The paper presents a method for checking the geometry of stamped car body parts using a 3D optical measurement system. The analysis focuses on the first forming operation due to the deformation and material flow associated with stall thresholds. An essential element of the analysis is determining the actual gap occurring between the forming surfaces based on the die and punch geometry used in the first stamping operation. The geometry of car body elements at individual production stages was analyzed using an optical laser scanner. The control carried out in this way allowed one to correctly position the tools (punch and die), thus introducing the correction of technological parameters, having a fundamental influence on the specific features of the final product. This type of approach has not been used before to calibrate the technological line and setting of shaping tools. The influence of the manufactured product geometry in intermediate operations on the final geometry features was not investigated.
Tomografia komputerowa (CT) jest najnowszą techniką pomiarową wśród metod współrzędnościowych. W artykule przedstawiono możliwość jej aplikacji do pomiaru i oceny profili uzyskiwanych w procesie gięcia. CT umożliwia ocenę grubości oraz analizę ewentualnych pocienień ścianek. Po uzyskaniu przestrzennego wyniku pomiaru pozwala również na ocenę w oparciu o model CAD. CT jest zaliczana do metod NDT, co pozwala również na kontrolę pęknięć czy porowatości. SŁOWA KLUCZOWE: tomografia komputerowa, dokładność pomiaru, profile aluminiowe, gięcie, obróbka plastyczna Computed tomography (CT) is the newest group belonging to coordinate measuring techniques. In the paper its application to measure and evaluate profiles obtained by bending was described. CT makes it possible to assess thickness of walls and detect places where it is too small. After obtaining a 3D image as a result of measurement it is also possible to compare the obtained data with a CAD file. CT is also considered as NDT technique, so all the pores and cracks can be easily inspected. KEYWORDS: computed tomography, measurement accuracy, aluminum profiles, bending, plastic deformation Tomografia komputerowa jest nową techniką pomiarową wśród metod współrzędnościowych. Znana jest w medycynie od lat 70., jednak jako technika pomiarowa stosowana jest od około 10 lat. Szerokie możliwości tomografii powodują dynamiczny rozwój obszarów jej aplikacji. Jednym z takich przykładów jest kontrola geometrii giętych profili aluminiowych o przekroju zamkniętym [1][2][3]. Profile aluminioweProfile produkowane są w przeróżnych kształtach i rozmiarach od standardowych po wykonywane na specjalne zamówienie. W zależności od wymagań profil aluminiowy musi spełniać różne funkcje. Są to m.in. wytrzymałość, skomplikowany kształt czy estetyka. Wymagania te powinny być spełnione zarówno po procesie wytłaczania, jak również po dalszych procesach obróbki plastycznej [4].Jednym z niekorzystnych zjawisk występujących w trakcie gięcia profili aluminiowych jest pocienienie ścianek. Zjawisko takie może spowodować utratę granicznych wła-ściwości wytrzymałościowych analizowanej konstrukcji. W omawianym przypadku badany profil aluminiowy, po odpowiednim ukształtowaniu w procesie gięcia, stanowi ramę nośną fotela, który może być stosowany w pojazdach komunikacji zbiorowej. Jest to zatem odpowiedziany element konstrukcyjny, od którego zależy wytrzymałość fotela na różnego typu obciążenia i będące podstawą uzyskania homologacji pozwalającej na jego użytkowanie. Jednocześnie najważniejszą rzeczą kwestią jest zapewnienie przez konstrukcję fotela bezpieczeństwa podróżujących w nim pasażerów.Ze względu konieczność spełnienia szeregu wymagań opracowano własny kształt profilu aluminiowego przypominający w przekroju literę D (rys. 1b). Dodatkowo dla uzyskania optymalnego stosunku wytrzymałości do masy profil charakteryzuje się inną grubością dłuższych i krót-szych boków.Rys. 1. Badany profil aluminiowy: a) model 3D gotowego profilu giętego, b) przekrój profilu w kształcie litery D Tomografia komputerowaW ...
The work presents the results of FEM simulations of extrusion process with the use of four – hole dies of various geometry. The traditional flat dies and pocket dies were adopted for comparison. The calculations were conducted for indirect extrusion of rods of 14 mm in diameter from the 6061 aluminium alloy. The distributions of strains, stresses, metal velocities and temperature within the deformation zone were the basis for metal flow analysis. Based on the conducted calculations the die configuration, leading to the best product quality was recommended. The product quality was evaluated by the flow direction of rods from the die orifices.
