0000000001173197
AUTHOR
E. Lo Valvo
Comparative analysis of bonding mechanism in solid state metal working processes
The Piwnik and Plata pressure-time bonding criterion was applied to Friction Stir Welding, Linear Friction Welding, Porthole Extrusion and Roll Bonding. A neural network was set up, trained and used to predict the bonding occurrence starting from the main field variable distributions calculated through specific numerical models developed for each process. The analysis of the results permitted to predict the occurrence of solid bonding and to highlight differences and analogies between the processes in order to obtain sound solid welds.
Optimal positioning of irregular shapes in stamping die strip
The nesting of two-dimensional shapes is a common problem, where raw material has to be economically cut. As for the single-pass single-row strip layout, several algorithms, based on established methods, have been proposed. Moreover, it should be noticed that the optimum layout should also consider a few constraints, like grain orientation for subsequent forming operation, correct bridge width, and the commercial roll of metal width in order to make solutions applicable in real industrial environments. Most of the procedures until now shown in literature are quite complex and often ignore these real constraints. They usually make use of sliding techniques and are not able to effectively wor…
H and P Mesh Refinement in the Metal-Forming F.E.M. Analysis
In this paper a comparison between H and P refinement techniques in the metal-forming F.E.M. analysis is carried out in order to evaluate their computational efficiency. The results are compared using a particular error estimator which locally allows determining the workpiece zones where the refinement is necessary.
A technical note on an experimental device to measure friction coefficient in sheet metal forming
Abstract In the paper the authors present the results of several experimental tests aimed to determine the Coulomb friction coefficient in sheet metal forming operations at the varying of the sheet metal material and for different operative conditions. In particular a few pressure and lubricating conditions have been investigated. In order to develop such experiments a dedicated fixture was designed and set-up starting from the one proposed by Wilson.
Computer-Aided Simulation of Die Filling Processes
Summary A numerical method for analysing the filling of axisymmetrical dies of complex shape is proposed. The method, which is a further development of a LP finite element model, is able to take into account the contact conditions directly in the mathematical formulation of the problem. In such a way the solution of the die filling process is obtained by solving a LP problem, avoiding problems of numerical convergence and the heavier calculations requested by other iterative methods.
Metal Matrix Composites - Mmc - Turning: Comparison of Tool Materials
The main properties required to the modem cutting tools to be employed in production, are both high wear resistance and chemical stability. In this last years, in the machining of MMCs several kinds of coated tools have been developed; they are characterized by high hardness to resist to the relevant strength and abrasive action of the reinforce fibers or particles, arranged inside the matrix. In turning of MMC the employ of Tungsten Carbide tools coated with Polycrystalline Diamond (PCD) have shown to be very effective, whereas they are very expensive thus increasing the production costs.
Wear of Ceramic Tools When Working Nickel Based Alloys
In order to improve the toughness of alumina materials, various trials have recently been made. These include toughening by the addition of zirconia and of significant amounts of titanium carbide to ceramic oxide Al2O3 and the more recent use of nitride based ceramics, which have resulted in an increase of fracture toughness and in a significant improvement of ceramic tool performance. Another very recent way of improving ceramic materials consists in adding SiC whiskers to Al2O3 matrix. This composite material is also suitable for machining nickel based alloys. In order to evaluate and to qualify these materials some test cycles have been carried out in continuous cutting conditions, emplo…
Wiper Tools in Turning Finishing of Quenched Steel
In the last years, the research on metal machining has been focused on the development of tools that can support an increment of the cutting parameters instead of the increment of tool life; this strategy is focused to obtain a relevant productivity increment without getting worse the final product quality. The new design of the tool corner radius has allowed preserving the same product quality due to the “wiper effect” generated during the cut. The employ of such re-designed tools can allow substantial productivity improvements and, by employing the same feedrate, it is possible to achieve excellent surface finish and eliminate the grinding operation. With the aim to verify the possibility…
WEAR PERFORMANCE OF CERAMIC CUTTING-TOOL MATERIALS WHEN CUTTING STEEL
Abstract Some test cycles have been carried out in continuous cutting conditions, employing cutting parameters (feed, depth of cut and cutting speed) chosen following experimental planes and suitable test fields. The wear tests have been carried out on AISI 1040 steel with cutting speeds from 5m/sec to 11m/sec. The silicon nitride, sintered carbide, cubic boron nitride and alumina reinforced with SiC whiskers inserts, have shown, at each assigned cutting parameter, poor wear resistance when cutting steel. Alumina and alumina in submicron grain, which has been toughened by ZrO2 phase transformation, and the oxide-based alumina, have been the better wear resistance. The mixed based alumina ha…
Wear rates and wear mechanisms of alumina-based tools cutting steel at a low cutting speed
Abstract Three ceramic insert materials, zirconia-toughened alumina (Al 2 O 3 –7vol%ZrO 2 ), mixed-based alumina (Al 2 O 3 –TiN–TiC–ZrO 2 ) and alumina reinforced with SiC whiskers (Al 2 O 3 –SiC w ), were used to cut AISI 1040 steel at 3.9 m s −1 . In addition, a traditional grade P10 insert (WC–TiC–Co) was tested. The lifetimes, according to KT/KM and VB B criteria, were determined using a profilometer and by image processing. The worn zones were observed with scanning electron microscopy techniques. Adhesion and plastic deformation were dominant wear mechanisms in zirconia-toughened alumina, mixed-based alumina and sintered carbide P10, both in the craters and in the cutting edges. As we…
Analysis of metal spinning processes by the ADINA code
Abstract The ADINA code, version 84, has been employed for the analysis of sheet spinning processes. The main process parameters have been evaluated in different working conditions; namely for various geometries and constitutive laws of the material.
