Experimental Investigation of Springback Variation in Forming of High Strength Steels

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Peng Chen ◽  
Muammer Koç ◽  
Michael L. Wenner
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Friction Condition ◽  
System Level ◽  
Process Conditions ◽  
Dual Phase ◽  
Blank Holder ◽  
Automotive Body ◽  
Aluminum And Magnesium Alloys ◽  
Springback Prediction

The use of high strength steels (HSSs) in automotive body structures is a prominent method of reducing vehicle weight as an alternative to use of aluminum and magnesium alloys. However, parts made of HSSs demonstrate more springback than parts made of mild steels do. Moreover, variations in the incoming material, friction, and other process conditions cause variations in the springback characteristics, which prevent the practical applicability of the springback prediction and compensation techniques. Consequently, it leads to amplified variations and quality issues during assembly of the stamped components. The objective of this study is to investigate and gain an understanding of the variation of springback in the forming of HSSs. Two sets of experiments were conducted to analyze the influence of the material property (dual-phase steels from different suppliers), lubrication, and blank holder pressure on the springback variation. The experimental results showed that the variation in the incoming blank material is the most important factor. In summary, the thicker the blank is, the less the springback variation. On the other hand, blanks without a coating show less springback variation. The application of lubricant helps us to reduce springback variation, although it actually increases the springback itself. The more uniform the friction condition, the less the springback variation. The influence of blank holder pressure on the springback variation is not distinguishable from the system-level noise in our experiment.

Texture analysis and joint performance of laser-welded similar and dissimilar dual-phase and complex-phase ultra-high-strength steels

2021 ◽  
Vol 174 ◽  
pp. 111035
Author(s):  
Ajit Kumar Pramanick ◽  
Hrishikesh Das ◽  
Ji-Woo Lee ◽  
Yeyoung Jung ◽  
Hoon-Hwe Cho ◽  
...  
Keyword(s):  
Texture Analysis ◽  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Complex Phase ◽  
Joint Performance ◽  
Ultra High Strength Steels

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

Metals ◽  
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.

Evaluation of Formability Under Different Deformation Modes for TWIP900 Steel

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Suleyman Kilic ◽  
Fahrettin Ozturk
Keyword(s):  
Twip Steel ◽  
High Strength Steels ◽  
High Strength ◽  
Material Model ◽  
Deformation Analysis ◽  
Advanced High Strength Steels ◽  
Element Simulation ◽  
Springback Prediction ◽  
Deformation Modes ◽  
Prediction Capability

Automotive manufacturers always seek high strength and high formability materials for automotive bodies. Advanced high strength steels (AHSS) are excellent candidates for this purpose. These steels generally show a reasonable degree of formability, in addition to their high strength. One particular type is the twinning-induced plasticity (TWIP) steel, which is a high manganese austenite steel, and represents a second generation in AHSS. In this study, comprehensive deformation analysis of TWIP900CR steel including tensile, bending, Erichsen, and deep drawing of cylindrical cups tests is made. Finite element simulation of U and V shaped bending processes is also performed. Results indicate that the TWIP steel has good mechanical properties and high formability. However, springback is quite significant. The coining force should be considered in order to reduce the amount of springback. For springback prediction, it is found that the Yld2000-2d material model has better prediction capability than the Hill48 model.

The influence of Mn Content on the wettability of dual-phase high-strength steels by liquid Zn—0.23 % Al

2012 ◽  
Vol 47 (24) ◽  
pp. 8477-8482 ◽  
Author(s):  
Yunkyum Kim ◽  
Joonho Lee ◽  
Sun-Ho Jeon ◽  
Kwang-Geun Chin
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Mn Content

Effect of Si content on wettability of dual phase high strength steels by liquid Zn-0.23 wt.%Al

2011 ◽  
Vol 17 (4) ◽  
pp. 607-611 ◽  
Author(s):  
Yunkyum Kim ◽  
Joonho Lee ◽  
Joongchul Park ◽  
Sun-Ho Jeon
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Si Content

Experimental Investigations on Wear Resistance Characteristics of Alternative Die Materials for Stamping of Advanced High Strength Steels (AHSS)

2008 ◽  
Author(s):  
O¨mer Necati Cora ◽  
Muammer Koc¸
Keyword(s):  
Wear Resistance ◽  
Surface Hardness ◽  
High Strength Steels ◽  
High Strength ◽  
Wear Testing ◽  
Experimental Investigations ◽  
Advanced High Strength Steels ◽  
Automotive Body ◽  
Die Materials ◽  
Aisi D2

Newer sheet alloys (such as Al, Mg, and advanced high strength steels) are considered for automotive body panels and structural parts to achieve lightweight construction. However, in addition to issues with their limited formability and high springback, tribological conditions due to increased surface hardness and higher work hardening effect necessitate the use of improved alternative die materials, coatings, lubricants to minimize the wear-related issues in stamping of such lightweight materials. This study aims to investigate and compare the wear performances of seven (7) different die materials (AISI D2, Vanadis 4, Vancron 40, K340 ISODUR, Caldie, Carmo, 0050A) using a newly developed wear testing method and device. We used DP600 sheets in the tests. Our results showed that almost all of the recently developed specially-alloyed die materials demonstrated higher wear resistance performance when compared with the performance of AISI D2 die material.

