The surgical point of view about persistent air leaks: prevention first

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Vena cava anomalies in thoracic surgery

Background: Vena cava anomalies are a rare group of anatomical variations due to an incorrect development of the superior or inferior vena cava during fetal life. They generally show no clinical relevance and the diagnosis is done due to the association with congenital heart diseases in most of cases. However, preoperative identification of these anomalies is mandatory for surgeons to proper surgical planning. If not recognized, lethal complications may occur, as already reported in literature. Case presentation: We report a case series of three different unidentified vena cava anomalies in patients undergoing lung resection. These unrecognized anomalies led to minor complications in two cases and required an accurate intraoperative evaluation in another. A careful retrospective evaluation of preoperative radiological images showed the anomalies. Conclusions: A careful evaluation of the vena cava anatomy at pre-operative imaging is mandatory for thoracic surgeons to properly plan the surgery and avoid complications

Influence of Manufacturing Constraints on the Topology Optimization of an Automotive Dashboard

Topology Optimization (TO) methods optimize material layout to design light-weight and high-performance products. However, TO methods, applied for components or assembly with high complexity shape or for structures with copious number of parts respectively, do not usually take into account the manufacturability of the optimized geometries, then a heavy further work is required to engineer the product, risking to compromise the mass reduction achieved. Within an Industry 4.0 approach, we propose to evaluate manufacturing constraints since early stages of the conceptual design to perform a TO coherent with the manufacturing technology chosen. Several approaches of TO with different manufacturing constraints such as casting and extrusion are proposed and each solution is compared. The optimum conceptual design is determined in order to minimize the component weight while satisfying both the structural targets and the manufacturing constraints; a case study on a high-performance sport car dashboard is finally presented

A Design Strategy Based on Topology Optimization Techniques for an Additive Manufactured High Performance Engine Piston

In this paper, a methodology for the design of a motorcycle piston is presented, based on topology optimization techniques. In particular, a design strategy is preliminary investigated aiming at replacing the standard aluminum piston, usually manufactured by forging or casting, with an alternative one made of steel and manufactured via an Additive Manufacturing process. In this methodology, the minimum mass of the component is considered as the objective function and a target stiffness of important parts of the piston is employed as a design constraint. The results demonstrate the general applicability of the methodology presented for obtaining the geometrical layout and thickness distribution of the structure

Shaft-hub press fit subjected to couples and radial forces: analytical evaluation of the shaft-hub detachment loading

A shaft-hub press fit subjected to two non-axisymmetric loading conditions is examined and the situation of incipient detachment between the shaft and the hub is determined. The first condition consists of a central radial load P applied to the hub, balanced by two lateral forces P=2 applied to the shaft at a distance d from the hub lateral walls. In the second condition, a central couple C is applied to the hub, and it is balanced by two lateral opposite loads withstood by the shaft at a distance d from the hub lateral walls. The shaft-hub contact is modelled in terms of two elastic Timoshenko beams connected by distributed elastic springs (Winkler foundation), whose constant is analytically evaluated. Based upon this enhanced beam-like modelling, the loading inducing an undesired shaft-hub incipient detachment is theoretically determined in terms of the shaft-hub geometry, of the initial shaft-hub interference, and of the elastic constants. Finite element forecasts are presented to quantify the error of this beam-like approximate analytical approach

Effective Mechanical Properties of AlSi7Mg Additively Manufactured Cubic Lattice Structures

Lattice structures, whose manufacturing has been enabled by additive technologies, are gaining growing popularity in all the fields where lightweighting is imperative. Since the complexity of the lattice geometries stretches the technological boundaries even of additive processes, the manufactured structures can be significantly different from the nominal ones, in terms of expected dimensions but also of defects. Therefore, the successful use of lattices needs the combined optimization of their design, structural modeling, build orientation, and setup. The article reports the results of quasi-static compression tests performed on BCCxyz lattices manufactured in a AlSi7Mg alloy using additive manufacturing. The results are compared with numerical simulations using two different approaches. The findings show the influence of the relative density on stiffness, strength, and on the energy absorption properties of the lattice. The correlation with the technological feasibility points out credible improvements in the choice of a unit cell with fewer manufacturing issues, lower density, and possibly equal mechanical properties

Load bearing capability of three-units 4Y-TZP monolithic fixed dental prostheses: An innovative model for reliable testing

In this work, three-units monolithic fixed dental prostheses (FDPs) have been analysed and a novel model for reliable testing has been proposed. Such model is based on a new design of the polymeric base of the FDP, realised via additive manufacturing (AM) - a solution that conveys at the same time quick manufacturability, low cost, custom-ability, and design freedom. By means of this new model, the load-bearing capability of three-units monolithic FDPs has been thoroughly tested; in particular, three different analyses were performed: (i) analytical with a beam-like model, (ii) numerical, using non-linear three-dimensional Finite Elements (FE) models and (iii) experimental, by static bending test. The FDPs considered in this work were manufactured using a fourth-generation zirconia, namely 4Y-TZP. The findings demonstrated the undoubted advantages of the new base configuration, which minimized the effect of the base (which as a matter of fact is absent in in-vivo conditions) on the stress state of the connectors in the FDPs, and increased the repeatability and reliability of the experimental bending tests, able to determine the load bearing capability of the 4Y-TZP FDPs