1,720,986 research outputs found
Ripensando l'Impero spagnolo: Alessandro Malaspina e politica illuminista in Patagonia
No full textRipensando l’Impero spagnolo: Alessandro Malaspina e politica illuminista in Patagoni
Wearing Evaluation in nickel super-alloys turning for the development of a predictive model for CAM Optimization
No full textNickel super-alloys are characterized by: high temperatures resistance, high hardness and low thermal conductivity. For this reason they are widely used in critical operating conditions. However, due to their excellent mechanical properties, nickel super-alloys are hard to machine. Tool wear is a major problem in nickel super-alloys machining; the high temperature at the tool rake face is a principal wear factor. Flank wear is the most common type of tool wear; it offers predictable and stable tool life evaluation. In this work, the authors present a flank wear evaluation in Inconel 718 turning, in order to develop a predictive model for CAM optimization. An appropriate database has been developed thanks to an experimental activity (V-B as a function of: the cutting time T, cutting speed S and feed rate F). The objective of the optimization procedure is to maximize the Material Removal Rate (MRR) under the constraint represented by the flank wear limit. The developed procedure operates directly on the part program code, using the original one as starting point for the application of the knowledge about the wear behaviour. After the optimization phase the given output is represented by a new part program code obtained in accordance with: the maximum MRR within the respect of the wear limi
Punch Radius Influence on “Large Size” Hydroformed Components
No full textSheet metal hydroforming has gained increasing interest during last years, especially as application in the manufacturing of some components for: automotive, aerospace and electrical appliances for niche productions. Different studies have been also done to determine the optimal forming parameters making an extensive use of FEA. In the hydroforming process a blank sheet metal is formed through the action of a fluid and a punch. It forces the sheet into a die, which contains a compressed fluid. Many studies have been focused on the analysis of process and geometric parameters influence about the hydroforming process of a single product with main dimensions till to 100 mm.
In this paper the authors describe the results of an experimental activity developed on two different large sized products obtained through sheet metal hydroforming. Different geometric and process parameters have been taken into account during the testing phase to study, in particular, the punch radius influence on the process feasibility. An ANOVA analysis has been implemented to study the influence of geometrical and process parameters on the maximum hydroforming depth. Through this work it has been possible to verify that in the hydroforming process of large size products geometry and, in particular, punch radius, are some of the main factors that influences the feasibility of the products. Different considerations can be made about the effects of the blankholder force and the fluid pressure on the maximum hydroforming depth. As further developments, the authors would perform a numerical study in order to enlarge the knowledge of the process design space to other possible values of the punch radius
“Progettazione e costruzione di un’attrezzatura flessibile per l’idroformatura di lamiere piane”
No full textTra le tecniche non convenzionali di deformazione plastica di lamiere piane l’idroformatura è da sempre considerata una valida opportunità nel caso di produzioni di lotti con volumi medio/piccoli. Una delle principali ragioni che non ne ha permesso un rapido sviluppo è sicuramente rappresentata dagli elevati costi di investimento relativi alle presse idrauliche progettate e costruite per essere appositamente dedicate a questa tecnica di formatura. L’attività descritta in questo articolo dimostra la fattibilità di un processo di idroformatura di lamiere piane utilizzando una pressa idraulica tradizionale senza ricorrere ad una pressa espressamente dedicata all’idroformatura di lamiere. L’utilizzo di un’attrezzatura flessibile progettata e realizzata appositamente con tempi e costi di sviluppo ridotti ha reso possibile tale applicazione. La definizione delle specifiche tecniche di detta attrezzatura ha fatto ricorso in modo esteso all’utilizzo delle tecniche CAE. Una adeguata fase di sperimentazione ha dimostrato la correttezza di quanto sviluppato
Computer Aided Engineering for a Warm Bulging Test Tooling Design
