scholarly journals Microstructure–property relation and machine learning prediction of hole expansion capacity of high-strength steels

2021 ◽  
Author(s):  
Wei Li ◽  
Martina Vittorietti ◽  
Geurt Jongbloed ◽  
Jilt Sietsma
Keyword(s):  
Machine Learning ◽  
High Strength Steels ◽  
High Strength ◽  
Experimental Procedure ◽  
Hole Expansion ◽  
Metal Sheets ◽  
Chemical Content ◽  
Property Relation ◽  
Expansion Capacity ◽  
The Relationship

Abstract The relationship between microstructure features and mechanical properties plays an important role in the design of materials and improvement of properties. Hole expansion capacity plays a fundamental role in defining the formability of metal sheets. Due to the complexity of the experimental procedure of testing hole expansion capacity, where many influencing factors contribute to the resulting values, the relationship between microstructure features and hole expansion capacity and the complexity of this relation is not yet fully understood. In the present study, an experimental dataset containing the phase constituents of 55 microstructures as well as corresponding properties, such as hole expansion capacity and yield strength, is collected from the literature. Statistical analysis of these data is conducted with the focus on hole expansion capacity in relation to individual phases, combinations of phases and number of phases. In addition, different machine learning methods contribute to the prediction of hole expansion capacity based on both phase fractions and chemical content. Deep learning gives the best prediction accuracy of hole expansion capacity based on phase fractions and chemical composition. Meanwhile, the influence of different microstructure features on hole expansion capacity is revealed. Graphical abstract

Effect of Surface Enlargement and of Viscosity of Lubricants on Friction Behaviour of Advanced High Strength Steel Material during Deep Drawing

2014 ◽  
Vol 1018 ◽  
pp. 253-260 ◽  
Author(s):  
Markus Singer ◽  
Mathias Liewald
Keyword(s):  
Friction Coefficient ◽  
Deep Drawing ◽  
Sheet Material ◽  
High Strength Steels ◽  
High Strength ◽  
Work Piece ◽  
Advanced High Strength Steels ◽  
Steel Material ◽  
The Relationship

Increasing demands on vehicle safety and weight reduction in the automotive industry lead to an increased use of “advanced high strength steels” for car body manufacturing purposes. Mentioned material grades are having high levels of tensile strength and are often used in conventional sheet metal forming processes. One of the most significant factors on quality of stamped components as well as its manufacturing process robustness is the friction between tool and sheet material. During the deep drawing process, superposition of tensile stresses is causing enlargement of the sheet surface by a few percent. This effect can damage the zinc layer. Due to that fact, lubricant has to keep tool and work piece separated in order to prevent adhesion and abrasion. For that very reason, sufficient amount of lubricant has to be applied onto the surface texture reservoirs. Furthermore, the viscosity of lubricant is mainly influencing its ability of wetting the surface. The aim of this study is to define the relationship between friction coefficient, surface enlargement and lubrication having different viscosities. In this investigation the same amount of lubricant with viscosity of ϑ=65 mm2/s, ϑ=200 mm2/s and ϑ=400 mm2/s was applied on strips made out of DP1000 and DC04 steel. Then, the strips were stretched uniaxially, and restraining forces were measured by strip draw test considering constant surface pressure and drawing speed. In this paper, the correlation between friction coefficient, viscosity and surface enlargement for two different sheet material grades is shown.

Observations on the Stress Corrosion Crack Propagation Characteristics of High Strength Steels

CORROSION ◽  
1971 ◽  
Vol 27 (11) ◽  
pp. 471-477 ◽  
Author(s):  
C. S. CARTER
Keyword(s):  
Stress Intensity ◽  
Stress Corrosion ◽  
Stress Corrosion Crack ◽  
Crack Velocity ◽  
High Strength Steels ◽  
High Strength ◽  
Testing Procedure ◽  
Crack Morphology ◽  
Wide Range ◽  
The Relationship

Abstract The relationship between stress corrosion crack velocity and crack-tip stress intensity is discussed. In most high strength steels, there is a wide range of stress intensity over which crack velocity is essentially constant. Methods of estimating this velocity are described. Values for a variety of high strength steels are presented and the effects of metallurgical variables are indicated. Implications with regard to testing procedure, crack morphology, and service performance are outlined.

scholarly journals Hole Expansion Characteristics of Ultra High Strength Steels

2014 ◽  
Vol 81 ◽  
pp. 718-723 ◽  
Author(s):  
Xinping Chen ◽  
Haoming Jiang ◽  
Zhenxiang Cui ◽  
Changwei Lian ◽  
Chao Lu
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Hole Expansion ◽  
Ultra High Strength Steels

Influence of Microstructure on Damage in Advanced High Strength Steels

2012 ◽  
Vol 706-709 ◽  
pp. 925-930 ◽  
Author(s):  
Frank Hisker ◽  
Richard Thiessen ◽  
Thomas Heller
Keyword(s):  
Work Hardening ◽  
Tensile Testing ◽  
Failure Modes ◽  
Tensile Elongation ◽  
High Strength Steels ◽  
High Strength ◽  
Body Parts ◽  
Hole Expansion ◽  
Advanced High Strength Steels ◽  
Dp Steels