Niobium Containing Advanced High Strength Steels for Automotive Applications – Processing, Microstructure, and Properties

2013 ◽  
Vol 773-774 ◽  
pp. 325-335 ◽  
Author(s):  
Debanshu Bhattacharya
Keyword(s):  
Automotive Industry ◽  
Fuel Efficiency ◽  
High Strength Steels ◽  
High Strength ◽  
Dual Phase ◽  
Trip Steels ◽  
Advanced High Strength Steels ◽  
Energy Absorbing ◽  
Bake Hardenability ◽  
Very High

Two major drivers for the use of advanced steels in the automotive industry are fuel efficiency and increased safety performance. Fuel efficiency is mainly a function of weight of steel parts, which in turn, is controlled by gauge and design. Safety is determined by the energy absorbing capacity of the steel used to make the part. All of these factors are incentives for the automobile manufacturers to use Advanced High Strength Steels (AHSS) to replace the conventional steels used to manufacture automotive parts in the past. AHSS is a general term used to describe various families of steels. The most common AHSS is the dual-phase steel that consists of a ferrite-martensite microstructure. These steels are characterized by high strength, good ductility, low tensile to yield strength ratio and high bake-hardenability. Another class of AHSS is the complex-phase or multi-phase steel which has a complex microstructure consisting of various phase constituents and a high yield to tensile strength ratio. Transformation Induced Plasticity (TRIP) steels is another class of AHSS steels finding interest among the U.S. automakers. These steels consist of a ferrite-bainite microstructure with significant amount of retained austenite phase and show the highest combination of strength and elongation, so far, among the AHSS in use. High level of energy absorbing capacity combined with a sustained level of high n value up to the limit of uniform elongation as well as high bake hardenability make these steels particularly attractive for safety critical parts and parts needing complex forming. A relatively new class of AHSS is the Quenching and Partitioning (Q&P) steels. These steels seem to offer higher ductility than the dual-phase steels of similar strengths or similar ductility as the TRIP steels at higher strengths. Finally, martensitic steels with very high strengths are also in use for certain parts. The most recent initiative in the area of AHSS is the so-called 3rd Generation AHSS. These steels are designed to fill the region between the dual-phase/TRIP and the Twin Induced Plasticity (TWIP) steels with very high ductility at strength levels comparable to the conventional AHSS. Enhanced Q&P steels may be one method to achieve this target. Other ideas include TRIP assisted dual phase steels, high manganese steels and higher carbon TRIP type steels. In this paper, some of the above families of advanced high strength steels for the automotive industry will be discussed with particular emphasis on the role of niobium.

Dissimilar Material Joint Strength and Structure for Friction Stir Forming Process

2014 ◽  
Author(s):  
Kenneth A. Ogata ◽  
Sladjan Lazarevic ◽  
Scott F. Miller
Keyword(s):  
Failure Modes ◽  
Dissimilar Materials ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Process ◽  
Experimental Conditions ◽  
Friction Stir ◽  
Automotive Body ◽  
Neck Fracture ◽  
Ultra High Strength Steels

Mass reduction of automotive body structures is a critical part of achieving reduced CO2 emissions in the automotive industry. There has been significant work on the application of ultra high strength steels and aluminum alloys. However, the next paradigm is the integrated use of both materials, which creates the need to join them together. Friction stir forming is a new environmentally benign manufacturing process for joining dissimilar materials. The concept of this process is stir heating one material and forming it into a mechanical interlocking joint with the second material. In this research the process was experimentally analyzed in a computer numerical controlled machining center between aluminum and steel work pieces. The significant process parameters were identified and their optimized settings for the current experimental conditions defined using a design of experiments methodology. Three failure modes were identified (neck fracture, aluminum sheet peeling, and bonding delamination i.e. braze fracture). The overall joint structure and grain microstructure were mapped along different stages of the friction stir forming process. Two layers were formed within the aluminum, the thermo-mechanical affected zone that had been deformed due to the contact pressure and angular momentum of the tool, and the heat affected deformation zone that deformed into the cavity.

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