1,599 research outputs found
Innovative methodology for the identification of the most suitable additive technology based on product characteristics
No full textThis paper reports the study and development case of an innovative application of the Cloud Manufacturing paradigm. Based on the definition of an appropriate web-based application, the infrastructure is able to connect the possible client requests and the relative supply chain prod-uct/process development capabilities and then attempt to find the best available solutions. In par-ticular, the main goal of the developed system, called AMSA (Additive Manufacturing Spare parts market Application), is the definition of a common platform to supply different kinds of services that have the following common reference points in the Additive Manufacturing Technologies (DFAM, Design For Additive Manufacturing): product development, prototypes, or small series production and reverse engineering activities to obtain Computer-Aided Design (CAD) models starting from a physical object. The definition of different kinds of services allows satisfying several client needs such as innovative product definition characterized by high performance in terms of stiffness/weight ratio, the possibility of manufacturing small series, such as in the motorsport field, and the possibility of defining CAD models for the obsolete parts for which the geometrical information is missed. The AMSA platform relies on the reconfigurable supply chain that is dynamic, and it depends on the client needs. For example, when the client requires the manufacture of a small series of a component, AMSA allows the technicians to choose the best solutions in terms of delivery time, price, and logistics. Therefore, the suppliers that contribute to the definition of the dynamic supply chain have an important role. For these reasons, the AMSA platform represents an important and innovative tool that is able to link the suppliers to the customers in the best manner in order to obtain services that are characterized by a high-performance level. Therefore, a provisional model has been implemented that allows filtering the technologies according to suitable performance in-dexes. A specific aspect for which AMSA can be considered unique is related with the given possibility to access Design for Additive Manufacturing Services through the Web in accordance with the possible additive manufacturing technologies
Sheet metal forming optimization methodology for servo press process control improvement
No full textIn sheet metal forming manufacturing operations the use of servo presses is gaining more interest due to the opportunity to improve process performance (quality, productivity, cost reduction, etc.). It is not yet clear how to proceed in the engineering process when this type of operating machine is used to achieve the maximum possible potential of this technology. Recently, several press builders have developed gap‐ and straight‐sided metal forming presses adopting the mechanical servo‐drive technology. The mechanical servo‐drive press offers the flexibility of a hydraulic press with the speed, accuracy and reliability of a mechanical press. Servo drive presses give the opportunity to improve the productivity of process conditions and improve the quality of stamped parts. Forming simulation and numerical optimization can be useful tools to define beforehand the optimal process parameter set‐up in terms of servo press downward curve properties. This is done by carrying out a sensitivity analysis of the forming parameters having influence on said curve. The authors have developed a numerical methodology able to analyze the influence factors, for comparison with the degrees of freedom made available by the usage of a servo press, in terms of stroke profile management, to obtain an optimized process parameters combination
CD30, Th2 cytokines and HIV infection: a complex and fashinating link
No full textCD30 is a member of the tumor necrosis factor (TNF)/nerve growth factor (NGF) receptor superfamily, and was originally described as a marker of Hodgkin's and Reed-Sternberg cells in Hodgkin's lymphoma. CD30 is preferentially expressed on CD4+ and CD8+ T-cell clones that produce T helper 2 (Th2)-type cytokines, and is also released in a soluble form by these cells. Elevated serum levels of soluble (s)CD30 have been found in some conditions in which a pathogenic role for Th2 cells has been suggested, such as atopy, Omenn's syndrome, systemic lupus erythematosus, as well as following infection with measles virus or human immuno-deficiency virus (HIV). Here, Gianfranco Del Prete and colleagues suggest a complex and fascinating link between the expression and release of CD30, and the immunopathogenesis of HIV infection
Lattice structures integration with conventional topology optimization