AHSS (Advanced High Strength Steels) combine high strength and good ductility. Their outstanding forming and work-hardening behavior predestines these steels for fabrication of strength relevant structural elements and automobile body parts. To characterize a material, not only tensile, but also hole-expansion and bending behavior are important and help predict the stretch-flange-formability. In this study, detailed analyses of the correlation between these three tests and the damage mechanisms during forming have been performed for selected steels. The results show that for AHSS one should differentiate between “local” and “global” failure. Furthermore, not only are certain materials more sensitive to local or global damage, but also various testing methods tend to provoke either local or global damage. Tensile testing provokes global failure whereas hole-expansion tends to induce local failure. A specimen fails during bending with a mixture of local and global modes. These failure modes are strongly attributed to the microstructure. DP-steels yield high elongation during tensile testing and poorer hole-expansion values. High-resolution EBSD has revealed that the microstructure of DP-steels is sensitive to localized damage, which is compensated by work-hardening around damaged regions and thus shifts the loading to un-hardened regions. This makes DP-microstructures well-suited to tensile loading but sensitive to hole-expansion. CP-steels of comparable strength show poorer tensile elongation and higher hole-expansion ratios due to a microstructure which is not sensitive to localized failure (but has limited capacity for work-hardening). The failure mode in TRIP-steels exhibits a similar character as in DP-steels, but only after the martensitic transformation of retained austenite.

scholarly journals Correlation Modeling Between Peening-Induced Hardness, Residual Stress and Roughness in Case-Hardened High Strength Steels

2021 ◽  
Author(s):  
Hsin Shen HO ◽  
Cheng LV ◽  
Yonghui HE ◽  
Erliang ZHANG
Keyword(s):  
Residual Stress ◽  
Compressive Residual Stress ◽  
Linear Trend ◽  
Roughness Parameter ◽  
High Strength Steels ◽  
High Strength ◽  
Initial Material ◽  
Material Hardness ◽  
Negative Effect ◽  
The Relationship

The present paper is focused on the investigation of the correlation modeling of hardness and compressive residual stress on the surface and subsurface regions of case-hardened 18CrNiMo7-6 steels subjected to shot peening. The results exhibit that the relationship between hardness and compressive residual stress can reasonably well be approximated by an inverse linear model. The analysis suggests that the slope and y-intercept of the inverse linear trend line can be related to the compressive residual stress level and the initial material hardness, respectively. It is further revealed that the negative effect brought by the peening-induced roughness on the measurement of experimental data computed on the surface can be compensated by performing the normalization using the roughness parameter called the maximum valley height (Sv).

Fracture characteristics of advanced high strength steels during hole expansion test

2020 ◽  
Vol 224 (2) ◽  
pp. 217-233 ◽  
Author(s):  
Vivek Kumar Barnwal ◽  
Shin-Yeong Lee ◽  
Seong-Yong Yoon ◽  
Jin-Hwan Kim ◽  
Frédéric Barlat
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Fracture Characteristics ◽  
Hole Expansion ◽  
Expansion Test ◽  
Advanced High Strength Steels ◽  
Hole Expansion Test

Forming Performance of 800MPa Grade Advanced High Strength Steels

2013 ◽  
Vol 455 ◽  
pp. 173-178 ◽  
Author(s):  
Mei Zhang ◽  
Yu Xiang Ning ◽  
Jun Zhang ◽  
Zi Wan ◽  
Tao Wang
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Expansion Ratio ◽  
Hole Expansion ◽  
Advanced High Strength Steels ◽  
Hsla Steels ◽  
Blank Holding Force ◽  
Hole Expansion Ratio ◽  
Test Hole ◽  
Springback Behavior

800MPa grade Advanced High Strength Steels (AHSS), including Complex Phase steel CP800 and Ferrite-Bainite steel FB800, were chosen to test the forming performance in different test conditions and compared with the reference traditional high strength low alloy (HSLA) steels HR700LA. Tensile test, hole expansion (HE) test, and HAT shape stamping test were taken to investigate the forming performance of the materials. Test results indicated that the studied 800MPa grade AHSS showed a better strength ductility balance compared with the reference steel. Among all the steels researched, FB800 showed the best hole expansion ratio (HER), and CP800 the worst. Springback angles of AHSS after HAT shape stamping tests were markedly smaller than those of HR700LA steels, though the springback angles of HR700LA decreased continuously with blank holding force (BHF) increasing. Steel FB800, CP800S and CP800B had much better shape stability compared with steels HR700LA. AHSS showed much smaller springback behavior under the same stamping condition, especially for steels CP800-B, FB800-2 and FB800-1. When increasing the BHF to 100KN, AHSS showed the largest springback deformation. Among the three kinds of CP800 steels researched, steel CP800-B indicated outstanding springback restrain trend in BHF further increasing attempt. So, springback behavior could be restricted obviously by using a larger BHF in AHSS CP800B forming operations.

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