Microstructure-Based Modeling of the Effect of Inclusion on the Bendability of Advanced High Strength Dual-Phase Steels

Advanced high strength dual-phase steels are one of the most widely sought-after structural materials for automotive applications. These high strength steels, however, are prone to fracture under bending-dominated manufacturing processes. Experimental observations suggest that the bendability of these steels is sensitive to the presence of subsurface non-metallic inclusions and the inclusions exhibit a rather discrete size effect on the bendability of these steels. Following this, we have carried out a series of microstructure-based finite element calculations of ductile fracture in an advanced high strength dual-phase steel under bending. In the calculations, both the dual-phase microstructure and inclusion are discretely modeled. To gain additional insight, we have also analyzed the effect of an inclusion on the bendability of a single-phase material. In line with the experimental observations, strong inclusion size effect on the bendability of the dual-phase steel naturally emerge in the calculations. Furthermore, supervised machine learning is used to quantify the effects of the multivariable input space associated with the dual-phase microstructure and inclusion on the bendability of the steel. The results of the supervised machine learning are then used to identify the contributions of individual features and isolate critical features that control the bendability of dual-phase steels.

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A Unified Model for Plasticity in Ferritic, Martensitic and Dual-Phase Steels

Metals ◽

10.3390/met10060764 ◽

2020 ◽

Vol 10 (6) ◽

pp. 764

Author(s):

Shuntaro Matsuyama ◽

Enrique I. Galindo-Nava

Keyword(s):

Grain Size ◽

Dislocation Density ◽

Carbon Content ◽

Grain Boundaries ◽

Uniform Elongation ◽

High Strength Steels ◽

High Strength ◽

Dual Phase ◽

Dual Phase Steels ◽

Dislocation Generation

Unified equations for the relationships among dislocation density, carbon content and grain size in ferritic, martensitic and dual-phase steels are presented. Advanced high-strength steels have been developed to meet targets of improved strength and formability in the automotive industry, where combined properties are achieved by tailoring complex microstructures. Specifically, in dual-phase (DP) steels, martensite with high strength and poor ductility reinforces steel, whereas ferrite with high ductility and low strength maintains steel’s formability. To further optimise DP steel’s performance, detailed understanding is required of how carbon content and initial microstructure affect deformation and damage in multi-phase alloys. Therefore, we derive modified versions of the Kocks–Mecking model describing the evolution of the dislocation density. The coefficient controlling dislocation generation is obtained by estimating the strain increments produced by dislocations pinning at other dislocations, solute atoms and grain boundaries; such increments are obtained by comparing the energy required to form dislocation dipoles, Cottrell atmospheres and pile-ups at grain boundaries, respectively, against the energy required for a dislocation to form and glide. Further analysis is made on how thermal activation affects the efficiency of different obstacles to pin dislocations to obtain the dislocation recovery rate. The results are validated against ferritic, martensitic and dual-phase steels showing good accuracy. The outputs are then employed to suggest optimal carbon and grain size combinations in ferrite and martensite to achieve highest uniform elongation in single- and dual-phase steels. The models are also combined with finite-element simulations to understand the effect of microstructure and composition on plastic localisation at the ferrite/martensite interface to design microstructures in dual-phase steels for improved ductility.

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Investigation Effect of Spring Back on Bending Test of (DP590) Dual Phase Steel

Journal of Engineering and Science Research ◽

10.26666/rmp.jesr.2018.6.10 ◽

2018 ◽

Vol 2 (6) ◽

pp. 55-62

Author(s):

Muhamad Sani Buang ◽

Keyword(s):

Sheet Metal ◽

Dual Phase Steel ◽

High Strength Steels ◽

High Strength ◽

Bending Test ◽

Dual Phase ◽

Spring Back ◽

Factors Affecting ◽

Advanced High Strength Steels ◽

Fitting In

: The use of advanced high strength steels as a metal in sheet metal forming in automotive industry currently has been increased where Advanced High Strength Steel (AHSS) especially Dual Phase (DP590) Steels have gained a great attention due to a combination of high strength and good formability. However, one of the major constraints in forming AHSS is the occurrence of high spring back caused by elastic relaxation after loading, which causes illness-fitting in part assembly and geometric deviation of the intended design. Spring back is the main problem of defect that occurs at sheet metal after the bending process which creates problems for the parts during the assembly. This paper presents an investigation the effect of spring back on bending test of Dual Phase Steel (DP590). Punch travel and thickness are among factors affecting the spring back behavior. Various parameter value; punch radius (5mm), die radius (5mm), die gap (70mm), thickness of specimen 1mm and 2mm, punch travel/stroke (25%, 50%, 75%, 100%) from 20 mm depth, punch speed (2mm/min) and Orientation of sheet cutting, which is in rolling (00°), diagonal (45°) and transverse (90°). From the analysis of V-bending test punch travel, thickness and orientation of sheet cutting are significant factor that affecting the spring back phenomena. The result form this experiment could be useful for design engineers and manufacturing engineers to make improvement of predict the spring back behavior and also to understanding the material properties of AHSS in order to eliminate spring back and achieve good final product.

