Legge 27 gennaio 2012, n.3 sulla composizione delle crisi da sovraindebitamento: riflessioni sulle prime applicazioni

Il lavoro si propone di fornire un quadro specifico della legge 3/2012. Attraverso una prima evoluzione storica si approda alla conoscenza ed all'introduzione, in particolari momenti di crisi, di importanti istituti giuridici. L'importanza è ovviamente da rilevarsi nella struttura stessa di quello che concepiamo come sovraindebitamento. E' quindi necessaria la rivisitazione di situazioni come l'insolvenza del debitore commerciale e del debitore civile così da rendere più facile il momento di comprensione e di approdo alla nostra legge. La particolarità e la differenziazione di trattamento sono alla base di una innovazione delle stesse figure di creditore e debitore. Si passerà poi all'analisi della presente legge, allo studio dei singoli istituti e delle diverse procedure previste dal legislatore. Avremo poi modo di effettuare un excursus delle diverse procedure da sovraindebitamento previste in altri ordinamenti. Passeremo infine ad analizzare le prime, e non molte, applicazioni nazionali giungendo ai pro ed ai contro della nostra legge e ad una valutazione delle singolarità della stessa

Numerical and experimental characterization of a railroad switch machine

This contribution deals with the numerical and experimental characterization of the structural behavior of a railroad switch machine. Railroad switch machines must meet a number of safety-related conditions such as, for instance, exhibiting the appropriate resistance against any undesired movements of the points due to the extreme forces exerted by a passing train. This occurrence can produce very high stress on the components, which has to be predicted by designers. In order to assist them in the development of new machines and in defining what the critical components are, FEA models have been built and stresses have been calculated on the internal components of the switch machine. The results have been validated by means of an ad-hoc designed experimental apparatus, now installed at the facilities of the Department of Industrial Engineering of the University of Bologna. This apparatus is particularly novel and original, as no Standards are available that provide recommendations for its design, and no previous studies have dealt with the development of similar rigs. Moreover, it has wide potential applications for lab tests aimed at assessing the safety of railroad switch machines and the fulfilment of the specifications by many railway companies

Effect of friction, surface treatment and adhesive-reinforcement on the behavior of threaded connections. Effetto dell'attrito, dei trattamenti superficiali e dell'incollaggio sul comportamento dei collegamenti filettati

This study aims at analyzing the phenomena which characterize threaded connections. This type of joint has been known for thousands years (one of the first applications is attributable to Archimedes) allows transforming a torque into an axial force, typically used to lock two or more components thanks to the friction forces that arise between the connected bodies. One of the main strengths of this type of coupling is the possibility to assemble and disassemble the assembled parts; in addition, it can be applicable to almost any type of material. However, the joint system is characterized by a low efficiency: only a modest amount of the tightening torque is actually converted into axial force. In addition, the obtained axial force is typically affected by a large scatter. This behavior is due to the combined effect of two different friction effects that arise between the under-head of the screw (or nut) and the surface of the elements to be locked in the first case, and between the screw threads and female screw in the second one. The relationship between tightening torque and preload axial force is very sensitive to the effect of the various friction coefficients that rule the tribological behavior of the joint:, these coefficients have a significant variability due to the processes used to manufacture the components, and to the different tightening parameters, such as the presence of lubrication or the tightening speed. Threaded connections do have a wide array of applications, both in the field of civil engineering and in mechanics. For instance, in the automotive compartment, due to a steadily growing strive towards weight reduction and increased automation of assembly procedures, an accurate knowledge of the performance of threaded connections has recently become critical in order to achieve the safety of the junction at an adequate production cost. In order to control a threaded connection, it is necessary to focus on the three main factors that characterize its behavior: the coefficients of friction at tightening, the self-relaxation phenomenon (decrease of axial preload in the first few seconds after tightening, due to sinking of the load bearing area in the clamped parts), self-loosening (loss of axial preload, typically due to the action of external shearing forces). In the following, literature review will be presented first, then it will be shown an experimental investigation on the effect of solid lubrication on the friction coefficients, carried out for repeated tightenings and different surface treatments. Moreover, the effect of the number of engaged threads on the performance of an anaerobic threadlocking adhesive will be examined. The need for these analyses arose from the study of an in-field failure occurred in a pinion shaft of a transmission for earth moving machines, which, as it will be shown in the following, probably failed due to a combination of the aforementioned typical issues of threaded components. The research has the aim of increasing the knowledge about the effect of lubrication on the different phenomena that contribute to determining the performance of a bolted connection

