Sheet Metal 2011

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Authors: Andrea Angelastro, Sabina L. Campanelli, Giuseppe Casalino, Antonio D. Ludovico, Simone Ferrara
Abstract: Direct Laser Metal Deposition (DLMD) is actually one of the most attractive techniques in the group of Material Accretion Manufacturing (MAM) processes. In fact, the DLMD technology is able to realize, to repair and restore, objects, moulds and tools, directly from the 3D CAD model in a rapid and economic way. A great variety of metals, including those very difficult to work with the conventional techniques, can be shaped in a large number of complex geometries. This technique is also well suited to produce very hard coatings. The metallic parts, which are obtained through melting coaxially fed powders with a laser, present very good mechanical properties, with minimum porosity and good adhesion to the substrate. The objective of this work was to optimise the scanning velocity of the laser beam in order to maximize the density of DLMD parts. The optimization procedure was worked out with a mathematical model together with an experimental analysis to study the shape of the track clad generated melting coaxially fed powders with a laser. The material tested was Colmonoy 227-F, a nickel alloy specially designed for manufacturing moulds. The presented methodology has permitted to select the better combination of parameters that produce almost full density parts, free of cracks and well bonded to the substrate sintered parts.
Authors: Thomas Schneider, Marion Merklein
Abstract: Due to ecological and economic challenges there is a rising demand on closely-tolerated complex functional components. Regarding short process chains and improved mechanical properties conventional forming processes are often limited. A promising approach to meet these requirements can be seen in the combination of traditional sheet and bulk metal forming processes, to form sheet metals out of the sheet plane with typical bulk forming operations. The challenge of applying conventional bulk forming operations on sheet metal is the interaction between regions of high and low deformation, which is largely unknown in literature. To analyze this topic fundamentally, a process combination of deep drawing and upsetting is developed for manufacturing tooth-like elements at pre-drawn cups. To fully understand material flow out of the sheet plane into the tooth cavity and to identify and qualify process factors depending on the functional elements´ geometry and friction, a single upsetting stage forming a simplified model of the blank is virtually analyzed with finite-element simulation. By inhibiting the forming history of the pre-drawn blank, the upsetting process can be investigated without interactions with a previous deep drawing operation.
Authors: Marion Merklein, A. Erman Tekkaya, Alexander Brosius, Simon Opel, Lukas Kwiatkowski, Björn Plugge, Sebastian Schunk
Abstract: The demand on closely-tolerated and complex functional components in the automotive sector, like e.g. synchronizer rings, leads to the development of a new process-class named “sheet-bulk metal forming”. Within this technology bulk metal forming operations are applied on sheet metals. In the following two novel approaches considering machines and tools for sheet-bulk metal forming are presented. The first approach aims on a technology based on rolling, which is suitable for mass production. The second one is an incremental forming solution for low batch production. Both machine concepts allow the application of different forming strategies to manufacture individual tailored semi-finished products in term of a pre-distribution of material. These products feature variable sheet thicknesses and mechanical properties, which can be adapted to their case of applica-tion. Depending on the individual batch size, the blanks can be finished to functional parts by sub-sequent forming processes like deep drawing and upsetting, extrusion or incremental forming. In this paper the case of an incremental tooth-forming is mainly considered. Forming sequences and resulting loads are modeled and calculated by finite elements simulations for all discussed processes to serve as a basis for the design and dimensioning of the machine components and forming tools.
Authors: Antonio del Prete, Gabriele Papadia, Barbara Manisi
Abstract: Ecological awareness and economic analysis force industry to decrease the weight of transportation vehicles and to achieve a higher product quality with a reduction of production costs [1]. Lightweight constructions made out of Tailored Blanks (TBs) and advanced manufacturing technologies, like sheet metal Hydromechanical Deep Drawing (HDD), help to reach these goals [1]. From this point of view, HDD techniques have been largely accepted by the industry [2] for the production of components characterized by: complex shapes, good surface quality and small residual stress. In this work, starting from previous studies of the same authors about hydroformed components with a redrawing area [3] [4], an original approach based on Thickness Percentage Reduction (TPR) distribution has been implemented to design a particular TBs for HDD applications. Numerical and experimental results about the studied test case have been allowed the verification of their correlation as well as the necessary reliability of the implemented process simulation methodology.
