The present paper deals with fatigue experimentation and with the application and improvement of predictive models; in addition, a sensitive analysis is performed on the main factors related to the shot‐peening treatment and on the efficiency of the aforementioned models. The research involved gears, made of high‐strength steel and carburised, quenched, ground, shot‐peened and superfinished. The experimental campaign initially dealt with the investigation into the influence of isotropic superfinishing; the attention was then focused on shot peening and how to optimise the fatigue limit, by a suitable choice of operative parameters. The option of duplex peening for further fatigue improvement was also considered. Results concerning component residual stress distributions and fatigue limits were then processed by investigating their sensitivity with respect to driving factors, namely the shot diameter and the Almen intensity. Two theories for fatigue prediction (the method of the relative stress gradient and the theory of critical distances) were reviewed for application to shot‐peened components, with a comparison between experimental and numerical results. A comparative analysis was then performed on the two theories, on the basis of the number of data inputs, advantages and drawbacks, while sensitivity analyses focused on how uncertainties affecting input data propagate to predictive results.

The distributions of sterols and organic-walled dinoflagellate cysts (dinocysts) in five NW Adriatic Sea surface sediment samples were investigated. Samples are representative of areas differently influenced by freshwater inputs, mainly coming from the Po River. All the investigated samples exhibit the same suite of principal sterols, with cholest-5-en-3b-ol (cholesterol), 4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol (dinosterol), 24-ethylcholest-5-en-3b-ol (sitosterol) and 24-methylcholesta-5,22E-dien-3b-ol (brassicasterol or epibrassicasterol) displaying the highest concentrations and relative abundances. The distribution of sterols in the samples is not related to their distance from the coast and/or with the C/N ratios and suggests a prevalent input of marine, autochthonous organic matter in the surface sediments. In particular, the high abundance of dinosterol underlines the importance of dinoflagellate productivity in this area and its contribution to the organic matter in sediments. However, absolute and relative abundances of dinosterol do not follow the trend observed for dinocyst concentrations in the investigated samples, with the exception of Spiniferites spp. cysts and cysts produced by Gonyaulax species.

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