On Hirth Ring Couplings: Design Principles Including the Effect of Friction

Rings with Hirth couplings are primarily used for the accurate positioning of axial-symmetric components in the machine tool industry and, generally, in mechanical components. It is also possible to use Hirth rings as connection tools. Specific industries with special milling and grinding machines are able to manufacture both tailor made and standard Hirth rings available on stock. Unfortunately, no international standard (for instance ISO, DIN or AGMA) is available for the production and the design of such components. In the best-case scenario, it is possible to find simplified design formulae in the catalogue of the suppliers. The aim of this work is to provide some accurate formulae and computational methods for design to provide better awareness on the limitations and the potential of this type of connection. The work consists of five parts: (i) a review of the base calculation derived mainly from the catalogues of manufacturers; (ii) an improved calculation based on a new analytical method including the friction phenomenon; (iii) an experimentation run for validating the method; (iv) a case study applied to a machine tool; and, (v) a closed form formulation to determine an upper threshold for friction, thus ensuring the Hirth coupling regular performance

Kinematic analysis of reaching movements of the upper limb after total or reverse shoulder arthroplasty

Studies have analyzed three-dimensional complex motion of the shoulder in healthy subjects or patients undergoing total shoulder arthroplasty (TSA) or reverse shoulder arthroplasty (RSA). No study to date has assessed the reaching movements in patients with TSA or RSA. Twelve patients with TSA (Group A) and 12 with RSA (Group B) underwent kinematic analysis of reaching movements directed at four targets. The results were compared to those of 12 healthy subjects (Group C). The assessed parameters were hand-to-target distance, target-approaching velocity, humeral-elevation angular velocity, normalized jerk (indicating motion fluidity), elbow extension and humeral elevation angles. Mean Constant score increased by 38 points in Group A and 47 in Group B after surgery. In three of the tasks, there were no significant differences between healthy subjects and patients in the study groups. Mean target-approaching velocity and humeral-elevation angular velocity were significantly greater in the control group than in study groups and, overall, greater in Group A than Group B. Movement fluidity was significantly greater in the controls, with patients in Group B showing greater fluidity than those in Group A. Reaching movements in the study groups were comparable, in three of the tasks, to those in the control group. However, the latter performed significantly better with regard to target-approaching velocity, humeral-elevation angular velocity and movement fluidity, which are the most representative characteristics of reaching motion. These differences, that may be related to deterioration of shoulder proprioception after prosthetic implant, might possibly be decreased with appropriate rehabilitation

INFLUENCE OF THE STIFFNESS AND FRICTIONAL CHARACTERISTICS ON THE SHANK TORQUE OF SCREWS IN BOLTED JOINTS

This work aims at determining the influence of tribological and stiffness characteristics of a bolted joint on the residual shank torque of the screw. Even if it is commonly accepted to consider such a residual torque equal to half the torque at the thread, the literature lacks experimental data about the topic. The residual shank torque combines with the axial preload and the external loads to bring about the overall stress on the screw. Hence, the higher the residual torque, the lower the admissible external load for given size and class of the screw. From there stems the need for an analytical tool allowing the designer to calculate the residual torque as a function of the key parameters of the joint

A methodology for the lightweight design of modern transfer machine tools

This paper deals with a modern design approach via finite elements in the definition of the main structural elements (rotary table and working unit) of an innovative family of transfer machine tools. Using the concepts of green design and manufacture, as well as sustainable development thinking, the paper highlights the advantages derived from their application in this specific field (i.e., the clever use of lightweight materials to allow ruling out high-consumption hydraulic pump systems). The design is conceived in a modular way, so that the final solution can cover transfers from four to 15 working stations. Two versions of the machines are examined. The first one has a rotary table with nine divisions, which can be considered as a prototype: this machine has been studied in order to set up the numerical predictive model, then validated by experimental tests. The second one, equipped with a rotary table with 15 divisions, is the biggest of the range: this machine has been entirely designed with the aid of the previously developed numerical model. The loading input forces for the analyses have been evaluated experimentally via drilling operations carried out on a three-axis CNC unit. The definition of the design force made it possible to accurately assess both the rotary table and the working units installed in the machine