scholarly journals Parameters Identification of High Temperature Damage Model of X12 Alloy Steel for Ultra-Supercritical Rotor Using Inverse Optimization Technique

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 695
Author(s):  
Xuewen Chen ◽  
Kexue Du ◽  
Yuqing Du ◽  
Tingting Lian ◽  
Jiqi Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
Alloy Steel ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Forging Process ◽  
Fracture Displacement ◽  
Temperature Damage ◽  
High Temperature Tensile ◽  
Critical Damage

X12 alloy steel is a new generation material for manufacturing ultra-supercritical generator rotors. Cracks will appear on the forgings during the forging process and the rotors will be scrapped in serious cases. To optimize the forging process of the rotor and avoid the occurrence of crack defects in the hot forming process, based on Oyane damage model, a high temperature damage model of X12 alloy steel was proposed by introducing the influences of temperature and strain rate on the damage evolution. A reverse analysis method was proposed to determine the critical damage value of Oyane damage model by comparing experimental and simulated fracture displacement in the tensile tests. Then, the critical damage value was determined as a function of temperature and strain rate. The high temperature damage model was combined to the commercial finite element software FORGE® to simulate the high temperature tensile test. The accuracy of the damage model was verified by comparing the difference of the fracture displacement between simulated and experimental samples. Additionally, as stress triaxiality is a significant factor influencing the damage behavior of ductile materials, the effects of temperature and strain rate on the stress triaxiality of X12 alloy steel was analyzed by simulating the high temperature tensile process, and the damage mechanism of X12 alloy steel under high stress triaxiality was analyzed by SEM (Scanning Electron Microscope).

Study on High Temperature Flow Stress Model of As-cast SA508-3 Low Alloy Steel

2020 ◽  
Vol 831 ◽  
pp. 25-31
Author(s):  
Pan Fei Fan ◽  
Jian Sheng Liu ◽  
Hong Ping An ◽  
Li Li Liu
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Alloy Steel ◽  
Flow Behavior ◽  
Peak Stress ◽  
Stress Model ◽  
Low Alloy Steel ◽  
Two Stage ◽  
Flow Stress Model

In order to obtain the high temperature flow behavior of as-cast SA508-3 low alloy steel, the stress-strain curves of steel are obtained by Gleeble thermal simulation compression test at deformation temperature 800°C-1200°C and strain rate 0.001s-1-1s-1. Based on Laasraoui two-stage flow stress model, a high temperature flow stress model is established by multiple linear regression method. The results show that the peak stress characteristics are not obvious at low temperature and high strain rate, which is a typical dynamic recovery characteristic. Meanwhile, the peak stress characteristics are obvious at high temperature and low strain rate, which is a typical dynamic recrystallization characteristic. By means of the comparisons between experiments and calculations, the Laasraoui two-stage flow stress model can truly reflect flow behavior of steel at high temperature, which provides theoretical guidance for the hot deformation of the steel.

The Precise Determination of the Johnson–Cook Material and Damage Model Parameters and Mechanical Properties of an Aluminum 7068-T651 Alloy

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
B. Bal ◽  
K. K. Karaveli ◽  
B. Cetin ◽  
B. Gumus
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Physical Simulation ◽  
Damage Model ◽  
Rolling Direction ◽  
Stress Triaxiality ◽  
Material Model ◽  
Tensile Tests ◽  
Model Parameters ◽  
Element Analysis

Al 7068-T651 alloy is one of the recently developed materials used mostly in the defense industry due to its high strength, toughness, and low weight compared to steels. The aim of this study is to identify the Johnson–Cook (J–C) material model parameters, the accurate Johnson–Cook (J–C) damage parameters, D1, D2, and D3 of the Al 7068-T651 alloy for finite element analysis-based simulation techniques, together with other damage parameters, D4 and D5. In order to determine D1, D2, and D3, tensile tests were conducted on notched and smooth specimens at medium strain rate, 100 s−1, and tests were repeated seven times to ensure the consistency of the results both in the rolling direction and perpendicular to the rolling direction. To determine D4 and D5 further, tensile tests were conducted on specimens at high strain rate (102 s−1) and temperature (300 °C) by means of the Gleeble thermal–mechanical physical simulation system. The final areas of fractured specimens were calculated through optical microscopy. The effects of stress triaxiality factor, rolling direction, strain rate, and temperature on the mechanical properties of the Al 7068-T651 alloy were also investigated. Damage parameters were calculated via the Levenberg–Marquardt optimization method. From all the aforementioned experimental work, J–C material model parameters were determined. In this article, J–C damage model constants, based on maximum and minimum equivalent strain values, were also reported which can be utilized for the simulation of different applications.

High-Temperature Mechanical Properties of As-Extruded ZK60

2005 ◽  
Vol 488-489 ◽  
pp. 753-758
Author(s):  
Wei Wu ◽  
C.M. Hong ◽  
Li Jia Chen ◽  
Yue Wang ◽  
Lin Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Strain Rate ◽  
Initial Strain Rate ◽  
Offset Yield Strength ◽  
High Temperature Mechanical Properties ◽  
Fracture Behaviors ◽  
Elongation To Failure ◽  
Zk60 Alloy ◽  
High Temperature Tensile

High-temperature tensile and fracture behaviors of as-extruded ZK60 alloy were investigated. It was evident from the experiments that with decreasing temperature and increasing strain rate, the 0.2% offset yield strength and ultimate tensile strength of the alloy increased while the elongation to failure decreased. The flowing stress of as-extruded ZK60 alloy during plastic deformation was proportioned to the reciprocal of temperature. At the initial strain rate of 5×10-4s-1, the calculated active energy at 300°C was about 93.4 kJ/mol.