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Dual-Phase Steels: The First Family of Advanced High Strength Steels

Reference Module in Materials Science and Materials Engineering ◽

10.1016/b978-0-12-819726-4.00057-0 ◽

2020 ◽

Author(s):

Sébastien Y.P. Allain ◽

Irina Pushkareva ◽

Julien Teixeira ◽

Mohamed Gouné ◽

Colin Scott

Keyword(s):

High Strength Steels ◽

High Strength ◽

Dual Phase ◽

Dual Phase Steels ◽

Advanced High Strength Steels

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Thermomechanical Processing of Medium Manganese Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.90 ◽

2016 ◽

Vol 879 ◽

pp. 90-94 ◽

Cited By ~ 5

Author(s):

Atsushi Ito ◽

Akinobu Shibata ◽

Nobuhiro Tsuji

Keyword(s):

Dual Phase Steel ◽

Thermomechanical Processing ◽

High Strength Steels ◽

High Strength ◽

Heat Treatments ◽

Dual Phase ◽

Advanced High Strength Steels ◽

Ferrite Transformation ◽

Thermomechanical Processes ◽

Manganese Steels

As third generation advanced high strength steels (AHSS) managing both high strength and good ductility/formability, medium manganese steels containing 3-7 wt% Mn have attracted attentions recently. However, the fundamental microstructure evolution during thermomechanical processing and heat treatments in medium-Mn steels is still unclear. In the present study, changes in microstructure and mechanical properties during various heat treatments and thermomechanical processes of 4Mn-0.1%C steel were studied. It was clarified from dilatometric measurements that ferrite transformation in the 4Mn-0.1C steel was quite slow, so that fully martensitic structures were obtained in many cases after cooling from austenite. On the other hand, hot-deformation of austenite greatly accelerated ferrite transformation, and dual phase microstrcutures composed of ferrite and martensite could be obtained. The dual phase steel showed good combinations of high strength and adequate tensile ductility.

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Laser Beam Welding of Advanced High-Strength Steels (Dual Phase Steels)

10.1007/978-981-16-4222-7_16 ◽

2021 ◽

pp. 141-148

Author(s):

P. V. S. Lakshminarayana ◽

Jai Prakash Gautam ◽

P. Mastanaiah ◽

G. Madhusudan Reddy ◽

K. Bhanu Sankara Rao

Keyword(s):

Laser Beam ◽

Laser Beam Welding ◽

High Strength Steels ◽

High Strength ◽

Dual Phase ◽

Dual Phase Steels ◽

Advanced High Strength Steels

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Limit Strains Analysis of Advanced High Strength Steels Sheets Based on Surface Roughness Measurements

Materials Science Forum ◽

10.4028/www.scientific.net/msf.930.349 ◽

2018 ◽

Vol 930 ◽

pp. 349-355

Author(s):

Lílian Barros da Silveira ◽

Luciano Pessanha Moreira ◽

Ladario da Silva ◽

Rafael Oliveira Santos ◽

Fabiane Roberta Freitas da Silva ◽

...

Keyword(s):

Surface Roughness ◽

High Strength Steels ◽

High Strength ◽

Yield Function ◽

Forming Limit ◽

Dual Phase ◽

Dual Phase Steels ◽

Advanced High Strength Steels ◽

Anisotropic Yield Function ◽

Localization Model

The limit strains of dual-phase steels DP600 and 800 were evaluated in this work with a localization model formulated in plane-stress conditions using elasto-plastic constitutive equations. In this model, a geometrical imperfection parameter is defined from the sheet nominal thickness, initial ferrite grain size and average surface roughness. The proposed identification procedure provided a more physically meaning for this parameter and at best more conservative predictions in the drawing Forming Limit Curve (FLC) range of both investigated dual-phase steels. Nevertheless, the corresponding limit strains in the biaxial stretching region are underestimated with the present theoretical model. Thus, more detailed anisotropic yield function and hardening descriptions must be implemented to improve the accuracy of the FLC prediction of advanced high strength steels.

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