In this work, the fracture mechanics properties of polyamide (PA) specimens manufactured by the selective laser sintering (SLS) technology are investigated, in which an embedded crack-like notch was inserted in the design and produced during the additive manufacturing (AM) phase. To cover a wide variety of mode I/II mixity levels, the inclined asymmetrical semicircular specimen subjected to three points loading (IASCB) was employed. The investigation was carried out by analyzing the full displacement field in the proximity of the crack tip by means of the digital image correlation (DIC) technique. To characterize the material, which exhibits a marked elastic-plastic behavior, the quantity J-integral was evaluated by two different methods: the first one exploits the full fields measured by the DIC, whereas the second one exploits the experimental load–displacement curves along with FEM analysis. The DIC methodology was experimentally validated and proposed as an alternative method to evaluate the J-integral. It is especially suited for conditions in which it is not possible to use the conventional LDC method due to complex and possibly unknown loading conditions. Furthermore, results showed that the AM technique could be used effectively to induce cracks in this type of material. These two aspects together can lead to both a simplification of the fracture characterization process and to the possibility of dealing with a wider number of practical, real-world scenarios. Indeed, because of the nature of the additive manufacturing process, AM crack-like notches can be sintered even having complex geometry, being three-dimensional and/or inside the tested structure.
This work investigates the fracture behavior of maraging steel specimens manufactured by the selective laser sintering (SLS) technology, in which a crack-like notch (sharp notch) was directly produced during the additive manufacturing (AM) process. For the evaluation of the fracture toughness, the inclined asymmetrical semi-circular specimen subjected to three points loading (IASCB) was used, allowing to cover a wide variety of Mode I and II combinations. The effectiveness of manufacturing crack-like notches via the SLS technique in metals was evaluated by comparing the obtained experimental results with the ones obtained with pre-cracks induced by fatigue loading. The investigation was carried out by using the digital image correlation (DIC) technique, that allowed the evaluation of the full displacement fields around the crack tip. The displacement field was then used to compute the stress intensity factors (SIFs) for various combinations of Mode I and II, via a fitting technique which relies on the Williams’ model for the displacement. The SIFs obtained in this way were compared to the results obtained with the conventional critical load method. The results showed that the discrepancy between the two methods reduces by ranging from Mode I to Mode II loading condition. Finally, the experimental SIFs obtained by the two methods were described by the mixed mode local stress criterium.
Three-dimensional thermography is a recent technique—with various fields of application—that consists of combining thermography with 3D spatial data in order to obtain 3D thermograms, high information objects that allow one to overcome some limitations of 2D thermograms, to enhance the thermal monitoring and the detection of abnormalities. In this paper we present an integration methodology that can be applied to merge data acquired from a generic thermal camera and a generic laser scanner, and has the peculiarity of keeping the two devices completely decoupled and independent, so that thermal and geometrical data can be acquired at different times and no rigid link is needed between the two devices. In this way, the stand-alone capability of each device is not affected, and the data fusion is applied only when necessary. In the second part, the real effectiveness of our approach is tested on a 3D-printed object properly designed. Furthermore, one example of an application of our methodology in the cultural heritage field is presented, with an eye to preservation and restoration: the integration is applied to a marble statue called Madonna with the Child, a fine work of the Florentine sculptor Agostino di Duccio (1418–1481). The results suggest that the method can be successfully applicable to a large set of scenarios. However, additional tests are needed to improve the robustness.
In the last decades, due to remarkable technological improvements in ceramics production cycles and materials, the manufacturing and the commercialization of large-sized ceramic slabs have risen. While some phases of the process are well defined, there are some routines that lack systematic procedures and rely uniquely on the internal know-how of the single companies. In particular, this paper focuses on the handling and transportation of large-sized ceramic slabs, which are, in the vast majority of cases, performed by suction cups-based gripping devices. The scope of this paper is to investigate how the type of suction cup pattern and its geometrical parameters affect slab stresses and deformations and to provide a guideline for the choice of the pattern, in order to cope with some critical aspects associated with wide surface and small thickness of the slabs. In particular, some of the most common large slab sizes and thicknesses available on the market are considered, and the most suitable suction cup patterns (and their geometrical parameters) for handling them are evaluated in order to minimize slab stresses and deformations.
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