No abstract

Modern metal forming and crash simulations are usually based on the finite element method. Aims of such simulations are typically the prediction of the material shape, failure, and mechanical properties during deformation. Further goals lie in the computer assisted lay‐out of manufacturing tools used for intricate processing steps. Any such simulation requires that the material under investigation is specified in terms of its respective constitutive behavior. Modern finite element simulations typically use three sets of material input data, covering hardening, forming limits, and anisotropy. The current article is about the latter aspect. It reviews different empirical and physically based concepts for the integration of the elastic‐plastic anisotropy into metal forming finite element simulations. Particular pronunciation is placed on the discussion of the crystallographic anisotropy of polycrystalline material rather than on aspects associated with topological or morphological microstructure anisotropy. The reviewed anisotropy concepts are empirical yield surface approximations, yield surface formulations based on crystallographic homogenization theory, combinations of finite element and homogenization approaches, the crystal plasticity finite element method, and the recently introduced texture component crystal plasticity finite element method. The paper presents the basic physical approaches behind the different methods and discusses engineering aspects such as scalability, flexibility, and texture update in the course of a forming simulation.

Im Rahmen eines gemeinschaftlichen Projektes der Stahl-und Automobilindustrie wurden an insgesamt 20 Stählen für Feinblech Kennwerte für die FE-Simulation ermittelt. Im Einzelnen handelte es sich um elastische, plastische und zyklische Kennwerte, die über einen Zeitraum von 3 Jahren von unterschiedlichen Prüfstellen erarbeitet wurden. Die Bedeutung des temperatur-und richtungsabhängigen E-Moduls für den Automobilbau ist in der Rückfederung beim Pressen von Blechen und der Steifigkeit von Automobilteilen begründet. Der E-Modul wurde mit dem Zugversuch für den Anlieferungszustand, nach Vorverformung und teilweise nach Wärme-behandlung bei Raumtemperatur sowie bei -40 C und 100 C ermittelt. Der E-Modul ist aufgrund der Walzbedingungen richtungsabhängig und kann in Gruppen zusammengefasst werden. Bereits eine Vorverformung von 2 % verursacht für ferritische Stähle eine Verringerung des E-Moduls um ca. 10 %. Nach einer Wärmebe-handlung bei 170 C erholt sich der E-Modul weitgehend. Die aus zerstörungsfreien Verfahren bekannte Temperaturabhängigkeit konnte bestätigt werden.Schlüsselworte: Zugversuch, E-Modul, Anisotropie, Vorverformung, Wärmebehandlung, TemperaturabhängigkeitWithin the scope of a common research project of the steel and automotive industry, 20 sheet steels have been investigated to obtain input data for FE-analysis. In detail, characteristical elastic, plastic and fatique values were determined by several testing institutes for a period of 3 years. Knowledge of dependency of Young's modulus from temperature and orientation is important for spring back at the press shop and stiffness of parts for automotive. Young's modulus was determined by tensile tests in delivered state, after prestraining, heat treatment at room temperature and -40 C and 100 C. Young's modulus is dependent from the orientation to rolling direction and can be classified in groups. Young's modulus of ferritic steels is decreased about 10 % by prestraining of 2 % but recovered after annealing at 170 C. Temperature dependency well known from non destructive tests are confirmed.

Different near-net-shape casting techniques are investigated in terms of solidification parameters, microstructure, and microsegregation of manganese in carbon steels based on experimental simulation methods: ingot casting of thick and thin slab samples, strip samples, and thin strip. The as-cast thicknesses were between 1.9 and 150 mm. By calculations and measurements data have been determined which lead to the solidification structure like solidification-and cooling-rate, secondary dendrite arm spacings, and the concentrations of rnlcrosegregations. Finally, some literature data of material properties of steel strip produced by the investigated methods are given.Untersuchung der Erstarrung und Segregation von endabmessungsnah vergossenem Kohlenstoffstahl. Unterschiedliche Verfahren zum endabmessungsnahen GieBen von Stahl fOr Flachprodukte -wie DOnnbrammen-, Vorband-und DOnnbandgieBen -wurden im Hinblick auf Erstarrung, Mikrostruktur und Mangansegregation an Kohlenstoffstahl untersucht. In den Laborexperimenten lagen die GieBdicken zwischen 1.9 und 150 mm. Berechnungen zur Erstarrungszeit und -geschwindigkeit sowie zu AbkOhlgeschwindigkeiten wurden durchgefOhrt und mit GefOgedaten -wie Sekundardendritenarmabstand und Seigerungswerten • verglichen. AbschlieBend werden einige Literaturdaten zu Eigenschaften von endabmessungsnah vergossenen C-Stahl-Bandern angegeben..

Within the scope of a common research project of the steel and automotive industry, 20 sheet steels have been investigated to obtain input data for FE-analysis. In detail, elastic, plastic and fatique characteristical values were determined by several testing institutes for a period of 3 years. The investigated sheet steels differ with regard to the microstructure and the steel concept. Beside several ferritic steels, multiphase steels like dual phase-, complex phase-and TRIP steels as well as 2 austenitic stainless steels were characterised. The starting materials and selected steels with a defined predeformation and heat treatment were investigated. Within this project, the partners developed a testing and documentation precept in which the ways and means were fixed to reach the defined steel condition and to enable a standardised testing and data output for the material database, realised by the automotive industry. Before the actual elastic, plastic and fatique testing, a reception test for all steels was carried out to characterise the materials with regard to the microstructure, surface condition, chemical composition and mechanical properties, obtained in the quasistatic tensile test. The results of the different testing institutes (elastic, plastic and fatique) will be presented in separate publications in detail. As a result of this project it became obvious that the investigated steels can be divided into steel groups which show a similar strain hardening behaviour. Thus, a prediction of mechanical values and flow curves for cognate steels within one steel group seems to be possible. This subject will be the focus of further investigations within the scope of a new project started on January 1 st , 2003.