Numerical Analysis and Experimental Validation of the Thermo-Mechanical Flow Behaviour of the Hot Stamping Steel MBW® 1500

2015 ◽  
Vol 639 ◽  
pp. 213-220
Author(s):  
Bhargav Potdar ◽  
Stéphane Graff ◽  
Björn Kiefer
Keyword(s):  
Elevated Temperatures ◽  
Hot Stamping ◽  
Tensile Tests ◽  
Flow Behaviour ◽  
Boron Steel ◽  
Virtual Design ◽  
Flow Curves ◽  
Rate Dependent ◽  
Important Input ◽  
Strain Paths

In virtual design of the hot stamping process, a reliable description of the material flow behaviour is an important input to ensure accurate estimations of the parts feasibility. Currently, to characterise the hot stamping material’s flow behaviour at elevated temperatures, tensile and upsetting tests are available. The measurement of the flow behaviour out of such tests, which is generally temperature and strain rate dependent, still remains a complex task. Therefore traditional methods to measure flow curves out of such measurements are not necessarily precise enough. In this contribution the authors focus on non-isothermal conductive tensile tests of the manganese-boron steel MBW® 1500 in order to understand its flow behaviour at elevated temperature. Numerical calculations using Finite Element Method (FEM) of the tests itself with correct boundary conditions as well as for all necessary phenomena are used to identify accurately the material’s flow curves by use of inverse optimisation. Finally, for validation purpose the identified flow curves out of the optimisation method were used to simulate the hot stamping of two different parts. Both geometries were chosen such that various strain paths are covered i.e. uniaxial tension to plane strain.

scholarly journals Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 884 ◽  
Author(s):  
Seyed Vahid Sajadifar ◽  
Emad Scharifi ◽  
Ursula Weidig ◽  
Kurt Steinhoff ◽  
Thomas Niendorf
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Forming Process ◽  
Softening Mechanism ◽  
Rate Dependent ◽  
Heat Treated ◽  
Different Temperatures ◽  
Die Forming

This study focuses on the high temperature characteristics of thermo-mechanically processed AA7075 alloy. An integrated die forming process that combines solution heat treatment and hot forming at different temperatures was employed to process the AA7075 alloy. Low die temperature resulted in the fabrication of parts with higher strength, similar to that of T6 condition, while forming this alloy in the hot die led to the fabrication of more ductile parts. Isothermal uniaxial tensile tests in the temperature range of 200–400 °C and at strain rates ranging from 0.001–0.1 s−1 were performed on the as-received material, and on both the solution heat-treated and the thermo-mechanically processed parts to explore the impacts of deformation parameters on the mechanical behavior at elevated temperatures. Flow stress levels of AA7075 alloy in all processing states were shown to be strongly temperature- and strain-rate dependent. Results imply that thermo-mechanical parameters are very influential on the mechanical properties of the AA7075 alloy formed at elevated temperatures. Microstructural studies were conducted by utilizing optical microscopy and a scanning electron microscope to reveal the dominant softening mechanism and the level of grain growth at elevated temperatures.

scholarly journals Measurement and Analysis of Heterogeneous Strain Fields in Uniaxial Tensile Tests for Boron Steel Under Hot Stamping Conditions

2020 ◽  
Vol 60 (9) ◽  
pp. 1289-1300
Author(s):  
R. Zhang ◽  
Z. Shao ◽  
J. Lin ◽  
T. A. Dean
Keyword(s):  
Temperature Gradient ◽  
Hot Stamping ◽  
Tensile Tests ◽  
Gauge Length ◽  
Image Correlation ◽  
Effect Of Temperature ◽  
Uniaxial Tensile ◽  
Boron Steel ◽  
Strain Fields ◽  
Dog Bone

Abstract Background A significant amount of uniaxial tensile tests has been carried out using Gleeble systems to investigate the viscoplastic deformation of boron steel (22MnB5) under hot stamping conditions. However, due to heat loss through the end clamps, a temperature gradient in the reduced parallel section of dog-bone shaped specimens is inevitable. Objective In the work reported in this paper, the effect of temperature gradient on measured outcomes is examined. Methods Uniaxial tensile tests on 1.5 mm thick boron steel specimens are carried out, under hot stamping conditions and strain fields are quantified using the digital image correlation (DIC) technique. The effect of gauge length on the properties of boron steel, as calculated from observed test results, is determined. Results Compared with the test at room temperature, a bell-shaped strain distribution occurs within the gauge length even before the appearance of the maximum load. Also, average strain within the gauge length, especially in the later stages, changes with gauge length within the investigated range, and thus, different engineering stress-strain curves and fracture strains are determined. In addition, normalized strain rate is significantly dependent on gauge length, which results in over 16% difference among the computed flow stresses by using a unified constitutive model. Conclusions The characterized properties of the material are dependent on gauge length and thus, a testing standard for measuring thermal-mechanical data of materials by using a Gleeble need to be defined.

