scholarly journals Hot Deformation Constitutive Equation and Plastic Instability of 30Cr4MoNiV Ultra-High-Strength Steel

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 769
Author(s):  
Gang Chen ◽  
Yuanchao Yao ◽  
Yuzhen Jia ◽  
Bin Su ◽  
Guoyue Liu ◽  
...  
Keyword(s):  
Constitutive Equation ◽  
Strain Rate ◽  
Hot Deformation ◽  
High Strength Steel ◽  
High Strength ◽  
Plastic Instability ◽  
Dynamic Strain ◽  
Stability And Instability ◽  
Ultra High Strength Steel ◽  
The Stability

In this work, the hot deformation behavior of 30Cr4MoNiV ultra-high-strength steel is investigated by isothermal compression tests using the Gleeble-3500 thermal simulation machine (Dynamic Systems Inc., New York, NY, USA) at a temperature range of 1173–1373 K under the strain rate of 0.01–10 s−1. A constitutive equation with strain-dependent constants and processing maps suitable for 30Cr4MoNiV ultra-high-strength steel are established. The results show that the combination of the hyperbolic sine function and the Zener-Hollomon parameter can accurately represent the influences of deformation temperature, strain rate, and strain on the flow stress of the 30Cr4MoNiV ultra-high-strength steel. The applicability of plastic instability criteria such as , , , and the instability parameter ξ are analyzed, the stability and instability regions are clarified accurately, and the optimized processing regions are given in the stability regions. The optimized regions are verified by the uniform equiaxed grains, and the plastic instability is validated by dynamic strain aging and the microstructure of the voids.

scholarly journals Constitutive Analysis on High-Temperature Flow Behavior of 3Cr-1Si-1Ni Ultra-High Strength Steel for Modeling of Flow Stress

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 42 ◽  
Author(s):  
Bingwang Lei ◽  
Gaoqiang Chen ◽  
Kehong Liu ◽  
Xin Wang ◽  
Xiaomei Jiang ◽  
...  
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Constitutive Equations ◽  
High Strength Steel ◽  
Flow Behavior ◽  
High Strength ◽  
Strain Dependence ◽  
Constitutive Analysis ◽  
Ultra High Strength Steel

High-temperature plastic flow is the underlying process that governs the product quality in many advanced metal manufacturing technologies, such as extrusion, rolling, and welding. Data and models on the high-temperature flow behavior are generally desired in the design of these manufacturing processes. In this paper, quantitative constitutive analysis is carried out on 3Cr-1Si-1Ni ultra-high strength steel, which sheds light on the mathematic relation between the flow stress and the thermal-mechanical state variables, such as temperature, plastic strain, and strain rate. Particularly, the hyperbolic-sine equation in combination with the Zener-Hollomon parameter is shown to be successful in representing the effect of temperature and strain rate on the flow stress of the 3Cr-1Si-1Ni steel. It is found that the flow stress of the 3Cr-1Si-1Ni steel is significantly influenced by strain. The strain-dependence on flow stress is not identical at different temperatures and strain rates. In the constitutive model, the influence of strain in the constitutive analysis is successfully implemented by introducing strain-dependent constants for the constitutive equations. Fifth-order polynomial equations are employed to fit the strain-dependence of the constitutive constant. The proposed constitutive equations which considers the compensation of strain is found to accurately predict flow stress of the 3Cr-1Si-1Ni steel at the temperatures ranging from 800 °C to 1250 °C, strain rate ranging from 0.01/s to 10/s, and strain ranging from 0.05 to 0.6.

scholarly journals On the Development of Material Constitutive Model for 45CrNiMoVA Ultra-High-Strength Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 374 ◽  
Author(s):  
Xin Hu ◽  
Lijing Xie ◽  
Feinong Gao ◽  
Junfeng Xiang
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
High Strength Steel ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Model Parameters ◽  
Hopkinson Pressure Bar ◽  
Simulation Accuracy ◽  
Ultra High Strength Steel ◽  
Split Hopkinson

