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Technical Paper

Simulation Based Solutions for Industrial Manufacture of Large Infusion Composite Parts

Today, LRI is a proven manufacturing technology for both small and large scale structures (e.g. sailboats) where, in most cases, experience and limited prototype experimentation is sufficient to get a satisfactory design. However, large scale aerospace (and other) structures require reproducible, high quality, defect free parts, with excellent mechanical performance. This requires precise control and knowledge of the preforming (draping and manufacture of the composite fabric preforms), their assembly and the resin infusion. The INFUCOMP project is a multi-disciplinary research project to develop necessary Computer Aided Engineering (CAE) tools for all stages of the LRI manufacturing process. An ambitious set of developments have been undertaken that build on existing capabilities of leading drape and infusion simulation codes available today. Currently the codes are only accurate for simple drape problems and infusion analysis of RTM parts using matched metal molds.
Technical Paper

Process Modeling in the Life Cycle Design - Environmental Modeling of Joining Technologies within the Automotive Industry -

For integrating Life Cycle Assessment into the design process it is more and more necessary to generate models of single life cycle steps respectively manufacturing processes. For that reason it is indispensable to develop parametric processes. With such disposed processes the aim could only be to provide a tool where parametric environmental process models are available for a designer. With such a tool and the included models a designer will have the possibility to make an estimation of the probable energy consumption and needed additive materials for the applied manufacturing technology. Likewise if he has from the technical point of view the opportunity, he can shift the applied joining technology in the design phase by changing for instance the design.
Technical Paper

Combination of Hydraulic Multipoint Cushion System and Segment-Elastic Blankholders

The costs for development and production of draw dies for car outer panels are extremely high and should be reduced. Furthermore it is necessary to reduce the time for developing, designing and producing the dies for the production of parts. This paper discusses new press techniques, die designs and an adjustment program for press operators. The trend goes to single action presses with CNC-controlled multipoint cushion systems in the press table and to special designed dies. These systems lead to a more robust and reproducible forming process with improved product quality. This paper deals with: Cushion Systems, New Binder Designs for Draw Dies for Sheet Metal Automotive Parts, New Computer Program to Adjust the Blankholder Forces of Modern Hydraulic Cushion Systems of Single Action Presses and Pressure Measurement for Detecting the Pressure between the Blank and the Binders of Draw Dies for Sheet Metal Automotive Parts.
Technical Paper

New Machine Concept for Hydroforming Tubes and Extrusions, Part 2

In cooperation with industrial companies at the Institute for Metal Forming Technology (IFU) of the University of Stuttgart, Germany, a new press concept specially for hydroforming tubes and extrusions was developed. The press has a capacity of 3500 tons closing force and a press table size of 2500 mm × 900 mm. A great reduction in costs can be achieved by integrating spacers between the frame of the press and the ram. This paper introduces this new press.
Technical Paper

Pulsating Blankholder Technology

In this paper the effects of pulsating blankholder forces in deep draw processes for sheet metal parts are discussed. Areas with and without tangential compressive stresses in the flanges, which are located between the binders, are discussed separately. Areas without tangential compressive stresses can be simulated by a special friction strip-draw test using a pulsating normal force ( representing the blankholder force ). Investigations using this equipment show that by pulsating blankholder forces it is possible to avoid galling and to reduce the friction force. Areas with tangential compressive stresses can be simulated by deep drawing axissymmetric cups using a pulsating blankholder force. Investigations with this equipment show that without increasing the danger of wrinkling the friction forces can be reduced by pulsating blankholder forces, when a certain frequency limit is reached.
Technical Paper

Closed Loop Binder Force System

When drawing non-axissymmetric sheet metal parts it is necessary to control the flow of material between the lower and upper binder in such a manner that prevents the occurrence of both tears and wrinkles in the drawn part. One possibility for the control of the material flow is through the deliberate adjustment of the normal forces. If one can measure the flow-in of the material into the die cavity as a function of punch stroke with a special sensor, and if this information can be used to produce an empirical flow-in curve over the stroke for good parts, then it is possible to construct a closed- loop BHF control system. Building such control system is feasible by implementation of special dies with hydraulically supported segmented binders. This system allows an automatic response to a change in the friction conditions.
Technical Paper

3-Dimensional Description of Sheet Metal Surfaces

During sheet metal forming processes, the friction conditions have a decisive influence on forming limits, the robustness of the production process and the quality of the parts produced, with significant forces required to overcome friction between the sheet and the tools. If lot-to-lot reproducibility is to be guaranteed, an appropriate method of characterizing the sheet surface topography is needed to monitor the sheet metal fabrication process. Newly developed optical measurement techniques and computer workstation technology are presented which enable the topography of sheet surfaces to be described in three dimensions.
Technical Paper

Fundamental Research and Draw Die Concepts for Deep Drawing of Tailored Blanks

According to the present state of knowledge, the use of “Tailored Blanks” with different sheet thicknesses and/or grades represents an interesting manufacturing alternative in the design and development of sheet metal parts in the automotive industry. In order to assess the forming behavior, fundamental research was conducted on laser and mash seam welded blanks. Based on this experimental findings, a segmented draw die was designed and built to determine the limits of the metal forming process by deep drawing of car body parts. The results with this draw die showed that a uniform blankholder pressure must be guaranteed during the forming process in the flange region of the part. This necessitated definite slots in the region of the weld line for the mash seam welded blanks. Furthermore, a die concept was presented to enable an equalization of both sheet thickness steps and sheet thickness fluctuations, without requiring replacement of the respective draw die components.