No full textAdditive manufacturing (AM) processes enable the production of functional parts with complex geometries, multi-materials as well as individualized mass production. Another significant benefit of AM is the ability to produce optimized geometries with near perfect strength to weight ratios. For several years now, the topology optimization techniques assist the designers in order to develop components that have a good material distribution in order to reduce the weight ensuring the request stiffness. Therefore, the topology optimization generates concepts based on the subtractive approach and usually these geometries require a further post processing in order to obtain a geometry "ready to produce" that represents a compromise between the topologic result and the manufacturing constraints. The advent of the AM opens new scenarios in terms of definition of innovative geometries that are not feasible with the conventional processes (such as lattice structures). In order to exploit the AM capabilities, new topology optimization tools are emerging that allow to define innovative concepts that could reach structural performance greater than the result obtainable with conventional topology optimization. In this paper the Authors have studied a new concept design and the performance improvement, of PIN installation equipment, used for thin-walled aerospace workpiece, in order to solve critical dimensioning issues, due to the overcoming of the allowable range tolerances (strain and displacement). Topology optimization has been applied in order to define a new concept design able to satisfy the functionality requirements. Moreover, it has been conducted a study to evaluate the possible advantages offered by the integration of the lattice structure in the topology design in order to improve the performance in terms of weight and structural characteristics
Misurare in vitro le proprietà biomeccaniche di tessuti biologici: applicazione ad un muscolo scheletrico
No full textIl lavoro descrive la messa in opera di un set up per la misura in vitro della
funzionalità biomeccanica del tessuto muscolare murino e lo sviluppo di un
protocollo di misura avanzato volto a migliorare la ripetibilità delle misure
eseguite sui provini biologici. La sequenza sperimentale permette di acquisire
in un unico “breve” esperimento tutti i parametri biomeccanici più rilevanti.
Sono riportati i risultati conseguiti in una ricerca sperimentale che ha
contribuito ad approfondire alcuni meccanismi biologici invalidanti alla
base della progressione della Sclerosi Laterale Amiotrofica.This paper describes the development of an experimental set-up for in vitro
measurement of murine skeletal muscle biomechanical properties. An
advanced experimental protocol, allowing to acquire the most relevant
parameters of muscle contractility within a single “short time” experiment,
has also been proposed to provide a high measurement repeatability with
biological samples. Finally, we give an account of an experimental study
that contributed to clarify some specific mechanisms of the progression of
the Amyotrophic Lateral Sclerosis disease
Optimization of Machining Fixture for Aeronautical Thin-walled Components
No full textThe aim of this work has been the optimization of the fixtures performance used in thin-walled workpiece machining depending on the local rigidity characteristics of the component to be machined. An extensive topology optimization activity has been performed both on fixture-workpiece systems modelled with shell elements and on fixture-workpiece systems modelled with solid elements, varying the topology design variables and/or optimization constraints for each optimization problem, in order to provide a new design of fixture. Finally, a new blended Solid-Lattice design of the fixture, starting by the design topologically optimized, has been created. In this way, it has been possible to identify void regions in the design space, where the material can be removed, regions where solid material is needed, and regions where lattice structure is required. This has allowed to generate the optimal hybrid or blended solid-lattice design based on desired functionality of the part having as natural consequence the definition of a new method for fixtures design
The use of FEA in the simulation of a metal cutting operations in the presence of random uncertainty
No full textForces and temperatures in specific orthogonal cutting conditions and calculated by finite element analysis, have been evaluated taking into account the uncertainty of some process conditions. A traditional deterministic approach, in machining simulations, is not able to explain the uncertain physical variations related to material characteristics (yield and tensile strenght, hardness, etc.) and tool/chip/workpiece interface conditions (friction and tool wear). During machining operations many different sources of non-controllable process variations usually display their effect leading to a degree of uncertainty in the final parts quality. Statistical tools and methods are increasingly being used in combination with FE numerical simulation, in order to take into account of the variability of the process. Then, if one of the purposes of process design is to study and model robustness or reliability of a given process in aleatory conditions, a CAE study might become a feasible way to do it. Today, the evaluation of the performances of a metal cutting process is possible using several commercial FEA packages. These software tools automatically allow the preventive evaluation of the robustness of technological decisions. In this work the authors, by means the integration between stochastic simulation tools and machining FE codes, have evaluated the process sensitivity to a random variation of uncontrollable parameters or conditions. Furthermore, a specific experimental and numerical activity has been performed in order to better understand the technical capabilities in terms of process simulation in stochastic conditions
