Structural S355 steel is widely applied in various sectors. Fatigue properties are of fundamental importance and extremely time consuming to be assessed. The aim of this research activity is to apply ...the Static Thermographic Method during tensile tests and correlate the temperature trend to the fatigue properties of the same steel. The Digital Image Correlation (DIC) and Infrared Thermography (IR) techniques have been used during all static tests. The Digital Image Correlation technique allowed the detection of displacements and strain, and so the evaluation of the mechanical properties of the material. Traditional fatigue tests were also performed in order to evaluate the stress-number of cycles to failure curve of the same steel. The value of the fatigue limit, obtained by the traditional procedure, was compared with the values predicted by means of the Static Thermographic Method (STM) obtained from tensile tests. The predicted values are in good agreement with the experimental values of fatigue life.
Collisions induced by {sup 9,10,11}Be on a {sup 64}Zn target at the same c.m. energy were studied. For the first time, strong effects of the {sup 11}Be halo structure on elastic-scattering and ...reaction mechanisms at energies near the Coulomb barrier are evidenced experimentally. The elastic-scattering cross section of the {sup 11}Be halo nucleus shows unusual behavior in the Coulomb-nuclear interference peak angular region. The extracted total-reaction cross section for the {sup 11}Be collision is more than double the ones measured in the collisions induced by {sup 9,10}Be. It is shown that such a strong enhancement of the total-reaction cross section with {sup 11}Be is due to transfer and breakup processes.
Abstract
The abundance of
26
Al carries a special role in astrophysics, since it probes active nucleosynthesis in the Milky Way and constrains the Galactic core-collapse supernovae rate. It is ...estimated through the detection of the 1809 keV
γ
-line and from the superabundance of
26
Mg in comparison with the most abundant Mg isotope (
A
= 24) in meteorites. For this reason, high precision is necessary also in the investigation of the stable
27
Al and
24
Mg isotopes. Moreover, these nuclei enter the so-called MgAl cycle, playing an important role in the production of Al and Mg. Recently, high-resolution stellar surveys have shown that the Mg–Al anticorrelation in red-giant stars in globular clusters may hide the existence of multiple stellar populations, and that the relative abundances of Mg isotopes may not be correlated with Al. The common thread running through these astrophysical scenarios is the
27
Al(p,
α
)
24
Mg reaction, which is the main
27
Al destruction channel and directly correlates its abundance with the
24
Mg one. Since available reaction rates show large uncertainties owing to the vanishingly small cross section at astrophysical energies, we have applied the Trojan Horse Method to deduce the reaction rate with no need of extrapolation. The indirect measurement made it possible to assess the contribution of the 84 keV resonance and to lower upper limits on the strength of nearby resonances. In intermediate-mass AGB stars experiencing hot bottom burning, a sizeable increase in surface aluminum abundance is observed at the lowest masses, while
24
Mg is essentially unaffected by the change in the reaction rate.
The excitation of the dynamical dipole mode along the fusion path was investigated in the formation of a heavy compound nucleus in the A=190 mass region. To form the compound nucleus, the 40Ca + ...152Sm and 48Ca + 144Sm reactions were employed at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion–evaporation and fission events were studied simultaneously for the first time. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.
The studies of the evolution of the hot Giant Dipole Resonance (GDR) properties as a function of excitation energy are reviewed. The discussion will mainly focus on the A ˜ 100-120 mass region where ...a large amount of data concerning the width and the strength evolution with excitation energy are available. Models proposed to interpret the main features and trends of the experimental results will be presented and compared to the available data in order to extract a coherent scenario on the limits of the development of the collective motion in nuclei at high excitation energy. Experimental results on the GDR built in hot nuclei in the mass region A ˜ 60-70 will be also shown, allowing to investigate the mass dependence of the main GDR features. The comparison between limiting excitation energies for the collective motion and critical excitation energies extracted from caloric curve studies will suggest a possible link between the disappearance of collective motion and the liquid-gas phase transition.
A new modular and high versatility hodoscope, OSCAR, has been developed and characterized. The aim of this hodoscope is to work as an ancillary detector of present large acceptance heavy ion ...detectors in specific angular regions where low thresholds and high granularities are needed. We discuss the capabilities of OSCAR in the ΔE–E identification of very low energy light particles, providing a precise map of the thickness uniformity of the ΔE (SSSSD, 20μm) stage and showing how the thickness gradient affects the identification of particles. Energy spectra of light identified particles produced in Ca+Ca collisions at 35AMeV are used to investigate isospin transport phenomena involving the emission of low energy particles from the quasi-target (QT) source in semi-peripheral nuclear collisions. The possibility to explore particle–particle correlations are also discussed.
The study of fusion in collision around the Coulomb barrier, induced by radioactive or stable weakly bound nuclei, has been the subject of many experiments in the last years. From a semiclassical ...point of view, direct processes like break-up or transfer may be favoured by the low binding energies and one might also expect suppressed fusion cross section due to the competition with the break-up. However, according to the Coupled Channel calculations (CC), it is well known that the presence of strong open reaction channels can be responsible for a fusion cross-section enhancement with respect to the single barrier penetration calculations and the break-up should be included in such calculations. In order to further investigate on this topic, the 6Li+64Zn collision has been studied at several energies around the Coulomb barrier, to extract the total fusion and the total reaction cross sections and to study the energy dependence of the optical model potential.
PDF
