This report contains the results obtained from the mechanical characterization tests carried out on two different stainless steel (duplex 6%Ni, 22%Cr and super-austenitic 31%Ni, 28%Cr) used for the manufacturing of pipes which are employed in the oil production. The activity has been performed in order to evaluate the effects of anisotropy, induced by cold rolling, on the mechanical characteristics of the investigated steels, measured in the three main directions. Considering the small size of the component, the method and the specimens used for the tests were not the standard one. The procedure carried out provided the strain measurement of the specimen during testing by means of resistive strain gages, bonded on the specimens.

Two parallel comparative ‘Conventional Method and Computer Simulation using ANSYS software’ for prediction of crack growth and its behavior in optical fiber are studied and presented in this work. Corresponding finite element analysis was performed to determine the evolution of stress and strain states. The method is developed and combined with the modified J-integral theory to deal with this problem. The effects of crack length, temperature and mechanical forces are investigated by Finite Element Method in the cracked body. The conditions where the Mode I stress intensity factor motivate fracture occurrence is investigated and variations of the different cases are discussed. The most deleterious situation is found to be that wherein the entire model reaches rupture at some stage. The accuracy of the method is investigated through comparison of numerical results with computerized simulation using commercial ANSYS software.

Careful observation of three-dimensional geometry of cracks and defects is necessary in order to study the mechanisms underlying the process of damage. Conventional methods used for this purpose are destructive or have an insufficient resolution. However, the imaging techniques using synchrotron radiation, and in particular the X-ray microtomography (micro-CT), are particularly interesting as they are able to combine the advantages of a non-destructive technique with high spatial resolution. A limit in the application of this technique is the propensity of the crack to reclose upon removal of the load that had caused the damage. This obstacle can be overcome through the use of a test rig capable of exerting a tensile load during the data acquisition. With reference to the experimental set-up of the line SYRMEP of Elettra, the synchrotron radiation facility in Trieste, and ignoring, for the moment, the constraints related to weight and size, it is possible to consider the insertion, between the ionization chamber and the CCD camera, of a commercial single-column machine for tensile testing, able to keep the defect open for the duration of a tomography. In this paper the impact of this constraint on the final quality of the reconstructions is estimated.

Microstructure influence on fatigue crack propagation resistance in five different ductile cast irons (DCI) was investigated. Four ferrite/pearlite volume fractions were considered, performing fatigue crack propagation tests according to ASTM E647 standard (R equals to 0.1, 0.5 and 0.75, respectively). Results were compared with an austempered DCI. Damaging micromechanisms were investigated according to the following procedures: - “traditional” Scanning Electron Microscope (SEM) fracture surfaces analysis; - SEM fracture surface analysis with 3D quantitative analysis; - SEM longitudinal crack profile analysis - Light Optical Microscope (LOM) transversal crack profile analysis