios of distances, GM not only includes these measurements indirectly, but also allows for body shape analysis using a semi-landmark approach. It can be equally standardized as TM by defining diagnostic landmarks. Data description by canonical variate analysis was most informative using GM data including semi-landmarks, whereas differences between populations were significant (p < 0.05) based on both morphological approaches