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Imola, Italy

Tovo R.,University of Ferrara | Lazzarin P.,University of Padua | Berto F.,University of Padua | Cova M.,SACMI Imola Science | Maggiolini E.,University of Ferrara
Theoretical and Applied Fracture Mechanics | Year: 2014

The paper presents new experimental multiaxial fatigue data on cast iron. Several sets of specimens, taken from a real large component, have been tested under uniaxial and biaxial, tensile and torsional loading; in-phase and out-of-phase combined loadings have also been considered. The obtained results have been compared with similar experimental data taken from the literature, and the tested material has shown high sensibility to the mean value of shear stress under torsional loading, as well as dependence on the mean value of tensile stress under tensile loading. The most suitable fatigue criterion should be related to the larger principal stress variation. The materials show an unusual sensibility to the out-phase loading. © 2014 Elsevier Ltd. Source


Bosi F.,University of Trento | Piccolroaz A.,University of Trento | Gei M.,University of Trento | Corso F.D.,University of Trento | And 2 more authors.
Journal of the European Ceramic Society | Year: 2014

Mechanical experiments have been designed and performed to investigate the elasto-plastic behaviour of green bodies formed from an aluminum silicate spray dried powder used for tiles production. Experiments have been executed on samples obtained from cold compaction into a cylindrical mould and include: uniaxial strain, equi-biaxial flexure and high-pressure triaxial compression/extension tests. Two types of powders have been used to realize the green body samples, differing in the values of water content, which have been taken equal to those usually employed in the industrial forming of traditional ceramics. Yielding of the green body during compaction has been characterized in terms of yield surface shape, failure envelope, and evolution of cohesion and void ratio with the forming pressure, confirming the validity of previously proposed constitutive models for dense materials obtained through cold compaction of granulates. © 2013 Elsevier Ltd. Source


Cova M.,University of Ferrara | Nanni M.,SACMI Imola Science | Tovo R.,University of Ferrara
Procedia Engineering | Year: 2014

Fatigue strength is known to decrease with increasing dimension of the component. This is due to a technological size effect, related to the production process, and to a geometrical size effect, due to a higher probability of finding a large defect. To investigate the latter, an heavy-walled component made of Ductile Cast Iron (DCI) has been trepanned and a fatigue test plan has been carried out using 4 different specimen geometries. An attempt has been made to relate the resulting fatigue strength using a weakest-link approach based on the effective volumes and surfaces. This approach seems to work well only in cases of different specimen's lengths. Some of the fracture surfaces were analyzed by means of SEM and the initiating defects were identified and measured. An approach in which the defects population can be randomly distributed in the specimen has been tried. Virtual fatigue tests have been carried out by considering pure propagation of the worst defect. The resulting fatigue curves showed that this approach is promising but needs further description of the initiation phase. © 2014 The Authors. Published by Elsevier Ltd. Source


Cova M.,University of Ferrara | Nanni M.,SACMI Imola Science | Tovo R.,University of Ferrara
MATEC Web of Conferences | Year: 2014

Fatigue strength is known to decrease with increasing dimension of the component. This is due to a technological size effect, related to the production process, and to a geometrical size effect, due to a higher probability of finding a large defect. To investigate the latter, an heavy-walled component made of Ductile Cast Iron (DCI) has been trepanned and a fatigue test plan has been carried out using 4 different specimen geometries. An attempt has been made to relate the resulting fatigue strength using a weakest-link approach based on the effective volumes and surfaces. This approach seems to work well only in cases of different specimen's lengths. Some of the fracture surfaces were analyzed by means of SEM and the initiating defects were identified and measured. An approach in which the defects population can be randomly distributed in the specimen has been tried. Virtual fatigue tests have been carried out by considering pure propagation of the worst defect. The resulting fatigue curves showed that this approach is promising but needs further description of the initiation phase. © Owned by the authors, published by EDP Sciences, 2014. Source


Cova M.,University of Ferrara | Nanni M.,SACMI Imola Science | Tovo R.,University of Ferrara
MATEC Web of Conferences | Year: 2014

The definition of the relationship between probability, fatigue stress and cycles to failure is of great importance, especially in applications which requires very low probability of failure (e.g. Pf=0.1%). In this paper a new formulation is presented, which allows to separately consider the probability of the endurance and the probability of existence of the initiating defect. This approach is then compared to a number of known models. For this purpose, the proprietary results of 8 fatigue test sets, each with at least 24 data points, have been analyzed. A ranking of goodness-of-fit based on the Relative Likelihood can be used to choose the best distribution within each model, but unfortunately cannot be used to compare different models. The conclusions were: 1- the better description of the HCF strength, in terms of performance and robustness, were obtained by the 2-p Weibull distribution; 2- the choice of the model has a great influence in the estimate of the low probability quantiles, but it still subjective and a definitive answer cannot be given after this benchmark; 3- the strength of the proposed model is its flexibility. © Owned by the authors, published by EDP Sciences, 2014. Source

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