Papers by Keyword: Sheet Metal

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Authors: Zhen Zhong Xiao, Jin Liang, De Hong Yu, Zheng Zong Tang
Abstract: To solve the problem of measurement for welding deformation of sheet metal, a non-contact three-dimension optical method is proposed. Firstly, photos of moving objects from different observation points are taken by two high-resolution and high-speed digital cameras simultaneously. Secondly, the three-dimensional coordinates of targets are calculated by three-dimensional reconstruction technique including collinear equation, photo orientation based on the coplanar equation, direct linear transform, epipolar geometric constraint and bundle adjustment method. Finally, the deformations at different moments are associated with points of the same name; the deformation of the observation points is calculated and the real time deformation curves are sketched. Compared with the traditional methods, this method is not subjected to the high temperature and strong interference and has the advantages of real-time, high efficiency and high precision. The application in the measurement for welding deformation of sheet materials is satisfying.
Authors: Horst Meier, H. Ermert, P. Knoll, Oliver Keitmann-Curdes
Abstract: With fluid forming processes getting more and more common in industrial application a lot of research is carried out to analyze the forming behavior of sheet metal within these processes. In order to gather experimental information about the forming behavior of the workpiece, an imaging system is presented, that will allow determining the actual shape within the forming process. The system has to be functional in liquid media as well as in a high pressure environment. Therefore an ultrasonic based system has been chosen, consisting of a small number of transducers which are alternately used as transmitter and receiver. It is possible to cover 100 by 100 mm² with only 10 by 10 transducers by the use of special algorithms. The reconstruction of the echographic images from the recorded data is done by a SAFTalgorithm (synthetic aperture focusing technique) followed by an analysis with special contourdetection algorithms, which are able to scan the image for contour data. It can be shown that the accuracy of the reconstruction is quite good in the 2.5-dimensional domain, if appropriate contour models for the description are used. Because of the small number of transducers and the specular reflection of the signals, the quality of the image can be improved significantly by the extension of the SAFT algorithm with an angle-weighted factor. The three dimensional reconstruction is also possible and will be demonstrated for simple geometries. The ability for sampling more complex geometries and enhancing the accuracy will be achieved by the integration of three dimensional contour models and three dimensional angle-weighting.
Authors: J. Valentin, M.A. Weber, R. Brodmann, A. Sharp
Abstract: The measurement and evaluation of sheet metal surface characteristics is of increasing importance, due to the significant functional impact on finishing processes like forming and varnishing. For a comprehensive and useful description of textured topographies including nonstatistical characteristics, a simple profile evaluation based on 2D roughness parameters is no longer sufficient. The introduction of area-imaging white light confocal microscopy offers, in contrast to tactile profiling methods of comparable accuracy, the clear advantage of contact-free and extremely fast 3D data capture. The capabilities and benefits of this technology in interaction with sophisticated 3D area analysis methods are demonstrated by measurement examples of sheet metal and roller surfaces. A newly-developed mobile confocal measurement system for direct roller measurements is introduced.
Authors: R.K. Abdel-Magied, H.M.A. Hussein
Abstract: The aim of this work is to develop an integrated system for facilitating the process of designing the drawing dies and their component. The developed system is based on the integration between Computer Aided Process Planning in Sheet Metal Drawn parts “CAPP”, and the Computer Aided Design in Deep Drawing Die components “CAD”. Both modules are coded using Visual Basic program and joined with AutoCAD. The CAPP module made to report the drawing load and to plot the shape of the drawn shell in each stage of the Axis-Symmetric Deep Drawing process. Based on the reported shell geometry, the dimensions of the die components are calculated and transferred to the CAD module. The CAD module, which is based on many data bases (standard parts, sheet metal data), plots the required deep drawing die components for each drawn stage on the AutoCAD monitor. A demonstrated example is presented to validate the developed system and to show that the system results are acceptable.
Authors: A. Albers, H. Weiler, D. Emmrich, B. Lauber
Abstract: Beads are a widespread technology for reinforcing sheet metal structures, because they can be applied without any additional manufacturing effort and without significant weight increase. The two main applications of bead technology are to increase the stiffness for static loading conditions and to reduce the noise and vibrations for dynamic loadings. However, it is difficult to design the bead patterns of sheet metal structures due to the direction-controlled reinforcement effect of the beads. A wrong bead pattern layout can even weaken the properties of the structure. In the past, the designs were predominantly determined empirically or by the use of so called bead catalogues. Recently, different optimization approaches for bead patterns were developed, which are based upon classical mathematical programming optimization algorithms together with automatically generated shape basis vectors. However, these approaches usually provide only vague suggestions for the designs. One of the most severe difficulty with these approaches is to transfer the optimized results into manufacturable designs. Furthermore, another severe difficulty is that the optimization problem is non-convex, which frequently leads the mathematical programming algorithms into a local optima and thus to sub-optimal solutions. The investigations in this article show an optimization method, which within a few iterations leads to bead structures with excellent reinforcement effects using optimality criteria based approach. Generally, the results can be transferred without large effort into a final design. The new optimization method calculates the distribution of the bending stress tensor and the principal bending stresses based upon the results of a finite element analysis. The bead orientations are calculated by the trajectories of the principal bending stress with the largest magnitude. The beads are projected on to the mesh of the component using geometric form functions of the desired bead cross section. A local bead ratio of 50% (defined as average area of the beads in relation to total area of the sheet) is used by the algorithm to determine the maximum moment of inertia. The proposed algorithm is numerical implemented in the optimization system TOSCA and available for being applied with the following finite element solvers: ABAQUS, ANSYS, I-DEAS, NX Nastran, MSC.Nastran, MSC.Marc and PERMAS. The optimization algorithm is successfully applied to static and dynamic real world problems like car body parts, oil pans and exhaust mufflers. In the present work several academic and industrial examples are presented.