Insight in the aluminium extrusion process can be gained with numerical simulations. This paper gives an overview of the research done to model aluminium extrusion with the Arbitrary Lagrangian Eulerian (ALE) FEM code DiekA. The ALE formulation is used to avoid mesh distortion, which is a major problem in the simulation of extrusion. The goal of this research is to increase the lifetime of extrusion dies and to decrease the number of corrections necessary to these dies. To model the rate-dependent behaviour of hot aluminium, normally a viscoplastic material model is used. However in the bearing the material behaviour is mainly elastic. The pressure and friction in the bearing are dominant factors in the extrusion process and an accurate modelling of this area is crucial for the final results. In this paper an elasto-viscoplastic material model is derived. This models can be simplified to a very efficient model that is elasto-viscoplastic for small deformation increments and viscoplastic for large increments. With this model it is possible to model the extrusion process including the elastic behaviour in the bearing without sacrifising efficiency. As an example the extrusion of a tube is treated. To avoid unacceptable calculation times, the simulation is split into three parts. First a detailed 2D simulation of the bearing area is made. The results of this simulation are used in a complex 3D simulation of the aluminium flow true the die. From this simulation, the loads on the die are determined. These loads are used in a stress analysis of the die. The results of these simulations give insight in the processes that occur in the aluminium and in the die.
In the work the distribution of stresses and strains as well as temperature field within the welding chamber of the porthole die were determined. The analysis was performed by the use of the computer program DEFORM based on a finite element method. The direct hot extrusion of 2024 aluminum alloy was investigated with the use of the porthole dies of different geometry. Particularly, a different height of the welding chamber was adopted in calculations. The calculations allowed determining both pressure and temperature levels and their distributions within the welding chamber leading to the best welding conditions for the alloy tested.
Numerical simulations of drawing and redrawing process of forming cylindrical elements from thin sheets are complicated issues due to the problem with describing finite elements in the complex calculation model. This type of simulation require the creation of the rheological model including the forming limit curve, the true-stress-strain curve and anisotropy defined in various directions. In addition, it is necessary to design optimal geometry of the forming tools. FEM calculations have been performed for 3XXX series aluminum tape in cold-hardening state. The initial data, boundary conditions have been defined, as well as technological data concerning the sheets have been specified experimentally. Numerical analysis of thin aluminum sheet drawing and redrawing process has been analyzed for 3 various sheet thicknesses, i.e.: 0,250 mm , 0,240 mm , 0,230 mm. Currently, the industry uses mainly sheets of 0.250mm thickness. A few manufacturers of beverage cans use sheets of thickness0.240mm while the sheet of thickness 0.230mmis the innovation which manufacturers try to introduce into the industry to minimize the quantity of material. For the selected thickness the clearance between the punch and the die has been calculated as well as the optimum hold-down force. The influence of sheet thickness on the distribution of thinning along generating line has been examined. In order to determine the thinnest possible sheet for obtaining the optimal thickness of the final product, the thinning of drawpiece has been analyzed. Moreover the value of deformations has been compared to FLC curve as well as the intensity of the stresses generated in the bottom and on side walls of the cup has been examined.
In industrial practice, where the amount of products produced in a minute is calculated in hundreds of units, the ironing process of thin-walled cylindrical shell products is carried out with very high speed. In the multi-stage forming process it is important to ensure the stability of parameters of the raw material. Properties of input sheets are defined in international standards, but after the rolling process the properties of input tapes may be various while still in the acceptable tolerance. Differentiation of properties of sheets has a significant impact on the progress of the examined process. The multi-stage forming process requires raw material with a high susceptibility to deformation and an adequate level of plasticity margin. In this study tapes of equal thickness and similar chemical composition from various suppliers have been analyzed. Selected aluminum alloys sheet are currently used in Europe in production of beverage packaging. On the basis of uniaxial tension test results, plasticity margin for a selected tape has been determined. Deformation range and plasticity margin have been analyzed in relation to the stability of production process Defining the correlation between identified strength parameters and the stability of production line allowed to examine the impact of plasticity margin for effectiveness and efficiency of the process. In mass production, each break in machine work results in loss of millions of units. The analysis allowed to compare the value of plasticity indicators of the raw tape deformability in the complex process of forming thin-walled cylindrical shell products and influence for increase the efficiency and reduction of defects.
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