Gestamp HardTech

Luleå, Sweden

Gestamp HardTech

Luleå, Sweden
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Golling S.,Lulea University of Technology | Ostlund R.,Gestamp HardTech | Oldenburg M.,Lulea University of Technology
Materials Science and Engineering A | Year: 2016

Hot stamping is a sequential process for formation and heat-treatment of sheet metal components with superior mechanical properties. By applying different cooling rates, the microstructural composition and thus the material properties of steel can be designed. By controlling the cooling rate in different sections of a blank, the material properties can be tailored depending on the desired toughness. Under continuous cooling, various volume fractions of ferrite and bainite are formed depending on the rate of cooling. This paper focuses on the ductile fracture behavior of a thin sheet metal made of low-alloyed boron steel with varying amounts of ferrite and bainite. An experimental setup was applied in order to produce microstructures with different volume fractions of ferrite and bainite. In total, five different test specimen geometries, representing different stress triaxialities, were heat treated and tensile tested. Through full-field measurements, flow curves extending beyond necking and the equivalent plastic strain to fracture were determined. Experimental results were further investigated using a mean-field homogenization scheme combined with local fracture criteria. The mean-field homogenization scheme comprises the influence of microstructure composition and stress triaxiality with usable accuracy, connoting auspicious possibilities for constitutive modeling of hot-stamped components. © 2016 Elsevier B.V.


Sandberg S.,Gestamp HardTech | Lundin M.,Lulea University of Technology | Nasstrom M.,Lulea University of Technology | Lindgren L.-E.,Lulea University of Technology | Berglund D.,Gestamp HardTech
Journal of Engineering Design | Year: 2013

Modern manufacturers rely increasingly on overlapping activities and frequent, bilateral exchange of preliminary information, adding to the complexity of information exchange and general reuse. The approach presented in this paper relies on a reuse process, embedded in the design environment already used, to avoid disrupting the design process and to increase the foundation upon which decisions are made. The proposed approach relies on knowledge-based extensions to commercial CAE systems and 3D CAE models to enable and ensure simulation-driven design capabilities and contextual communication within the early stages of product development. The approach has been shown to increase the simulation-driven capabilities in a business-to-business scenario, and in extension, increase the foundation upon which decisions are made and the likelihood of reaching a feasible and optimal final design. In conclusion, a simulation-driven design approach to product development has to be more than enabled to truly make a difference in the development process. Investigation and evaluations show that supporting tools and relevant information must be made readily available, intuitive, integrated into the environment where they are needed and, ultimately, be perceived as a natural part of daily development in order for them to be accepted and used. © 2013 Copyright Taylor and Francis Group, LLC.


Golling S.,Lulea University of Technology | Ostlund R.,Gestamp HardTech | Oldenburg M.,Lulea University of Technology
Materials Science and Engineering A | Year: 2016

Developments of the hot stamping technology have enabled the production of components with differential microstructure composition and mechanical properties. These can increase the performance of certain crash-relevant automotive structures by combining high intrusion protection and energy absorption. This paper presents a comprehensive experimental investigation on the flow and ductile fracture properties of boron-alloyed steel with a wide range of different microstructure compositions. Three types of dual phase microstructures at three different volume fractions, and one triple phase grade, were generated by thermal treatment. Flow curves extending beyond necking and the equivalent plastic strain to fracture for each grade was determined by tensile testing using full-field measurements. The influence of phase composition and microstructural parameters were further investigated by means of a multi-scale modeling approach based on mean-field homogenization in combination with local fracture criteria. Inter-phase and intra-phase fracture mechanisms were considered by adopting two separate fracture criteria formulated in terms of the local average stress field. The micromechanical model captures with useful accuracy the strong influence of microstructure and processing conditions on the flow and fracture properties, implying promising prospects of mean-field homogenization for the constitutive modeling of hot stamped components. © 2016 Elsevier B.V.

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