Authors: Marion Merklein, Andreas Maier, Daniel Kinnstätter, Christian Jaremenko, Emanuela Affronti
Abstract: The forming limit diagram (FLD) is at the moment the most important method for the prediction of failure within sheet metal forming operations. Key idea is the detection of the onset of necking in dependency of different sample geometry. Whereas the standardized evaluation methods provides very robust and reliable results for conventional materials like deep drawing steels, the determined forming limits for modern light materials are often too conservative due to the different failure behavior. Therefore, within this contribution a new and innovative approach for the identification of the onset of necking will be presented. By using a pattern recognition-based approach in combination with an optical strain measurement system the complete strain history during the test can be evaluated. The principal procedure as well as the first promising results are presented and discussed.
Authors: Bernd Arno Behrens, Anas Bouguecha, Claus Peter Eckold, Ilya Peshekhodov
Abstract: A novel clinching process design to join thin metal sheets and foils is proposed. In this process a small cup is first stretched out of the sheet plane. A shape interlock between the two sheets is then created by a movement of the die and blank holder in the sheet plane lateral to the cup wall. Such an approach makes the undesired upsetting of the cup bottom redundant, which promises less energy consumption and a longer tool life when compared to conventional clinching processes. The process principle and its finite element analysis for austenitic steel sheets as well as deep-drawing steel sheets (both 0.3 mm thick) are presented. The numerical results suggest feasibility of the proposed design to produce a good shape interlock between two thin sheets.
Authors: Fei Han, Mathias Liewald
Abstract: Because of the extensive use of thin sheet metals to reduce the weight of vehicles, wrinkling is becoming a more common and one of the most undesirable failures in the sheet forming process. Generally, experiments for studying wrinkling phenomena can be divided into two methods: actual forming of typical parts such as annular cup test on the one hand and the tests of specially designed sample geometries like the Yoshida Buckling test on the other. Recent experiments indicate that the plastic strains at the onset of wrinkling in the Buckling Test with Yoshida samples are too small to reflect reality of deep and stretch drawing conditions. Therefore, in this paper, in order to enhance the accuracy of the prediction of wrinkling, a new modified Yoshida specimen is provided for numerical simulation. The fundaments of the different buckling phenomena are going to be explained considering the energy theory in metal forming processes. Meanwhile, the influences of the changeable sample geometries in order to cause different stress distribution within loaded area of specimen have been investigated.
Authors: Horst Meier, O. Dewald, Jian Zhang
Abstract: This paper describes a new sheet metal forming process for the production of sheet metal components for limited-lot productions and prototypes. The kinematic based generation of the shape is implemented by means of a new forming machine comprising of two industrial robots. Compared to conventional sheet metal forming machines this newly developed sheet metal forming process offers a high geometrical form flexibility and also shows comparatively small deformation forces for high deformation degrees. The principle of the procedure is based on flexible shaping by means of a freely programmable path-synchronous movement of the two robots. The sheet metal components manufactured in first attempts are simple geometries like truncated pyramids and cones as well as spherical cups. Among other things the forming results could be improved by an adjustment of the movement strategy, a variation of individual process parameters and geometric modifications of the tools. Apart from a measurement of the form deviations of the sheet metal with a Coordinate Measurement Machine rasterised and deformed sheet metals were used for deformation analyses. In order to be able to use the potential of this process, a goal-oriented process design is as necessary as specific process knowledge. In order to achieve process stability and safety the essential process parameters and the process boundaries have to be determined.
Authors: Philipp Hildenbrand, Michael Lechner, Marion Merklein
Abstract: Applying bulk forming processes on sheet metals enables the manufacturing of functional components with local wall thickness distributions. Using tailored blanks improves the forming of the functional components and increases the material efficiency. One process for manufacturing tailored blanks with defined sheet thickness distributions is a flexible rolling process. However, this process requires a complex process strategy. Additionally, tailored blanks out of high-strength steels from this process have failed in subsequent forming. Thus, a new rolling concept with a defined shaping of the material into a die cavity has been developed. This new concept requires the development of a new process strategy. In this paper, the general qualification and first results of the new concept are presented.
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