Computer vision profilometer: equipment and evaluation of measurements
Abstract This paper describes a new equipment that measures roughness values by a computer vision (CV) technique. Measurements carried out by a CV profilometer are also evaluated. A laser source (power 2 mW), a cylindrical lens and a charge coupled device (CCD) TV-camera with a suitable optical system form an image of the profile of the sample under inspection. This image is then transformed into a binary image by thresholding and the line that divides the bright zone from the dark zone is the sample profile. From this line the characteristic roughness values can be calculated. The roughness measurements are carried out both by the CV profilometer and a stylus profilometer on eight specimen…
Error Estimates and Automatic Adaptive Mesh Refinement for the Metal Forming FEM Analysis
The Authors propose a new technique which enables a estimation of the error inherent with the FEM analysis of metal forming processes. The aim is to evaluate the zones where the error is higher in order to proceed to a refinement of the mesh in such zones, and to obtain a smaller value of the global error. Moreover, to simplify the analyst work in the progressive refinement of the mesh, it has been prepared a software able to read the drawing created by a CAD program and to generate, automatically, all the geometrical and topological data necessary to perform the analysis on Personal Computer. The automatic renumbering of the elements in the refined mesh has been performed with the aim to r…
Real-Time Routing Selection in Flexible Manufacturing Systems
Routing flexibility is one of the main peculiarities of Flexible Manufacturing Systems. This paper proposes three methods for real-time routing selection. The first one makes decisions comparing the current workload of machines in each alternative path. The second method considers the current workloads at the bottleneck machines in each allowed route. The third approach makes real-time decisions minimizing a merit index that represents a measure of the still required resource amount. The index is computed by short discrete-event simulation runs. Some case studies evaluate and compare the proposed approaches.
A New On-Line Roughness Control in Finish Turning Operation
A new on-line control method for the wear state of sintered carbide tools for finish turning operations is proposed.
An Automated System for Dimensional Control Based on Computer Vision
A totally automated control method for the dimensional control of pieces has been developed by Computer Vision techniques, combined with a movement equipment managed by the control system. By employing this technique it’s possible to perform the dimensional control on manufactured articles having geometric characteristics that don’t allow a trouble-free image acquisition maintaining a good resolution. By employing the same equipment an automated three-dimensional control system, based on stereoscopic vision has been developed.
Cutting Temperatures Evaluation in Ceramic Tools: Experimental Tests, Numerical Analysis and SEM Observations
The authors propose a multiple approach for the evaluation of cutting temperatures in ceramic tools. The first approach was the experimental evaluation of equitemperature lines, obtained in three-dimensional cutting by employing constant melting point powders scattered on planes parallel to rake face. In the second approach, a numerical finite element analysis was performed. At this step the determination of the percentage of total heat produced in the operation that flows into the tool was considered and, consequently, the temperature distribution within the whole volume of the insert. Finally, the examination of the crater zone with SEM microscopy confirmed the temperature levels as previ…
Sheet Metal Fastening by Self-Piercing Riveting
WEAR MECHANISM OF CERAMIC TOOLS
Abstract Cutting tests were performed using ceramic cutting tools under continuous cutting conditions. The tests were carried out on AISI 1040 steel, with cutting speeds ranging from 5 to 11 m s −1 . The wear mechanism was investigated for both crater and flank. Alumina-toughened zirconia of submicron grain size showed the best wear resistance. Alumina with TiC, TiN and ZrO 2 inclusions exhibited a wear resistance a little lower than the above-mentioned materials. Low chemical stability seems to be the reason for the poor performances of the silicon carbide whiskers-reinforced alumina, silicon nitride and the tungsten carbide inserts.