1,721,089 research outputs found
Analisi teorica del forzamento di campioni cilindrici in operazioni di stampaggio di precisione
No full textAnalisi del forzamento all'interno della matrice di acciaio nello stampaggio di precisione
No full text
Optimization of laser micromachining process for biomedical device fabrication
No full textLaser machining is commonly used for fabrication of medical devices with microscale features, including vascular stents, drug delivery devices, and scaffolds for tissue engineering with controlled pore size and porosity. The process can also be used to produce structured scaffolds for controlling cell growth, orientation, and location. Moreover, lasers may be used to fabricate complex channel nets in which cells are subsequently seeded or to pattern channels for microfluidic devices. Traditionally, these micro devices were fabricated using silicon substrates, but recently the use of titanium allowed to produce more robust devices at a reasonable cost. In particular, the high quality surfaces that can be obtained with laser machining reduce the liquid flow turbulence and avoid micro cavities formation, critical for bacteria proliferation. The present research reports the results of an investigation on the process capability of laser ablation to produce micro pockets fabricated on titanium sheet (0.5 mm thick). A first experimental campaign was designed for identifying a set of laser ablation cycles able to realize the micro pockets by changing the process parameters as scanning speed, laser power, q-switch frequency, loop number, and duty cycle. Moreover, a process optimization was executed in order to produce the pockets with a highly flat surface. The results were acquired by a confocal laser scanning microscope (CLSM) to obtain high-resolution images with depth selectivity and were analyzed with statistic methods for the identification of the best parameter configuratio
Advances in Material Modeling for Manufacturing Analysis and Simulation (Deformation and Cutting Processes)
No full textThere are many different reasons to use a model in the cutting and forming operations fields, such as the following: processes design, processes optimization, processes control, processes simulation, and equipment design. This chapter describes how the features to build a good simulative and analytical model. In order to realize a reliable simulative and/or analytical model for cutting and forming environments, it is important to know some parameters since they strongly influence the final results. The most significant parameters are material characterization (known also as flow stress law); friction model and value; and failure criteria of the material. In manufacturing processes, the knowledge of the friction conditions between a workpiece and a tool or die is very important for determining the material flow and the part feasibility. In order to quantitatively express the interface friction, it is normal to refer to two models: the Coulomb model and the Schley model
Process parameters influence on friction coefficient in sheet forming operations
No full textIn conventional sheet forming processes, such as stamping or drawing, significant contact phenomena take place between workpiece and die surfaces. Especially, relative motion and normal loads generate friction which influences some aspects of processes such as material flow, tools wear and life and total force needed to complete the process. In the current paper an experimental test campaign has been carried out using a large scale pin-on-disk device designed and realized by the Authors to investigate the influence of pressure, sliding velocity and temperature. The purpose is to test the developed device and to find which and how these parameters mostly affect friction. The pin-on-disk test consists of two specimens, a pin and a plate representing respectively die and workpiece, which are compressed by means of a known force and then moved one over the other. Compression and friction forces are sampled during the tests and the friction coefficient is estimated as the ratio of these two forces. The tested materials are H13 die steel on FeP04 and AZ31 sheets
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Driver roll speed influence in Ring Rolling process
Full text linkRing Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. To produce a high-quality ring different speed laws should be defined: the speed laws of the Idle and Axial rolls must be set to control the ring cross section and the Driver roll angular velocity must be chosen to avoid too high localized deformation on the ring cross section. Usually, in industrial environment, a constant rotation is set for the Driver roll, but this approach does not guarantee a constant ring angular velocity because of its diameter expansion. In particular, the higher is the ring diameter the lower is its angular velocity. The main risk due to this constrain is the generation of a non-uniform ring geometry. An innovative approach is to design a Driver Roll speed law to obtain a constant ring angular velocity. In this paper a FEM approach was followed to investigate the Driver roll speed influence on the Ring Rolling process. Different Driver roll speed laws were tested starting from a model defined in an industrial plant. Results will be analyzed by a geometrical and physical point of view
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