Studies of the thermo-mechanical material response of a Boron steel by inverse modelling

2004 ◽  
Vol 120 ◽  
pp. 625-633
Author(s):  
P. Åkerström ◽  
M. Oldenburg
Keyword(s):  
Elevated Temperatures ◽  
Mechanical Response ◽  
Hot Stamping ◽  
Boron Steel ◽  
Compression Tests ◽  
Object Function ◽  
Austenitic Phase ◽  
Material Response ◽  
Tension Tests ◽  
Complementary Approach

In numerical forming simulations of the hot stamping process, the lack of reliable material data, especially at higher temperatures gives quite rough estimations of the stamping forces, strains, residual stresses and achieved final product shape. Traditionally, the material is characterised by several isothermal compression or tension tests at elevated temperatures and strain rates. The present work have pointed out an alternative/complementary approach to reduce the number of experiments and to obtain good results by using Gleeble compression tests at continuous cooling with different compression start temperatures. The isothermal mechanical response was established by means of inverse modeling, with start values obtained from isothermal test results. Three different functions describing the flow stress as function of temperature and plastic strain have been tested and compared in usefulness for the steel grade used. The main object function consists of three parts, one from each compression start temperature. The object function in the inverse problem is based on the deviation in compression force-displacement data and radial displacement at the mid point of the specimen. Minimisation of the objective function with respect to the material parameters were performed using an in-house optimization software which is based on the subplex method. The established material response has been evaluated by comparison with data from a separate forming test. For the boron steel in the austenitic phase, the Nemat-Nasser model was found to describe the material response with acceptable agreement within the temperature and strain interval studied in the experimental validation.

Mechanical Properties and Plastic Anisotropy of the Quenchenable High Strength Steel 22MnB5 at Elevated Temperatures

2007 ◽  
Vol 344 ◽  
pp. 79-86 ◽  
Author(s):  
Marion Merklein ◽  
Jürgen Lecher ◽  
Vera Gödel ◽  
Stefania Bruschi ◽  
Andrea Ghiotti ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Hot Stamping ◽  
Plastic Anisotropy ◽  
High Strength ◽  
Tensile Tests ◽  
Inductive Heating ◽  
Processing Conditions ◽  
The Press ◽  
The University

Within the scope of this paper, the formability of the press hardenable steel 22MnB5 will be investigated with regard to its anisotropic properties at elevated temperatures under the processing conditions of hot stamping. Two different experimental setups have been realized, one at the University of Erlangen-Nuremberg using conductive heating, and the other one at the University of Padova using inductive heating. Both of these equipments enable the characterization of the material anisotropy behavior by performing uniaxial, hot tensile tests in the range of hot stamping temperatures.

Indirect Hot Stamping of Boron Steel 22MnB5 for an Upper B-Pillar

2011 ◽  
Vol 314-316 ◽  
pp. 703-708
Author(s):  
Jun Ying Min ◽  
Jian Ping Lin ◽  
Li Jiu Xin ◽  
Jia Yue Li
Keyword(s):  
Phase Transformation ◽  
Cooling Rate ◽  
Hot Stamping ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Boron Steel ◽  
Heating Process ◽  
Air Cooling ◽  
Stamping Process ◽  
Vehicle Components

During the indirect hot stamping process of boron steel, the pre-deformed component undergoes air cooling, one-side-contact cooling and both-side-contact cooling phases successively. The effects of pre-deformation and cooling rate on the phase transformation should be understood before conducting indirect hot stamping experiments of vehicle components. Uniaxial tensile tests of boron steel at RT were carried out to obtain specimens with different pre-strain levels. Then they were heated to 900°C according to the indirect hot stamping process and quenching tests were performed on them at different cooling rates. Metallographic observations were performed on the quenched specimens and their hardness was measured. The results show that the pre-strain at RT has little influence on the phase transformation of boron steel. This is due to the dislocation structure introduced by deformation at RT recovered during the heating process and it is good for the indirect hot stamping. Upper B-pillar parts were first cold pre-formed, and then were heated and hot stamped. The microstructure and hardness results at different locations on the indirect hot stamped components are demonstrated qualified.

