The creep response in the air of commercially pure titanium was investigated at 550, 600, and 650 °C to assess the effect of oxidation on the mechanical response. Experiments demonstrated that prolonged exposures at high temperatures produced a marked reduction in the minimum creep rate under a given applied stress. Microhardness measurements showed that a hardened zone formed in proximity to the surface due to oxygen penetration into the metal. A simplified composite model was then used to describe the creep response. In this model, the sample consisted of two zones, the hard case that was enriched in oxygen and the soft pure-titanium core, both creeping with similar strain rates. Calculations led to an estimation of the dependence of the minimum creep rate on stress and temperature for the hard high-oxygen zone. The simplified composite model presented here provided a good description of the experimental creep data for pure titanium, tested in its air, and a reliable picture of the effect of oxidation on complex Ti alloys.

<p><strong>Abstract.</strong> In the last few years, the evolution of acquisition techniques allowed to acquire reality-based models increasing accurate and rich of information. On the contrary, the ability to exploit the acquired data in the most efficient, economic (in terms of invested time), and impartial way (in terms of arbitrary choices of the operator) represents the most significant gap. Interoperability theme between points cloud and informative systems becomes relevant. Excellent results were achieved in 3D data exploitation in HBIM and GIS environments, as well as in VR and AR applications, whereas the structural analysis with the Finite Element Method (FEM) still lacks robust workflows based on point clouds. The present paper proposes a methodology allowing to transform the TLS point cloud obtained from the survey directly into a 3D FEM, in a semi-automatic way and, therefore, proposes a hybrid reverse engineering approach that aims to: (i) maximizing the correspondence between the model for structural analysis and the real object; (ii) minimizing the time and the operator’s decision. The strategy is validated on the belfry of the Metropolitan Cathedral-Basilica of Saint Cyriacus in Ancona, Central Italy. The reliability of the proposed model is assessed through a comparison between the model obtained from the Boolean modelling within a FEM software and the model obtained directly from points cloud processing. The comparison between the two numerical models highlights the enormous potential of the exposed method. The proposed case study shows how it is possible to develop high-quality 3D models, able to connect geometrical-historical survey with thematic analysis about structural behavior.</p>

The creep response of the 17-4PH precipitation hardening steel produced by a new additive manufacturing technology (Bound Metal Deposition) was investigated at 482 °C (900 °F), under stresses ranging from 350 to 600 MPa. Two different sets of samples produced with different deposition parameters were considered. Prior heat treatment consisted of ageing either at 482 °C (state H900) or at 621 °C (H1150). The minimum creep rate and time to rupture dependencies on applied stress were obtained. The creep response in terms of time to rupture under a given stress, in particular, was compared with the only other available literature dataset on a similar steel processed by traditional technologies. The analysis of the experiments demonstrated that the presence of dispersed defects causes, in the Bound Metal Deposited steel, a substantial reduction (35–40%) of the creep strength.

The austenitic stainless steels utilized in the production of osteosynthesis devices are susceptible to crevice corrosion. Several studies have compared the corrosive behavior of austenitic and duplex stainless steels (DSS), both of which are recognized as viable biomaterials for tissue engineering applications. All of the in vitro and in vivo studies on animals and clinical results reported to date indicate that austeno-ferritic duplex stainless steel can be recommended as a suitable alternative to ASTM F138 steel, since it is resistant to crevice corrosion in the human body and presents superior mechanical properties. The use of DSS for biomedical applications is still under discussion, mainly due to the lack of knowledge of its behavior in terms of device heating or induced movement when exposed to magnetic fields, a potentially harmful effect for the human body. As a breakthrough production technology, additive manufacturing (AM) has demonstrated significant benefits for the fabrication of metal devices with patient-specific geometry. Laser powder bed fusion has particularly been used to manufacture DSS-based components. A fine control of the processing conditions allows for an understanding of DSS microstructural evolution, which is essential for selecting processing parameters and estimating performance, including mechanical properties and corrosion resistance. Furthermore, scientific investigation is necessary for determining the relationships among material, process, and magnetic properties, in order to establish the underlying principles and critical responses. The purpose of this review is to highlight the key performances of DSS for biomedical applications and to point out the relevant role of advanced processing technologies such as additive manufacturing.

The creep response of commercially pure titanium was investigated in air at 550, 600 and 650°C, to assess the effect of oxidation on the mechanical response. Experiments demonstrated that exposure at high temperature produced a marked reduction of the minimum creep rate under a given applied stress. Microhardness measurements showed that a hardened zone forms in proximity of the surface, due to oxygen penetration into metal. A simplified composite-model was then used to describe the creep response. In this model, the sample consisted of two zones, the hard case, enriched in oxygen, and the soft pure-titanium core, both creeping with similar strain rates. Calculation led to an estimation of the dependence of the minimum creep rate on stress and temperature for the hard high-oxygen zone. The simplified composite-model here presented gave an excellent description of experimental creep data for pure titanium tested in air and also provided a reliable picture of the effect of oxidation on complex Ti-alloys.