RESEARCH PAPER Analysis of Yield Criteria and Flow Curves on FLC for TWIP900 Steel S. Kilic 1 & F. Ozturk 2,3 & S. Toros 4 Received: 15 October 2018 /Accepted: 13 May 2020 # The Society for Experimental Mechanics, Inc 2020 Abstract In this study, the applicability of yield criteria and flow curve models to predict forming limit curve (FLC) via the Marciniak- Kuczynski (M-K) model is investigated for TWIP900 steel. Forming limit characteristics of TWIP900 are determined experi- mentally and numerically. The yield criteria of Hill48, Barlat89, YLD2000-2d, and BBC2000 are tested and compared with each other. Results indicate that the YLD2000-2d and the BBC2000 yield criteria are found to be more accurate than the other criteria. The YLD2000 criterion has the best prediction capability with the Krupskowsky flow curve while the BBC2000 model has the best prediction with the Ludwick flow curve model. Keywords Yield criteria . Forming limit curve . TWIP steel . M-K model Introduction Fossil fuel reserves in the world have been swiftly decreased and environmental pollution has dramatically increased. Tremendous amount of efforts have been made in many in- dustries to reduce fuel consumption and reduce carbon diox- ide emission. The automotive industry is one of the major players on the impact of environmental pollution. Recently, the automotive industry has primarily focused on fuel con- sumption reduction of the vehicles by lightening the struc- tures, using hybrid systems in which both fossil fuels and electric power are used with together or electric vehicles which also decrease environmental pollution. However, the travel range of these new hybrid systems is a serious limitation and the investments and investigations on the battery technol- ogies have been increased. The lightening of the system com- ponents in the automotive industry without sacrificing strength is one of the most important research topics for Original Equipment Manufacturers (OEMs) and scientists from past to present. The light vehicle can easily satisfy envi- ronmental regulation, restriction, and minimum emission re- quirements. Advanced High Strength Steels (AHSS) are a commonly used material group for the structural lightening projects since their thinner forms are able to satisfy the desired safety and formability requirements [1]. It is expected that new generation material groups like AHSS or some special non-ferrous materials in the structural lightening projects will have positive impact on carbon emissions without sacrificing safety or even increasing safety requirements. In the automo- tive industry, aluminium-magnesium (Al-Mg) alloys and AHSS are widely considered to reduce the weight of the ve- hicle. In the AHSS group; Dual Phase (DP), TRansformation Induced Plasticity (TRIP), and TWinning Induced Plasticity (TWIP) steels are the most commonly used materials steels. For example, in a hood construction, the use of DP590 steel with a thickness of 0.55 mm instead of BH340 steel with a thickness of 0.7 mm resulted in a 21% reduction in hood weight [2]. Among these materials, TWIP steels are of interest because of their high mechanical properties and formability. TWIP steels which are the second generation of the AHSS, were developed to provide the weight reduction of the vehi- cles. In Fig. 1, the general comparison of the steels is displayed with respect to tensile strength vs. elongation. As can be seen in the figure, it is clear that the main target of steel producers is to increase the strength and formability of the materials. Typical applications of TWIP steels in automotive components are, in A-Pillar, wheelhouse, front side member, wheel, lower control arm, front and rear bumper beams, B- * S. Kilic suleymankilic@ahievran.edu.tr 1 Department of Mechanical Engineering, Kırşehir Ahi Evran University, Kırşehir, Turkey 2 Turkish Aerospace Industries, Inc., Ankara, Turkey 3 Department of Mechanical Engineering, Ankara Yıldırım Beyazıt University, Ankara, Turkey 4 Department of Mechanical Engineering, Omer Halisdemir University, Niğde, Turkey Experimental Techniques https://doi.org/10.1007/s40799-020-00382-9