Shape factors and feasibility of sheet metal hydroformed components
No full textThe authors have investigated, in another paper, the problem related to the definition of a "set of shape factors" in order to declare the feasibility of a product through sheet hydroforming. In particular the defined shape factors are three different a-dimensional coefficients by which it is possible to declare the feasibility of a product through the calculation, in different sections, of the three previous shape factors. The robustness of this methodology is related to the correct calculation of the "limit value" of each shape factor. In fact the feasibility is reached if, in any section, the calculated shape factors are higher than their respective limit values. In this paper the authors have performed an extensive numerical and experimental campaign, taking into account a different geometry respect to that of the first paper, in order to: re-calculate the limit value for each shape factor and, then, verify the correctness of the limit values exposed in the previous first paper. The numerical campaign has been used, after the evaluation of the accuracy of the numerical model, in order to study the feasibility of the product without engaging the hydroforming machine. Finite Element Analysis (FEA) has been extensively used in order to investigate and define each shape factor with a proper comparison to the macro feasibility of the chosen component geometry. The limit values that have been calculated by the authors in this paper are slightly different from those calculated in the first paper. From this point of view it is possible that, although the shape factors are a-dimensional coefficients, they are affected by different choices of the users as, for example, the dimensions of the initial blank. Anyway, the small differences in the shape factors limit values do not adversely affect the use of the shape factors in order to predict the feasibility of the product
Numerical and analytical estimation of rolling force and torque in hot strip rolling
No full textIn this paper, both numerical and analytical method were developed for computing, in strip or plate rolling, the distribution of roll pressure, rolling force, and rolling torque (from which also rolling power can be estimated), assuming an homogeneous deformation of the rolled material. Unlike other similar models present in the literature, which solve the resulting rolling differential equation for the roll pressure, the model presented in this work solves the problem for the horizontal force. In this way, it is possible to avoid the calculation of the derivative of material flow stress curve, which is not always analytically easy and possible (i.e., point material flow stress data). The proposed numerical model is based on the friction law proposed by Chen and Kobayashi while the analytical one is based on the simple shear friction model and brings to useful analytical formulas for a quick calculation of rolling torque and force. Moreover, a relationship between the shear friction factor and Coulomb friction coefficient in rolling was found. The developed models show good agreement with experimental measures, in terms of rolling force and torque, found in literature
The use of FEA packages in the simulation of a drawing operation with springback, in the presence of random uncertainty
No full textThe springback response on a stamped part, calculated by finite element analysis has been evaluated taking into account the uncertainty of some process conditions. In fact, in the simulation of sheet metal forming and springback, a traditional deterministic approach is not able to take into account the uncertain physical variations related to material characteristics, friction conditions, tools active surfaces status, etc.
During sheet metal forming operations many different sources of non-controllable process variations usually display their effect leading to a degree of uncertainty in the final parts’ quality. For this reason, statistical tools and methods are increasingly being used in combination with FE numerical simulation. Then, if one of the purposes of process design is to study and model robustness or reliability of a given process in aleatory conditions, a CAE study might become a feasible way to do it.
Today, the evaluation of the performances of a sheet metal stamping process, under uncertainty of the main variables, is possible using several commercial FEA packages. These software tools automatically allow the pre-emptive evaluation of the robustness of technological decisions and the process sensitivity to a random variation of uncontrollable parameters or conditions. For accurate calculations these innovative numerical approaches usually require a considerable amount of computational work both in terms of CPU time and in terms of number of CPUs. A specific experimental and numerical activity has been developed in order to better understand the technical capabilities in terms of process simulation in stochastic conditions
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