Authors: Aleš Petek, Karl Kuzman, Renato Fijavž
Abstract: The paper presents a modern manufacturing concept called the “backward incremental hole-flanging process”. It enables drawing necks on the final products that can be very complex or even closed with minimal expense. Special attention is dedicated to researching the most influential process parameters affecting the neck height and the thinning of the neck using empirical modelling. Results show that forming tool diameter, and horizontal and vertical step sizes have the greatest influence on the forming results.
Authors: Francesco Lambiase, Antoniomaria di Ilio
Abstract: The effect of roll drawing process parameters on geometrical characteristics of flat roll draw wires is analyzed. Low carbon steel wires AISI 1010 are used in the experimental tests to assess the final geometry, mainly characterized by the width of flat wires, varying among several experimental levels the main process parameters i.e., initial wire dimensions, height reduction and lubrication conditions. Design of experiment technique was used to define the experimental plan and statistical techniques, such as analysis of mean (ANOM) and variance (AVOVA), were used to evaluate the effective influence of previous cited process parameters on final geometry of wire. A finite element model is developed to investigate a further process parameter i.e. the working rolls dimensions. In order to validate the finite element model, a campaign of experimental tests was conducted and the geometrical predictions of FE model were compared with experimental mea-surements with particular attention to final wire width, width of contact area and wire elongation. A linear regression analysis was performed and an empirical formulation to forecast the lateral spread of wire according to the main process parameters was developed.
Authors: Sebastian Rösel, Marion Merklein
Abstract: The need of light weight constructions and parts with tailored or even more homogeneous mechanical properties especially for structural components leads to the use of alternative forming technologies. These forming processes like sheet metal hydroforming are established to gain more flexibility and to increase the forming limits. But to apply this forming technology successfully, it is necessary to overcome some obstacles. One typical challenge for hydroforming of blanks, which has prevented further application of this technology, is the sealing of the cavity in the flange area. Nowadays there are a lot of basic approaches to accomplish a sealing in this tool area. Commonly a sealing can be reached by increasing the contact pressure in the outer region of the blank. This approach reduces the possible blank draw in and hence abates the possible realisation of complex part geometries. One possible approach to increase the ratio between cavity pressure and contact pressure in the flange area is the choice of a capable active fluid medium. The aim is to reduce the contact pressure in the flange area and nevertheless ensure a complete sealing. In this case the magnetorheological fluid (MR-fluid) BASF Basonetic 5030 is used as a pressure medium for hydroforming. For characterizing this fluid under different amounts of magnetic flux density and in comparison to a common hydraulic medium, an experimental setup was built up to gain process relevant data for hydroforming processes. Therefore different experiments were carried out with different media and different flux densities for the MR-fluid. To get more information about the mode of action and the accessible amounts of cavity pressure and related contact pressures in the flange area, these two process parameters were varied.
Authors: Fahrettin Ozturk, Remzi Ecmel Ece, Naki Polat, Arif Koksal
Abstract: Ti-6Al-4V (Ti64) is the most commercially used heat treatable high strength/weight ratio, high corrosion, and thermal resistance alloy in titanium alloys. However, room temperature (RT) formability of this alloy is very poor and springback after forming is very severe due to the high yield strength and low elasticity modulus. In this research, the applicability of electrical resistance heating process which is a new and rapid heating process for hot forming application is investigated in order to improve formability and eliminate springback. The electrical resistance heating method is found to be effective for T64 alloy. Results reveal that the changes in hardness and grain size of the alloy have been found inconsiderable when the method is used. Springback compensation is achieved at high temperatures and springback free part is almost produced.
Authors: Anja Neumann, Dirk Hortig, Marion Merklein
Abstract: This paper provides first results of a contact-free measurement system for monitoring the material flow in series production which has been under investigation for more than one year. An inductive proximity sensor with analog output was used to measure its own sheet metal coverage. Multiple sensors were integrated in the blank holder without affecting the deep drawing process. The robustness of the monitoring principle was assessed under series production conditions by using optical measurement equipment. This paper describes the basic information of the inductive measurement, the comparison of the inductive and optical measurement results and analyses correlations between the sensors.
Authors: M. Mehrara, Mohammad Javad Nategh
Abstract: In the present work the elastic bending of thin plate resting on rubber pad has been analyzed. The governing differential equations have been derived. An analytical solution to these equations has been presented. In addition numerical solution to these equations has also been worked out by using finite difference method. An equation has been derived to estimate the indentation depth of plate at the onset of plastic bending of the plate in terms of the process parameters. The analytical solution has then been verified by experimental results.

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