For the implementation of simulations for large plastic deformation processes such as cutting and impact, the development of the constitutive models for describing accurately the dynamic plasticity and damage behaviors of materials plays a crucial role in the improvement of simulation accuracy. This paper focuses on the dynamic behaviors of 45CrNiMoVA ultra-high-strength torsion bar steel. According to investigation of the Split-Hopkinson pressure bar (SHPB) and Split-Hopkinson tensile bar (SHTB) tests at different strain rate and different temperatures, 45CrNiMoVA ultra-high-strength steel is characterized by strain hardening, strain-rate hardening and thermal softening effects. Based on the analysis on the mechanism of the experimental results and the limitation of classic Johnson-Cook (J-C) constitutive model, a modified J-C model by considering the phase transition at high temperature is established. The multi-objective optimization fitting method was used for fitting model parameters. Compared with the classic J-C constitutive model, the fitting accuracy of the modified J-C model significantly improved. In addition, finite element simulations for SHPB and SHTB based on the modified J-C model are conducted. The SHPB stress-strain curves and the fracture morphology of SHTB samples from simulations are in good agreement with those from tests.

Dynamic Tensile Behaviour and Full Field Strain Measurement of High Strength Steel

2013 ◽  
Vol 275-277 ◽  
pp. 1859-1865 ◽  
Author(s):  
Jin Gui Qin ◽  
Fang Yun Lu ◽  
Yu Liang Lin ◽  
Xue Jun Wen ◽  
Ming Zu Liang
Keyword(s):  
Strain Rate ◽  
High Strength Steel ◽  
Testing Machine ◽  
High Strength ◽  
Image Correlation ◽  
Dynamic Strain ◽  
Uniaxial Tensile ◽  
Tensile Behaviour ◽  
High Speed Photography ◽  
Full Field

Uniaxial tensile tests were conducted on high strength steel 600 (HS600) in Split-Hopkinson Tension Bar at different strain rates in the range of 1100 to 3200s-1and in electromechanical universal testing machine at the strain rate of 1.1×10-3s-1. Digital image correlation was used together with high-speed photography to obtain full-field displacement and strain in the tensile specimens at dynamic strain rate tests. This high strength steel shows significant strain rate sensitivity. Based on the experimental results, the material parameters of Johnson-Cook model are determined. This model fits the experimental data well in the plastic zone.

A Study at the Workability of Ultra-High Strength Steel Sheet by Processing Maps on the Basis of DMM

2017 ◽  
Vol 36 (7) ◽  
pp. 657-667 ◽  
Author(s):  
Yu Feng Xia ◽  
Shuai Long ◽  
Tian-Yu Wang ◽  
Jia Zhao
Keyword(s):  
Activation Energy ◽  
Strain Rate ◽  
High Strength Steel ◽  
High Strength ◽  
Strain Rate Range ◽  
Diffusion Activation Energy ◽  
Processing Maps ◽  
Rate Range ◽  
Temperature Range ◽  
Ultra High Strength Steel

AbstractThe hot workability of the ultra-high strength steel BR1500HS has been investigated by processing maps. A series of hot deformation tensile tests were carried out on a Gleeble-3500 thermal simulator in the deformation temperature range of 773–1,223 K and strain rate range of 0.01–10 s–1. The obtained flow stress curves reveal that the peak stress increases with the rising of strain rate and decreases with the rising of temperature. Based on dynamic materials model (DMM), the processing maps at the strains of 0.05, 0.10 and 0.15 were developed, and the optimum hot working conditions were recommended as the temperature range of 1,200–1,223 K and the strain rate range of 0.01–0.1 s–1, where the peak power dissipation efficiency is about 37 % revealing the occurrence of typical dynamic recrystallization (DRX). The main instability defects are deformation twinning and micro-crack occurring mainly at the temperature range of 773–873 K with the strain rate higher than 1 s–1. In order to deeply understand the microstructure mechanisms, the Zener–Hollomon parameter is solved, and then the self-diffusion activation energy is compared with the apparent activation energy Q at different deformation temperatures and strain rates.

