Plasticity effects in subsequent simulations of car structures

In order to further reduce the weight of car components while at the same time\ud maintaining performance and safe life it is necessary to enhance the simulation process. This\ud is especially important for chassis parts which have not only a high dynamic load but are also\ud partly undamped. To reach this goal, the logical step is to couple the successive operations of\ud forming, assembly and virtual performance testing.\ud The objective is a complete determination of the mechanical state of the (sub-)assemblies.\ud It is therefore necessary to consider all forming and joining processes a part has previously\ud undergone and to consider them in the virtual model. This virtual model is ideally suited for\ud virtual prototyping (e.g. structural analysis, fatigue, crash) because the complete history of\ud every part is contained. In contrast to standard models, the changed thickness of sheet metal\ud parts and residual stresses due to forming and joining as well as the new material state at\ud every point are known prior to any external loading. This results in a more reliable prediction\ud of product performance.\ud Using a relatively simple part it is demonstrated how the performance of chassis parts\ud changes with the inclusion of plastic forming effects as compared to the exclusion of these\ud effects. The transfer of the results of the forming process to the comprehensive model is shown\ud first. Hereafter the model is subjected to static and dynamic external loads. The results are\ud compared to calculations that use a standard model and show clearly that the inclusion of the\ud plastic history has a significant influence on the product performance

Recent advances in industrially applied numerically aided springback compensation

Springback is a common and intrinsic phenomenon of every deep drawing operation. For\ud various reasons the application of high strength steels and aluminum in automotive industry is\ud still increasing. Unfortunately, these materials tend to larger springback than mild steels.\ud Therefore it is more difficult to guarantee the accuracy of the part shape without a proper\ud springback compensation. Several countermeasures can be applied to minimize springback, but\ud it is not always possible to reduce springback sufficiently. Additionally, the overbending\ud technique has been developed to counter springback by modification of the tool shape. This\ud method gives satisfactory results for a whole class of parts which are very susceptible to\ud springback. In this paper an improvement, the smooth displacement adjustment (SDA) method,\ud is presented. Basically the shape deviation of the part is calculated and subsequently\ud approximated by an L2-projection of sufficiently smooth global analytical functions. Due to the\ud restriction to analytical functions the computed shape deviations can be easily transferred to the\ud tool surface in order to compensate them. The use of the new method is demonstrated on an\ud industrial part. The paper ends with conclusions and recommendations

Mechanische Schweißersatzmodelle für gekoppelte Simulationen

Die Entwicklung von Bauteilen in der Automobilindustrie wird durch die Forderung\ud nach Gewichtsminimierung bei kurzen Entwicklungszeiten bestimmt. Mit der\ud Kopplung einzelner Simulationsprogramme zu einer virtuellen Prozesskette können\ud die Fertigungsstufen im Rechner abgebildet werden, wobei in jeder neuen\ud Fertigungsstufe die Vorgeschichte des Bauteils berücksichtigt wird. In diesem Beitrag\ud wird näher auf den Baustein Schweißen in der Prozesskette eingegangen.\ud Heutzutage findet die Schweißsimulation noch keinen Eingang in die Industriepraxis,\ud hauptsächlich wegen des hohen Vorbereitungs- und Rechenaufwandes. Mit Hilfe der\ud hier präsentierten mechanischen Ersatzmodelle lassen sich in kürzester Zeit\ud Vorhersagen bzgl. Verzügen oder Eigenspannungszustand im Bauteil treffen. Dies\ud wird an zwei Beispielen aus der Industrie demonstriert, einem Querlenker und einem\ud Federlenker. Die Ergebnisse beider Modelle stimmen sehr gut mit der Realität\ud überein

Methoden der Schweißverzugssimulation für die Anwendung in der Automobilindustrie

In diesem Artikel wird eine Übersicht über die Methoden zur numerischen Berechnung schweißbedingter Bauteilverzüge für industrielle Anwendungen gegeben. Zunächst werden die Anforderungen der Automobilindustrie an die benötigte Software dargestellt. Dabei wird zwischen der industriellen Forschung und der Entwicklung/Produktionsplanung differenziert. Es werden die verschiedenen zurzeit verfügbaren Ansätze zur numerischen Schweißsimulation vorgestellt und deren Möglichkeiten zur Erfüllung der dargestellten Bedürfnisse erläutert. Anhand eines aktuellen Bauteils aus der Automobilindustrie (B-Säule VW Golf) wird beispielhaft die Verzugsoptimierung mit Hilfe einer Berechnungsmethodik aufgezeigt, welche sich durch eine schnelle Modellerstellung, kurze Rechenzeiten und einfache Handhabung auszeichnet. Ein Vergleich der Simulationsergebnisse mit experimentell ermittelten Daten zeigt sehr gute Übereinstimmungen und verdeutlicht das immense Potential einer numerisch unterstützten Prozessoptimierung

Friction testing of thermoplastic composites

Friction phenomena play a major role in thermoplastic composite forming processes. In order to make use of the large potential these materials have, accurate CAE tools are needed that as a consequence incorporate temperature, pressure and velocity dependent friction behavior. To obtain a sound understanding of friction behavior a large number of friction measurement set-ups have been described in literature. A benchmark to compare different testing methods was proposed during the Esaform2010 conference.\ud In this paper the material (Twintex PP) and testing conditions for the benchmark are briefly revisited and first testing results employing the in-house developed friction tester are presented. It is observed that the results reproduce very well at different conditions. Based on the Hersey number the Stribeck curve for the tested material combination is derived. It is concluded that a full state of hydrodynamic lubrication was reached with friction coefficients between 0.15 and 0.5. This opens up good perspectives for numerical modeling since all parameters are readily available in process simulations. Future comparisons within the context of the benchmark will assess the quantitative level of the identified coefficients of friction

Iterative solvers in forming process simulations

The use of iterative solvers in implicit forming process simulations is studied. The time and memory requirements are compared with direct solvers and assessed in relation with the rest of the Newton-Raphson iteration process. It is shown that conjugate gradient{like solvers with a proper preconditioning can signicantly improve the overall time performance of a forming process simulation as compared to the use of direct solvers. For the presented examples the time spent in the solver is not dominating the total solution time anymor