Arrhenius-Type Constitutive Equation Model of Superplastic Deformation Behaviour of Different Titanium Based Alloys

2018 ◽  
Vol 385 ◽  
pp. 45-52 ◽  
Author(s):  
Ahmed O. Mosleh ◽  
Anastasia V. Mikhaylovskaya ◽  
Anton D. Kotov ◽  
Vladimir K. Portnoy
Keyword(s):  
Strain Rate ◽  
Superplastic Deformation ◽  
Elevated Temperatures ◽  
Deformation Behaviour ◽  
Constitutive Models ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Equation Model ◽  
Flow Behaviour ◽  
Forming Process

Modelling and predicting the flow behaviour of metallic materials subjected to superplastic deformation is mandatory for providing useful information about the metal forming process. This information helps the designers to reduce the manufacturing time and costs by choosing appropriate deformation conditions based on the models results. The study developed a constitutive model to predict the flow behaviour of various Ti-based alloys (Ti-2.5Al-1.8Mn, Ti-6Al-4V and Ti-4Al-1V-3Mo) at elevated temperatures. The constant strain rate tests within the superplastic temperature and the strain rate ranges for each alloy were performed. The experimental tensile tests results were used to develop the hyperbolic sine Arrhenius-type constitutive models for each alloy. The performance of the developed model for each alloy was evaluated regarding the correlation coefficient (R), the mean absolute relative error (AARE) and the root mean square error (RMSE). The results revealed that the predicted flow stresses have a good agreement with the experimental flow stresses for the studied alloys.

Effect of the Si and Al Content in Ferritic Electrical Steels on the Flow Behaviour and Dynamic Softening in Hot Rolling

2013 ◽  
Vol 762 ◽  
pp. 747-752
Author(s):  
Pablo Rodriguez-Calvillo ◽  
M. Perez-Sine ◽  
Jürgen Schneider ◽  
Harti Hermann ◽  
Jose María Cabrera ◽  
...  
Keyword(s):  
Hot Rolling ◽  
Flow Behaviour ◽  
Flow Curves ◽  
Electrical Steels ◽  
Al Content ◽  
Wide Range ◽  
Dynamic Softening ◽  
Hot Rolling Conditions ◽  
Hardening And Softening

FeSi steels with and without addition of Al are widely used as electrical steels. To improve the knowledge of the effects by the addition of Si and Al on the hardening and softening under hot rolling conditions, the behaviour of the flow curves in a wide range of temperatures and deformation velocities have been studied.

scholarly journals Mechanical and thermal stability of retained austenite in plastically deformed bainite-based TRIP-aided medium-Mn steels

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Aleksandra Kozłowska ◽  
Adam Grajcar ◽  
Aleksandra Janik ◽  
Krzysztof Radwański ◽  
Ulrich Krupp ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Retained Austenite ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Mechanical Stability ◽  
Electron Backscatter Diffraction ◽  
Cost Effective ◽  
Tensile Tests ◽  
Thermal Stability Of

AbstractAdvanced medium-Mn sheet steels show an opportunity for the development of cost-effective and light-weight automotive parts with improved safety and optimized environmental performance. These steels utilize the strain-induced martensitic transformation of metastable retained austenite to improve the strength–ductility balance. The improvement of mechanical performance is related to the tailored thermal and mechanical stabilities of retained austenite. The mechanical stability of retained austenite was estimated in static tensile tests over a wide temperature range from 20 °C to 200 °C. The thermal stability of retained austenite during heating at elevated temperatures was assessed by means of dilatometry. The phase composition and microstructure evolution were investigated by means of scanning electron microscopy, electron backscatter diffraction, X-ray diffraction and transmission electron microscopy techniques. It was shown that the retained austenite stability shows a pronounced temperature dependence and is also stimulated by the manganese addition in a 3–5% range.

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