Dynamically recrystallized austenitic grain in a low carbon advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions

2012 ◽  
Vol 1485 ◽  
pp. 143-148 ◽  
Author(s):  
I. Mejía ◽  
E. García-Mora ◽  
G. Altamirano ◽  
A. Bedolla-Jacuinde ◽  
J. M. Cabrera
Keyword(s):  
Grain Size ◽  
Hot Deformation ◽  
High Strength Steel ◽  
Picric Acid ◽  
True Strain ◽  
Research Work ◽  
High Strength ◽  
Low Carbon ◽  
Ultra High Strength Steel ◽  
Wide Range

ABSTRACTThis research work studies the dynamically recrystallized austenitic grain size (Drec) in a new family of low carbon NiCrCuV advanced ultra-high strength steel (A-UHSS) microalloyed with boron under hot deformation conditions. For this purpose, uniaxial hot-compression tests are carried out in a low carbon A-UHSS microalloyed with different amounts of boron (14, 33, 82, 126 and 214 ppm) over a wide range of temperatures (950, 1000, 1050 and 1100°C) and constant true strain rates (10−3, 10−2and 10−1s−1). Deformed samples are prepared and chemically etched with a saturated aqueous picric acid solution at 80°C in order to reveal theDrecand examined by light optical (LOM) and scanning electron microscopy (SEM). TheDrecis related to the Zener-Hollomon parameter (Z), and thereafter theDrecdivided by Burger's vector (b) is related to the steady state stress (σss) divided by the shear modulus (µ) (Derby model). Results shown that theDrecin the current steels is fine (≈ 23 μm) and almost equiaxed, and the recrystallized grain size-flow stress relationship observed after of plastic deformation is consistent with the general formulation proposed by Derby. It is corroborated that boron additions to the current A-UHSS do not have meaningful influence on theDrec.

Modeling the Hot Tensile Flow Behaviors at Ultra-High-Strength Steel and Construction of Three-Dimensional Continuous Interaction Space for Forming Parameters

2017 ◽  
Vol 36 (1) ◽  
pp. 29-43 ◽  
Author(s):  
Guo-zheng Quan ◽  
Zong-yang Zhan ◽  
Tong Wang ◽  
Yu-feng Xia
Keyword(s):  
Strain Rate ◽  
High Strength Steel ◽  
Three Dimensional ◽  
High Strength ◽  
Interaction Space ◽  
True Stress ◽  
Ann Model ◽  
Ultra High Strength Steel ◽  
Strain Data ◽  
Continuous Interaction

AbstractThe response of true stress to strain rate, temperature and strain is a complex three-dimensional (3D) issue, and the accurate description of such constitutive relationships significantly contributes to the optimum process design. To obtain the true stress–strain data of ultra-high-strength steel, BR1500HS, a series of isothermal hot tensile tests were conducted in a wide temperature range of 973–1,123 K and a strain rate range of 0.01–10 s−1 on a Gleeble 3800 testing machine. Then the constitutive relationships were modeled by an optimally constructed and well-trained backpropagation artificial neural network (BP-ANN). The evaluation of BP-ANN model revealed that it has admirable performance in characterizing and predicting the flow behaviors of BR1500HS. A comparison on improved Arrhenius-type constitutive equation and BP-ANN model shows that the latter has higher accuracy. Consequently, the developed BP-ANN model was used to predict abundant stress–strain data beyond the limited experimental conditions. Then a 3D continuous interaction space for temperature, strain rate, strain and stress was constructed based on these predicted data. The developed 3D continuous interaction space for hot working parameters contributes to fully revealing the intrinsic relationships of BR1500HS steel.

scholarly journals Dynamic Behaviors and Microstructure Evolution of Iron–Nickel Based Ultra-High Strength Steel by SHPB Testing

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 62 ◽  
Author(s):  
Hongge Fu ◽  
Xibin Wang ◽  
Lijing Xie ◽  
Xin Hu ◽  
Usama Umer ◽  
...  
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
High Strength Steel ◽  
High Strain ◽  
High Strength ◽  
Compression Tests ◽  
Static Compression ◽  
Dynamic Behaviors ◽  
Ultra High Strength Steel ◽  
Iron Nickel

Iron–nickel based ultra-high strength steel (wt. 18~20% Ni) is characterized by its high strength and low thermal conductivity, and is normally used to make key components by forming and machining processes. The optimization of these processes is based on a deep understanding of the mechanical and dynamic behaviors under high strain, high strain rate, and high temperature. In this paper, the relationship of stress to strain, strain rate, and temperature is systematically investigated by the dynamic compression tests combined with quasi-static compression tests, and the hardening and softening is associated with the transformation in microstructures. According to the analysis, dynamic recrystallization around 600 °C is assumed to be one important influencing factor, hence hot deformation equations are established and the critical strain for dynamic recrystallization and the volume fraction of the dynamic recrystallized grains are defined.

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