High Temperature Tensile Properties of Mg-5Li-3Al-1.5Zn-2RE Alloys

2012 ◽  
Vol 182-183 ◽  
pp. 189-193
Author(s):  
Ting Qu Li ◽  
M. Gao ◽  
S.H. Wang ◽  
Zhan Yi Cao
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
Tensile Properties ◽  
Deformation Mechanism ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Fracture Elongation ◽  
Dominant Deformation Mechanism ◽  
High Temperature Tensile ◽  
High Temperature Tensile Properties

In this paper, the high temperature tensile properties of the LAZ532-2RE alloy prepared by hot extruded processing after vacuum casting was investaged. The tensile properties of the extruded LAZ532-2RE alloy specimens were tested at different temperature with different strain rate. The microstructures near the fractured surfaces were observed using microscope in order to investigate the dominant deformation mechanism. The activation energy was calculated to explain the high temperature deformation mechanism. The result indicated that the strength of LAZ532-2RE alloy was high at the temperature range from 398K to 423K. Meanwhile, the fracture elongation of the alloy reaches 121% at 523K under strain rate 1×10-3s-1.

scholarly journals Hot Deformation Behavior and Strain Rate Sensitivity of 33MnCrB5 Boron Steel Using Material Constitutive Equations

2021 ◽  
Author(s):  
Emre Teker ◽  
Mohd Danish ◽  
Munish Kumar Gupta ◽  
Mustafa Kuntoğlu ◽  
Mehmet Erdi Korkmaz
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
Yield Stress ◽  
Maximum Stress ◽  
Tensile Tests ◽  
Simulation Software ◽  
Boron Steel ◽  
Element Analysis ◽  
Static Tests ◽  
High Temperature Tensile

AbstractIn this paper, the constitutive equation parameters (Johnson–Cook parameters) of the 33MnCrB5 material were determined with the help of tensile tests. Initially, Johnson–Cook (JC) model was used for performing the simulations of the sample with finite element analysis with the help of ANSYS software. For these operations, the sample was first used at a certain temperature (24 °C) and low strain rates (10−1, 10−2, 10−3 s−1) and quasi-static tensile tests were performed. Then, high temperature tensile tests were performed with strain rate values of 10−3 s−1 at temperatures of 300 °C, 600 °C, and 900 °C, respectively. Finally, JC parameters belonging to test materials were found in accordance with the results obtained from the high temperature tensile and quasi-static tests. In the last stage, the results obtained from the simulation software for the yield stress, maximum stress, and elongation values were compared with the experimental results. As a result, deviation values for quasi-static tests are calculated as 5.04% at yield stress, 5.57% at maximum stress, and 5.68% at elongation, while for high temperature, yield stress is 9.42%, maximum stress is 11.49% and the elongation value is 7.63%. The accuracy of JC parameters was verified with the comparison made with the obtained data.

scholarly journals ADI 1050-6 Mechanical Behavior at Different Strain Rates and Temperatures

2018 ◽  
Vol 925 ◽  
pp. 196-202 ◽  
Author(s):  
Andrew Ruggiero ◽  
Gianluca Iannitti ◽  
Stefano Masaggia ◽  
Federico Vettore
Keyword(s):  
Strain Rate ◽  
Damage Mechanics ◽  
Damage Model ◽  
Stress Triaxiality ◽  
Continuum Damage Mechanics ◽  
Tensile Tests ◽  
Yield Function ◽  
Strain Rates ◽  
The Continuum

An experimental characterization of the austempered ductile iron ISO 17804/JS/1050-6/S was performed carrying out tensile tests under different strain rates, temperatures and stress triaxiality levels. Then, composing a yield function surface, a hardening relation, and a damage criterion, a constitutive model was developed to describe the salient features of the observed macroscopic response. In particular, the Mohr-Coulomb yield function was selected to account for the pressure effect observed on the yield surface. A new hardening relation was proposed in order to account for both strain rate and temperature effects. The Bonora’s damage model, developed in the framework of the continuum damage mechanics, was adopted to capture the failure condition under different stress triaxiality levels. The damage model was appropriately modified to account for the effect of strain rate and temperature on the failure strain.

scholarly journals Influence of Strain and Stress Triaxiality on the Fracture Behavior of GB 35CrMo Steel during Hot Tensile Testing

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Zheng Li ◽  
Yajun Zhou ◽  
Sanxing Wang
Keyword(s):  
High Temperature ◽  
Tensile Testing ◽  
Crack Formation ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Fracture Morphology ◽  
Tensile Tests ◽  
35Crmo Steel ◽  
Size Growth ◽  
High Temperature Tensile

To better understand cavitation nucleation and crack initiation in 35CrMo steel during high-temperature tensile processing and the effect of stress triaxiality on its fracture behaviors, uniaxial and notch high-temperature tensile tests were performed. The microstructure, fracture morphology, fracture strain, and stress triaxiality of the tested 35CrMo steel were then characterized and discussed. The results showed that crack formation in 35CrMo steel included stages of nucleation, growth, and microcavity aggregation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy demonstrated that crack formation was closely related to the presence of steel inclusions. High-temperature tensile testing of samples with different notch radii showed that the fracture strain of 35CrMo steel was decreased with increasing stress triaxiality, that is, increased stress levels corresponded to decreased material plasticity. In addition, the recrystallization degree was decreased with increased stress triaxiality, and the grain size growth was slowed. The failure of 35CrMo steel occurred via ductile fracture, and low stress triaxiality, and high temperature conditions induced large and deep dimples on the fracture surface.

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