No full textWarm bulging test is a particular kind of sheet hydroforming. The presence of a warm fluid requires a proper tooling design in order to achieve the benefits related to these particular forming conditions, minimizing blank ruptures and wrinkles presence. The fluid is injected in a properly designed chamber and it produces a sheet bulging deformation. Also the tooling and the sheet are warmed in order to maintain a constant process temperature. In this working conditions, it is necessary to accurately design the tooling layout taking into account: interaction forces, fluid volume, vision system in order to record the deformation conditions and safety systems in order to prevent damage to the workers caused by the warm fluid possible leakage (approximately 200° ÷ 300° C). CAE techniques have a relevant role in order to define proper process parameters such as: sheet thickness, bulging height, fluid pressure. An explicit solver has been used to calculate the forces distribution, developed during the warm sheet bulging, and the needed fluid volume. The obtained values have been used as input data in the structural tooling validation. The authors have designed a warm bulging test layout. The sheet deformation, etched with a grid, is detected through CCD cameras. Diffuse lights, a thermometer and a laser beam adopted to detect the dome height complete the tooling control system
EXPERIMENTAL DEVELOPMENT OF RSM TECHNIQUES FORSURFACE QUALITY PREDICTION IN METAL CUTTING APPLICATIONS
No full textThe aim of this work is to analyze the influence of cutting conditions on surface roughness with slot end
milling on AL7075-T6. The considered parameters are: cutting speed, feed, depth of cutting and mill radial engage.
Response surface models based on experimental data obtained with physical tests have been developed, the authors
have performed a consistent set of experimental tests based on design points selected within the four-dimensional
design space. Each test has been repeated 3 times to ensure the stability of the collected statistical data. These welldistributed
results has been subsequently used to create RS models through approximation techniques based on
polynomial and neural network methods and to verify their reliability in terms of correct responses behaviour. The
obtained results show that the most significant factors affecting the surface roughness are feed and speed
PRE-BULGING INFLUENCE ON AN INVERSE DRAWN SHAPE OBTAINED WITH HYDROMECHANICAL DEEP DRAWING (HDD)
Full text linkThe HDD process performance and the quality of the formed parts can be influenced by many process variables, such as: fluid pressure, blankholder force, pre-bulging pressure, friction and punch speed [1]. Many studies report how pre-bulging characterization may be done in accordance with the fluid pressure variation [2] or with the maximum bulge height [3][4] value. In this paper, the authors use the maximum bulge height to characterize pre-bulging levels influence on the process feasibility. The effects of three different pre-bulging levels as well as the traditional geometric and process parameters on a specific component characterized by an inverse drawn shape have been analyzed. In the experimental phase, for each considered process condition the Thickness Reduction (TR) has been detected on the formed component in sixteen different points of interest, to verify numerical and experimental correlation. The good accuracy shown by the numerical model allowed to develop an appropriate numerical campaign to obtain an ANOVA analysis to evaluate the pre-bulging heights influence on TR distribution. The obtained results have shown that the pre-bulging height influences the TR distribution significantly but in a less way than punch radius and blankholder forces profile
Computer Aided Simulation as valid tool for sheet hydroforming process development
No full textSheet Hydroforming is considered a good opportunity when it is necessary to deal with complex shapes. However, it is common knowledge that it is quite difficult to control such a kind of technology because of an appropriate press tooling is necessary and the press tooling supplier is often the technology supplier for the given problem [1]. Within a larger research program it is demonstrated that it is possible to use traditional hydraulic press tooling having the chance to manage a high level of process variables thanks to the development of a dedicated forming tool named hydroforming cell. The architecture and the number and type of process variables are developed thanks to the extensive usage of CAE techniques. An implicit solver is used to verify the structural behaviour of the hydroforming cell in terms of maximum stress levels and components stiffness while an explicit solver has helped to define the samples shapes and their main features and thanks to them it is possible to explore the process design space. An appropriate experimental phase has demonstrated the effectiveness of the developed procedure
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